DEPARTMENT OF THE INTERIOR. 

FRANKLIN· K. LANE, Secretary 

UNITED STATES GEOLOGICAL SURVEY 

GEORGE OTIS SMITH, Director 

Professional Paper 113 

IRON-DEPOSITING BACTERIA AND THEIR 

GEOLOGIC RELATIONS 

BY 

EDMUND CECIL HARDER 

WASHINGTON 

GOVERNMENT PRINTING· OFFIOE 

1919. 

CONTENTS. 

Pnge. 

~~~-~~~~~~~c~~l:~-- ~~-- ~~~~~~ ~.-· .. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~-~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ -~ -~ ; 

Ackno\vledgn1ents ............................... ·....................................................... 7 

The iron-depositing bacteria .......................... ~ ............... ~................................... 8 

General classification and morphology .......... ~ ........ : . ............................... ·. . . . . . . . . . . . . 8 

General physiology.................................................................................. 11 

Results of the present investigation ....... · ..................... : ................ ·......................... ·13 

Occurrence and morphology of iron-depositing thl·ead bacteria ........... ·............................... 13 

Crenothri.'C ])Olyspora Cohn .......... : ....................................... · ............ ·. . . . . . . . . . 13 

Leptothri.'C ochracea K i.i tzing ............................................................. : . . . . . . . 16 

Gallionella ferruginea Ehren burg ................................................. : . . . . . . . . . . . . . . . 22 

Spirophyllumjerrugineum Ellis .................................................. · ...... .' .. ~....... ·24 

Other iron-depositing bacteria .......... ·~ ......................................... · ........... ·. . . . . . . . . 29 

Experiments on precipitation of iron from solutions by bacteria......................................... 31 

Precipitation of ferric hydroxide and basic ferric salts from ferric ammonium citrate solutions. . . . . . . . 31 

Precipitation of ferric hydroxide and basic ferric saltS' fi·om other solutions containing-organic iron. . . . 36 

Precipitation of ferric hydroxide a.nd basic ferric salts from solutions containing inorganic iron......... 38 

Precipitation of ferrous sulphide from solutions containing iron ........ _".............................. 40 

Geologic importance of iron-depositing bacteria ................. ." .................... ·.· .... :........... 44 

Iron in the earth's crust ...................................................................... :... 44 

Decomposition of iron-bearing minerals ......... ~ .... : . ."........................................... 45 

Types of sedimentary iron ores and iron formations ............................. : ... ·.·.............. 48 

General features ..•................................... : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 

Deposits originally laid down mainly as ferric hydroxide .. :...................................... 49 

Deposits originally laid down mainly as ferrous carbonate ......... · ............. :. . . . . . . . . . . . . . . . 54 

Deposits originally laid down mainly as iron silicates .............................. .-..... :. . . . . . . 57 

Deposits originally laid down mainly as iro~ sulphide.......................................... 60 

Formation of sedimen~ary iron-bearing deposits .... · .................................. : ." ~ ~ . . . . . . . . . . 64 

Depositiori. of iron by mechanical processes. · ........ : . .................... · ......... ~- ... ~. . . . . . 64 

Deposition qf iron by chemicaJ processes......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 

Formation of deposits of ferric hydroxide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 

Formation of deposits of ferrous carbonate ............... · ....... : ................. -........ 71 

Formation of deposits of iron silicate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 

F?r~natim~ of depos~ts o~ iron su~phide .............................. : . ................ ~.... 74 

Depos1t10n of uon by biologic agencies ........................................ : . ..... :. . . . . . . 75 

Formation of deposits of ferric hydroxide. . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 

Formation of deposits of ferrous sulphide ...................... : . . . . . . . . . . . . . . . . . . . . . . . . . . 82 

13ibliography ........................................ · ................................. :........... . . . . . . 84 

Index ........................ ~.· .............. : . ............... -.· ............ -.- ................ · ... -.-.- 87 

s 
ILLUSTRATIONS. 

PLATE I. A, a, Thread of Crenothrix polyspora; b, Upper portion of the same thread showing conidia in the 

'Upper part of the sheath and ordinary vegetative shells in the lower part; c, Portions of threads of 

Crenothrix polyspora, showing vegetative cells, conidia, and germination of cells within the sheaths; 

Page. 

B, Photomicrograph of threads of Crenothrix polyspora from city water of Madison, Wis.......... l4 

II. A, B, Photoinicrographs of threads of Crenothrix polyspora from city water, Madison, Wis ........... · 15 

III. A, B, Photomicrographs of threads of Crenothrix polyspora from city water, Madison, Wis........... 16 

IV. A, B, Photomicrographs of ocherous scum in iron spring near Lake Kegonsa, Madison, Wis . . . . . . . . 17 

V. A, Photomicrograph of material from 262-foot level, Kennedy mine, Cuyuna, Minn.; B, Photomicrograph of ocherous scum on 262-foot level, Kennedy mine, Cuyuna, Minn................... 18 

VI. A, B, Photomicrographs of ocherous, gelatinous scum from 100-foot level, Federal mine, Hazel 

Green, Wis .................... ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

VII. A, Photomicrograph o{ ocherous, gelatinous scum from 100-foot level, Federal mine, Hazel Green, 

Wis.; B, Photomicrograph of double twisted ribbon-like form of Spirophyllum jerrugineum from 

city water, Madison, Wis. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . 22 

·VIII. A, Photomicrograph of ocherous scum from 300-foot level, Judson mine, Alpha, Mich.; B, Photomi~ 

crograph of ocherous scum from 200-foot level, Judson mine, Alpha, Mich.......................... 23 

IX. A, Photomicrograph of ocherous scum from iron spring near Vermilion Lake, Soudan, Minn.; B, Photo~ 

micrograph of limonite powder from tubercle of iron rust........................................ 26 

X. A, B, Cultures showing the precipitation of ferric hydroxide from solutions of ferric ammonium citrate. 2 7 . 

XI. Cultures showing the effect of sterilization in the precipitation of ferric hydroxide from solutions of 

ferric ammonium citrate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 

XII. A, Petri dishes showing colonies of lower bacteria which precipitate ferric hydroxide from agar con~· 

taining ferric ammonium citrate; B, Photomicrograph of a pure culture of one type .of lower bacteria 

which has the power of precipitating ferric hydroxide from solutions of ferric ammonium citrate... 33 

FIGURE l. Portion of a thread of Crenothrix polyspora showing formation of conidia.......................... 15 

2. Portion of a thread of Crenothrix potyspora showing thick coating of ferric hydroxide............... 16 

3. Diagrammatic sketch of Spirophyllumjerrugineum, Gallionellajerruginea, and Leptothri.-r; ochracea... 19 

4. ~rtions of threads of Leptothri.-r; ochracea showing straight and curved forms........................ 20 

5. Portions of threads of Leptothrix ochracea . ........................................... ~. . . . .. . . . . . 20 

6. Portions of threads of Leptothrix ochracea, one of them showing nodular projections. . . . . . . . . . . . . . . . 21 

7. Loosely twisted ropelike form. of Gallionella ferruginea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 

8. Closely twisted ropelike form of Gallionellajerruginea.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 

9. Various forms of Spirophyllumjerrugineum ................................... . ·.................. 27 

10. Irregularly twisted forms of Spirophyllumjerrugineum........................................... 28 

11. Single and double twisted ribbon-like forms of Spirophyllumjerrugineum . . . . . . . . . . . . . . . . . . . . . . . . 28 

12. Irregularly twisted fornis of Spirophyllumjerrugineum with granular coatings probably consisting of 

ferric hydroxide ................................... ·.·....................................... 29 

13. Various forms of fossil Spirophyllumjerrugineum from tubercle of iron rust........................ 29 

14. Various forms of lower bacteria which have the power of precipitating ferric hydroxide from solutiom 

of ferric ammonium citrate..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 

4 
PREFACE. 

By F. L. RANSOl\IE. 

The enormous importance of bacteria in all 

that pertains to the huti·ition and well-being 

of animnJs and of the higher plants is to-day 

a matter of wide recognition, even by those 

whose knowledge of the part played by these 

minute and wonderful organisms is far from 

exact. The investigations o~ Pasteur opened 

our eyes to their dendly power in disease and 

their enormous efficiency in processes of fermentation and decay. R.ealization of the influence 

of bacteria in affecting the character ·and fertility of soils, in bringing about rock decay, and 

in producing other geologic results has come 

more slowly. · 

It has been known, however, since 1836 that 

certnJn bacteria have the power of withdrawing iron from solution nnd causing its precipitation as :ferric hydroxide. The precipitation 

of iron sulphide by bacterial processes has also 

been known for some time. The geologic applications of these discoveries, though predicted by some to be fur-reaching, have been 

rather .slowly mitde, and it is safe to ·say that 

many geologists have paid little· attention to 

the possible extent of. bacterial action in the 

deposition of iron ores. Lately, in ~onnection 

with the studies in the geology of the Coastal 

Plain, now in progress under the direction of 

T. ·v\r. Vaughan, the part played by bacteria in 

the deposition of limestones has been specially 

investigated and found to be importapt. Similarly when ~1r. !-larder, who has devoted particular attention for some years to the occurrence of iron ores both in the United States 

and abroad, was detailed to study the Cuyupa 

Range, ~1inn., he found an opportunity in 

the laboratorie$ of the University of ';Viseansin to pursue investigations on the iron-depositing bacterin. The report here presented 

records the results of this research. 

Opinions . have differed as to the mode 

whereby the bacteria withdraw iron from solution. Some investigators have maintained that 

the deposition of iron hydroxide is one of the 

vital processes pf the organism and as such iseffected directly by the action of the living 

cell; others that the ·precipitation is purely 

chemical and is incidental rather than essential to bacterial life; and still others that the 

accumulation is mechanical, particles of· iron 

hydroxide present in the water being caught 

and held by mucilaginous parts of the bacteria. 

In the course of his .work Mr. Harder has. 

found that in addition to the iron-depositing 

bacteria proper, chiefly the higher or thread 

bacteria, probably many ·of the common bacteria ofsoil and water are active in the precipitation of ferric hydroxide or basic ferric salts 

from solutions containing iron salts of o~ganic 

acids .. This result is believed to be new. Such 

bacteria apparently utilize some constituent of 

the salt other than iron, the iron hydro~ide 

being left us a waste product. 

~1r. !-larder concludes that, according to 

present knowledge, there are three principal 

groups of iron-depositing bacteria-(1) those 

that precipitate ferric hydroxide :from solutions of ferrous bicarbonate, using the carbon 

dioxide set free and ~he available energy of the 

reaction for their life processes ; ( 2) those 

that do not require ferrous bicarbonate for 

their vital proce.sses but that cause the· deposition of ferric hydroxide when either inorganic or organic iron salts are present; and (3) 

those that attack iron salts of organic acids, 

using the organic.acid radicle as food and leaving ferric hydroxide, or basic ferric salts that 

gradually change to ferric hydroxide. 

. In addition to recording much that is ·new 

concerning iron-depositing bacteria, Mr.· Harder's report constitutes a valuable critical summary of previous work and should serve a useful purpose in bringing before geologists a digest of practically all that is known on the subject, supplemented by a carefully prepared 

bibliography. 

5 

IRON-DEPOSITING BAC~ER.IA AND THEIR GEOLOGIC RE~ATIONS. 

By EDMUND CECIL HARDER: 

INTRODUCTION. 

As early as 1836 it was found by. Ehrenberg 

that organisms play an important ·part in the. 

formation of ocherous deposits of bog iron ore. 

Since that time the.se organisins have been 

studied by .various investigators, who have de.:. 

termined their position in the classification of 

lower plant forms, have investigated the life 

histories of some of them, and have studied 

their morphology and their physiologic processes. Nearly all of this work, however, has 

been done from the standpoint of the biologist, 

nnd the geologic significance has received only 

n1inor consideration. 

For a number of years I have been engaged 

in a· study of iron ores in different parts of the 

world and have paid special attention to the 

mode of or:igin of these deposits. I have been 

impressed 'vith the difficulty of explaining the 

accumulation of la.rge masses of ferric oxide 

by simple chemical processes. Certain ironore deposits, such as limestone-contact ores; 

ores formed by magmatic segregation, and 

some types of veins undoubtedly owe their 

origin to igneous agencies, but there are other 

deposits of enorrnous extent, such as sedimentary otes, bog ores, and deposits formed by surface concentration, which have no igneous associations and the origin of which has usually 

been attributed to simple oxidation and preci pi.tation from solutions containing ferrot~s iron. 

It is with reference to the last class that I have 

endeavored ·to find a 1i1ore efficie~t agent of precipitation under an conditions and have taken 

up the study of the organisms which precipitate iron oxide. 

· In order to pursue this investigation intelligently, it was of course necessary to study the 

organisms both in tlu~ laboratory and in the 

field. It was neces.sary to show the widespread 

occurrence of the organisms, as well as to prove 

their effectiveness iri precipitating ferric hydroxide from solution. 

In the field work many iron springs, bogs, 

mines, and streams were examined for the 

presence of deposits of ferric hydroxide, and 

when found samples were taken to -the laboratory and examined micr~scopically and some 

of them chemically. The morphology of the 

organisms was studied and laboratory cultures 

were made fron1 them in attempts to study the 

physiology. l\1any different iron compounds 

were used in the· laboratory work, 'organic as 

\veil as inorganic, and th~ activity oi the organisms in precipitating ferric hydroxide from 

each compound was studied. 

In general it was found that iron-precipitat-. 

ing organisms were present wherever ironbearing waters occur, both underground in 

wells and mines and in surface waters. It was 

found that the ocherous scums which occur in 

such localities consisted mainly and in many 

places entirely of i1~on.:precipitating organisms 

or their remains. These were found to belong 

chiefly to the class of organisms known as· 

thr.ead bacteria. 

It was determined also that solutions of 

certain iron compounds, when inoculated with 

almost any type of natural water or of soil, 

showed a precipitation of ferric hydroxide by 

certain types of lower bacteria, thus indicat-· 

ing the almost universal presence in nature of 

organisms capable ·Of precipitating iron from· 

solution. · · 

ACKNOWLEDGMENTS. 

The investigations on ·which this report is 

based were made largely· in the bacteriologic 

7 
8 IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

laboratory of the Agricultural Experiment 

Station of the University of vVisconsin. Many 

helpful suggestions, as well as material aid, 

were given me by members· of the bacteriologic 

staff of the university. I wish, however, 

especially to acknowledge my indebtedness to 

Prof. E. G. IIastings, head of the department 

of agricultural bacteriology, and to Prof. E. 

B. Fred, in charge of soil bacteriology; who 

0 kindly placed the laboratory and all its facilities at my disposal and who always aided me 

with willing criticisms throughoilt the course 

of the investigations. From Prof. C. 1{. Leith, 

of the geologic department of the University. 

of Wisconsin, I received suggestions regarding 

the method of attack of the geologic problems 

involved. Prof. W. H. Hunter; of the department of chemistry, University of Minnesota, 

read and criticised the sections of the report 

which are largely chemical in nature. Mr. F. 

T. Thwaites, Dr. vV. L. tJglow, Mr. A. D. 

Wheeler, Prof. E. B. Fred, and many others· 

rendered assistance in collecting material for 

investigation. 

THE IRON-DEPOSITING .BACTERIA. 

GENERAL CLASSIFICATION AND MORPHOLOGY. 

Until recently the term" iron bacteria" was 

applied to a certain group of filamentous bacteria that have the power of precipitating ferric hydroxide from iron solutions. These organisms were Classified by Migula under the 

general term Trichobacteria or " higher bacteria" to distinguish them from the Haplobacteria or "lower ba.cteria" to which ordinary coccus, bacillus, and spirillum forms belong. Besides the iron bacteria, such as 

Crenoth.r.im, Gallionella, Spiroph.yllttm, Leptothrix, and Olonothrix, there were included 

under " higher bacteria " certain soil and 

pathogenic bacteria·, such as Olai!Joth.rix, Streptoth.rim, Phragmidiothrix·, and ActinOmAJ'Ces, 

and a third group, the "sulphur bacteria," 

also a higher bacterial type, was classed independently as Thiobacteria. It was supposed 

that all iron bacteria belonged to the higher 

type, until about 1908, when Molisch discovered certain coccus forms that had the power of 

precipitating ferric hydroxide. Still more recently Mumford claims to have isolated a 

bacillus that has the same power, and it· seems 

quite probable that many other species of both 

lower and higher bacteria may be found that 

precipitate ferric hydroxide from iron solutions. 

· The higher bacteria are distinguished from 

the lower bacteria by thei~ morphology and 

their methods· of reproduction. 1 Lower bacteria occur as Sl)herical, rod-shaped~ or spiral 

forms and reproduce by simple cell division. 

I-Iigher bacteria occur as long threads, which 

are usually composed of many individual cells, 

and whiqh generally reproduce by the formation of conidia or swarm spores. In some species of higher bacteria conidia or swarm spores 

are produced by the division of cells which 

form part of the thread, whereas in other 

species small protrusions are said to . form 

along the sides of the threads and in time 

separate themselves from the th1·eads as 

conidia. 

Higher iron ·bacteria present a variety o£ 

forms, such as single threads composed of cylindrical cells placed end to end and generally 

inclosed in sheaths; ribbon forms~ twisted spirally; cylindrical threads showing false branching, or coiled threads or ribbon forms produced 

by the bending of the filaments in the middle 

and the twist~ng of the (~nds around each other 

like rope. 

According to Migula's general classification, 

the iron bacteria may be grouped as follows: 2 

A. Eubacteria (true bacteria). 

1. Hap1obacteria ( 1ower bacteria). 

a. Coccnceae (2 species of iron bacteria 

known). 

Siderocapsa treubii. 

Siderocapsa major. 

b. Bacteriaceae ( 1 species of iron bacteria 

described). 

Bacillus M. 7. 

c. Spirillaceae (no known species of iron bac~ 

teria). 

1 Beneclw, Wilhelm, Bau und Leben der Baktcrl~n, pp, 

487-498, Leipzig, 1912. · 

Rullman, W., Eisenbakterien, Cladotricheen, Streptotri· 

cheen, und Actinomyceten, in Lafar's flandbuch der technischen Mykologie, Auflage 2, Band 3, pp. 190-214, Jena, 

1904-5. 

Migula, W., System der Bakterien, Band 2, p. 1031, Jena, 

1897-1900. 

Molisch, Hans, Die Eisenbakterien, .Tena, HllO. 

Ellis, David, The iron bacteria: Sci. Progress, vol. 10, 

pp. 374-392, 1916. 

. 2 Adapted in part from Migula and in part from BO'Ilecke 

and Ellis. · 
THE IRON -DEPOSITING BACTERIA. 9 

A.. JDnbtlct:erin (true bacterin )-Continued. 

2. Tl'ichobncteria (higher bacteria) ( numerou~ 

species of· iron bacterin). 

. n. Tht·end bacterin consisting of sheaths with 

included cells generally plainly visible; reproduction by internally produced conidia 

or by the sepnration of motile or nonmotile 

cells. 

Crenothrix polyspora. 

Clndothrix dichotomn. 

Olonothrix fusca. 

Lept:othrix ochracea (Chlamydothrix ochrncen). 

Chlnmytlotbrix sideropous (Leptothrix 

siclet·opous). 

Megalothrix discophora. 

b. 'l'hrend bnct:eria showing no division into 

separate cells; 1i1ethod of reproduction not 

definitely established but supposed to be by 

bren king off of parts of threads and perhnps by external abstriction of conidia. 

Gnllionelltl . ferruginea ( Chlamyclothrix 

ferruginea). 

Spirophyllum ferrugineum. 

Nodofolium ferrugineu·m .. 

Couicliothrix. · ( ?) 

B. 'l'hiobacteria (sulphur bacteria) (no known species 

of iron bacteria).. · 

Sidm·ocapsa was found by Molisch1 to occur 

on the submerged leaves or stems of certain 

water plants on which it exists in the form of 

little irregular ringlike colonies. Frequently 

it :forms a brown incrustation covering the entire submerged portion of the plants. It is a. 

common coccus form and is said to be one of 

the 1nost abundant of water bacteria. It is 

believed by J\1olisch to be· nn important agent 

in the forrnation of'bog iron ores. 

Bacillus A!. 7 was discovered by Mumford2 

during an examination of iron-bearing colliery waters in England. lie examined the 

brownish ocherous scum which formed in a 

basin into which the mine waters emptied and 

found that it consisted of a mass of ferric 

hydroxide of fine granular texture with some 

scattered threads of higher iron bacterin. 

After various inoculations of this granular 

material in culture media a bacillus was isolated which produced an enzyme that had the 

power of precipitating ferric. hydroxide from 

either ·ferrous or ferric solutions. Mumford 

states thn.t he succeeded in isolating the enzyme 

frorn the organism by filtration. 

11\foliRch, Hans, Shlerocapsa, treu.bii Mollsch, cine neue 

wcltverureltcte Elsenuaktet·ic: Cent:rnlbl. Bal{teriologie, Abt:. 

2, Bnnd !!!), p. 24:{, 1011; Die Eisenbal,tcrlcn, .Tena, 1.!)10. 

2 Mumford, E. 1\f., A new Iron bacterium : Chern. Soc. Jour., 

vol. 103, vv: 645-650, 1913. 

Crenotkrix 3 is the largest of the iron bacteria and is found most commonly at the bottoms of wells and in city water pipes. Less 

than 2 parts of iron per million in water is 

sufficient to support the activity of Orenothrix .. 

In its manner of growth and reproduction, 

Orenoth1·ix is one of the most interesting of 

the iron bacteria. It is sessile; the attached 

end is thin and the organism gradually thickens toward the free end .. The separate cells 

that :tnake up a thread of Orenothrix are 

clearly distinguishable, being rod shaped and 

placed end to end in a sheath. Toward the upper end of the filament the cells are seen to 

divide, at first transvm~sely and then longitudinally, so that a large number of small spherical cells are formed near the upper end of the 

filament. These are the conidia, which leave 

the parent sheath and form new threads. Frequently conidia. are prevented from leaving· 

the sheath, and then they germinate within 

the sheath an·d thrust their filaments through 

the walls,· giving the appearance of numerous little branches extending from the parent 

filament. 

Olonothrix 4 and Oladothrix 5 are forms related to Cre'IUJthrix but differ from it in showing false branching. This is caused by one 

cell pushing by the next n hove it and then 

dividing and pushing its way through the 

sheath. Olonotkrix reproduces by the forma3 Cohn, F. J., Ueber den Brunncnfaden (Orenothriw poly8pora.) mit Bcmerlmngen ueber die mikroskoplsche analyse 

des Brunnenwassers: Beitt·. Biologic Pflanzen, Band 1, Heft 

1, pp. 108-131, 1875. 

Zopf, W., Entwicklungsgeschlchtliche Untersuchungen i.iber 

Orenoth1·ix polyspora, die Ursachc der Berliner Wasserlmla.-

mitiit, Berlin, 1879. 

Rossler, 0., Ueber Kultivlerung von Grenothrix polysp01·a 

auf fest:em Niihrboden : Archlv Pharmncic, Band 233, pp. 

189-191, 1805. 

Adler, Oscar, Ueber Elsenbakterien und lhrer Beziehung zu 

den therapeutisch verwendeten naturlichen ElsenwUsscrn: 

Centralbl. Bakteriologie, Abt. 2, Band ll, pp. 215-219, 277-

278, 1903-4. 

Schorler, B., Beltriige zur Kenntnls der Eisenbal,terlen : 

Centralbl. Bakteriologie, Abt. 2, Band 12, pp. 681-6!)5, 1904. 

Beythien, Hempel, and Kraft, Belt:rHge zur Kenntnis des 

Vorkommens von G1·enothl'ix 1lOl?J8J)o1·a, in Brnnncnwiissern : 

Zeitschr. Untersuchung Nahrungs- und Genussmittel, 1904, 

Heft 4, p. 215. 

Rullmann, W., Ueber Eisenbakterien: Cenf:ralbl. Bakterlologie, Abt. 2, Band, 33, pp. 2i7-289, 1912. 4 Schorler, B., Beitriige liUr Kenntnls der Elsenbalderien : 

Centrp.lbl. Bnl;:teriologie, Abt, 2, Band 12, pp. 681-G!)5, 1!)04. 5 Cohn, F. J., Untersuchungen ueber Bakterien: Beitr. · Biologic Pflanzen, Band 1, Heft 3, p. 1SG, 1875. 

Zopf, W., Zur Morphologic der Spaltpflanzen, Leipzig, 

1882. 

Ellis, Dnvid, An investigation into the life history of 

Cladothrix dicl10toma: Roy. Soc. rroc., B, vol. 85, pp. 344-

358, 1912. 
10 IRON-DEPOSITING· BACTERIA AND THEIR GEOLOGIC RELATIONS. 

tion of conidia resembling those of Orernothrix 

and by vegetative cells which slip out of the 

sheath. The threads are· similar to those of 

Orenothriw but taper toward the free end 

while those of Orenothriw thicken toward the 

free end. Oladothrix is primarily a soil organism and does not belong to the iron bacteria· 

proper, but it is capable of depositing ferric 

hydroxi~e on its sheath. It reproduces by motile and nonmotile conidia, resembling vegetative cells, which either leave the ends of the 

threads or are set free by the breaking 'up of 

the threads. 

Leptothrix 1 is a sii11ple thread form, usually 

free but sometimes attached at one end. The 

threads are straight or curved. They generally have the same width throughout and consist of a sheath inside of which rod-shaped 

cells lie end to end. Only rarely, however, can 

·the cells in the sheath be distinguished, due to 

the coloring ·in the sheath, and besides many 

dead, empty sheaths are 1nixed with the living 

organisms. The sheaths are yellowish brown 

fron1 ferric hydroxide. The organism commonly reproduces by fragmentation but may 

reproduce also bjr the separation of vegetative 

cells and by swarm cells. 

Leptothrix is found abundantly in chaly- _ 

beate springs, where it forms soft fluffy botry"' 

oidal masses attached to the bottom or sides of 

the basins. Less commonly it occurs underground in mines or tunnels where iron-bearing 

waters issue from the rocks. The occurrence 

of iron bacteria in deep mines has to n1y 

know ledge not previously been ment_ioned in 

the literature. 

11! egalothrix discophora, a form recently described by Sch~ers,2 somewhat resembles Leptothrix but differs from it in beirig thicker and 

in possessing a very thick sheath. · Inside of 

this sheath is a: narrow canal in which long 

cylindrical cells are oc;casionally seen. The 

1 Kiitzing, Phycologia generalis, p. 198, 1843. 

Migula, W., System der Baktericn, Band 2, p. 1031', Jena, 

1900. 

Winogradsky, S., Ueber Eisenbakterien: Bot. Zeitung, 

Band 46, pp. 262-270, 1888. 

Schorler, B., Beitrllge zur Kenntnis der Eisenbakterien : · 

Centralbl. Baktcriologie, Abt. 2, Band 12, pp. 681-695, 190-1. 

Ellis, David, A contribution to our knowledge of the thread 

bacteria: Centralbl. Bakteriologie, Abt. 2, Band 19, pp. 502-

518, 1907; Band 26, pp. 321-329, 1910. 

Molisch, Hans, Die Eisenbakterien, Jena, 1910. 

· 2 Schwcrs,- Henri, Megalothriw d·iscophora, eine neue Eisenbaktcric : Centralbl. Bakterio1ogie, Abt. 2, Rand 3:3, pp. 27:3-

276, 1912. 

threads have a holdfast at one end by means 

of which they attach themselves to foreign 

objects. Some of them show dichotomous 

branching. 

Gallionella 3 in its typical form consists of 

spiral threads coiled together. into double or 

quadruple coils like rope. The individual 

threads, which are yellow to brown,.are cylindrical like those of Leptoth'rix but are generally n1uch thinner. Cells have not been distinguished within them. Though usually 

tightly wound into coils, loosely wound threads 

are frequently ,seen and occasionally even sin.:. 

gle spiral threads.-

Gallionella is said to occur in iron-bearing 

surface waters with Leptothrix, but more commonly it is associatBd with Spirophyllum in 

iron-be.aring well waters and in certain mines 

where iron-bearing waters issue from the 

walls. In such places Gallionella and Spirophyllum form soft, spongy ocherous masses on 

the walls beneath the openings where iron waters issue. 

Spirophyllum 4 is perhaps the u1ost abundant of the iron thread bacteria. It has the 

form of flat ribbon-like or tapelike- threads 

twisted in the :form of spirals. These spiral 

bands may occur as single filaments or they 

may be coiled together as in Gallionella. Reproduction ~n Spirophyllum is commonly by · 

:fragmentation but is said to take place also by 

means of conidia, which form budlike projections on the flat sides of the bands. This 

meth~d of reproduction is questioned by some 

investigators. 

Spirophyllum is abundantly distributed in 

nature. It occurs with Leptothrix in chalybeate springs and other iron-bearing surface 

3 Ebrenburg, D. C. G., VorHiutl.ge 1\fittheilungen ueber das 

wirklige Vorkommen fossiler Infusorien und ihre grosRe :Verbreitung: Poggendorf's Annalen, Band 38, pp. 213-227, 1836. 

Migula, W., Ueber Gallionella fcrruginea Ebrenburg: 

Deutsch. bot. Gesell. Ber., Band 15, p. 321, 1897. 

Kiitzing, Species algarum, p. 250, 1849. 

Ellis, David, A contribution to our knowledge of the 

thread. bacteria : Centralbl. Bakteriologie, Abt. 2, Band Hl, 

pp. 502-518, 1907 ; Band 26, pp. 321-329, HHO. 

Schorler, B., Die Rostbildungen in den Wasserleltungsrohren : CentralbL Bakteriologie; Abt. 2, Band 15; jP· 564-

568, Hl06. 4 Ellis, David, On the disc~very of a new genus of thread 

bacteria (Spirophyllmn ferrttginett1n Ellis) : Roy. Soc. Edinbu·rgh Proc., vol. 27, pt. 1, pp. 21-34, 1907; A contribution 

to our knowledge of the ·thread bact:eria: Centralbl. Bakteriologie, Abt. 2, Band 19, pp. 502-518, 1907 ; Band 26, pp. 321-

329, 1910. 

Lieske, R., Beitriige zur Kenntnis der Physiologic von 

Spirophyll1t1n ferrttginettm Ellis: Jahrb. wiss. Botanik, Band 

49, pp. 91-127, 1911. 
THE IRON-DEPOSITING BACTERIA. 11 

waters, alone or with GalUonella or LezJtothrim 

in iron-bearing mine waters, and with Orenoth,riw in city water pipes. In the latter it occasionally becomes so abundant as to cause 

tur?idity of the '~ater and even a blocking of 

the pipes due to the deposition of ferric hydroxide. 

N odofoliwm 1 is described by Ellis as being 

related to Spirophyllum. It is said to consist 

of flnt. elliptical disks plnced end to end so that. 

each succeeding one is at right angles to the 

last, the whole forming a chain. Investigators 

~ho do not follow Ellis claim that N odofoliwm 

is simply a form of SpirozJhyllum. 

The name Oonidiothriw is suggested by 

Benecke 2 for a simple thread form resemblinO' 

Leptothlriw which has been desc.ribec(by Elli; 

It differs frorr1 Leptothriw in that its cell structure is not visible and in that it reproduces by 

conidia which form projections on the outside 

of the sheath. This form has n.ot been definitely iden~tified. 

The separation of the higher iron bacteria 

into two groups, one characterized·by internally 

produced conidia and the other by the external 

a bstriction of conidia, seems to me questionable. 

Several investigators doubt the occurrence of 

external conidia, Ellis being practically the 

only nuthor on record who states definitely 

that he has seen their formatio.n and germination. In my work, during which I have examined iron bacteria from many different localities, I have never certainly identified external conidia, and although I have often noted 

nodular projections or attached bGdies on bacterial threads, most of these projection,s have 

turned out to be granules of ferric hvdrox:ide 

or other foreign particles. It is not i~possible, 

however, that further work may prove Ellis's 

contention to be correct and that other investigators will be able to definitely confirm this 

method ·of reproduction aniong iron bacteria. · 

A number of other organisms besides iron 

bacteria are lmown '''hich deposit ferric hydroxide in their C\)atings or in certain parts of 

their bodi~s. 3 Among tl~ese,.are included algae, 

such as !'swhohormi-um, Oedogonium, Euglena,, 

Gloste~um, and Trachelomonas, as .well as prolJJJllis, David, A contribution to our knowledge o'f the 

thread buctel'ia : Centralbl. Bakteriologie Abt. 2 Band 26 

pp. 321.-329, 1.910. ' ' ' 2 Benecl<e, Wilhelm, Bau·uud Leben der Bakt~rien pp 489-

492, r~etpzlg, 1912. ' . 3 1\folisch,. Huns, Die Etsenbakterlen,. pp. 53-58, 1910. 

tozoa, such as-R hizJidodend'ro.n P hallansterium ' . ' Spongomonas, Oarchesiu'ln, and especially a 

c~rtain flagellate called Anthophysa, a branchlike organism whieh commonly becomes heavily incrusted with ferric hydroxide. In my 

own work I have also found that the mycelia 

o~ various fungi often become· ·impregnated 

With or coated by ferric hydroxide. 

GENERAL PHYSIOLOGY. 

Several ~xplanations have been offered for 

the deposition of fen~ic hydroxide by iron bact~r~a. .son~e investigators belieYe that the preCipitatiOn 1s merely a chemical process, in no 

way connected with the internal activity of 

the cell, whereas others claim that the process 

is one of oxidation of ferrous to ferric compounds and that it is ·necessary for the life 

processes of the organisms. · 

Among the first to· study the activities .of 

iron-depositing thread bacteria were Cohn and 

~opf. Cohn 4 • believed that the ferric hydroxI~e. was deposited as a result of the activity of 

h v1ng cells artd that the deposition occurred in 

the same manner as the deposition of silica 

takes place in the tests of diatoms. Zopf 5 

some years later stated that he found ferric 

hydroxide being deposited on empty sheaths 

from w hieh all living cells had been re~oved. 

l-Ie .was of the opinion, therefore, that the storing up of ferric hydroxide in the sheaths was 

~nerely th~ result of mechanical processes, the 

Iron compounds being taken up by a niucilaginous coating on the sheaths. 

~ater 'Yinogradsky 6 investigated the physiology of Iron bacteria. His experiments were 

co~ducted with Leptothriw, and in a publication .. of his results in 1888 he states that Leptothriw will live and grow only in solutions in 

which iron is present in the ferrous form, ~nd 

that only where liYing cells are· present in a 

sheath is there any coloration of the sheath due· 

to the.· oxjdation of ferro'us salts. He also 

found that the sheaths would not take up mechanically any ferric hydroxide which may be 

present in the solution and believed that the 

~Cohn, F. J., Ueber den Brunnenfaden (Orenothri:v voiyspora) mit Bemerkuugen ueber die mikr"oskoplsche Analyse 

des Brunnenwassers : Beitr. Biologic Pflanzen, Band 1, lleft 

1, pp. 108-131, 1875. 5 Zopf, W., Zur 1\:lorphologle der Spaltpflanzen Leipzig 1882. ' ' ' 

0 Wiuograusl<y, · S., Ueber Elsenbakterlen: Bot. Zeitung 

Band 46, pp. 262-270, 1888. ' 
12 IRON -D;EPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

colorati.on is due to ferric .hydroxide being 

given ·off by the cells and. caught in the sheath 

which incloses them. 

He concludes from this that the oxidation of 

ferrous compounds to form ferric hydroxide 

. is necessary for the life and growth of the organisms and that this process furnishes energy 

to the cell for the assimilation of food. The 

food· consists of organic compounds present in 

the water. Only a small amount of organic 

matter, however, was found to be necessary to 

sustain life. · Winogradsky worked with solutions of ferrous carbonate (FeC03 ). 

Molisch 1 (1892 and 1910), in a series of 

experiments, proved that Leptothriw will grow 

profusely .in an iron-free medium, forming 

perfectly colorless sheaths. He found that 

peptone solutions were especially favorable 

for its development. If either iron or manganese· compounds were. present in the solu-· 

tions, however, he found that they were oxidized and taken up by the sheaths. Likewise, 

~1olisch states that Leptoth.riw forms thicker 

and longer threads when iron or ;manganese is 

present in solution and that sheaths containing 

live cells accumulate ferric hydroxide more 

abundantly. However, threads in which the 

cells have been killed by boiling in water are 

still capable of talring up ferric hydroxide in 

their sheaths. He determined further that 

where there was little chance of oxidation, a 

ferrous compound would accumulate in· the 

sheath and cause the same luxuriant growth 

as ferric hydroxide. Therefore he concludes 

that th~ugh these organisms show a marked 

attraction for iron or manganese compounds, 

the reason for this is a physicochemical one: 

and the change of ferrous to ferric compounds 

is due to simple oxidation and is not connected with the life ·processes of the cells as 

was claimed b.y Winogradsky. That dead, 

empty sheaths do not take up ferric hydroxide 

to a marked e~tent he explains by stating that 

living cells probably have some influence in 

keeping the sheath in a condition in which it 

is able to accumulate more material. 

James Campbell Brown 2 made some interesting observations on the black slime which 

1 :Molisch, Hans, Die Eisenbakterien, pp. 44-52, Jena, 1910; 

Die Pflanze in ihren Beziehungen zum Eisen, p. 71, Jena, 

1892. 2 Brown, J. C., Deposits in pipes and other channels conveying potable water : Jnst. Civ. Eng. Proc., vol. 156, Sess. 

1903-4, pt. 2, pp. 1-17' 1!)04. 

collects in pipes, culverts, and ~ther \Yater 

channels. He finds that it consists mainly of a 

mixture of ferric hydroxide, manganese oxide, 

and organic matter and that it contains among 

other organisms abundant iron-depositing 

thread bacteria. He states that such slimes 

fonn only in acid waters, that they do not occur 

in neut~al or alkaline waters, and that they 

frequently form in waters in which iron is not 

present as ferrous bicarbonate. 

From his observations he concludes that 

where black slime;:; form in water channels iron 

is carried in solution in the form of soluble organic salts. He believes that the iron.:.depositing thread bacteria which are found in the 

slimes use the organic salts ~s food and set free 

ferric hydroxide, which is then deposited in 

the sheaths. The mangane;:;e oxide he believes 

is a simple oxidation product. A small amount 

of ferric hydroxide is perhaps also formed by 

simple oxidation and becomes mixed with the 

slime. · 

Ellis 3 in 1907 published a paper in which ~1e 

sets forth his helief that the deposition of ferric hydroxide around bacterial threads is 

purely mechanical. He does not believe that 

"Tinogradsky had a valid basis for his conclusions and thinks with Zopf that the accmnulation is the result of the catching up of particles 

of ferric hydro~ide present in the water by a 

mucilaginous covering which surrounds the 

sheaths. The presence of such a 1nucilaginous 

coating 'vas demonstrated by Zopf 4 in 1878. 

Ellis, like Winograclsky, worked principally 

with Leptothrix but also examined cultures of 

Spirophyllwm and Gallionella, and believes that 

what is true of Leptothriw is true of all iron 

bacteria. 

Lieske 5 in a report publish~d in 1911 gives 

the results of various experiments made with 

Spirophyllum. He finds that this organism 

will grow only in solutions containing ferrous 

carbonate and that other ferrous salts will not 

take the place of ferrous carbonate. He finds 

not only that much organic matter impairs the 

growth of Spirophyllu?'}'b and.may stop it altos Ellis, David, A contribution to our knowledge of the 

thread bacteria: Centralbl. Bakteriologie, Abt. 2, Band 19, 

pp. 502~518, 1!)07. 4 Zopf, W., Entwicklungsgeschichtliche Untersuchungen 

ueber Crenothria: polyspora., die Ursache der Berliner Wasserkalamitlit, Berlin, 1879. 5 Lieske, Rudolf, Beitriige zur Kenntnis der Physiologic 

von Spirophyll.um fc1'r1I·Oincum Ellis: Jahrb. wiss, Botanik, 

· Band 49, pp. 91-127, 1911. 
OCCURRENCE AND MORPHOLOGY OF IRON-DEPOSITING THREAD BACTERIA. 13 

gether, but· that where abundant carbon dioxide is present in water and organic matter is 

entirely absent this organism will grow profusely. lie concludes from this that the carbonate radicle furnishes food for Spirophyll,um and that the latter oxidizes ferrous carbonate to ferric hydroxide 1nainly for the 

. purpose of obtaining carbon. l-Ie believes with 

Winogradsky that the oxidation may furnish 

energy to the organism for the assimilation of 

food, which in this case is carbon dioxide. 

Lieske gives the following reaction as indicating what probably takes pl~ce in this process of oxidation : 

2FeCO:,+ I-I20 =Fe2(0H)o+2C02}+29 kg. cal. 368 kg. cal. 207 kg. cal. 398 kg. cal. 206 kg. cal. . . 

Mumford 1 in a short paper published in 

1913 describes experiments with Bacillus )Jf. 7, 

a new type of iron bacterium discovered by 

him. I-Ie states that this organism forms a 

precipitate of ferric hydroxide in ferric a.s well 

as ferrous solutions. Organic compounds were 

used as a source of food. He found that ferric 

hydroxide was precipitated only under aerobic 

cond·itim.1s and that under anaerobic conditions 

.the ferric hydroxide already precipitated was 

simply somewhat dehydrated, forming limonite or bog ore. l-Ie ascribed these reactions to 

an enzyme which, he states, he succeeded in isolating from the organisms by filtration. This 

filtered enzyme produced the same phep.omena 

as the Jiving organism. 

It is difficult to reconcile these various conflicting hypotheses regarding the physiologic 

activity of iron-depositing bacteria. Some of 

the d!~crepancies can probably be explained by 

the fact that some of the observers were working with different organism-s and under different conditions, but other discrepancies ~eem to 

be due to faulty observation. J\1olisch worked 

with Leptothriw and found that it required organic matter but that it did not require iron 

in solution. Lieske, on the other hand, in 

working with Spirophyllum, finds that it requires ferrous carbonate in solution but that 

it can live in the absence of organic matter. 

:Here are two diff3rent organisms that clearly 

show entirely different characteristics. Such 

an explanation, however, does not apply to the 

discrepancies between the observations of ~1o1 Mnmford, E. l\1., A new Iron bacterium : Chern. Soc. Jour., 

VOl. 103, pp, 645-650, 1913. 

lisch and "\Vinogradsky. Both of these Investigators 'were working with Leptothrix and yet 

their results differ radically. Similarly, James 

Campbell Brown, who finds that iron-depositing thread bacteria grow in solutions containing no ferrous bicarbonate, concludes that iron-· 

precipitating organisms do not use inorganic 

iron compounds but must have soluble organic 

iron salts in solution. Such a: conclusion is 

speculative, for although Molisch has shown 

that Leptothrim will thrive on certain organic 

iron salts in solution, Lieske has proved that 

Sp~rophyllum undoubtedly will not. Beside.s, 

very little is lmown definitely about the carrying of iron in solution in natural waters in the 

form of soluble organic salts, although indications of this possibility exist. The ob~erYatio~s of Mumford also are open to doubt, for 

the reason that he did not use control cultures 

.and the possibility of chemical oxidation taking place in his ferrous solutions has not been 

eliminated. 

In general it seems reasonable to believe that 

certain iron-depositing organisms, such as 

Spirophyllum, require .ferrous bicarbonate in 

solution and can not live without it; that 

others, such· as Leptothrix, can live without 

any iron compounds, but if they are present 

can use either ferrous bicarbonate or soluble 

org~nic iron salts; and that still others, such 

as various lower bacteria (see pp. 29-31) will 

use the organic radicle of certain· soluble organic iron salts when present but can not 

utilize any inorganic iron salts. The physiologic activity of iron-depositing organisms 

''rill be frequently referred to in the following 

discussion. 

RESULTS OF THE PRESENT INVESTIGATION. 

OCCURRENCE AND MORPHOLOGY OF IRON-DEPOSITING THREAD BACTE~IA. 

CnENOTI-IRIX POLYSPORA. Cohn. 

The common habitat of Orenothriw polyspora is in .wells and in city water pipes in localities where the water contains an appreciable amount of iron in solution. It is so common in many places both in the United St~tes 

and in Europe that it has become known as the 

"water-pest bacterium," because of its· tendency to produce turbidity in water due to the 

precipitation of ferric hydroxide. In Ger-

' 
14 IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

many CrenothrixJ" is commonly - known as 

" Brunnenfaden " (well thread)·, on ac_count of 

i~s frequent occurrence in wells, although various German investigators mention its occurrence in streams, canals, and other water 

bodies as well. In wells Crenothriw is de·-

scribed ·aS OCCUrring in dark-bfOWn Or black 

scumlike masses at the bottom or along the 

sides. The ·newer outer portions· of such 

masses are usually lighter colored than the 

older portions. In distributing pipes Crenothrix occurs in association with SpiroP'hyllum 

and Gallionella, which are attached to. th~ interior of the pi pes, where they often form hard 

iro.n crusts. 

Most of the Orenothrim cultures for my investigations were obtained from the city water of Madison, Wis. (See Pls. I, II; and III.) 

This water, although its iron content is comparatively low, contains an abundance of 

Crenoth.riw, as well as- Gcdlionella and Spirophyllwm. It is obtained from several deep 

wells which penetrate the Cambrian sediments and end in the underlying granite more 

.than a thousand feet below the surface. The 

following is a partial analysis of the mineral 

constitu'ents of Madison· city water by W. G. 

Crawford, of the University of. "Visconsin: 

Partial analysis of city water from .Madison, Wi8. 

.rarts per million. 

Silica ( Si02) ------------------------------- 10. 3 

1

Ferric oxide (Fe20a) _______________ ,:.._________ 1. 8 

Calcium _(Ca)--------------'------------------: 62. 5 

~fagnesium (~fg)---~------------------------ 36.4. 

Bicarbonate radicle (HOOa) ------------------ 324. 5 

Sulphate radicle (SO.) _______ :________________ 15. 5 

Chlorine (01) -----------,-------------------- . 4 

Free carbon dioxide ( 002) -------------------- 5. 8 

The analysis shows that the water contains· 

an abundance of calcium. and magnesium carbonates and is a typical "hard water." No attempt is made to combine the constituents into 

salts. The' usual method of making such combinations is at best. artificial, and here it seems 

preferable· to show the actual facts. . The ·carbon dioxide in the bicarbonate radicle is that 

which is combined with the bases, such as calcium," magnel3ium, and iron; to "form carbonates or bicarbonates. The carbon dioxide 

present as free gas is show~ separately. The 

_sulphate _radicle, .which forms an appreciable 

percentage, is probably present combined with 

calcium and iron. The iron present is shown 

·as ferric oxide-; although in the water practically all of it is present in the ferrous form, 

mainly as carbonate or bicarbonate and perhaps as sulphate. It is not possible to tell in 

what relative proportion these salts occur. The 

actual quantity of me-tallic iron present in the 

water amounts to 1.26 parts per million. This 

seems a very small amount to cause the·growth 

of iron bacteria, yet it was sufficient to produce turbidity in the water upon standing with 

free access of oxygen. 

Crenoth:rim poly8pora is easily obtained from 

city water, in which it is present, by filtering .. 

The best method is to attach a thoroughly 

cleaned and sterilized Berkefeld porcelain 

"filter to a screw spigot and allow the -water to 

pass through for 24 to 36 hours. At the end of 

this period a thin yellowish-brown deposit of 

ferric hydroxide will be found to coat the filter, 

unless the water is turbid, and then a heavy 

blackish-brown coati.ng may be found. The 

l~tter, however, is not so desirable for cultures. 

· The filter, after being removed !rom the 

spigot, should be itnmersed in a sterile solution 

of well water to which has been added, previou~ to sterilizing, about O.{ per cent of pow.:. 

.dered ferrous carbonate (FeC03 ) and about the 

same amount of .sodimn or potassl.um acetate. 

This solution should be placed in a large beaker 

(preferably about 3,000 cubic centimeters), and 

the filter should be suspended so as to . hang 

freely in the liquid. The beaker should be covered in order to prevent dust from settling on 

the solution. 

For incubating the cultures it is best to place 

them in an ice chest at a temperature of about 

6° to 8° C. for this retards the growth of . . ' 

molds, which otherwise rapidly develop on the 

surface of the filter and prevent the growth of 

other organisms. "Vithin a few days Crenothriw will be found to develop on the filter and 

ca~ be obt~ined for examination under the mic.roscope by scraping ~;aterial from the surface 

of the filter with a platinum needle. Impure 

cultures prepared in this manner may be kept 

for several weeks. 

Pure cultures of Oreiwthriw p·oly8pora are 

difficult to ·.obtain, not only ~ecaus~ of the difficulty. o{. finding artificial media in which 

Creno"thriw will grow but also because the 

threads are so large that it is difficult to make 
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 113 PLATE I 

b 

.A. a, THREAD OF CRENOTHRIX POLYSPOil.A, X80; b, UPPEH PORTION OF THE SAME THREAD, X940, SHOWING 

CONIDIA IN THE UPPER PART OF TilE SHEATH A D ORDINARY VEGETATIVE CELLS IN TilE LOWER PART; 

c, PORTIO S OF THREADS OF CRENOTHRIX POLYSPORA, X 550, SHOW! G VEGETATIVE CELLS, CONIDIA, AND 

GERMINATION OF ·CELLS WITHIN THE SHEATHS . 

• 

B. PHOTOMICROGRAPH OF THREADS OF CRENOTHRIX POLYSPORA FROM CITY WATER, MADISON, WIS. , X 450. 

Material obtained on filter. Some threads show ordinary vegetative cells; others show conidia. Stained with geo-tian violet. 
U . S . GEOLOGICAL SURVEY PROFESSION AL PAPER 113 PLATE II 

A. PHOTOMICROGRAPH OF THREADS OF CRENOTI-IRIX POLYSPORA FROM CITY WATER, MADISON, WIS., X 450. 

M aterial obta ined on filter. Thread.s.2!!2w v~ge tativ e cells a nd germination of cells within the shea th. Sta ined with carbo! fuchsin. 

t 

B. PHOTOMICROGRAPH OF THREAD OF CRENOTHRIX POLYSPORA FROM CITY WATER, MADISON, WIS., X 640. 

Shows ordinary vegetative cells and disk like cells formed by transverse division of ordinary cells. Shows also a thickening of the thread towa rd the upper part o(_the shea th (on the right). The sheath is faintly seen. Stained with gentian viole t. 
OCCURRENCE AND. MORPHOLOGY OF IRON-DEPOSITING. THREAD BACTERIA. 15 

transfers of the organism without taking other 

form.s which may be attached to them. Rossler 1 claims to have obtained pure cultures of 

Crenothriw on sterilized bricks immersed in 

water to w·hich a small amount of ferrous sulphate was added. I-Iowever, .he does not state 

how he obtained his material for inoculation 

nor does he mention the presence in the solution of any other nutrient material besides ferrou.s·sulphate. Molisch 2 repeated th.ese experiments .. but without success, and states that he 

has not been able to cultivate Crenothriw in any 

kind of artificial media even in impure cultllres. l-Ie concludes that the·grmvth of Ore1wtlwim is dependent on special conditions which 

are difficult to reproduce in the laboratory. 

Recently, however, Rullmann 8 succeeded in 

producing cultures of 01·enothr·iw both in liquid 

media and on ~gar plates. 

As a.lready mentioned, O'renothriw occurs as 

unbranched. threads (see Pls. I, II, and III, 

and figs. 1 and 2), one end of which· is attached while the other end is free. A gradual 

thickening takes place from the attached end 

to the free end with the result that the free 

end commonly has three or four times .the 

width of the ·attached end. The individual 

cells ma.king up the thren.d suffer the same decrea.se in width toward the ~ttached end as the 

sheath inclosing them and hence appear much 

more elongated at the attached end. 

Crenothriw t~reads are generally ~olorless 

and can only be seen with the microscope when 

the light is greatly ·reduced. The separate 

cells are then clearly distinguishable, as is also 

the sheath which incloses them. The threads 

vary in length up to several millimeters, but 

usually under the microscope one does not see 

threads that exceed 0.5 millimeter in length. 

In diameter the threads vary between 2 and 9 

micra. 4 Only very young threads or the a.ttached ends of the older threads are as thin as 

2 micra, and the maximum diameter, 9 micra: 

. is only found in old sheaths when complete 

formation of conidia. has taken place. The 

diameter of the threads is ordinarily between 

1 Rossler, 0., Ueber Kultlvlerung von Crenotlwi:c poly8porcr :nif festem Ni!hrboden : AI:chiv Phnrmncie, Bnnd 233, 

pp. 189-191, 1895. . 

. !l Molisch, Hans, Die Elscnbnktel'ien, p. 29, Jena, 1910. 3 Hullmonn, W., Ueber Elscnbol;:terien: Centralbl. Bakter1-

ologle, Abt. 2, Band 33, p. 283, Hl12. 

· • ~he m~cron equals 0.001 millimeter. 

3 and 5 micra near the attached end and between 5 and 6 micra at the free end. 

The individual vegetative cells (see Pls. I, A, 

II, B, and III, B) forming the thread range in 

width from 2 to 5 micra and in. length from 2 

to 9 micra. The normal shape of the cells is 

cylindrical, the length being about twice the 

diameter. Just after 

cell division, however,· 

which takes place 

t r a n s v e r s e 1 y '. the 

length and diameter 

are nearly equal. In 

the lower portion of 

the thread many of 

the cells have a rectangular outline with 

the square ends, 

'v hereas in the upper 

part of the thread ·the 

ends are rounded. The 

sheath inclosing the 

cells is generally. thin, 

in some speci~ens 

being hardly distinguishable from the cell 

walls themselves. 

· In spore formatiou 

the division of cells 

takes. place both transversely and longitudinally~that is, there 

is cell division in three 

directions. (See Pis. 

I and II, A.) This 

process results in the 

formation of a lttrge 

number of spherical or 

mo1~e or less · irregular spores or conidia, 

·which increase in size 

FIGURE !.-Portion of U 

thread of Crenothri:c 

polyspora showing formation of conidia. The 

lower part of the thread 

. consists of ordinary· vegetative cells. In the upper 

part are disk-sh:~ped cells 

and conidia. Drawing 

with camera lucida. 

X 550. 

somewhat after their formation so that different spores range in diameter from less than 2 

micra to 4 micra. The division of cells into 

spores as a rule takes place at the end of the 

thread, but frequently it occurs at differen1 

points in the upper part of the thread, so that 

small round spores may be inclosed between 

cells as yet undivided. (See fig. 1.) 

The spores are · nonmotile conidia. They 

are washed- from the ends of the sheaths, 

distributed by currents of water, and eventu-
16 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

ally become attached and germinate into new with a dilute solution of hydrochloric acid bethreads. It often happens that conidia ger- fore staining .. 

1ninate before they have a chance to leave the LEPTOT~Rix_ ocHRACEA I\: i.itzing. sheath, and then the new threads push their 

way through the sheath, forming a radiating Leptothrix ochrracea I\:i.itzing, also known as 

mass of threads which appear like branches of Ohlamydothrix ochracea Migula, is found 

,the old thread all coming out at one place. mainly in iron-bearing surface waters of bogs, . 

(See Pls. I, A/ II, A/ and III, B.) In many streams, and springs, but I have found it also 

thread;:; gennination .takes place at several· in mine waters in. the Cuyuna iron range of 

points. · central Minnesota and in the lead and zinc 

Though the young Orenothrix threads ·are region of south~estern 1Viscons]n. In some 

colorless, older threads are commonly coated iron springs Lepothrix is extremely abu~1dant, 

FIGURE 2.-Portion of a 

with a thick brown de- but in others not even a trace of it can be 

posit of ferric hydrox- found. This irregularity in its distribution is 

ide, which frequently probably clue to a difference in composition of 

has a thickness of sev- the spring waters, perhaps influenced by other 

eral times the diam- contributing factors. In streams and bogs it is 

eter of the original found principally where the water is stagnant. 

threads. (See fig. 2.) I found Leptothrix growing profusely in a 

Yotmger threads never chalybeate spring on· a small creek west of 

have this coatii1g and Lake I\:egonsa, about 14 miles s·outheast of 

rarely show even a 1\fadison. (See Pl. IV.) The water of this 

yellowish tint to indi- spring contains an abundance of ferrous iron 

cate the presence of in solution and has a distinct iron taste. It 

ferric hydroxide. issues fr~m the hillside about 10 feet above 

Orenothrix is read- the level of the creek, forming a little basin 2 

ily stained with either or 3 feet in diameter. At the top of the slope 

carbol-fuchsin or gen- at various points in the vicinity are outcrops 

tian violet. The cells of' Madison sandstone (Lower Ordovician), and 

stain deeply, but the the water probably derives its iron. from this 

sheath remains almost ·:formation either from disseminated pyrite or 

colorless. When it )s from siderite. The iron is probably present in 

desirable to stain the solution as ferrous carbonate (or bicarbonate)' 

spores the thread may judging from the following partial analysis, 

be stained first with made by G. 1V: Crawford, of the University of 

car hoi-fuchsin and Wisconsin: 

then treated with 2t 

per cent glacial acetic PaTtial analysis of 'Water from spring on c1·eeTc west 

acid. This will · re- of Lake. J(egonsa, Wi.s. 

move the stain from Parts per million. 

thread of 01·enothri:JJ 

polyspora showing thick 

coating of ferric hydroxide. Thin y o u n g 

threads are formed by, 

germination of conidia 

in parent sheath. Drawing with camera lucida. 

X 1,080. 

Silica ( Si02) --------------------------~----- 18. 9 

Ferric oxide (Fe20a) ------------------------- 5. 2 

Calcium ( Ca) -------------------------------- 78. 1 ~iagnesium (~fg) ____________________________ 32.5 

Bicarbonate radicle (HCOa) ------------------ 354. 4 . 

Sulphate radicle ( S04) ----------------------- . 0 

Chlorine ( Cl) -------------------------------- . 4 

Free carbon dioxide (C02)------------------- 11.6 

all parts of the thread 

except the spores. The mount may then bo 

stained with gentian violet or methylene blue, 

which will restain the vegetative cells and also 

to some extent the sheath. The most satisfactory method of staining Orenothrix is to prepare. a weak staining solution consisting of 1 

part concentrated carbol-fuchsin to 10 parts of 

distilled water. The slide on which the organ~ A large volume of water is given off .by the 

ism is mounted should be allowed to remain in spring and there is a constant flow winter and 

this solution for 12 or 14 hours·. It is fre- summer. The water does not freeze in the 

quently advantageous to treat the material w.inter. As there is no sulphate rad_icle pres-
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 113 PLATE III 

.· 

A. PHOTOMICROGRAPH OF THREAD OF CRENOTHRIX POLYSPORA FROM CITY WATER, MADISON, WIS., X 640. 

Shows the formallon of conidia from vegetative cells. Conidia occur in the upper part of1hc sheath (on the right) and veget.ativc cells in the lower part (on the left). Shea th is faintly outlined. Stained with gentian viole t. 

B. PHOTOMICROGRAPH OF THREAD OF CRENOTHRIX POLYSPORA FROM CITY WATER, MADISON, WIS., X 640. 

Shows the germination of cells within the sheath. Sheath is also well shown in small threads. Stained with gentian violet. 
U. S . GEOLOGICAL SURVEY PROFESSIONAL PAPER 113 PLATE IV 

A. PHOTOMICROGRAPH OF OCHEROUS SCUM IN IRON SPRING NEAR LAKE KEGONSA, MADISON, WIS., X 640. 

Shows simple straight and curved threads of L eptothrix ochracea. Unstained. 

) . 

B. PHOTOMICROGRAPH OF OCHEROUS SCUM IN IRON SPRING NEAR LAKE KEGONSA, MADISON, WIS., X 640. 

Shows threads of L eptothrix ochracea anCi one of Spirophyllum jerrogineum. Thread of very regularly twisted Spirophyllum on the 

right. Unstained. 
OCCURRENCE AND MORPHOLOGY OF IRON-DEPOSITING THREAD BAC.TERIA. 17 

eut, and as the chlorine is negligible, it seems 

that in this spring at least all the calcium, 

magnesium, and iron are present in the form 

of carbonate (or bicarb_onate). The iron, ·although given as ferric oxide in the analysis, 

is all present in the ferrous form, as is shown 

by the fact that the water as it 1ssues from the 

spring is beautifully ·clear but upon standing 

soon becomes turbid on account of the oxidation of the iron by atmospheric oxygen. After 

a few days a distinct yellowish-brown deposit 

has formed at the bottom of vessels .in which 

the water is kept and at the end of a week or 

two the iron is so completely precipitated that 

less than 0.2 part per million of ferric oxide ren;ains in the solution, although the original 

content was 5.2 parts per million, as shown in 

the analysis. The 5.2 parts ferric oxide are 

equhralent to 3.69 parts metallic iron. 

Leptothrirc1 forms soft, fluffy brown botryoidal masses attached to the bottom and sides 

of the spring. The masses may be an inch or 

more in thickness and form a sort of lining 

locally along the siqes and bottom of the 

spring. They consist of an almost pure culture of Leptotkrim threads, both living and 

dead, .but with these here and there are threads 

of Spirophyll''wln, all interwoven into a thick 

matting. 

During the ·course of several visits to this 

spring I had an opportunity of noting the effect of seasonal changes on the growth of the 

iron bacteria. The most abundant growth apparently occurred in the spring and. early in 

the summer; late in the fall the growth seemed 

to be at its lowest, being less n1arked even than 

in midwinter. During the period of lowest 

growth Spirophyllwm se~ms to be somewhat 

more abundant relatively than during periods 

of luxuriant growth. 

At the Rowe mine, an open-pit iron mine 

near Riverton, in the Cuyuna district in central J\1innesota, a number of springs of ironbearing water issue directly fr01n the ore. at 

the enst end of the pit. The ore is a mixture 

of limonite and more or less hydrated hematite, but the water issuing from it probably 

. contains ferrous iron in solution and supports 

nn abundant growth of Leptothrix and various 

algae in little depressions on the surface of the 

ore. 

In spring water from J\1iddleburg, V a., procured for n1e by Dr. E. B. Fred, of the University of yvisconsi~, I found Leptothrix occurring in abundance associated with some 

Spirophyllwrn and various types of algae. The 

spring is 11nile northwest of Middleburg. The 

iron-bearing wate1~ issues fr01n red clay probably derived by decomposition from Triassic 

r·ed shale (Newark), outcrops of which occur 

within 50 feet of the spring. The waters fiow 

into vVauquipin Creek, a tributary of Goose 

Creek, which empties into Potomac River 10 

to 15 miles distant. 

In the J(ennedy n1ine, in the Cuyuna iron 

ore district, Leptothriw occurs abundantly on 

some of the lower levels. (See Pl. V.) On 

the 262-foot level two long crosscuts penetrate 

a succession of iron ore, ferruginous chert, 

cherty siderite rock, and green chloritic schist. 

The walls of these crosscuts, where they consist of cherty siderite rock and green schist 

and where water is abundant, support a luxuriant growth of Leptothrix associated with 

some Spirophyll'l.l/l'IU and ·oallionella. Locally 

also pools. of water on the floors of the crosscuts are filled with yellowish-brown to darkbrown masses of these organisms. 

l\iicroscopically the material is seen to consist very largely of Leptothrix, but here and 

there threads of Grillio?wlla and Spirophyllum 

are common. Most of the Leptothrix threads 

are light yellowish-brown and transparent, but 

some are dark brown and have a thick irregular coating of ferric hydroxide. vVith careful 

handling very long threads of Leptothrim were 

obtained, some of which had a thick brown 

coating of ferric hydroxide at one end, though 

the other end was. smooth and transparent, 

there being a gra.dation between the two ends. 

A few nearly. colorless threads were seen which 

showed cell structure very plainly. Some of 

the cells were elongated cylindrical, some short 

cylindrical, and some were platelike. Whether 

these thread$ were really Leptothrix or whether 

they were some form of almost color less algae 

or fungi it is not possible to say. In size~ and 

general fonn they were like Leptothrix. Other. 

threads of Leptothrix occur which have little 

projections ·along them at intervals. These 

projections are probably little lumps of ferric 

·hydroxide. but they resemble very closely the·. 
18 ·IRON-DEPOSITING BACTERIA AND .THEIR GEOLOGIC RELATIONS. 

conidia described by Ellis in connection with 

the form for which Benecke 1 has suggested the 

·name 0 onidiothrix. · 

· A sample of the scum of iron oxide collected 

from the walls of the drifts of the l(ennedy 

mine and dried at 105° C. was analyzed by W. 

G. Crawford, of the Unive~sity of Wisconsin, 

with the following results: 

Analysis of scum, of iron oxide from J(ennedy mine, 

.Minn. 

[Dried at 105° C . .J. 

Ferric oxide (Fe20s) ------'------------------- 70. 56. 

Silica ( Si02) -------------------------------- 7. 21 

Lime ( CaO) --------------------------------- 3. 41 

Magnesia ( MgO) ------------------------------ . 40 

Combined water ( ILO) ----------------------- 13. 75 

Loss above 105° C. (besides combined water)__ 4. 60 

99.{)9 

This analysis shows that the material precipitated by the iron bacteria is practically 

pure ferric hydroxide, for the impurities may 

be attributed to small rock particles which 

were unavoidably included in the sample in 

collection. On the supposition that the iron is 

all present in the form of ferric hydroxide or 

limonite, 11.95 per cent of water is required to 

combine with 70.50 p~r cent of ferric oxide, 

making a total of 82.51 per cent limonite, or of 

49.3 per cent metallic h~on. This amount leaves 

1.8 per cent of combined water unaccounted 

for, which probably means that the ferric oxide 

is in a slightly higher state of hydration than 

in the mineral limonite. The loss above 105° 

C., besides the combined water, is probably 

mainly carbon dioxide, derived from the oxidation of the carbon present in the bacterial 

sheaths. The silica, lime, and mag:hesia are accounted for by the presence of rock particles. 

Besides finding Leptothrix in iron springs 

· and mines I have found it in river ·waters and 

in bogs. In river waters I have found it especially common where pools of more or less 

stagnant \Vaters occur along the banks between 

boulders or outcrop,s of rock. In some places 

it seems that these rocks yield iron for its 

growth. _ 

In bogs ferric hydroxide frequently occurs 

as a thin iridescent film on the surface of the 

water. This film results from the oxid.ation of 

iron compounds in solution in the water. With 

1 Benecke, Wilhelm, Bau und L~ben der Bakterien, 1912. 

such occurrences there is almost always associated a yellowish-brown scum or ooze along 

the sides and bottom of the pools of water. 

This scum generally consists of Leptothrzx associated with more or less algae. It is well · 

known that, on account of the abundant presence of decaying organic matter, bog waters 

can take a considerable amoun:t of iron into solution. A thin layer of water near the surface, 

which is in direct contact with the oxygen of 

the air, probably suffers oxidation, and the 

iron in solution is changed to ferric hydroxid.e 

and forms the surface film. Below the surface it seems reasonable to suppose that the 

iron is kept in solution to some extent by products of decaying organic matter but that some 

of it is taken up by the iron bacteria and that 

ferric hydroxide is deposited on their sheaths. 

This material gradually accumulates and eventually forms deposits of bog iron ore. 

On account of the abundant presence of ferric hydroxide in the sheaths, cultures of Leptothrix (and also of Spirophyllum and Gallionella) may be kept in water for an almost indefinite length of time for purposes of study. 

It seems that although the organisms die the 

sheaths retain their natural form. 

Leptothrix ochracea has been grown in the 

laboratory by a number of investigators. Tlie 

first laboratory cultures of Leptothrix were 

obtained by vVinogradsky. 2 He used for the 

purpose a glass cylinder about 8 inches tall 

and placed in the bottom of this crushed hay 

which had been previously cooked. On this 

material he sprinkled some freshly precipitated ferric hydroxide and then filled the cylinder with well water. As soon as gas formation occurred, little. ocher-colored· flakes and 

masses appeared on the surface of the water. 

and on the sides of the ,glass cylinder. In 8 

or 10 days a thick, yellowish-brown deposit was 

found to cover the sides of the cylinder and on 

the surface of the water large zoogloea of the 

same color formed and gradually sank to the 

bottom. The ocher-colored masses were found 

to consist almost entirely of organisms, amorphous flocculent ferric hydroxide being very 

uncommon. Among these organisms Leptothrix \Vas almost always present. The difficulty with . t1lis culture method was that be2 WinogradslQ•, S., Ueber Eisenbakterien: Bot. 7.:citung, 

Band 46, pp. 262-270,, 1888. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 113 PLATE V 

/ 

~~ 

• 

/ j ~ ) ;I 

----- '::-....,_ / ~ 

""' -... 

A. PHOTOMICROGRAPH OF MATERIAL FROM 262-FOOT LEVEL, KENNEDY MINE, CUYUNA, MINN., X 640. 

'rhreads of Spirophyllum f eriugineum are near t'he upper left corner and near the center. Threads of Leptothrix ochracea and Gallionella 

f erruginca are scattered; lhe latter show braid like forms. Unstained. 

'•. 

,. 

~ ... 

I 

'.~ 

_.;• 

ll •• 

..... · ... 

I •\ -

,,-' ---- ' 

,. :;-~ _:l' 

. . _,-~ 

' 

;< 

1'1 

.. 

·'' .... , 

'' 

B. PHOTOMICROGRAPH OF OCHEROUS SCUM ON 262-FOOT LEVEL, KENNEDY MINE, CUYUNA, MINN., X 640. 

Shows simple threads of Leptothrix ochracea, coiled, braidlike forms of Gallionella ferruginea, and a few spiral ribbon-like forms of 

Spirophyllum. ferrugineum. Unstained. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 113 PLATE YI 

·~ ~-

\) 

A. PHOTOMICROGRAPH OF OCHEROUS, GELATINOUS SCUM FROM 100-FOOT LEVEL, FEDERAL MINE, HAZEL 

GREEN, WIS., X 640. 

Shows braidlike forms of Gallionella j erruginea and also single spiral threads of Gallionella jerruginea. Twisted ribbon-like forms of Spiro- phyllum jerrugineum are abundant. Unstained. 

/ 

I ,, 

'I 

~ 

B. PHOTOMICROGRAPH OF OCHEROUS, GELATINOUS SCUM FROM 100-FOOT LEVEL, FEDERAL MINE, HAZEL 

GREEN, WIS., X 640. 

Shows ropelike forms of Gallionella ferruginea, one near the center consisting of four single threads; also single spiral threads of Gallio- . nella and twisted ribbon-like forms of Spirophyllumjerrugineum of different sizes. Unstained. 
OCCURRENCE AND MORPHOLOGY OF IRON-DEPOSITING THREAD BACTERIA. 19 

sides Leptotlw··iw numerous other bacteria as 

well as protozoa of many varieties developed, 

so tha.t the culture was impure. 

Adler 1 made some imprm7 ement by adding 

0.05 per cent iron ammonium citrate to water 

:from the city supply of Prague, which was 

taken from J\1oldau River, and allowing the 

solution to stand in a glass beaker. After 

some .clays yellowish flakes of Leptoth1·iw, Olacloth?"iw, and .A. nthoph.ysa developed abundantly, as well as a few protozoa. 

J\1olisch,2 after many attempts, finally succeeded in getting pure cultures of Leptothriw. 

In an attempt to repeatAdler's experiments by 

using ·water from the city supply 

of Vienna, which was derived from 

springs, he was unsuccessful, and therefore he used :water from J\1oldau River 

in all his experiments. I-Iis first experiments were for the purpose of obtaining an abundant growth of Leptothriw with the least possible development of other forms.- He took various 

organic compounds of iron and manganese and dissolved them in water from 

J\1oldau River, in which Leptotlw·iw 

was known to be present. The strength 

of the solutions used was usually about 

a 

dau River, 0.05 gram of manganpeptone, and. 

10 grams of agar. This medium. was inoculated with Le[Jtotlw·iw which . was obtained 

from impure cultures and was incubated at 25° 

C. In a few da);S, among numerous other bacterial colonies, certain· light-brown colonies developed which soon became ·clark rusty brown 

and upon examination. were found to consist 

entirely of Leptothriw. 

Montfort 3 m~ntions the occurrence of heavy 

growths of Leptotlwiw ochracea in tanks containing moderately strong solutions of ferrous 

sulphate. He states also that the organism is 

easily grown in a 5 to 10 per cent solution of 

c 

0.05 per cent. The compounds with 

which he was most successful in obtaining growths of Leptothriw were 

manganpeptone, iron ammonium 

FIGUltE 3.-Diagrarnma tic sl•ctch of Spirophylllt1n ferrttghtettm (a), 

GalUonella ferrttginea (b), and Lcptothrim ochracea (c). Shows 

difference in size and struc~ure of the organisms. X about 1,080. 

citrate, peptone with manganese carbonate, 

manganum phospholacticiun, iron sulphide 

with peptone, . and iron-ammonium tartrate. 

l-Ie found that in these solutions, which were 

kept in beakers in diffused light, little brown 

spots appeared near the surface in a; few days 

. and that ~dter a week or two a thick mn.tting 

formed over the surface. This was found to 

consist mn.inly of LeJJtothriw, but .A.nthoph.ysa 

and Oladoth,riw were generally abundant, and 

other protozoa and algae also frequently developed. 

'l\1olisch then attempted the isolation of 

LezJtothriw by growth on soHd media. The 

medium which he found best adapted consisted 

of 1,000 cubic centimeters of water. frmn Mol1 Adlet·, Oscnr, Ueber Elscnbaktericn nnd ihrcr Beziehung 

zu den thernpcutlsch vcrwendeten natlirlichen Eisenwiissern: 

Ccntmlbl. Bal,tcrlologlc, Abt. 2, Band 11, pp, 215-219, 277-

278, lf)O:l-4. ' 

D Moliscb, Hans, Die Eisenbakterien, Jena, 1910. 

ferrous sulphate, and develops under such conditions in a few days. At my request Mr. 

J\1ontfort sent me samples of the ferrous 

sulphate with which he had obtained cultures. 

llowever, I was unable to duplicate his results, 

::!]though I made several attempts. The solutions gave an abundant yellowish-brown ocherous, flocculent precipitate, due to oxidation, 

which upon examination under the microscope 

gave no trace of any organic forms except occasional filaments of mold mycelium, some of 

which had a brown. coating of ferric hydroxide. The precipitate consisted mainly of 

brownish-yellow mixed granular and flocculent 

material, probably partly basic ferric sulphate 

and partly ferric hydroxide. 

Leptothriw ochracea (see Pis. IV and V and 

figs. 3, 4, 5, and 6) commonly occurs as unBl\fontfort, W. F., Dry feed of chemicals in water purification: Am. Waterworks Assoc. Jour., vol. 2, pp. 204-205, 1915. 
20 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS • 

. . branched threads of the same width throughout and 'vith usually no visible differenti~tion 

FIGUitE 4.-Portions of threads of Leptothrirc ochra.cea showing straight and curved forms; . Drawing with camera 

Iucida. X 550. 

between the two ends. Ellis 1 described Leptothrix threads as being free at both ends and 

being held in place. only because numerous 

threads intertwine with each other to 

form a thick matting which becomes 

attached to. foreign objects. Benecke/ 

on the other hand, states that some of 

the threads are sessile and that then 

. they show a thickening toward the attached end. Ohlamydothriw sideropus~ 

a related species, has a well-developed 

holdfast. 3 

Threads of Leptothrix ochracea almost invariably have a light yellowishbrown color, due to the pr:esence of 

ferric hydroxide in the sheaths, which 

enables them to be studied without 

staining. They are very difficult to 

stain. I have tried staining with gentian violet, carbo! fuchsin, and methylene blue, both with and without preing for 10 or 12 hours in a dilute solution of 

carbol fuchsin, I have succeeded in staining the 

sheaths, but. I have not been able by any 

method to bring Qut clearly the cell structure. 

The average width of the threads of Leptothrix is about 1-! n1icra, but they range in 

width from 1 n1icron to 2 micra. The longest 

thread that I have noted measured about 120 

micra, or about one-eighth of a millimeter, but 

doubtless the threads grow to a much g~·eater 

length, being broken during the manipulations 

necessary for 1nicroscopic examination. Generally the threads are slightly curved or undulatory, but some short threads are quite 

straight. Rarely Leptothrix may be twisted 

spirally into a corkscrew form. 

In fresh cultures of Leptothrix ·I have occasionally seen threads that show a differentiation 

into cells. The cells are usually long cylindrical in shape with slightly rounded ends. 

They vary greatly in length, but generally the 

length is many times the width. By far the 

greater mass of thr~ads in ordinary cultures, 

however, shows· no cell structure whatever, 

which may be due to the cells being obscured 

by the ferric hydroxide that colors the sheath 

) 

vious treatment with dilute hydrochlo- FIGURE 5.-Portions of threads of Leptoth1·irc ochracca. Drawing 

. ric acid,. and the results have been very · with camera Iucida. x 1.oso. 

unsatisfactory. By careful treatment with di- or to the sheaths being empty. Molisch 4 states 

lute hydrochloric acid, however, and then stain- that by treatment of the threads with a 2 to 5 

1 Ellis, David,. A contribution to our knowledge of the 

thread bacteria: Centralbl. Bakteriologie, Abt. 2, Band 19, 

pp. 503-505, 1907. . 

2 Benecke, Wilhelm, Bau und Leben der Bakterien, p. 489, 

1912. 

s Molisch, Hans, Die Eisenbakterien, pp. 14-16, 1911. 

per cent solution of hydrochloric acid. he was 

able to dissolve the ferric hydroxide from the 

sheath and thus brought out very plainly the 

4 Moliscb, Hans, op. cit., p. 22. 
OCCURRENCE AND MORPHOLOGY OF IRON-DEPOSITING THREAD BACTERIA. 21 

cell structure in threads that ·under ordinary 

conditions showed no cell structure whatever. 

I have attempted this with many cultures but 

without success, perhaps because the cultures 

used were tqo old. 

Leptothriw ochracea is said by Molisch 1 toreproduce in tluee ways-by fragmentation (that 

is, by the breaking off of small fragments of 

· threads w h:ich in tinie grow into new threads), 

by the forcing out of end cells fron1 the thread, 

and by swarm cells. The swarn1 cells are cylindrical rods 'vith rounded ends 0.6 to ·o.s 

micron in width and attain a maximum length 

of 14 micra. Some of them are threadlike and 

consist of several cells. Their movement is 

Fzoun~J G.-Pot·tlous of threads of Lcptothri:c ochracca,. one 

of them showing nodular projections. Dmwing with 

camcm lucidu. X 1,080. 

backward and forward, as well as rotational 

around the longer axis. The svirarm cells after 

they leave the cell swim around and finally 

attach themselves and form new threads. Frequently: they attach then1selves t.o old threads 

and thus simulate branching forms. · Swarm 

cells ::u·e said to stain readily with aniline dyes. 

Ellis,2 in his descriptions of LezJtothriw,states 

that it repro:du~es by· the formation of conidia. 

l-Ie described Leptotlllriw as a simple thread, 

straight or curved, which shmvs no cell structure. The conidia forrn small spherical· projections on the sides of the threads and gradually detach themselves and are carried away 

1 1\follsch, Hn.ns, op. cit., p. 43. 

ll Ellis, David, op. cit. 

by currents to. other places, where they germinate and produce new threads. According to 

Ellis, this is the common mode of reproduction 

for Leptothriw. Molisch, however, states that 

he has never seen these conidia and doubts 

their existence, believing that the, projections 

observed by Ellis may have been lower bacteria 

which have attached themselves to the Leptothriw threads, or that perhaps they were swarm 

cells of Leptothriw itself. Benecke,8 in reviewing the facts, suggests that the form described 

by Ellis may be a new species related to Gallionella, and proposes the term Oonidioth1'iw 

for it if such a form is proved to exist by further investigations. 

In several of the cultures which I have collected recently, notably a culture of Spiroph.yllum and Gallionella, from the 100-foot level of 

the Federal mine, ·near Hazel Green, in southwestern vVisconsin, I have found a form resembling that de~cribed by Ellis. It consists of 

a thread similar to Leptothriw in size and general form. (See Pl. VII, A, and fig. 6.) However, no threads were found which gave any 

semblance of cell structure, but_1nany threads 

showed small, rounded projections at irregular 

interv.als along the thread. "Vhether these pro-

·jections were attached particles of ferric hydroxide or other foreign material, or whether 

they were really conidia, was difficult to determine. They seemed, however, to be part of the 

thread, not having any distinct partition wall 

separating them from the thread. It is also 

rather significant that in only a few out of. 

many cultures of Leptotlww which I examined 

have I found these forms. On the other hand, 

many of the cultures contain threads of Leptoth.?'irc, some of them thickly coated with ferric 

hydroxide, which show little projections and 

irregularities, consisting, without much doubt, . 

of ferric hydroxide. It is therefore difficult to 

say whether the form mentioned above is ·the 

same as that described by Ellis as Lep·toth?~ix 

m: whether all the projections are simply foreign bodies, as is suggested by Molisch. I lutve 

nev"er found these bodies in a germinating condition, nor have I found them where they have 

been completely separated from the parent 

thread by abstriction. 

In view of the fact that some investigators, 

such as Molisch and Benecke, describe Lepto8 Benecke, Wilhelm, op. cit. 
22 IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

th/rix as ·having well-developed cell structure, 

whereas others, such as Ellis, have not been 

able to find any evidence of cell structure, there 

is some question as to whetl~er there may not 

exist two similar forms both widely distributed, 

the one showing cell structure and the other 

consisting of simple undifferentiated threads 

resembling those of G_allionella and Spirophyllurn. Careful work is necessary not only to 

deter-mine whether the latter fornY exists, but . 

if so, whether it reproduces by the external 

abstriction of conidia or simply by the breaking off of, parts of the threads. The method 

of reproduction has to be definitely determined 

for Spirophyllum and Gallionella as well. 

G ALLIONELLA FERRUGINEA Ehrenberg. 

The term Gallionella was applied by Ehrenberg 1 in 1836 to all the organisms which are 

concerned in the formation of the brown· iron 

scums of bogs and springs. That. the brown 

scum at the bottom of certain wells was composed of organisms was also recognized by him 

and these organisms are mentioned as being 

a related type. He classified the iron organ-

'isms as infusoria ·and th<;mght that they were 

related to the diatoms, which he had studied 

and which he also believed to be infusoria. 

Thus iron bacteria were at one time classed as 

unicellular animals, but later 1t was recognized 

·that they were really plants and for sori1e time 

they were grouped with .the algae. Gradually as the investigations progressed it was 

determined that more than one species of 

iron bacteria were concerned in the formation 

of iron scums, and thus Leptothrix, Orenothrix, and more recently Spirophyllwnv and 

Olonothrix were recognized as distinct types. 

At present the term Gallionella is restricted to 

the ropelike form that consists of double 

spirally twisted threads. " 

Up to the present time I have found Gallionella in only three localities, namely, in the 

Federal mine, near Hazel Green, in southwestern Wisconsin, where it occurs in great abundance in association with Spirophyllumj in the 

Kennedy mine, in central Minnesota, where it 

is found in minor amount with predominating 

Leptothrix and some Spirophyllwmj and in 

1 Ehrenberg, C. G., Vorlilufige M:ittheilungen ueber das 

wirklige Vorkommen fossiler Infusorien und ibre grosse Verbreitung: Poggendorf's Annalen, Band 38, pp. 213-227, 1836. 

the filtrate frmn water from the city supply 

of Madison, Wis., where it is associated with 

Spi1'ophyllwm and Orenothrix. 

The material in the Federal mine and the 

Kennedy mine occurs in brown gelatinous 

masses, which are attached to the walls of the 

tunnels beneath small openings from which 

-streams of iron-bearing water issue, and which 

is also found in pools along the floors of the 

drifts. 

The cultures from the Federal 1nine (see 

Pls. VI and VII, A), when examined microscopically, were found to contain abundant 

Gallionella of various forms and sizes. Perhaps the most common form is a short twisted 

ropelike thread consisting either of two or 

four single threads closely twisted together. 

The twisting is accomplished by the bending 

of single threads in the middle and twisting 

. the ends around each other. There are also 

present very loosely twisted forms and sin-

. gle spiral or corkscrew-like threads, resembling 

a single· strand from a rope when untwisted. 

The ropelike forms of Gallionella vary considerably in width from end to end, the thick 

end being usually that where the loose ends 

of the threads ·project. Different inclividuals 

also vary in wi~th and length, not only among 

the ropelike forms but also among the single 

t~1reads, which show a considerable range in 

SIZe. 

In the cultures from the ICennedy mine (see 

Pl. V) Gallionella is not very abundant, and 

most of it has the ropelike· form. Many in elividuals are quite thin and transparent, not 

much thicker than the· associated Leptothrix 

threads, whereas others ar~ thick and heavily 

coated with brown ferric hydroxide. Some 

show the free ends of the ~eparate threads 

projecting at one end, but most of them are 

short thick braids. Some have the same width 

throughout, but others taper toward one end. 

Spirophyllum, Gallionella, and Orenothrix 

occur together in the distributing pipes of the 

·water system of Madison, "Vis. Upon filtering with a porcelain filter a dark-brown 1nud 

·is frequently obtained, especially when the 

'vater is turbid. Upon examination with a 

microscope this mud is seen to consist largely 

of flocculent textureless masses of ferric hydroxide with scattered strands of Spirophyllum and Gallionella and here and there short 

pieces of Orenothr-ix threads. The Orenothrix 
. U. S. GEOLOGICAL SUR VEY 

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P R OF ESSION AL PAPE R 113 PLATE VII 

\ '"' ' 

A . PHOTOMICROGRAPH OF OCHEROUS, GELATINOUS SCUM FROM 100-FOOT LEVEL, FEDERAL MINE, HAZEL GREEN, 

WIS., X 640. 

Shows irregularly twisted ribbon-like forms of S pirophyllumferrugineum, a few braidlike forms of Gallionella [erruginea , an d a thread of 

Leptothrix ochracea with nodular projections. On the right is a double form of Spirophyllum. Unstained. 

) 

B . PHbTOMICROGRAPH OF' DOUBLE TWISTED HIBBON-LIKE FORM OF SPIROPI-IYLLUM FERRUGINEUM FROM 

CITY WATER, MADISON, WIS., X 640. 

The dark masses are gelatinous ferric hydroxide. Unstained. 
U. S . GEOLOGICAL SURVEY 

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PROFESSIONAL PAPER 113 PLATE VIII 

pk 

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A. PHOTOMICROGRAPH OF OCHEROUS SCUM FROM 300-FOOT LEVEL, JUDSON MINF, ALPHA, MICH., X 640. 

Short twisted rihhon-Jike forms of Spirophyllumferrugineum mixed with irregular masses a nd scattered specks of granular and gelatinous ferric hydroxide. Some Spirophyllum is coated with granules of ferric hydroxide. On the left is a double twisted form. Unstained. 

B , PHOTOMICROGRAPH OF OCHEROUS SCUM FROM 200-FOOT LEVEL, JUDSON MINE, ALPHA, MICH., X 640. 

Shows numerous small, irregularly twisted forms of Spirophyllumferrugineum. Near the bottom is a short form thickly coated with granular ferric hydroxide. The dark irregular masses are gelatinous ferric hydroxide. Unstained. 
OCCURRENCE AND MORPHOLOGY OF IRON-DEPOSITING THREAD BACTERIA. 23 

will grow and develop into long threads when 

placed in culture media, as previously described, but apparently no growth· of Spirophyllwm and Gallionella takes place on the 

filter. 

'Vater pipes in cities where the water contains an appreciable amount of iron in solution 

are a common habitat of Gallionella, Spi-

'l.O?Jkyllum,, and Orenothrix. In some places 

the precipitation. of ferric hydroxide by the 

iron bacteria is so abundant that crusts are 

formed around the inside of the distributing 

pipes. These crusts increase 'in thickness until 

they completely fill the pipes· and block the 

passage of the water. The material composing 

the crusts has bee:p. examined and has been 

found to contain large numbers of bacterial 

casts, so that little doubt exists as to its origin. 

It is claimed by son1e investigators that the 

growth of 01·enothrix and associated iron bacteria in city 'vater pipes is not dependent on 

the original i1~on content of the water but is 

due to iron taken into solution from the pipes, 

and that the most abundant growth takes 

place in newly laid pipes. Doubtless the solution of iron from distributing pipes is a con: 

tributing factor, yet it seems evident that some 

iron must be in solution originally or iron bacteria would be found in all city waters and not 

confined to certain localities, in most of which 

the water is known to have a high original 

iron content. I have tried to find Orenothrix 

and other iron: bacteria in distributing pipes 

·where the water was obtained from lakes and 

had a low iron content but have been unsuccessful. 

Schorler/ while examining some iron· crusts 

from pipes from the city of Dresden, found 

tlutt pipes which were thickly encrusted on the 

inside with iron oxide and ,~Yhich had been in 

use for 30 years had suffered no corrosion" on I 

the inside underneath the iron crust. This condition he thought indicated that the iron forming the incrustation came from some source 

other than the pipes the.mselves and that the 

deposition on the walls occurred through the 

n1edium of iron bacteria; which here found a 

favorable place for growth. In this locality 

Schorler found t~utt the organism responsible 

for the precipitation was principally Gallio1 Schorler, B., Die Rostblldungen in den Wasserleitungsrobren : Centralbl. Bakteriologie, Abt. 2; Band 15, pp. 564-

568, 1906. 

nella, casts of which he found to be abundant 

in the iron crust. 

Gallionella ferruginea may be likened to a 

hairpin the two· ends of which have been 

twisted around each other. (See figs. 3, 7, and 

8, and Pls. V, VI, and VII, .A.) Sometimes 

such a twisted form may be bent again in the 

middle and the two ends be twisted around 

each other, thus forming a rope of four single 

strands. (See Pl. VI, B.) In some individuals the twisting is very loose, in others 

close. (See figs. 7 and 8.) i have found different coiled forms to range in width from 1 

to 3! micra. In individual coils the difference 

in width between the two ends may be as much 

as 1 micron. The longest coiled form that I 

FIGUUE 7.-Loosely 

twisted, ropelH:e form 

of GaUioneUc tert'Uginea. Drawing with 

camera lucida. x· 

1,080. 

FIGURE 8.- C 1 0 S e 1 Y 

twisted, ropelike form 

of Gallionella ferruginea. Drawing with 

camera Iucida. X 

1,080. 

have observed was about one-fourteenth millimeter in length, or 70 micra. 

The single threads which compose these 

ropes or coils are very thin and have the same 

width throughout, although different individuals vary in size. The common range is from 

less than 0.5 to about 0.75 micron. The longest single thread I have noticed was ·about 

0.05 ·millimeter in length. Most of the single 

threads which occur are probably detached 

parts of coils, for they generally· show 'the 

spiral form. As in SpirozJhyllum, no differentiation has ever been noticed between the two 

ends of the threads of Gcillionella, nor has any 

cell structure ever been distinguished. The 

organisms appear to be simple threads. 

Gallionella has a yellowish-brown to brown 

color. The ropelike forms are quite .dark 
24 IRON -DEPOSITING BACTERIA AND THEIR 'GEOLOGIC RELATIONS. 

brown, much darker than similar focms of 

s pirophyllum. 

The methods of reproduction of Gallionella 

have not been thoroughly studied. Migula 1 

describes the reproduction as taking place by 

the breaking off of parts of the threads these . ' bmng carried away by water currents to other 

strands and the develop;ment of the textureless 

ferric hydroxide mass typical of the older portion of the crust. . 

From this and other descriptions it appears 

that various investigators have noticed the formation of granules and projections on Gallionel~a and Spirophyllum threads, but only 

Elhs has connected them with the formation 

of conidia. -

SPIROPHYLLU~I FERRUGINEU~I Ellis. 

localities · and growing into new threads. 

Ellis 2 claims that in addition to the above 

method of reproduction Gallionella also mul-. 

tiplies by the external abstriction ~f conidia 

similar to Spiroph.yllum and the form which 

he describes as Leptothrix. In connection with Spi1•ophyllun~ ferrugineum Ellis appears to 

Gallionella and Spirophyllwm he describes the be· the most widespread of the iron bacteria. 

formation of abundant little projections all It occurs abundantly in iron-bearing surface 

over the surface of the threads. In some indi- waters, as well as in underground waters. It 

-vidu.als their .development is so profuse as to is almost always associated in greater or· less 

almost conceal the parep.t thread. These little abundance with other iron-depositing thread 

projections after b.ecoming separated from the bacteria and frequently occurs where other 

thread are said to germinate and form new iron-depositing thread bacteria are absent. 

threads. I have frequently seen GallioneUa '\Vith Leptothriw it is found in springs and 

and especially Spirophyllum covered with clear stream waters, even. where Leptothrix 

small light-brown spherical or somewhat ir- grows very profusely. '\Vith Orenothrix and 

regular bodies of fairly uniforill size such as Gallionella it is found in city water systems 

Ellis describes but have never become con- ~nd ~ith Gcillionella or Leptothrix it is found 

vinced as to whether they are conidia or par-· ~n. mrne waters. In some. iron springs and 

ticles of ferric hydroxide. Upon treatment .nnnes almost pure cultures of Spirophyllum 

with hydrochloric acid they disappear, as they o.ccur, Leptothrix and Gallionella being enwould if they consisted of ferric hydroxide trrely absent. 

yet it is true also that the entire thread is de~ I first encountered Spirophyllu1n abunstroyed in a very short time by similar treat- d~ntly i~ cult~res obtained from the Federal 

ment. mrne, a· zrnc m1ne located near Hazel Green, in 

. Schorler,3 in connection with his investiga- southwestern Wi~consin .. (See ~Is. VI and 

trons. on the.formation of crusts of iron rust by VII, A.) The mrne ';orlnngs are- rn ~he lower 

Gallwnella rn the city water pipes of Dresden, part .of the G~lena hmestone, and zrnc, lead, 

found numerous strands of Gallionella in the and 1ron sulph1des occur with calcite in veins 

outer portion of the crust, whereas the older in the limestone. 

interior portion of the crust consisted of a Waters issue frqm fissures and openings at 

structureless mass of ferric hydroxide. He numerous points in the mine. vVhere the cuifound that the individual strands of Gallio- ture was obtained a little stream of iron-bearnella had granular coatings of ferric hydrox- ing) water issued from a small fissure in the 

ide, which increased in thickness with the age rock wall a short distance below a horizontal 

of the strand and gradually caused its struc- vein containing sphalerite, marcasite, and calture to disappear. l-Ie d~scribes the develop- cite. Below the opening, attached to the rock 

ment of small hexagonal crystals of hydrated wall and forming a streak to the floor, was a 

ferric oxide on the sides of the older threads soft gelatinous brown deposit of ferric hydroxand states that they gradually increase in size ide which had a maximum thickness of oneand incorporate within them the surrounding half inch and a maximum width of 2 inches. 

granules of ferric hydroxide. Their growth A short distance from this point a basin in the 

reSults in the gradual disappearance of the rock floor was filled with water and contained 

a thick brown deposit of . ferric hydroxide. 1 Migula, w., System der Bakterien, Band 2, p. 1031, 1900. The material forming the str'ealr beneath the 2 Ellis, David, op. cit., pp. 505-507. · "' a Schorler, B., ov. cit. , fissure opening upon examination proved to 
OCCURR.ENCE AND MORPHOLOGY OF IRON-DEPOSITING THREAD BACTERIA. 25 

consist largely of Spirophyllum and Gal- bility that iron bacteria may· be active in 

· lionella, w":ith some Leptothrix or perhaps Con- fissures or other large underground openings 

i(Uothrim. (See pp. 17-18.) Various forms of entirely unconnected with mine's and may thus 

Spi'rophyll'um were present, the most.common be instrumental in the formation ·of many o~ 

being a wide, irregular, loosely twisted form. tl~e fissure. deposits and replacement deposits of 

(See Pl. VI.) Other types are very regu- .iron ore which are so common. Their presence 

lnrly twisted and have the appearance of i11 such ·localities is of course difficult to prove 

strings of beads. Their variation in size is unless they should be actually found in underconsiderable, some being almost as narrow as gromid openings which are penetrated during 

a single thread of Gallionella, whereas others mjning operations. Such a phenomenon to my 

are as wide as rope forms of Gallionella. know ledge has not been observed, but it 1night 

Both single and double threads occur. easily escape nptice unless particular attention 

Subsequently I obtained almost pure cultures v:ere called to it. 

of Spi'l'O]Jhyllwni on the 200 and 300 foot The cultures obtained from the Judson mine 

levels of the Judson mine, south of Crystal showed only Bpirophyl'Vum, and these. were 

Falls, ~1ich. (See Pl. VIII.) Th.is mine is mainly in the form of short pieces of filaments. 

located on a steeply dipping deposit of red A peculiarity about these. cultures, however, 

hematite inclosed in .slate walls. The foot- was that most of the filaments· were thickly 

wall consists of dark-gray pyritic slates. covered with small spherical bodies of the same 

'Vater issues from numerous Sinall fissures brownish color as the filaments. (See fig. 9.) 

throughout the mine and yellowish~brown 'Vhether the~e little bodies are granules of fergelatinous masses of iron bacteria are abundant ric hydroxide or whether they are conidia, as 

along the drifts, both where they cut the slate described by Ellis, has not been determined. 

and where they cut the ore. The occurrence of Spi1·ophyllum associated 

It seems pJ;obable that all the water issuing with LeptothriaJ and .Gallionella at the. ICenin the mine has at one time or another passed neely mine, on the Cuyuna range in central 

through the slate, and by its dissolving action ~1innesota, has already been described . 

. on the disseminated iron sulphide and iron In addition to these underground localities 

carbonate has become heavily loaded with.iron. I have found Spi'l·ophyllum in a number of 

No analysis of the water has been made as yet, places in. iron-bearing surface waters, but it 

but it seems probable that the iron is in solu- occurs in clear, fresh waters rather than in 

tion mainly as ferrous bicarbonate, though stagnant bog waters like those in which Lepperhaps a part of it may be in the form of toth.rix is often found. 

ferrous sulphate. These waters issuing from In the Vermilion iron-ore district of norththe mine openings either in the ore deposit or ern Minnesota· I o):>tained cultures of Spiroalong the sJate walls give abundant oppor- phyllum from two iron springs, both issuing 

tunity for the growth of bacteria. at the bases of extensive ridges, composed 

The question naturally arises, B;ow do the largely of banded jasper and associated greeniron bacteria come into the mines~ Are they stone. One of these springs is at the base of 

carded by the waters themselves through in- Soudan I-Iill, on the south shore of Vermilion 

tervening soil and rock or are they brought Lake; the other is at the western foot of Jasper 

clown into the mine on mine timbers, tools, Peak, a few miles south of Soudan. 

or machinery~ I have seen cultures of iron At the spring on Vermilion Lake the water 

bacteria in places in mines where it seems issues from an iron pipe at the base of a ·ridge 

quite improbable that they could have been consisting mainly of greenstone and jasper and 

brought by any other agency than the water some slate. It empties into a small basin from 

itself, and it does not seem at all impossible which it flows down a short slope into the lake. 

that they may have been carried downward Brown scum occurs in the basin and for some 

by surface waters through the larger open- distance along the little rivulet down toward 

ings in the ·soil or rock for many hundreds the lake. '~There the water is quiet the brown 

of feet. This opens the interesting possi- scum lies on the bottom and elsewhere it is 
26 IRON -DEl?OSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

attached to the sticks, grass blades, and other 

matedal lying in the water. The water has it 

strong iron taste. 

At the spring at Jasper Peak the water 

comes directly out of the hillside into a small 

basin from which it flows through a series of 

larger pools into a marsh. Jasper Peak_ consists mainly of banded jasper and associated 

greenstone. A yellowish-brown scun1 of iron 

bacteria occurs at the bottom of the basin at 

the mouth of the spring and also in the pools 

in the marsh. It is not gelatinous but rather 

in the form of a fluffy precipitate. 

When examined microscopically the scum 

of iron oxide from both of these localities is 

seen to c~ntain an abundance of threads of 

Spirophyllum, but with these threads is associated a large amount of brown flocculent, 

textureless material in large and small irregular masses. (See Pl. IX, A.) The textureless 

masses probably consist largely of ferric hydroxide, but whether this material is precipitated by simple chemical action or whether its 

formation is due perhaps to the activity of 

lower forms of iron-depositing bacteria has not 

·been determined. Probably it results from simple oxidation. The Spirophyllum in these cultures is of medium size and has regular but not 

very close twisting. In general the threads 

are cleai· and do not have the deposits of granular material on them that: is so characteristic 

of the cultures from the Judson mine. Howeyer, many of the granular masses of ferric 

hydroxide can be seen to contain spiral threads, 

these forming a sort of nucleus around ·which 

the ferric hydroxide collects. 

In the Rowe and Hillcrest mines, in the 

Cuyuna iron range, both of which are· openpit mines in red and brown hen1atite, seepages 

of iron-bearing waters issue from glacial sand 

and gravel which overlie the iron ore. The 

iron is taken into solution by the water while 

it is percolating through the sand and gravel, 

· probably being derived from iron silicates, carbonates, and sulphides disseminated through 

the glacial material. 

Thin coatings of yellowish-brown scum cover 

the pebbles over which the water flows and 

this material upon examination is seen to consist of Spirophyllum associated with more or 

less granular and flocculent ferric hydroxide, 

which is probably a chemical precipitate. In 

localities like these iron bacteria develop in a 

surprisingly short time, deposits being formed 

by them within a week after the glacial sand 

and gravel are laid bare by stripping operations. 

In the Pennington open-pit n1ine a very 

curious form of Spirophyllwm was found. The 

water, which issues in the form of a small 

spring ~lirectly from the ore, apparently contains enough ferrous iron in solution to support a growth of iron bacteria. The material 

collected was brown in color and contained 

some SpirozJhyllum and algae. Upon standing 

for a week or so it became black, but over its 

surface a light-brown scum formed, which 

upon examination was found to consist of an 

almost pure culture of a variety of very small 

Spirophyllum. The threads are ribbon-like 

but very narrow and very loosely and irregularly twisted and are intergrown into a thick 

matting mixed with . considerable granular 

ferric hydroxide. A great map.y of the threads 

· show no twisting at all, and double ropelike 

threads are rare. There seems to be a great 

uniformity in the size of the threads, though 

here and there occur larger threads which resemble the ordinary Spirophyllu1n seen in 

other cultures. · 

At several points in the Pennington pit there 

are steel bars and rails which during the closed 

season for. mining operations become submerged by water that accumulates in the pit. 

On several of these bars and rails I foun:d 

beautifully developed porous tubercles of iron 

rust, which upon microscopic examination 

proved to contain abundant casts of Spirophyllwm. (See Pl. IX, B, and fig.' 13.) The greatest diameter of the tubercles is 2 inches or more · 

at the base, and they rise from the surface of 

the bar or rail from a quarter to perhaps half 

an inch. The surface of such tubercles is 

formed by a thin, smooth, brittle film, and 

the interior consists of porous cellular ocherous 

material . which on handling breaks up into 

fine powder. It is this material which contains 

abundant casts of Spirophyllwm. Many of the 

casts still show the original texture of the 

threads clearly under the microscope, some of 

them being single and some double threads. 

Most of them, however, are thickly coated with 

granules of ferric hydroxide and appear like 

thick brown cords with rough surfaces. Some 

of these are twenty or more times the thi.ckness of the original Spirophyllum. Frequently 
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 113 PLATE IX 

·-

"t 

fi 

,1 .,• 

;.>1 ~\ 

A. PHOTOMICROGRAPH OF OCHEROUS SCUM FROM IRON SPRING NEAR VERMILION LAKE, SOUDAN, MINN., 

X640. 

The dark irregular masses arc ferric hydroxide. 'Vith it are mixed numerous forms of Spirophyllum jerrugincum, some double and some single. Unstained. 

~ 

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B. PHOTOMICROGRAPH OF LIMONITE POWDER FROM TUBERCLE OF IRON RUST, X640. 

Shows a number of scattered forms of Spiro11hyll'lLm jerrugineum and irregular masses and scatlcred specks of granular iron rust. Unstained. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 113 PLATE X 

A. CULTURES SHOWING THE PRECIPITATION OF FERRIC HYDROXIDE FROM SOLUTIONS OF FERRIC 

AMMONIUM CITRATE. 

1, Water with freshly dissolved fe rric ammonium citrate; 2, water from IJake Mendota, Wis., with ferric ammonium citrate after standing one month; 3, city wat.er, Madison, Wis., which contained ferric ammonium citrate but from which the iron h as been precipitated as ferric hydroxide; 4, water with hay infusion containing freshly dissolved ferric ammonium citrate; 

5, water with hay infusion which contained ferric ammonium citrate but from which the iron has been precipitated as ferric 

liydroxide. 

B. CULTURES SHOWING THE PRECIPITATION OF FERRIC HYDROXIDE FROM SOLUTIONS OF FERRIC 

AMMONIUM CITRATE. 

I , Water with freshly dissolved ferric ammon ium citrate; 2, water from Lake Mendota, Wis., which contained ferric ammonium cit.rate but from which the iron has been precipit.ated as ferric hydroxide; 3, city water, Madison, Wis., which contained f.erric ammonium citrate but from which the iron has been precipitated as ferric hydroxide; 4, water from iron spring near Lake Kegonsa, Wis., which contained ferric ammonium citrate but from which the iron has been precipitated as ferric bydroxide; 5, distilled water with ferric ammonium cilrate after standing one month. 
OCCURHBNCE AND MORPHOLOGY OF IRON-DEPOSITING THREAD BACTERIA. 27 

they are intertwined to form networks. Besides the threads and cordlike forms an abundance of small specks and granules of ferric 

hydroxide occur,. and. also large irregular 

n1asses of granules which do not show the 

corcllike forms. 

Spiroplbyllurn was originally ~ultivated in the· 

laboratory by Lieske.1 In his first attempt he 

used sand nnd old leaves obtained fr01n a 

st:ream in which Spi1·ozJhyllum occurred. He 

placed this mn,terial in a vessel, added to it a 

thin iron wire, and then filled the vessel with 

water fr01n the public supply of the city of 

Dresden. In this manner he obtained an 

abundant growth of Spirophyllwm. Later he 

used nn Erlemeyer flask containing water fr01n 

the same system to which had been added a 

small amount of extract of old leaves and thin 

iron wire or coarse filings. After three or four 

days SzJirozJhyll'tt'ln had developed. By making 

transfers to sterile flasks he was able to obtain 

approximately pure cultures. 

l-Ie finally obtained pure cultures in ·a 

specially prepared culture medium through 

which carbon dioxide was passed. The medium 

had the following composition: 

ComtlosUio·n of cnltm-r:J me(Umn 1tsecl by L-ieske. 

( NH4) ~so,-----------------~------ ___ grams__ 1. 5 

J(Cl-----------------------------------~0____ .05 

MgSO. ----------------------------... ---clo____ . 05 

K~B:P04 -------------------------------do____ . 05 

CuNOn -----------~--------------------c1o____ . 01 

Distilled wnteJ· _____________ cubic centimeters __ 1, 000 

Erlemeyer flnsks of 100 cubic centimeters 

each were filled up to 2 centimeters with this 

mediurn and a;fter sterilization were allowed 

tc, stand in atmospheric air for two days. 

Coarse iron filings, which had been dry steri- · 

lized at 160° C. for one hour, were then added, 

0.05 gram being used for each fln.sk. The 

flasks were then inoculated with a small 

amount of culture of iron bacteria, placed 

under a bell jar in a cool place, and carbon· 

dioxide was added up to 1 per cent. This resulted in the formation of ferrous bicarbonate 

in the solution to the nmount of about 0.01 

per cent. SzJi?·ozJhyllu'ln developed· in four 

days. By repeated transfers to sterile flasks 

pure cultures were obtained. 

1 Lieske, Rudolf, Beitriige zur Kenntnis d~r Physiologie vmi 

S1Ji1·ophyllmn jen·1t{Jinemn Ellis: Jahrb. wiss. Botanik, Band 

49, pp. 91-127, 1911. 

Spirophyllum occurs as flat unbranched ribbon-like filamentS twisted spirally about the 

longer axis. There appears to be no differentiation between the. two ends of the filaments, 

and apparently no variation in the width or 

the thickness of the filament from end to encl. 

Along the edges, however, they are somewhat 

thicker than along the center. Like Leptothriw, Spirophyllwm is always colored yellO\vish brown to brown fron1 the ferric hydroxide 

in the filament. I have not been able to stain 

it satisfactorily with any of the common 

aniline stains. 

The closeness of the spiral twisting of Spirophyllum varies with the individual; possibly 

there may be several speyies. Some filaments 

are very l~osely twisted, but others are very 

FIGURE 9.-Various forms . of S1J·iro7Jhyll1t1n jen·ugineum. 

Drawing with .camera lucida. X 550. 

closely twisted. In some the twisting is irregular, varying in closeness in different parts of 

the filament, whereas in others it is very regular 

and diagranunatic. (See figs. 9, 10, and 11, and 

Pls. IV, B / V, .A/ VI, .A/ VII; VIII, .A/ and 

IX, .A.) This difference may indicate a separn,tion into different species. In f)Ome cultures 

there are numerous filaments which are bent in 

the middle and the ends of which have been 

twisted about each other around a conimon 

axis, as in Gallionella. In such an individual 

the two ends frequently form a fork, thus giving it the appearance of a single branching 

. filament. (See Pl. VII, .A.)· More often, 

however, the . two filaments forming such a 

thread can be traced with more or less distinctness. (See Pl. VII, B.) 

In the cultures examined I have found 

Spirophyllwm to vary in width from 1 tn 3 

0 
28 IRO-N-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

micra, the average width being perhaps a little over 2 miqra. The longest filaments that 

have come to my notice were about 0.1 millimeter in length. However, the filaments are 

very brittle and, like those of Leptothrix, are 

easily broken during mounting operations. 

FIGUitE 10.-IrregularJy. twisted forms of Spirophyllum jerrugineum. Drawing with camera l:ucida. X 1,080. 

Up to the present time no cell structure has 

ever been ob$erved in Spirophyllum by any investigator. The organism appears to consist of 

simple, flat, ribbon-like filaments, undifferen-. 

tiated in its parts and without visible interior 

structure. 

According to Lieske 1 the only method of reproduction of Spirophyllum is by fragmentation-that, is, by the breaking off of pieces of 

filaments and ·their growth into new filaments. 

Ellis,2 however, claims that Spiroph.yllu1n reproduces by means of conidia, which grow as 

small spherical bodies ~n the flat sides of the 

filament and gradl.tally become detached and 

are carried away, eventually germinating and 

forming new filaments. Ellis gives descriptions of the conidia and of their germination. 

Lieske, who did much careful work on the 

growth and isolation of Spirophyllum, does 

not credit these observations of Ellis; believing 

that what Ellis saw were probably foreign 

bodies attached to filaments of Spirophyllum. 

During my own observations I have found 

many cultures of Spirophyllum in which not 

a trace of the formation of conidia was visible. 

However, certain other cultures that I have 

examined, especially . those from the Judson · 

mine, show filaments of Spirop.hyllum which 

are covered with small spherical, elliptical, or 

1 Lieske, Rudolf, op. cit. 

!! Ellis, David, A contribution to our knowledge of the 

thread bacteria : Centralbl. Bakteriologie, Abt. 2, Band 19, 

pp, 507-512, 1907. 

oval bodies, sometjmes so thickly as to conceal 

the filament itself. . (See fig. 12 and Pls. VIII 

and IX, A.) These bodies are colored brown 

just like the filan1ent and average about twothirds of a micron in diameter. I have not 

seen these bodies in the process of gennination, 

so that I can not say whether they are 

conidia or whether, as seems n1ore probable, 

they are small, chemically precipitated granules of ferric hydroxide. Although usually ferric hydroxide is precipitated in the 

form ?f structureless gelatinous masses, it is 

frequently found in the granular form as well. 

It also seems possible that these bodies might 

be lower iron-depositing bacteria of the· coccus 

or bacillus types which live under the same 

conditions as Spirophyllum and might readily 

become attached . to the filaments in large 

numbers. 

Spirophyllum was first described as a sepal~ate species by Ellis 3 in 1907. Previously it 

had been included under the species GaUionelkt 

first· described by Ehrenberg in 1836, which 

included also other types of iron bacteria. 

After Leptothriw, Ore1Wthm, Olo1Wthrix, and. 

others had been described as distinct genuses, 

Ellis found that the organisms still groti ped 

under the term Gallionella were of two types 

very closely related in __ · ---------. 

occurrence and general 

characteristics. 0 n e 

of these consisted of 

a double twisted cy lindrical thread and the 

other of a twisted 

ribbon-like thread. 

l-Ie named the latter 

Spirophyllum ferrugineum, applying the 

.name Gallionella only 

to the cylindrical 

threads. J\1olisch,4 in 

his work published ih 

1910, does not accept 

E 11 is's classification 

and believes that the 

FIGURE 11. - Single and 

double twisted ribbonlike forms of Spirophyllttm jcrrugincum. Drawing with camera lucida. 

X 1,080. 

two types distinguished by Ellis are merely 

different forms of .the same organism. He 

calls the ribbon-like form Gallionella ferruginea var. lata. Lieske, in his work with 

3 Ellis, David, On the discovery of a new genus of thread 

bacteria ( Spirophyllum jC?·rugincmn Ellis) : Roy. Soc. Edinburgh Proc., vol. 27, pt. 1, p. 21, 1907. 4 Molisch, Hans, Die Eisenbakterien, 1910. 
OTHER IRON -DEPOSITING BAC:r'ERIA. 29 

S]Jiropl~yllu1n, does not conm1it himself with 1 casionally, where the twisting is very close, 

regard to the classification but see1ns rather the dobule threads greatly resemble those of 

inclined to believe that Spiropl~yllum is Gallionella. 

a distinct genus. fie gives the differences 

between Gallionella and Spirophyllum as follows: (1) Spirophyllurn is ribbon-shaped 

whereas Gallionella is cylindrical. (2) SpiroOTHER IRON-DEPOSITING BACTERIA. ' 

Besides the group of iron thread bacteria, 

the most important members of 'vhich have 

just been described, two groups of lower 

·iron-depositing bacteria are commonly 

present in soils and natural waters-(1) 

those which precipitate ferric hydroxide 

or basic ferric salts, and (2) those which 

precipitate ferrous sulphide. To the fitst 

• group belong Siderocapsa treubii and its 

relatives described by Molisch as being 

abundant in natural iron-bearing waters 

froni which they deposit ferric hydroxide, 

and also certain other lower bacteria that 

occur in soils and natural waters and that 

precipitate ferric hydroxide .or basic 

ferric salts from solutions of organic iron 

Fwu~tN 12.-It·t·egutarly twisted fot·ms of Spiro]JhyUum terru- salts. To the second group belong the . ginczm~ with gnwulat· coatings probably consisting of ferric sulphate-reducing bacteria and the hy- bydroxlde. Drawing with camera Iucida. X 1,080. · 

]Jhyllu'ln is not found with two strands twisted 

around .each other, but only as single strands. 

(3) Spirophyll'unn is twisted around its own 

longitudinal axis whereas GalUonella is 

twisted arou:pd an axis outside of the thread. 

( 4) Spi'l''O]Jhyllwm grows into longer threads 

than GaUionella. (5) In cultures of Spirophyllu'ln the typical form always develops and 

transitions t.o · Gallion.ella are never seen. 

Lieske apparently never observed double 

strands of S]J'irO]Jhyllwm probably because he 

was working mainly with artific.ial cultures. 

In nearly all cultures growing under natural 

conditions double strands are very common. 

Spi'l''O]Jhyllum, therefore, is twisted about an 

axis outside of the thread just as is Gallionella. 

The other differences between the two forms, 

however, exist. 

After examining cultures of iron bacteria 

from many different localities it appear~ to me 

that Ellis's view is probably reasonable. Although the t~vo forms are undoubtedly closely 

related, there seem to be no gradational forms 

from one to the other and one form may be 

present in cultt1res to the exclusion of the 

other. There i!?, however, a danger of. confusing double strands of Spirophyllwm with 

those of G.allionella. Usually the ribbon-like 

form of the threads is clearly seen, but ocdrogen sulphide forming bacteria which 

are commonly present wherever decaying organic matter is fo'Q.nd. 

It has been known for a long time that 1nany 

.natural. iron-bearing waters contain types of 

bacteria such as have been described which 

~ zs:;.;r ~.u-·· ... 

FIGURE 13.-Various forms of fossll Spiro]Jhyllmn (errugi1ieum from tubercle of iron rust. X 1,080. 

deposit ferric hydroxide, but it has not been 

known that practically all soils and all natural 

waters contain bacteria which are capable o{ 

precipitating ferric hydroxide or basic ferric 

salts from solntions of .certain organic iron 

salts. These. organisms are not iron bacteria 

proper in the sense that they require iron in 
30 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

solution for their development. It appears 

rather that they use other constituents present 

in the iron salts and that ferric hydroxide is 

thrown dmvn as a waste product. In the 

course of my experiments I have noted the 

presence of such organisms in various natural 

waters, such as well water, lake water, river 

water, and spring water, and have also found 

then1 in different 'kinds of soil, such as silt, 

loam, clay, an:d sand. It seems probable that 

many of' the com:rpon types of soil and water 

bacteria are active in the precipitation of ferric 

hydroxide or basic ferric salts from solutions 

which contain organic iron salts. o 

Up to the present time I have succeeded in 

isolating several individual types ·which pre-

.cipitate iron. Although I have worked with 

different organic and inorganic solutions and 

have prepared cultures in liquid media that 

precipitated the iron from soh~tions of several 

organic iron salts, all the organisms which I 

have isolated anq. studied have been grown on 

solid media containing ferric ammonium citrate. Most of the other iron salts that I have 

used are unsatisfactory to work with, some, 

especially the inorganic salts, because they 

oxidize or hydrolyze too readily' and others because they render the media unfavorable for 

growth because of their toxic nature, harmful 

reaction, or other cha.racteristics. 

In experimenting with the precipitation of 

iron from solution by organisms it is, of course, 

necessary to use iron salts, which are readily 

soluble and which are not precipitated on account of oxidation when exposed to the atmosphere ·or when subjected to sterilization. Besides, the solutions must not be either too acjd 

or too alkaline to sustain organic life. In my 

work I have u~ed the following organic Iron 

and manganese salts in culture media: 

Organic i1·on and manganese salts used in culture 

media. 

Reaction to litmus. 

Ferric· ammonium citrate __________ Very slightly acid. 

Ferric citrate ____________________ _A._cid. 

Iron acetate ______________________ .f\..cid. 

Iron lactate _______________________ Slightly acid. 

Ferric oxalate _______________ -:._ ____ .A.cid. 

Albuminizecl iron------~----------·N eutral. 

Manganese citrute-----~----------..A.cid. 

Mnnganese acetate ________________ .Slightly acid. 

Of these salts I h~n'e found ferric ammonium 

citrate to be the most satisfactory, because (1) 

i~ is readily soluble, (2) it does not produce an 

unfavorable reaction, and ( 3) it is resi~tant to 

ordinary o;xidation processes. 

The solutions of inorganic iron salts tested 

in atte1npts to prochice cultures of ferric hydroxide precipitating bacteria were ferrous 

sulphate, ferrous ammonium sulphate, ferrous 

carbonate, and ferric chloride. Deposits of 

ferric hydroxide formed in these solutions under some conditions but the formation was 

·always readily explained as due to simple hydrolysis or to oxidation and hydrolysis rather 

than to the action of organisn1s. 

The bacteria which produce hydrogen sulphide and .those which reduce ferrous sulphate 

and thus precipitate ferrous sulphide fron1 

solution have also long been known, and many 

of them have been isolated and studied. The 

formation of ferrous sulphide by the bacteria 

which produce· hydrogen sulphide 1s due to 

the action of hydrogen sulphide on iror1. salts 

in solution or on ferric hydroxide previously 

precipitated, whereas with the sulphate-reducing bacteria the formation is due to the reInoval of oxygen from the sulphate and this 

results in the precipitation of the sulphide 

directly. 

Hydrogen sulphide is formed by bacteria in 

two ways-by the decomposition of sulphurbearing proteins and by the reduction of sulphur. Many decay-producing bacteria have 

the power of changing organic .sulphur compounds to hydrogen sulphide.· 'Vhen free sulphur is present with decomposing organic matter it is attacked through the action of bacteria and reduced to hydrogen sulphide as 

well. Hydrogen sulphide reacts wi~h any iron. 

salts present and ·forms ferrous sulphide. 

A number of species of bacteria have been 

isolated which act on sulphates, reducing them 

to sulphides. Among these are Proteus vulgaris, Vibrio hydrosulf~treus, and Spirillum 

desulfuricans. Some sulphate-reducing bacteria have the power of reducing also thiosulphates and sulphites. ''Then the compounds 

thus attacked are iron compounds ferrous sul-. 

phide is formed directly and precipitated. If 

sulphides of other metals are formed they may 

be attacked by carbon dioxide, and hydrogen 

sulphide may be formed. Hydrogen sulphide 

will then react with the iron salts to form 

ferrous sulphide. 

() 
• 

BXPBIUMENTS ON PRECIPITATION 0~ IRON FROM SOLUTIONS BY BACTERIA. 31 

Cultures were made in liquid and solid media 

o:f the bacteria which reduce sulphates and 

those which produce hydrogen sulphide. Ordinary synthetic nutrient media were used for 

sulphate reducers, and ferrous sulphate was 

added for reduction to sulphide. Cultures of 

bacteria which produce hydrogen sulphide 

were made :in solutions .. containing decomposing organic matter, organic iron salts such as 

iron ] actn.te or iron tartrate being used as 

indicators of hydrogen .sulphide formation. 

Experiments on the precipitation of ferric 

hydroxide and ferrous sulphide from solutions 

of iron sn.lts by various species of lower bacteria are described on the following pages. 

EXPERIMENTS ON PRECIPITATION OF IRON FROM 

SOLUTIONS BY BACTERIA. 

I'RI~CTPlTATJON O:l!~ l"lmRIC HYDROXIDE AND B.L.SIC 

J?tmm:C SALTS FROl\I :l!~EHIUC A1\I1\IONIUl\i CITRA 'l'E 

SOLUTIONS. 

It wns noted by :Prof. E. B. Fred, .of the 

University of "\Visconsin, that when ferric 

nmmonimn citrate was added to jars containing water and marsh mud in which bacteria of 

various kinds were nbundant, the deep reddishbrown color which it impai'ted to the solution 

disappeared after a few weeks, owing to the 

precipitation. of the iron. It ·was supposed 

that this precipitation was caused by the 

activity of ordinary iron-depositing thread 

bacteria, and upon this supposition I started 

a series of cultures. 

The first experiments were performed with 

the object of determining whether pur~ natural 

waters had the smi1e effect in precipitating the 

iron from ferric ammonimn citrate solutions 

ns impure 1nuddy cultures, and whether this 

action varied with different kinds of natural 

waters. For this purpose three glass jars were 

each filled with 500 cubic centimeters of water, 

the first· one being filled wi.th \Vater froni Lake 

1\ienclota, the second with water frmn the city 

wells of 1\1adison, "\7\Tis., and the third 'vith hay 

extract-that is, water in which hay had been 

boiled. To each of these jars 2.5 grams of 

ferric ::w1n1onimn citrate was then added. 

They were allowed to stand at room. temperature (about 18° C.) for one month and were 

then photographed. (See Pl. X, .A..) The results are well shown in the photograph. Jar 

No. 1 shows the appearance of the freshly prepar:ed ferric ammonium citrate solution in 

clear water, and jar No. 4 shows the same in 

hay extract. Jar No. 2 contains water from 

Lake Mendota with ferric ammonium citrate. 

It ·shows that decided bacterial action has 

taken place after one month, but no pre~ipitate 

has formed. This jar was allowed to stand for 

another month and 'at the end of that time the 

iron had. been completely precipitated. Jar 

No. 3 contains water from Madison city supply, which has had the same treatment as jar 

No. 2. It will be seen that in this jar the 

iron had been completely precipitated after 

one month, the solution being perfectly clear 

and transparent. Tufts of ferric hydroxide 

are attached to the inside surface of the jar 

and a thick deposit of ferric hydroxide with 

perhaps some basic ferric salts occurs at the 

bottmn. Jar No. 5 contains extract of hay 

which has had the same treatment as jars Nos. 

2 and 3. It will be seen that here also complete precipitation of the iron has taken place 

within one 1nonth, leaving a clear solution, 

which, ho\vever, is somewhat darker on account of the hay extract it. contains. 

Having obtained these results it was thought 

best to duplicate the experiment with slight 

variations. A set of four jars was therefore 

prepared~ each being filled with 500 cubic centimeters of a different type of ·water. Two and 

one-half grams of ferric animonium citrate 

v:ere added to each. Two of these jars contained water from Lake Mendota and. from the 

1\1adison city supply as before. A third, however, was filled with water from an iron spring 

near Lake ICegonsa; about 14 miles southeast 

of 1\1adison. This spring contained an 

abundant growth of Leptothriw. A fourth jar 

was filled wjth distilled water. The jars were 

allow~d to stand at room tempm~ature and were 

photographed after five weeks. (See Pl. X, B.) 

Jar No. 1 again shows the appearance of the 

freshly prepared solution of ferric ammonium 

c]trate in clear \Vater. Jar No.2 and jar No. ·3 · 

show the action of water from Lake 1\1endota 

and from the Madison city supply respectively 

on· feTric ammonium citrate in solution. Both 

waters precipitated the iron after four weeks. 

The masses of ferric hydroxide and perhaps 

some basic ferric salts are seen at the bottoms 

of the jars. Jar No. 4 contained iron spring 

water. The precipitation of ferric hydroxide 
• 

IRON -DEPOSITING BACTERIA AND· THEIR GEOLOGIC RELATIONS. 

took place in this jar also after about four contents in an autoclave at 130° C. for 15 

weeks. Jar No. 5 contains distilled water with minutes. 

ferric ammonium citrate in solution. Some Both sets of flasks were allowed to stand at 

bacterial action has taken place after five room temperat.ure for four months, at the end 

weeks, as is shown by the darkening of the of which time the photograph was taken. As 

solution. Complete precipitation of ferric may be clearly· seen, the contents of. the lower 

hydroxide in this jar, however, did not take row of flasks have suffered no change, whereas 

place until after about seven or eight months. in the upper row the contents of all the flasks 

In order to see whether soil would have the except the fifth have suffered complete presame effect as natural waters on iron am- cipitation of the iron in solution. The fifth 

monium citrate in solution, several flasks con- flask, which contains distilled water, shows 

taining 500 cubic centimeters of water with 2.5 only a darkening of the solution. The tbne of 

grams of ferric ammonium citrate in solution precipitation varied in the different flasks. 

were each inoculated with 20 grams of a dif· The water from the city supply of Madison 

ferent kind of soil-a black loamy soil, brown precipitated the iron fron1 solution in about 

sandy soil, or clayey soil. Precipitation of two months, the water frmn Lake Mendota in 

ferric hydroxide took place in these jars after about seven weeks, the iron spring water in 

about two weeks, which showed a more rapid about one month, and the soil infusion in abot1t 

action with soils than with natural waters. two weeks. 

Although the results of the preceding ex- This experiment showed conclusively that 

perirrients seemed- to show fairly conclusively the sterilized material did not suffer precipitathat the precipitation was due to biologic tion of the iron in solution. There still reagencies rather than to chemical processes, it mained the possibility, however, that during 

seemed best to make sure of this point. There the process of sterilization the iron salt in 

are some iron salts, especially inorganic but solution might have suffered some change 

also organic, in which precipitation occurs on which rendered it less subject to hydrolysis. 

account of oxidation or on account of ·hydroly- To investigate this possibility severai of the 

sis, the precipitates consisting either of ferric sterilized solutions, after having stood for 

hydroxide or of basic organic or inorganic fer- four n1onths, were reinoculated with a small 

ric salts. In order to show conclusively that the amount of fresh soil· infusion. 'This resulted 

precipitating action \vas due to biologic agen- in the precipitation of tli.e iron within a very 

cies, the following expedment was performed. short time and showed beyond doubf that the. 

Two sets of five flasks of 1,000 cubic centime- precipitation of the iron was due to biologic 

ters capacity were prepared with culture solu- agencies. 

tions, one set being a duplicate of the other. vVhile these experiments were being conEach of the fl!'lsks contained 500 cubic· centi- ducted the precipitates were frequently exmeters of water in which 2.5 grams of ferric amined. The material forming the deposits 

ammonium citrate were dissolved. The dif- was reddish brown and flocculent and resemferences between the culture solutions in the bled the ferric hydroxide which is precipidifferent flasks were as follows: The first flask. tated when ammon!un1 hydroxide is added 

in each set contained water from the city sup- to a solution of a ferric salt, such. as ferric 

ply of Madison, Wis. ; the second, water from chloride or ferric nitrate. It usually ~ettled to 

Lake Mendota; the third, water from the iron .the bottom of the containing .vessel and after 

spring near Lake l(egonsa; the fourth, water stand{ng for some tin1e became compacted 

inoculated with 20 grams of garden soil; and into a fluffy, gelatinous deposit. After prothe fifth, distilled water. One of these sets longed standing it contract~d and changed 

was sterilized, so as to stop all organic action, from reddish brown to dark brown in color. 

whereas in the. other set the organisms' were At the outset it was supposed that upon miallowed to develop freely, as in the previous croscopic examination this material would be 

P.Xperiments. The flasks are shown in Plate found to- consist mainly of matted threads of . 

XI, those of the lower r:ow being stel,'ilized iron bacteria such as I had already seen in 

duplicates of those of the upper row. The gelatinous iron scums from many localities. 

steriliz~tion consisted in heating t~e flasks and I found, however, that the precipitate ap-
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 113 PLATE XI 

r 

... 

CULTURES SHOWING THE EFFECT OF STERILIZATION IN THE PRECIPITATION OF FERRIC HYDROXIDE FROM SOLUTIONS OF FERRIC 

AMMONIUM CITRATE. 

Upper row, natural waters which cont.aioed ferric ammonium citrate but from all but one of which the iron has been precipitated as ferric hydroxide by bacteria; lower row, different waters containing ferric ammonium citrate in solution which were sterilized before bacteria had an opportunity to precipitate the iron. The flask~ of the lower row are duplicates of those of the upper row. The first flask in each row contains Madison city water; the second, water from Lake Mendota; the th1rd, iron-spring water; the fourth, water with soil; and the fifth, distilled water. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 113 PLATE XII 

...., 

, 

, 

• .. 

• 

• 

• 

••• 

• • • . . •• . .. 

-

• 

~ •• 

A. PETRI DISHES SHOWING COLONIES OF LOWER BACTERIA WHICH PRECIPITATE 

FERRIC HYDROXIDE FROM AGAR CONTAINING FERRIC AMMONIUM CITRATE . 

• .. , ' • 

• '· :4- ' c 

'!9 •• J ,. .. _ r • • \ I ' ' - -.tv ... '_,._, - , 

• - \ ~ ' - ,, I - I \.. 

' ' ,. , - I ' 

, .__..., • a'~ } ' , 

·~ • I \ • 

"r • I - • ' -- ' ' ,_ . \ ., ' 

" • -~ '*' .. 

~ - ·'~' ... ' , .. ,. .... • • • '"f-: , ~ I , ' I 

\ , ~ • 

" · J. ' \ A 

- "' , '~ I ,_,. ). - • • I . ,.. ' ' 

,_ 

, . ~I' I .. , ·.. r " ·~ • • ' - . • "' 

.. , , 

• 

I 

B. PHOTOMICROGRAPH OF A PURE CULTURE OF ONE TYPE OF LOWER BACTERIA WHICH HAS THE POWEll. 

OF PRECIPITATING FERRIC HYDROXIDE FROM SOLUTIO S OF FERRIC AMMONIUM CITRATE, X l,310. 

Stained wiLh carbo! fuchsin. 
EXPEIUMENTS ON PRECIPITATION OF IRON FROM SOLUTIONS BY BACTERIA. 33 

peared light brown, transparent, and was apparently colloidal. There were no tl:aces of 

iron bacteria in the Inaterial, except that in 

the flask containing iron spring water a few 

tln·cads of LeJJtoth/rim were found. These 

threads probably develop in ferric ammonium 

citrate solutio11s to some extent, as ·was determilled by ~1olisch. 1 J\1any of tlu} threads, however, were probably present in the water before 

the ferric a1mnonium ·citrate was added. Upon 

prolonged standing I found that mold mycelia 

frequently developed in the gelatinous material and sometimes became quite abundant. 

There appear to be several varieties of molds 

which grow in these solutions, but I have not 

attempted to identify or describe them. 

A partial analysis was n1ade by W. G. Crawf<;>rd, of the University of 'Visconsin, of the 

precipitate formed from a solution of ferric 

atmnonimn citrate in wa.ter from the city supply of J\1adison with the following result: 

A.nalys·is of tJrecitJitnte to1·med from sol1tUon of ferric 

am.monimn citrate. 

[Dried at 105° C.] 

Ferric oxide (Fe20s)------------------------- 72.50 

Cornbinetl water (II~O)----------------------- 7.11 

Loss nbove 105° C. (exclusive of combined 

water)------------------------------------ 20.12 

99.73 

The material 'vas examined qualitatively for 

traces of citrate in order to determine if basic 

ferric citrate ·was present i:U the precipitate. 

The indications of its presence were very 

slight, however. It appears fr01n the analysis, 

thcre:fore, that the nuttcrial is one of the less 

hydrated forms of ferric oxide, approaching 

goethite in composition. A percentage of 72.50 

ferric oxide requires 8.15 per cent combined 

water to forn1 ,goethite. However, the analysis 

only shows 7.11 per cent of combined water, 

which probably means that the material is between goethite (Fe 20 3.H20) and turgite or 

hydrohmnatite (2Fe20 3 .H20) in composition. 

It is possible, however, that insoluble basic 

ferric citra.te is precipitated with the ferric 

hydroxide, but that upon standing the citrate 

radicle ~s gradually used up by the bacteria, 

finally leaving only ferric hydroxide in the 

precipitate. The composition of the precipi1 1\.follsch, Hnns, Die Elsenbakterlen, pp. 34, 35, 1910. 

GG629° -19-3 . 

tate would, therefore, change with the time it 

is left standing and probably also with the 

treatment it receives previous to ·analysis, stich 

as washing. 

The large percentage of loss above 105° C. 

besides the combined water is difficult to explain, because of the small amount of organic 

matter visible in the precipitate when examined microscopically. It is possible, ho~vever, that besides the mold mycelia there are 

present abundant remains of lower bacteria 

which developed in the solution and which 

would be difficult to identify with the microscope. 

The series ef experiments performed up to 

this time made the following points evident: 

(1) That the precipitation of iron from solutions of ferric ammonium citrate is due to 

some biologic agency; (2) that the precipitate is hydrated ferric oxide with perhaps a 

small amount of basic ferric citrate; and ( 3) 

that it consists of a colloidal, textureless mass 

in which b'acterial forms are unrecognizable. 

The latter fad seems to indicate that, as the 

ferric hydroxide is not taken up by the cells 

of the org~inisms causing the precipitation, it 

is probably only a waste product, other constituents of the salt, such as citric acid or ammonia, being utilized and the. ferric hydroxide 

thrown clown. 

In order to determine 'vhether oxygen is 

necessary for the precipitation of ferric hydroxide or whether the action could take place 

under anaerobic conditions, carbon. dioxide was 

run continuously for several weeks through 

ferric ammonium citrate solutions inoculated 

with soil. This produced a saturation of the 

solution with carbon dioxide and caused the 

removal of practically all traces of oxygen. 

The precipitation, however, took place pc; 

before. 

Solutions preparetl and inoculated 'vith soil 

in the same manner as those mentioned above 

were placed under a bell jar and all the air 

removed, so as to produce a vacuum capable of 

supporting a mercury column 23.5 inches high. 

This reduction of air did not seem to affect 

the precipitation, which occurred after about 

the same period of time had elapsed as· was 

required for similar cultures in the open air. 

What remained now to be done was to isolate 

the organisms ·.which threw the iron out of 
34 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

solution and to study their morphology and 

the conditions under which they are active. It 

required considerable experimental work before I su~ceeded in cultivating the organisms 

on solid media. ' 

The first attempt was made with 1.5 per .cent 

'vashed agar, containing no nutrient material. 

To this substance 0.5 gram of ferric ammonium 

citrate was added for ·every 100 cubic centimeters of agar. Plates were poured from this 

medium and were inoculated from various impure cultures. They ·were then ·allowed to incubate at room temperature for several weeks. 

Numerous colonies of different kinds of microorganisms developed on the plates, but none 

caused the precipitation of ferric hydroxide 

from the agar. 

The second attempt was made by adding 

nutrient material in the form of soil and hay 

extract such ~s is used in media .for protozoa. 

The agar was so prepared that 1,500 cubic 

centimeters of 1.5 per. cent agar contained 

50 cubic centimeters of hay and ·soil extract and 7.5 grams of ferric ammonium 

citrate. · Plates were poured from soil infusion prepared by adding 20 grams of 

soil to a 400 cubic centimeter sterile water 

face owing to the precipitated ferric hydroxide. The plates inoculated with soil infusion 

of the fourth dilution gave much more satisfactory results than the plates inoculated with soil 

infusion of the fifth dilution. 

Several kinds of coJonies of bacteria. precipitating ferric hydroxide developed under ·these 

conditions. The most typical ones were i:r;regular flat colonies with ragged corrugated or 

feathery edges, most of them lying on the surface of the aga.r. These p'recipitated ferric hydroxide almost immediately after they began 

to develop, and after five or six days becaine 

coated with a brittl~, dark-brown crust of ferric hydroxide, whose surface was shining and 

generally iridescent. · 

Another type of colony around which ferric 

hydroxide begins to precipitate soon after it 

develops is large and flat but differs from the 

preceding type in having smooth edges and a 

0 0 0 

0 oo 0 

0 0 0 

0 0 0 0 0 0 0· 0 

blank, then ·transferring 25 cubic centimeters of this infusion to another 400 cubic FIGonE 14.-Various forms of lower bacteria which have the 

centimeter sterile water blank, and so on. to power of precipitating ferric hydroxide from solutions of 

· ferric ammonium citrate. X about 1,350. the fifth dilution. Inoculations were made 

from the fourth a~d fifth dilutions, 1 cubic centimeter being used for each plate. Abundant 

growth of .various organisms occurred on the 

plates after several days, but again there was 

no precipitation of ferric hydroxide.· 

In the third attempt, which was successful, 

Heyden Nahrstoff agar was used as a medium 

and ferric ammonium citrate was added to it 

in the proportion of 1 gram of ferric ammonium citrate to 100 cubic centi1neters of agar. 

Inoculations were made from soil infusion prepared as already described. The plates were 

incubated at a temperature of 28° C. for three 

or four days, and by that time showed an abundant development of micro.organisms. (See Pl. 

XII, .A.) Even after the second day certain 

of the colonies were seen to develop a. darkbrown halo around them, and after five or six 

days these colonies became very dark brown 

and opaque and developed an iridescent surmoist surface. This type does not become as 

dark and opaque as the preceding one. 

There are a few other types· of colonies of 

microorganisms which begin to precipitate ferric hydroxide. soon after they appear on the 

agar. They are mainly small circular colonies 

-\v hich do not show any distinctive characteristics. 

· After a considerable period a great many 

other colonies on the plates begin to develop 

dark areas around them. Among these are 

small, raised, fluffy white colonies of Actinomyces and several varieties of ~mall, · raised 

cream-colored bae;terial colonies. Some of these 

develop a small dark spot in the center. Bacteria from a number of the colonies were examined microscopically and it was found that 

there were several distinct species of ·organisms, some of them bacillus and ·some coccus 

forms. (See fig. 14.) 
EXPERIMENTS ON PRECIPITATION OF IRON FROM SOLUTIONS BY BACTERIA. 35; 

Slopes of 1-Ieyden Nahrstoff agar, to which with the following culture solutions, the first 

ferr.ic ammonium citrate had bee.p. added, and being a synthetic medium and the second an 

also of bouillon agar similarly treated were in- ordinary nutrient medium: 

oculated from various colonies and the result-

:ing streak cultures showed ~tbundant formation 

of ferric hydroxide. Slopes of Heyden Nahrstoff agar to which no ferric ammonium citrate 

had bee11 added 'vere similarly inoculated but 

showed practically no growth. Slopes of Heyden Niihrstoff agar which contained manganese 

citrate also showed no growth. On the other 

hand, slopes of !-leyden Nahrstoff agar to 

which sodium citrate had been added showed 

considerable growth upon inoculation, and the 

snme was true of plain bouillon agar, either 

with or without the addition of sodium citrate.· 

Pure cultures were made by inoculating another set of plates with organisms from one of 

the colonies which shmved the most abundant 

forma-tion of ferric hydroxide. These plates 

showed two distinct types of colonies as fol-. 

lows: (1) Circular, flat colonies with irregular 

corrugated edges formed ·on the surface of the· 

uga.r. These colonies were quite thin and re-· 

sembled the colonies already described as 

forming on plates of impure cultures. The 

formation of ferric hydroxide by the organism 

composing these colonies began in a few days. 

(2) 'i\T:ithin the agar colon1es of another type 

dev~loped. These were very small, lightbrown, lenticular colonies which commenced 

the formation of ferric hydroxide only- after 

a week or two. There is little doubt that these 

two types of colonies were produced by the 

same species of microorganism, the difference 

being due to the different conditions under 

which they grew. . 

The org~tnisin composing these pure cultures 

was examined under the microscope and was 

. found to be a short bacillus averaging about 

1.4 micra in length, and about 0.5 micron in 

thickness. ·(See Pl. XII, B.) . .It was found 

to be difficult to stain, owing probably to the 

presence of ferric hydroxide in the cell walls. 

Upon prolonged treatment with carbolfuchsin, 

however, it assumed a distinct red color. 

An attempt was made to determine the composition of the material precipitated from 

solution by a pure culture of this bacillus. 

For this purpose two flasks were prepared 

Media 1tsed to. obtain a mtre· culture in sol'ution of the 

bacill1ts shown in Plnte XII, B. 

Flask No. 1. 

K2HP04----------------------------'--grams __ 

MgSO. -------'"'--.----------------------do ___ _ 

NH.NOs--------------------·-----------t1o ___ _ 

CaCI2---------------------------------do ___ _ 

NaNOs ---------------~-----------------tlo ___ _ 

0.5 

.5 

0 5 

.2 

. 5. 

Ferric ammonium citrate _______________ (}o____ 10. (l 

Distilled watet· ____________ cubic centimeters __ 1, 000 

Flask No.2. 

Heyden Nahrstoff _____ ~ _______________ grams__ 7. 5 

Distilled water ____________ cubic centimeters__ 250 

Heated for 2 hours in a steamer nnd filtered; 1,000 

cubic centimeters distilled water and 10 grams ferric 

ammonium citrnte then added to filtrate. 

The solutions were both sterilized 1n the 

autoclave and then were inoculated from pure 

cultures. The synthetic solution sho·wed precipitation of the iron after an incubation period of about five 'veeks at room temperature 

(about 17° to 19° C.) The Hey ¢len Nahrstoff 

solution showed no precipitation of iron even 

aftm- a. period- of four and a half months. The· 

precipitate from the synthetic solution was 

analyzed by ,V. G. Crawford, University o£ 

Wisconsin, with the following. results: 

Analysis of precipita,te from flasTc No. 1. 

[Dried at 105° C.l 

Ferric oxide (Fe20a) ----------------------- 65. 00 

Phosphoric acid (P20o) -------------------- 7. 60 

Combined water (H20) _______ _: ___ :__________ · 27. 20 

Chlorine ( Cl) ___ :_ _______ .______________ _____ •.rrace. 

Sodium (Na) ------------------------------ 1 'Trace . 

Potassium (K) ----·------------------------ None. 

Calcium (Ca) ------------------------------ None. 

Magnesium (Mg) --------------------------

Ammonia (NHs) ---------------------------

Nitrate radicle (NOs) ----------:------------

None. 

None. 

None. 

99.80. 

A comparison of this analysis with the 

analysis. of ·a sin1ilar precipitate obtained 

with impure cultures from a solution of ferrie 

· 1 With spectroscope. 
36 IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

ammonium citrate to which no other nutrient 

material had been added (see p. 33) shows 

marked differences. In the analysis of the 

preci pita.te obtained from the impure culture 

the ferric oxide amounts to 72.50 p·er cent as 

compared· with · 65 per cent in the analysis 

under consideration, and there is in the pure 

culture 7.60 per cent. of phosphoric acid, which 

is entirely lacking in the impure culture. The 

. presence of phosphoric acid is easily explained 

as being due to the presepce of phosphate in 

the synthetic medium. Phosphorus almost invariably comes down with ferric oxide or 

alumina upon precipitation. Another difference, however, and one much more difficult to 

explain, is that in the analysis from the impure 

culture combined water amounts to 7.11 per 

cent and the loss, exclusive of water, to 20.12 

per cent, whereas in the analysis of the precipitate from the pure culture in the synthetic 

medium the combined water amounts to 27.20 

per- cent and the loss due to volatilizing other 

substanc~s is nil. There may be several explanations for this difference. In the first 

place, the presence of phosphoric acid in addition to the iron oxide may . require a much 

larger percentage of combined water than iron 

oxide alone. The presence of this substa.nce: 

however, does not account for the absence of 

other constituents, such as organic matter, included under loss. This difference, however, 

may be accounted for in part by the fact that 

the precipitate :from the synthetic medium, on 

account of its slimy consistency, required 

washing by decantation for three weeks in 

order to clean it and to prepare it for analysis. 

This washing rna y have resulted in dissolving 

out any basic citrate and other material that 

may have been present and which in the precipitate from the impure cuJture was not removed in the comparatively short period of 

~ashing ( 1 hour). According to Crawford, 

the water obtained from the precipitate from 

the synthetic medium varied with the amount 

of heat applied, being only 19 per cent when 

the medium was heated to 300° C. but increasing to 27.20 per cent when it was heated on 

platinum to· as high a temperature as could be 

obtained. No distillation of carbon was noted. 

The material is therefore apparently a hydrous 

ferric phosphate of indefinite· composition. 

PRECIPITATION OF FEIU{IC HYDROXIDE .AND BASIC 

FERRIC SAL'J.'S FROl\I OTHER SOLUTIONS CONTAINING ORGANIC IRON. 

At the same time that the experime11ts were 

being performed with ferric ammonium citrate 

a number of other organic iron salts were used 

as culture media with varying results. In the 

first place a series of cultures was prei)ared by 

inoculating diffexent solutions containing organic iron with soil in order to see what effect 

the organisms in the soil had on the different 

salts in solution. The following organic iron 

salts were used, 2 grams of the salt being dissolved in 300 cubic centimeters of 'vater in each 

experiment and. the solution inoculated with 20 

grams of sandy soil. 

Appearance and reaction of solut·ions containing organic 

iron inoculated w-ith soil. 

Ferric ammonium citrnte __ ,Solution clear, light brownish red. Slightly acid. 

Ferric citrate ______________ Solution clear, yellow with 

brownish tinge. Acid. 

Ferric oxalate ____________ Solution clear, light lemonyellow. Acid. 

Iron lnctr.te_.:. ____________ .Solution clear, light reddish 

brown. Slightly acid. 

Iron acetate ______________ Solution 

. brown. 

da~·l~ 

Acid . 

reddish 

Iron albuminate (5 pe.x . Solution clear, light browncent Fe20a). ish red. Neutral. 

Manganese citrnte _________ .Solution colorless. Acid. 

Manganese acetnte ________ Solution colorless. Slightly 

acid. 

These cultures were kept in wide-mouthed 

bottles plugged with cotton, a small circular 

piece of sterilized filter paper being immersed 

in.the solution in each bottle in order to cover 

the layer of soil at the bottom so as to· prevent 

the precipitate that formed from. mixing with 

the soil. They were allowed to incubate at 

room temperature for two months. Ferric 

ammoniun1 citrate was used along with the 

other salts to serve as· an indicator of the nature of the changes taking place in the other 

solutions. The organic n1anganese salts were 

used in order to determine whether the organ- -· 

isms would precipitate manganese from solution as well as iron. The following results 

were obtained : · 

From the ferric anunonium citrate solution 

flocculent, brownish-red ferric hydroxide was 

precipitated in about two weeks and formed 
EXPERIMENTS ON PRECIPITATION OF IRON :FROM SOLuTIONS BY BACTERIA. 37 

tufts on, the sides of the bottle and a thin layer became coated with a thick brown deposit. The 

on the filter paper. Mold mycelia developed precipitate probably consisted chiefly of a mixabundantly in this upon standing. A thin ture of basic ferric acetate with some ferric hybrittle brownish fihn formed over the surface droxide. It ~eems likely, to judge fron\t later 

of the solution. The solution became colorless experiments, that the precipitation in this exbut remained turbid. periment resulted from hydrolysis rathm~ than 

In the ferric citrate solution precipitatiqn was frmn bacterial action. 

only partial at the end of .,two weeks but was. The solution of iron albuminate began to 

complete in nbout three weeks. The precipi- ferment a day or two after it was p1!epared. 

tate consisted of flocculent black material, It gradually became black and a thick brown 

which for1ned a layer about one-fourth inch scum formed on the surface. The changes 

thic.k on the filter paper. The nature of the probably resulted froni complex processes of 

precipitate is unknown. It may· have been decomposition due to the presence of albumin. 

l1ydrous ferrous sulphide. A da1~k-brown to No precipitation occurred in the solutions of 

black thin brittle. film developed on the sur- manganese salts, but molds developed . abunfu,ce of the solution and from it a n1atting of dantly. In the manganese citrate solution mold 

black filaments, probably mold, extended down mycelia developed as black filaments forming 

into the solution. Mold 1nycelia also developed a matting below a light-brown brittle surface 

ltbundantly in the black.precipitate on the filter film. This growth eventually dropped to the 

paper, ns shown by microscopic examination. bottom and formed a dark-gray deposit on the 

The solution became clear and colorless. filter paper; Besides mold mycelia this deposit. 

The ferric oxalate solution gave a very thin, was found to contain filaments of algae and 

light-brown deposit on the filter paper and on protozoa. In the manganese acetate solution 

the sides of the bottle in about one and one- the n1old grew as a· white, woolly n1atting on 

half weeJ{s. The nature of the deposit was not the filter paper. The deposit gradually bedetermined. A thin brown brittle film fonned came darker and more compact. The solution 

on the surface of the solution. The solution remained clear in both experiments. 

became slightly turbid and retained a brow:p.- The results in general showed that precipiish tinge e\ren after standing for two months. tation of ferric hydroxid~ and basic ferric 

In the iron lactate solution the precipitation salts took place in solutions of other. organjc 

did not begin until after bvo or three weeks iron salts besides ferric ammonium citrate but 

and :was not complete even after two n10nths. that the time and manner of precipitation 

The precipitate was brovn1ish -red and floccu- varied in different solutions. They also 

lent nncl settled very slowly on the filter paper, showed that manganese was not precipitated 

so that at the end of two months the deposit from solution in the same manner as iron, alwas nearly one-half inch in thickness. Small though microorganisms developed abundantly 

masses attached themselves to the sides of the in solutions of organic manganese salts . 

. bottle. The solutiDn remained light brownish It now became necessary to determine 

owing to fine, suspended, flocculent material. whether the precipitation from these iron soluUpon microscopic examination the precipitate tions was due to chemical action or to the acw~s seen to consist n1ainly of colloidal material tivity of organisms. For this purpose another 

with here and there mold mycelia, some of set of solutions was prepared in the same way 

which had a brown coating. The precipitate as the set just described except that iron alprobably consisted of ferric hydroxide and buminate was omitted. After inoculation with 

more or less basic iron lactate. soil the cultures were sterilized in an autoFrom the iron acetate solution a flocculent clave. The sterilization produced a. slight 

reddish-brown material was precipitated in change of color in some of the solutions, and 

about n, week and formed a fluffy layer about in the iron acetate solution it caused the formathree-fourths inch thick on the filter. paper. tion of a reddish-brown flocculent precipitate 

After a period of several weeks molds de- due to hydrolysis. This precipitate· probably 

velopecl abundantly in this deposit and some · consisted mainly of basic ferric acetates and 
38 IRON -DEPOSITING BACTERIA AND THEI~ GEOLOGIC RELATIONS. 

appeared to be similar to that formed in the growth. Whether this experiment indicates 

iron-acetate culture already described. The that bacteria do not grow in the presence of 

solutions were allowed to stand for six 'weeks ferric oxalate and iron lactate and that the 

at roQm temperature, and during this period precipitation in the solutions was due to the 

did not alter their appearance. At the end of action of molds which do not grow· readily on 

six weeks the solutions were reinoculated by _solid media is difficult to say. It is very desir- -

adding 1 cubic centimeter of fresh soil infusion able that further work should be done along 

to each, and were allowed to stand under the this line with other organic iron salts, such as 

same conditions as before for another period iron tartrate, iron formate, iron butyrate, irm\ 

of six weeks. malate, iron anunonium tartrate, iron magPrecipitation in the ferric ammonium citrate nesium citrate, and others. Only in this way' 

solution took place in about one week after is it possible to determine how general is the 

the inoculation, but in the other solutions the precipitation of insoluble iron compounds from 

precipitation was slower. At the end of six solutions of organic iron salts by microweeks, however, precipitates had forn1ed in organisms. Frmn the experiments performed 

all the iron solutions, and molds were growing ·it seems reasonable to suppose that it is fairly 

in the manganese solutions. The precipitate general and that in certain cases bacteria are 

from the ferric citrate solution was flocculent responsible and in other cases molds. 

and brownish yellow · in color and formed a 

coating over the layer of soil: The precipitates 

from the. other iron solutions (iron lactate, 

ferric oxalate, and ferric ammonium citrate) 

were very similar to those which occurred in 

the previous cultures that had not undergone 

sterilization. In general they formed brown, 

flocculent deposits. 

After obtaining precipitates from solutions 

containing organic iron inoculated with soil, 

under different conditions as described above, 

several attempts were made to obtain precipitates from solutions of these salts in natural 

waters. However, .no precipitation occurred, 

although some of the cultures were allowed 

to stand for six months at room temperature. 

At the end of this period only a slight turbidity was noticeable in some of them. 

Attempts to isolate bacteria which might 

cause precipitation of ferrjc hydrox_ide or insoluble basic ferric salts. from ferric oxalate 

and iron lactate solutions were also unsuccessful. Pure cultures of bacteria obtained from 

agar containing ferric ammonium citrate were 

transferred to slopes of Heyden Nahrstoff 

agar containing ferric oxalate and iron lactate, but no growth took place. Later plates 

of the same agar and also of plain bouillon 

agar were inoculated directly with a fresh infusion of soil, but no colonies either of bacteria 

or molds formed on the plates,· although plates 

of agar containing ferric ammonium citrate 

that were inoculated at the same time from 

the same soil infusion showed abundant 

PRECIPIT~TION OF FERRIC HYDROXIDE AND BASIO 

FERRIC SALTS FROl\f SOLUTIONS CONTAINING INORGANIC IRON. 

Several attempts were made to obtain, in solutions of inorganic iron salts, cultures of Lacteria from soil and natural waters other than 

the iron thread bacteria already described. It 

seemed possible that Sideroeapsa, described by 

Molisch 1 as being a very abundant water bacterium, or Bacillus M. 7, described by Mumford,2 might be cultivated in artificial media 

containing inorganic iron salts. It seemed possible also that other lower baeteria might exist 

in the soil or natural waters which could use 

constituents present in certain inorganic iron 

salts with the result that ferric hydroxide or 

basic ferric salts would he precipitated. Such 

a process would be analogous to that just described as occurring when ferric hydroxide or 

basic ferric_ salts are precipitated from solutions of organic iron salts through the action 

of microorganisms. 

However, my attempts to obtain· such cul~ 

tures have all been unsuccessful. Although 

precipitation of insoluble ferric compounds 

occurred in nearly all the inorganic iron solutions used, this precipitation seemed to be due 

to oxidation and hydrolysis or to hydrolysis 

alone, rather than to biologic processes. A 

1 Molisch, Hans, Die Eisenbakterien, pp. 11-14, 1910. 2 -Mumford, E. M., A new iron bacterium : Chern. Soc. 

Jour., vo!. 103, pp. 645-650, 1913. 
EXPERIMENTS ON PRECIPITATION OF IRON FROM SOLUTIONS BY BACTERIA. 39 

brief statement coricerning the solutions. used· 

and the results obtained is given below. 

The inorganic iron salts used in the experiInents were ferrous sulphate ( FeSO 4• 7H20), 

ferrous ammonium sulphate (FeS04(NH4) ~-

804.61-120), ferrous carbonate (FeC03 ), and 

ferric chloride (Fe2C1 6 .ni-I20). All of these 

solutions when allowed to stand where oxygen 

fron1 the titmosphere was accessible became 

oxidized or hydr.olyzed, forming yellow or yellowish-brown ochet'ous precipitates consisting 

either oi ferric hydroxide or of a mixture of 

ferric hydroxide and basic ferric salts. 

Attempts to make bacterial cultures in ferrous sulphate solutions were made ·with different strengths of solutions from very dilute to 

saturated. Yellowish-brown flocculent ocherous precipitates formed in all of them, and 

these were ·examined with the microscope from 

tbne to time for evidences- of the presence of 

microorga.nisms. The precipitates in general 

had a. granular appearance under the microscope, the granules being brownish yellow in 

color and somewhat rounded and fairly regular in size and·shape. }lowever, mixed with 

this granular material, many of the precipitates showed large irregular masses of a lightcolored, textureless colloidal substance, resembling in appearance, though not in color, the 

precipitates formed in solutions containing 

organic iron or those formed by adding ammonium hydroxide to inorganic ferric salts, 

such ns ferric chloride. The only organic 

forms found in the precipitates were scattered 

threads of mold-mycelia, which were found in 

one or two of them after standing for several 

weeks. · 

It seems possible, of course, that the flocculent granular precipitate itself was the result 

of bacterial action, as is the flocculent, reddishbrown precipitate which forms in the organic 

iron solutions. I-Iowever, with the inorganic 

iron salts sterilization apparently has no effect 

on the precipitating action, except that with 

some of them it hastens precipitation. 

J\1ontfort/ as has been stated (p. 9), claims 

that Leptotlurix. develops in solutions of ferrous sulphate, but I have not been able to 

identify it in my cultures. Up to the present 

time I have found no microorgar1isms with the 

1 Montfot·t:, W. F., Dry feed of chemicals in water purification: J"om·. Am. 'Vatenvorks Assoc., vol. 2, pp. 200-206, 

lOHi. 

exception ~f n1olds in any cultures prepared 

with inorganic iron salts except those containing ferrous bicarbonate. 

· The pr~cipitation of ferric hydroxide and 

basic· ferric salts from solutions of ferrous 

sulphate differed from that taking place in 

organic iron solutions likewise in that it was 

not complete. A flask containing 750 cubic 

centimeters of water in which were dissolved 

3.5 grams of ferrous sulphate was allowed to 

stand under oxidizing conditions for 6 months. 

An abundant precipitate of yellowish-brown 

ocherous material formed during this period, 

but much ferrous sulphate remained in solution at the end of this time, as was shown by the 

flocculent, light-green precipitate of ferrous 

hydroxide (Fe ( OH) 2 ), which formed upon 

the addition of ammonium hydroxide to the 

solution. 

An interesting experiment was performed 

with solutions of ferrous ammonium sulphate 

inoculated with soil. ·Three bottles each containing a solution of 2 grams of ferric ammonium sulphate in 300 cubic centimeters of 

water were inoculated with 20 grams of soil. 

One of the bottles was left where oxygen of 

the atmosphere had free access to the solution, 

but the other two, qne of which was sterilized, 

were attached to an apparatus generating carbon dioxide, and the solutions tliey contained 

were kept saturated with carbon dioxide~ Precipitation begari in the first bottle within 15 or 

20 minutes after the solution was prepared, 

and in two oi· three days. a deposit of yellowish-brown ocherous material covered the layer 

of soil and the inside of the bottle. The solutions .saturated with carbon dioxide, however, 

shmved no precipitation and no cloudiness, although they were left for several weeks . con- · 

nected with the apparatus that generated carbon dioxide. When they were finally disconnected, however, and _the solutions became ac-

·cessible to oxygen of the atmosphere a yellowish-brown, ocherous precipitate formed in a 

short time in both the sterilized and unsterilized solutions.· . This experiment showed 

that the precipitation of ferric hydroxide from 

solutions of ferrous ammonium sulphate ·was 

clue to simple oxidation and hydrolysis. 

Mumford describes the ~solation of~ bacillus 

from the water of the tunnels on the Bridgewater Canal, ne~r Worsley, Lancashire, Eng-
40 . IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

land, which is strongly charged with iron, ow- about 0.01 per cent. 2 It is much more satis-. 

ing to the. entr·ance of iron-bearing colliery factory, however, to work with natural ironwaters. He states that he made cultures of this bearing waters. The oxidation and precipita-

. organism in solutions of both ferric ammonium tion, .however, take place very rapidly in such 

citrate and ferrous ammonium sulphate; and waters. ·A natural solution of ferrous bicarfound that it precipitated ferric hydroxide i'n bonate which contained 5.0 parts per million 

24 to 36 hours at 37° C. The strength of the of ferric oxide in the form of ferrous bicarsolutions used was 0.05 per· cent, and they con- bonate was ·left in a bottle with a rubber stoptained 0.00;) per· cent of peptone. He states per. It soon became cloudy, and a yellowishthat in both solutions the precipitation took brown precipitate· began to form in about art 

place only under aerobic conditions and that hour and continued forming for several days. 

the precipitation was complete, no iron re- After about 10 days only 0.2 part per million 

maining in solution. Under anaerobic COllCli- of ferric oxide remained in solution. 'the pretions he found that precipitation did not take cipitate which formed 'vas examined microplace, but that freshly precipitated ferric hy- scopically and was found to consist of light 

drox'ide was changed under these· conditions to yellowish-brown semitransparent gelatinous 

black compact bog ore.1 ferric hydroxide with strands of iron thread 

The results obtained by Mumford with fer- bacteria, chiefly Leptothrix. The presence of 

ric ammonium citrate solutions are similar to the gelatinous ferric hydroxide would seem to 

those which I have already described as ob- oindicate that the precipitation at least in part 

tained with various solutions containing or- was due to simple oxidation. The presence of 

ganic iron, except that ·in my experiments I Leptothrix is explained by the fact that it 

was able to cause the precipitation both under occurred in the spring from. which the water 

aerobic and anaerobic conditions. In my ex- was taken. 

periments, also, the complete precipitation re- A dilute solution of ferric chloride in na.tquired a longer period of time. The results · ural water was allowed to stand at room ternobtained with ferrous ammonium sulphate, perature for several n1onths with free access of 

however, are difficult to understand, because, oxygen of the atmosphere. A brownish-yellow 

as I have shown, precipitation takes place in precipitate, probably ferric hydroxide, similar 

this solution under oxidizing conditions, to that which forms in inorganic ferrous soluwhether organisms are present or not, whereas tions, forn1ed in it. There was no evidence of 

in· the absence of oxygen precipitation appar- bacterial action. This precipitate is notable, 

ently does not take place. It is difficult to see for normally upon the oxidation of feiTic 

under what conditions lVIumford · conducted chloride by the addition o~ ammonimn hydroxhis experiments in order to determine that it ide a brownish-red, flocculent precipitate of 

was the organism and not simple oxidation ferric hydroxide forms. After two or three 

that caused the precipitation. months apparently no ferric. chloride remained 

Experimentation with solutions of ferrous in solution . 

. bicarbonate is somewhat difficult, because Qf 

the difficulty of getting ferrous carbonate into 

solution, and because of the small amount capable of being taken into solution even under 

favorable conditions. It is difficult also to retain it in solution because of its susceptibility 

to oxidation. A common way of obtaining 

solutions of ferrous bicarb.opate is to place iron 

filings in water which is kept saturated with 

carbon dioxide. In this manner ferrous bicarbonate may be ·obtained in solution up to 

PRECIPITATION OF FERROUS SULPHIDE FROl\:[ 

SOLUTIONS CONTAINING IRON. 

The precipitation of ferrous sulphide (FeS) . 

from iron-bearing solutions occ~u·s abundantly 

under the influence of microorganisms. It 

takes place under reducing conditions and 

usually in the presence of abundant decaying 

organic matter. The formation is usually due 

to the action of hydrogen ,sulphide (H2S), 

2 Lieske, Rudolf, Beitriige zur Kenntnis der Physiologie 

1 Mumford, E. M., A new iron bacterium : Chern. Soc. von Spirophyllu.rn jm-ruginettrn Ellis, einen typischen EisenJour., vol. 103, pp. 645-650, 1913. baktel'ium: Jahrb. wiss. Botanik, Band 49, pp. 91-127, 1911. 
BXPERIMENTS ON PRECIPITATION OF IRON FROM SOLUTIONS BY BACTERJA. 41 

formed under these conditions, on ferrous salts 

in solution, but may be due also in part to the 

reduction of iron salts. of sulphurous or sulphuric: :1cicl. Ferrous sulphide may be formed 

in four distinct ways. 1 ( 1) I-Iydrogen sulphide 

is commonly produced by the decomposition of 

sulphur-bearing proteins in organic matter, 

due to the action of various decay-producing 

bacteria. By reaction with a ferrous salt in 

solution ferrous suiphide is precipitatBd by it. 

(2) Certnin bacteria, commonly known as sulphate reducers, have the power, in the presence 

of decaying organic matter, of taking the oxygen away from sulphites, sulphates, or thiosulphates, and reducing them to sulphides. If 

these compounds happen to' be compounds of 

iron, ferrous sulphide is formed directly. (3) 

I:f, however, some other sulphide, such as €al-

.cium sulphide (CaS), is formed in this manner, it mny react with carbon dioxide and 

water to form hydrogen sulphide, according to 

the following reaction: 2 

CaS+C02+1I20=CaCOa+H2S 

The hyclrogen sulphide thus formed may then 

react upop ferrous salts in solution, precipitating ferrous sulphide. ( 4) Certain bacteria, 

in the presence of decaying organic matter, act 

directly upon free sulphur,· reducing it to hydrogen sulphide, which may precipitate ferrous 

sulphide (FeS), if iron salts are present. 

1-Iydrogen sulphide is formed from decaying sulphur-bearing proteins, either by processes of reduction or by the splitting off of 

the hydrogen sulphide molecule as a hydrolytic cleavage product. The power of producing hydrogen sulphide from protein is common 

not only tq practically all the putrefying bacteria but is possessed also by various other 

bacteria 'vhich use proteins as food. The formatim~ is accelerated by the absence of oxygen, 

and is nlso favorably influenced by the presence of peptone. 

The production of hydrogen sulphide from 

organic matter :may be shown by hangi;ng lead 

1 Omcllnnski, W., Dcr Krcislnuf des Schwefels, in F. Lafar's Hnndbuch det• Tccbnischen Mycologic, Band 3, pp. 

214-220, 1004-1006. 

Lipmnn, J. G., 'l\llcrobiology of soil, in l\larshall's Microbiology, pp. 288-290, 1912. 

Phelps, B. B., Microbiology of sewage, in Marshall's Mict·o-

.blolo~y, pp. 217-218, 1012. 2 Lipman, J. G., op. cit., p. 290. 

foil in a flask in which some organic matter is 

decomposing. Hydrogen sulphide will combine with lead, producing lead sulphide 

(PbS), which will form as a black coating 

on the lead foil. In solid media iron salts are 

used as indicators of the presence o'f hydrogen 

sulphide. Thus, 3 per cent of iron tartrate or 

iron saccharate in bouillon-peptone-gelatin indicates the presence of hydrogen-sulphide producers by the formation of iron-sulphide halos 

around the colonies. 3 

The method of the formation of hydrogen 

sulphide from decaying protein is not definitely known. If. formed as a product of reduction it may result from special activities 

inherent to the protoplasm of the Inicroorganisms or it may be due to the reducing action of 

other products, such as hydrogen, which microorganisms form. ''7here hydrogen sulphide 

forms as a direct cleavage product, it is supposed that the molecule was present in the 

protein as such and was released by bacterial 

action .. Ifowever, the composition of protein 

is very imperfectly understood, and its decomposition is largely a matter of conjecture. 

The reduction of sulphates, thiosulphates, 

and sulphites by sulphate-reducing bacteria 

commonly produces metallic sulphides but is 

usually accompanied also by the formation of 

considerable quantities of hydrogen sulphide. 

This is probably clue to th~ fact that carbon 

dioxide present acts upon the metallic sulphides immediately upon their formation, producing hydrogen sulphide. A considerable 

numb.er of bacteria probably have the power 

of reducing sulphates, among which the best 

known 4 are Vibrio hydrosulfureus· and B acterium l~ydrosulfureum ponticwm, isolated 

from the Black Sea muds by Selinsky and 

Brussilowsky, Proteus vulgaris and Bacillus 

mycoides, shown by N adson to reduce calcium 

1 

sulphate to calcium sulphide in the presence of 

a limited supply o£ oxygen, S1Jirillu1n desulfur~cans, proved by Beijerinck 5 to reduce· sulphates energetically, anc11Jficrospira aestuarii~ 

a form similar to Spirill'lilnu desulfWf'icarns, 

isolated by Van Delclen.. Of these organisms 

the first two besides reducing sulphates n.ls~ re3 Omelianski, W., op. cit,, pp. 214-216. 4 Idem, pp. 216-218. 5 Beijerlnck, l\:1., Spirilhun dcsttlphuricans: Centralbl. Bnk-

. teriologie, Abt. 2, Band 1, p. 1, 18D5. 
42 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC ·RELATIONS. 

duce thiosulphates when no organic sulphur 

is present, and the. last two, one of which 

(Spirillum desulfurica1U3) is a fresh-water 

form ·and the other a salt-water form, reduce 

sulphates, thiosulphates, and sulphites. Another organism, B aeterium sulfureum, has been 

found which reduces sodium thiosulphate. 

Judging. from the fact that some of the sulphate-reducing organisms work more effectively in the absence of organic sulphur com~ 

pounds, such as proteins, it appears that many 

of them are capable of decomposing organic 

sulphur compounds as well as of reducing sulphides. 

Thiosulphates ·and sulphites, according to 

Beijerinck, are reduced also when added to 

fermenting sugar solution or other yeast cui~ 

tures, sho,ving that yeasts as· well as bacteria 

have the power of sulphate reduction. 

Brussilowsky 1 isolated three varieties of bacteria which are chiefly concerned in the reducing processes characteristic of the black ferrous sulphide-bearing muds of limalfS: These 

grew on n1eat-peptone-agar and produced the 

characteristic odor of th~ liman mud. The 

principal one isolated was Vibrio hydrosulf'ureus. When oxidized gray liman mud in 

which this organism occurs was sterilized ·it 

was found to keep indefinitely, but upon inoculation with pure cultures it showed reduction 

and again turned black. A great many other 

anaerobic bacteria probably have the same 

power, the functions not being confined to a 

few species. 

An artificial medium for sulphate-reducing 

organisms was prepared by Brussilowsky by 

mixing a 2 per cent solution of aluminum 

chloride (AIC13 ) with a little ferric chloride 

and a little of a 0.33 per cent solution of thiosulphate, and adding ammonium hydroxide to 

make it alkaline: This, when inoculated with 

a bouillon culture of the bacteria, showed ferrous sulphide formation in 24 hours. 

N adson produced a reduction of sulphates 

with B accilus mycoides and Proteus vulgaris, 

under anaerobic conditions and in the presence 

of peptone. 

Beijerinck prepared cultures of sulphate reducers by using a medium consisting of ordinary ditch water and a small quantity of mineral salts, such as sodium carbonate, calcium, 

1 Omeliansld, W., op. cit., pp. 220-224. 

or magnesium sulphate, a~d ferrou,s ammonium 

sulphate, and traces of organic compounds 

such as sodium mal~te or asparagin. He 

found that small quantities of organic compounds were necessary in 01;der to supply carbon for the organism. Impure cultures in 

the absence of oxygen and at a temperature of 

25° to 30° C. showed reduction of sulphate, 

accompanied by the formation of an appreciable amount -of hydrogen sulphide in 12 to 

24 hours. Pure cultures of S1Jirillum desulfuricans were obtained. by him on plates of 

agar and gelatin prepared with the above -medimn. The organisn1 isolated is a slightly 

coiled Spirillum about 4 micra in length and 

1 micron in thickness. 

Microspira aestuarii was isolat~d later from 

salt. water by Van Delden. Its close resemblance to.Spirillwrn desulfuricansled to the belief that it might be the same form living under 

different conditions. The addition of gradually increasing quantities of common salt to · 

the culture solutions, however, was found to 

have entirely different effects on the two organisms. 

It was found that in pure cultures of these 

two microorganisms the amount of hydrogen 

sulphide formed 'vas very large, amounting 

to several hundred milligrams per liter of culture solutio.n. Pure cultures also thrive and 

react on sulphates in the presence .of a larger 

percentage of orgap.ic material, such as bouillon, than impure cultures, because there is no 

competition with ordinary putrefying bacteria, 

which otherwise crowd out the sulphate reducers. 

A good :medium to use for the detection and 

isolation of sulphate reducers is th~ one used 

by Prof. E. B . .Fred, of the University of' Wisconsin, for class work, as follows: 

Culture sohttion tor sttll)hate-redtteing bactet·ia. 

Water ___________________________________ } iter__ 1 

Ammoni mu sulphate ( ( NH4) 2S04) _______ grams__ 2 

Sodium lactate __________________________ do ____ 5 

Dibasic potassium phosphate (K2HPO.) ___ do____ . 5 

li'errous sulphate (FeS04) ------------------- Trace. 

'rhi.s medium may be placed in bottles and to 

it should be added a small amount of garden 

soil (1 gram) or of marsh slime ( 0.1 cubic 

centimeter). The bottles should be filled with 

the medium and then .corked a.nd rendered airtight by immersing the mouth and stopper in 
EXPERIMENTS ON PRECIPITATION OF IRON FROM SOLUTIONS BY BACTERIA. 43. 

hot paraffin. Upon incubating at 37° C. for 

three or four days a blackening of the solution 

takes0place, owing to the formation of ferro~s 

sulphide by the reduction of the sulphates 

preserit. After a period of several weeks the 

solution may be tested for sulphates by adding 

a little barimn chloride (BaCl2 ) to a sman 

mnount of the liquid culture poured into a test 

tube. If sulphat~s are still present. a white 

. precipitate of barium sulphate (BaS04 ) forms. 

In time all the sulphates present will be reduced. 

Pure cultures of the organisms may be obtained by using an agar· n1edium. This is prepared by adding 15 grams of agar to 1 liter 

of the liquid medimn described above. The 

sulphate agar medimn may be inoculated frmn 

the bottle cultures. After incubating for a 

few days colonies with black halos wiJl develop. Organisms from these colonies may 

then be reinoculated into sterile liquid media 

or on to other plates and pure cult1_1res thus 

obta,ined. 

The following medium developed by Freel 

wn.s found to be very satisfactory for obtaining cultures of sulphate-reducing organisms: 

Onlt1t1·c nu:idi1t1n for s1tl1Jhate-red1teing bacte1·ia .. 

Iron lactate (Fe ( 03H~On )2SH20) ______ grnms__ 5. 0 

Ammonium sulphate ( (NH.)2SO.) ______ do____ 2. 0 

Dlhnsic potassium phosphate (K2fiPO.) _do____ . 5 

Dlsti.Jied water _________ _. ___ cubic centimeters __ 1, 000 

A solid medium may be prepared with this 

solution by adding it to a 15 per cent bouillon 

gelatin and sterilizing in an autoclave at 10 

pounds pressure for .15 minutes. Colonies of 

sulphate-reducing bacteria growing on plates 

prepared from this medium will develop the 

characteristic dark halo clue to the formation 

of ferrous sulphide. 

· The physiology of sulphate-reducing bacteria is not yet thoroughly understood. Some 

investigators have claimed that the reducing 

action is not a property of any particular 

species of bacteria. but that it is due to nascent 

hydrogen, which is liberated by many anaerobic organisms. Others believe that the action 

is due to :methane liberated during the fermentation of cellulose by certain groups of 

organisms,. the reaction being 

C:H4+MS04=MC0a+li2S+I-I2 0 

Beijeri~ck rejects these· ex1~lanations and 

cites a number of experiments in ·which hydrogen or methane producing bacteria did not 

reduce sulphates and in which sulphate reducers did not reduce other substances, such as 

nitrates. This indicates that the property of 

reducing sulphates is a special characteristic 

of certain bacteria, which use the oxygen taken 

from the sulphates for the production of energy within their cells by the oxidation of carbon to carbon dioxide. The reaction may be as 

follows: 

MS04+2D=2C02+MS 

The sulphide maythen·be acted upon by carbon dioxide and water, and the production of 

hydrogen sulphide results according to the following equation: 

MS+C0 2+H20=H2S+MC0 3 

It is chiimed that hydrogen sulphide is also 

produced by bacteria by the reduction of free 

sulphur in the presence of organic matter.1 It · 

was noticed that sulphur present in cultures 

containing decomposing organic matter grad"' 

ually disappeared and that hydrogen sulphide, 

or, if iron salts were present, ferrous sulphide, 

formed abundantly. Thus "\tVinogradsky found 

that the sulphur granules of dead cell~ of sulphur bacteria, such as Beggiatoa, gradually disappeared during decomposition with the formation of. hydrogen sulphide. Later it was 

found that flowers of sulphur were attacked 

under the same conditions and that hydrogen 

sulphide was formed abundantly. 

Beijerinck prepared two flasks \vith meat 

bouillon containing 1 per cent iron lactate as 

indicator. The oxygen present was removed 

by boiling and then flowers of sulphur were 

added to one of them. After inoculation with 

impure bacterial cultures and. incubation for 24 

hours both solutions became black through the 

formation o{ ferrous sulphide, but though the. 

ferrous sulphide formation in the flask containing no free sulphur soon reached a limit 

that in the other flask continued for a long time 

and a large quantity of the hlac~{ precipitate 

was formed. · The formation of hydrogen sulphide from fre-e sulphur is believed to be a 

secondary process, resulting from the various 

1 Omelianskl, W., op. cit., pp. 219, 220. 
44 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

reactions which take place in decomposing 

organic matter. 

Associated with the hydrogen sulphide 

forming. and the sulphate-reducing bacteria is 

an important and very interesting group of 

organis1ns known as the Thiobaoteria or sulphur bacteria. A considerable number of morphologically different varieties of bacteria belong to this group, the principal members being the colorless varieties Thiothriw and Beggiatoa and the red or violet-colored varieties 

known collectively as Rhodobacteria. The sulphur bacteria have the power of oxidizing 

hydrogen sulphide to free sulphur and sulphuric acid, thus· obtaining energy for the 

assimilation of food. The sulphuric acid 

formed immediately unites with bases present 

to form sulphates. The food of these bacteria 

is derived from organic matter, while the oxygen necessary for the oxidation of hydrogen 

sulphide is derived from free oxygen dissolved 

in the water. · · 

As sulphur bacteria require both hydrogen 

sulphide and • oxygen, and as an increase in 

hydrogen sulphide in solution results in an 

expulsion of oxygen, there is a certain horizon in the solution where the oxygen, which 

comes down ·from the surface, and the hydrogen sulphide, which comes up from the decaying organic matter on the bottom, are both 

present in the right proportions for these organisms to thri-\re on. At this horizon they 

form a platelike film, and it is below this film 

that sulphate-reducing and hydrogen sulphide 

forming bacteria are most active. 

J egunow 1 found that in limans (see p. 63), 

'vhere the water is shallow and the mud is grayish and slightly oxidized, the sulphur bacteria 

lie on the bottom. With increasing depth and 

decrease of oxygen, the sulphur bacteria are 

forced to leave the bottom and form a thin 

layer through the water, while the mud becomes black in consequence. He believes that 

such a layer of·bacteria.is probably found over 

the entire Black Sea. at a depth of about 2.00 

meters. 

Laboratory cultures made of black liman 

muds in water in a high glass jar showed a 

cloudy platelike swarm of organisms 0.2 to 0.3 

millimeter thick in the water. The height of 

1 .Jegnnow, 1\f., Bakterien-Gesellschaften : Centralbl. Bakteriologie, A.bt. 2, Band 2, p. 20, 1896. 

this layer above the mud depended· on the 

amount of hydrogen sulphide formed. vVhen 

it. sank down to the mud the mud becam~ gra.y 

through oxidation, but upon the exclusion of 

oxygen it again became black and the swarm 

layer rose in the water. 

The sulphates formed abundantly by the sulphur bacteria from hydrogen sulphide are attacked by the associated sulphate-reducing 

bacteria and are again reduced to sulphides . 

and hydrogen sulphide, thus n1aking a com-' 

plete cycle. If ferrous or manganese sulphide 

are formed, they are precipitated. 

GEOLOGIC IMPORTANCE OF IRON-DEPOSITING 

BACTERIA. 

IRON IN THE EARTH'S CRUST. 

In a study of the deposition of sedimentary 

iron-ore deposits there are four important 

points to consider: ( 1) The source and the 

manner of solution of iron compounds, (2) the 

transportation of iron- compounds, (3) the 

manner of deposition of iron compounds, and 

(4) the conditions under 'vhich iron compounds are deposited. 

Iron is abundant in the earth's crust in both 

the ferrous and ferric forms. Ferrous iron occurs in nearly all rocks. In the original crystalline rocks, such as granite, diorite, gabbro, 

pyroxenite, and peridotite, ferrous iron forms 

an important con~tituent of the ferromagnesian silicates, mainly biotite, amphibole, pyroxene, olivine, and chlorite. It is also present in 

the oxides of iron, n1a~etite and ilmenite, 

which form a noticeable percentage of the more· 

basic crystalli_ne rocks. In sedimentary rocks 

ferrous iron is present in original undecomposed silicates that occur in shales and graywacke, in secondary silicates, and also in secondary iron carbonate, which occurs in varying 

abundance in nearly all sedimentary rocks. In 

·metamorphic rocks ferrous iron occurs mainly 

in the secondary iron silicates, especially in bio- · 

tite, amphibole, chlorite, and garnet, but to 

so~e extent it is also present as recrystallized 

iron carbonate. 

Ferric iron occurs in original crystalline 

rocks, mainly as the oxides magnetite, hematite, and ilmenite, but it is also found in 

smaller -amounts in some of the silicates, such 

as biotite, amphibole, pyroxene, and epidote. 
GEOLOGIC IMPORTANCE OF IRON -DEPOSITING BACTERIA. 45 

In sedimentary rocks it is found mainly as the 

oxides hematite and limonite, and in some iron 

silicates, such as glauconite, and in nletamorpl~osed sediments it occurs as the oxides hematite and 1nagnetite and in the silicates biotite, 

amphibole, n,nd garnet. 

In addition to these 1ninerals, iron is present :in nearly all rocks in the form of the sulphides pyrite or marcasite, and occasionally in 

basic igneous rocks as pyrrhotite. 

Thus iron is one of the n1ost abundant and 

wiefely distributed metals on the surface of 

the earth, the only metal exceeding it in abundance being aluminum. In Clarke's average 

analysis of the earth's crust to a depth of 10 

miles,t ferrous ttnd ferric oxide, con.sidered together, rank third in abundance of all the oxides, being exceeded only by silica and alumina. 

The principal constituents in the average rock 

and in the avernge igneous rock as given by 

Clarke, rank as follows : 

Cont,posU·ion of altJem,ge 1·ooli; of the ea,1·th's ernst ana of woe1·a,go ·igneo·us rock. 

Si02 •••••••••••••••••• : ••••••••••••••• 

~!§.a:.'.' .... .': ~ : : ~ : : : : : : : : : : : : : : : : : : : : : : 

1\fgO .............. · ................... . ]<'eO •••.............................. Na..,O .......... ~ ..................... . 1(20 .. ·.· ............................ . 

]~~§.a: ~ ~ ·. ~ .. .': : : : : : : : : : : : : : : : : : : : : : : : : : 

Afl other constituents ................ . 

Average Average 

rock.a igneous 

rock. 

59.77 

14. 89 

4.86 

3. 74 

3.39 

3.25 

2.98 

2:69 

2.02 

2.41 

59. 83 

14.98 

4.'84 

3.81 

3.46 

3.36 

2. 99 

·2. 65 

1.89 

2. 19 

100.00 100.00 

nTJl tho avemgo rock which 1 according to Clarke, represents the 

earth's crust to a depth of 10 nulcs, ·the following percentages of igne- ous and sedimentary rocks arc taken: Igneous, 95 per cent; shale, 4 per cent; sandstone, 0.75 per cent; limestone, 0.25 per cent. 

DI~COl\f~O.Srl.'ION 01" IUON-BEAlUNG MINERALS. 

vVhen the rocks forming the earth's crust 

suffer disintegration and decomposition in their 

change to soil the iron compounds are dissolved by the action of the acids that are present in surface and ground waters. These acids 

are pdncipally carbonic acid (H2C03 ) and 

various organic acids, such as butyric, propionic, formic, lactic, acetic, citric, tartaric, 

valerianic, and the lit.tle:.known humic acids. 

t Clnrl;:e, 1!'. W., '.rhe data of geochemistry, 3d ed. : U. S. 

(;col. Sut·vey Bu:ll. 616, p. 32, 1916. 

Van Rise 2 n1entions the common occurrence in 

the soil of certain other organic acids, such as 

crenic, apocrenic, and ulmic acids. Inorganic 

acids are present" in the soil in small quantities 

and occur more or less loca.Ily. The principal 

ones probably are nitrous, nitric, sulphuric, 

and perhaps hydrochloric. Phosphoric and 

silicic acids also are present, but they are not 

important in processes of rock decay. 

The presence of these gases and acids in the 

soil results from two conditions: First, and 

most important, is the ~ecay of organic matter, due to bacterial action, and, second, is the 

·decomposition of inorganic material, due to 

chemical agencies, which in part also owe their 

origin to .bacterial action. 

Carbon dioxide, which is the most important 

of these agents in the process of rock decay, is 

in part derived from the decomposition of carbonates, due to the action of acids, but mainly 

it i.s derived from the decay o£ organic carbon 

compounds under the action of various fe.l:.'-

menting and decay-producing microorganisms,. 

such as bacteria, yeasts, and molds. 

The carbon in animals and plants may be in 

the form of carbohydrates, fats, or proteins. 

Carbohydrates, in which form by far the most 

carbon occurs in nature, are decomposed to carbon dioxide and water by the action of certain 

hydrolytic enzymes, commoi1ly produced by various organisms, the decomposition taking 

place in a s~ries of steps as is shown by the follmving formulae, which illustrate acetic fermentation as an example. Decomposition to 

other fatty acids, such as lactic, tartaric, and 

butyric, goes on along similar .Jines. 

(Starch.J . ~ouble sugar.) 

2Cul-Ito0s + H20- C12H22ou . (Single sugars.) 

Ct2FJ220u + H20 = C6H1206 + C6I-I1206 

(Alcohol.) · 

C6Ht20o = 2C2H50I-I + 2002 · {:_<\cetic aldehyde] 

C2HsOH + 0 = C2H40 + H20 

(Acetic acid.) 

02I-I40 + 0 = C2H40 2 

C2H40 2 + 40 = 2C02 + 2H20 

The ?h~nge from starch to the double sugars, 

maltose, saccharose, or lactose, is due to the 

action of the enzyme diastase produced by all 

green plants, many molds, and a few bacteria. 

Tlw decomposition from double sugars to single. 

2 Van Rise, C. R., A treatise on metamorphism: U. S. Geol. 

Survey Mon. 47, pp. 461-462, 1004. 
46 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. . 

sugars is due to the action of the enzymes maltase, invertase, and lactase, each acting on a special sugar. These three enzymes differ in dis:-

tribution but in general are· present in green 

plants and in various microorganisms. Single 

sugars are acted upon directly by fermenting 

enzymes, the change to alcohol being due mainly 

to the action of yeasts, and the further decomposition of alcohol to fatty acids and carbon 

dioxide taking place under the action of bacteria and molds. The principal acids formed 

in this manner in the soil are butyric, pro pionic, acetic,· formic, and lactic acids. · The end 

products of the fermentation are large quanti..: 

ties of carbon dioxide· and water: 

Though these changes are the typical. ones 

through which most carbohydrates pass in the 

process of decomposition, many irregularities 

and variations occur. .Cellulose,. for example, 

which is probably the most abundant carbohydrate in the soil, is decomposed by a special 

group of microorganisms known .as cellulose. 

. fermenters. During the decomposition it may 

be changed directly to fatty acids, or it may 

be changed first to sugar and then to different 

gases, such as methane, hydrogen, and carbon 

dioxide. 

The carbon in fats and proteins also suffers 

the change to fatty acids and carbon dioxide. 

The decomposition· of the ·proteins, however, 

ia very complex, and many little known compounds, including those of nitrogen, sulph_ur, 

and phosphorus, are formed during the process. 

The carbonaceous material that resists de, 

composition by fermenting and decay-producing microorganisms collects in· the soil in the 

_form of humus. Humus consists mainly of 

cellulose, which is the most difficult of the different forms of organic carbon to decompose. 

·The fu.rther decomposition of humus goes on 

very gradually, and during the process the different gases and organic acids already men-· 

tioned are produced, as well as humic acids. 

The composition of humic acids is not well 

understood, but it is now supposed that they 

are colloidal mixtures of various complex organic acids or of their acid salts.1 Humus, 

therefore~ acts as a constant source of soil acids 

and gases. Humic· acids and their acid salts 

(humates) may be so abundant as to cause 

·acidity of the soil in places where bases are not 

1 Lipman, J. G., Microbiology of soil, in Marshall's Microbi~logy, p. 250, 1912. 

present in sufficient quantity to neutra1ize the 

acids produced. _ 

Inorganic acids in the soil are i~ part derived from the decomposition of certain minerals, such as sulphides, sulphates, and chlorides, and when so derived are local in their 

occurrence. Nitrous and sulphuric acids, however, are produced also during certain very 

important soil processes known as nitrification 

and sulphur oxidation. 

The nitrogen content of proteins, urea, and 

other nitrogenous organic· compounds_ is 

changed during decomposition by ammonifying bacteria ·into the form of ammonia (NI-13 ). 

The aminonia is acted upon by nitrifying bacteria, and. the nitrogen is oxidized first to the 

nitrous and then to the nitric form. During 

the first p~rt of the process nitrous acid is 

'formed from ammonia, and this immediately 

reacts upon bases present in the soil to form 

nitrites, which are then oxidized to nitrates. 

Thus the nitrogen, and the bases with which it 

oombines, were first present in a relatively insoluble form and have been changed by bacterial action to soluble nitrates, in this manner 

hastening rock decomposition. 

Sulphur oxidation in general is very similar 

to nitrification. During the putrefaction and 

decay of sulphur-containing organic n1atter by 

ordinary putrefying bacteria, sulphur is liberated in the form of hydrogen sulphide (H2 S). 

This gas is oxidized by a special group of bacteria, the sulphur bacteria, .first into free sulphur and then into ·sulphuric acid. The sulphuric acid immediately reacts upon the bases 

present to form sulphates, which for the most 

part are more or less soluble. 

Thus it is clear that processes of bacterial decomposition are of unusual importance in promoting rock decay. They not only result in the 

for~1ation of most of the carbon dioxide produced in the soil but ·also of many organic and 

a few inorganic acids, which locally become of 

importance ~n promoting decomposition. 

By far the most abundant of the acids i~ the 

soil is carbonic acid or carbon dioxide. Although relatively wea.k, its abundance and continued action cause most metals, including 

iron, to be taken into solu~ion in the form of 

carbonates. Nearly all ferrous compounds, but 

especially ferrous ·carbonate, are readily acted 

upon by carbonic acid dissolved in meteoric 
GEOLOGIC IMPORTANCE OF IRO~ -DEPOSITING BACTERIA. 47 

water, are· taken into solution in the form of 

carbonate or b:icn,rbonate, and are' carried thus 

as long as the wn,ters contain an excess of carbon dioxide in soh1tion. J\.Ioody 1 says that carbonic acid exerts a greater corrosive influence 

on iron than equivnJent amounts of hydrochloric or sulphuric acids. Some compounds 

of iron, however, especially ferric oxide, 

are pract:icaJly insoh1ble in waters that carry 

only carbon dioxide, and in the solution of 

these compounds various other soil acids and 

decitying organic matter become effective. 

There is little doubt, therefore, that all iron 

com.pouncls, even the most ~nsoluble, such as 

ferric oxide, are acted upon to some extent by 

soil waters, especially :if decaying organic matter :is present. The intensity of the action differs in different places according to the compos:ition of the water, and this depends more or 

less upon the character of the soil .or rocks 

through which the 'vater passes and upon the 

presence o:f vegetation. ':(he influence of rock 

compos:ition is well iUustrated by certain rocks 

which are rich in ferric oxide and co11tain locally particles or bunches of sulphide of iron. 

In the neighborhood of the decomposing iron 

s~llphide the ferriy oxide is commoJ;!ly reduced, 

by the liberated· sulphuric acid, to the ferrous 

form, which is indicated by a change in color 

from yellow or red to white or.green. The influence of vegetation is shown in some bog 

limonite deposits, where in places near abundant decomposing orgnnic matter, such as rotting logs, the yellow bog scum is often bleached 

to a white or green color. This reduction is 

proba:bly in part clue to organic acids, which 

nrc abundant under these conditions, and in 

part to the action of decomposing organic matter, which requires oxygen and takes some of it 

from the ferric oxide. IGndler,2 as early as 

1836, cnJlecl attention to the fact that decaying 

vegetable matter has a marked effect on the 

solubility of ferric hydroxide. He noticed that 

ferruginous quartzose sand was rendered colorJess around . decaying roots and in a few 

months became. as white as if it had been 

treated by an acid. A root one-sixth of an 

inch in cliam~ter, upon decaying, whitened the 

sand to a distance of 1 to 2 inches around it. 

This action is ascribed to . organic acids pro11\loody, G. T., ~L'he rusting of iron : Chern. Soc. Jour., Yol. 

80, p[}. 720 et: seq., 1906. 2 Poggcndorff's Annalen, Band 37, p. 203, 1836. 

duced during the decay. Ferric hydroxides are· 

in this manner reduced to the protoxide, which 

at the same time combines with carbon dioxide 

to form carbonate. Iron carbonate· becomes 

soluble and remains in solution in the presence 

of excess carbon dioxide. 

The decomposition of iron sulphides, which 

is caused principally by partial oxidation, 

probably results in the formation of soluble 

ferrous and ferric sulphates. These sulphates 

may be carried in solutiop. for some time if 

conditions are favorable. They are not very 

stable, however, and upon further oxidation 

and hydrolysis for ·the ferrous or simple hydrolysis for the ferric su~phate, they readily 

change to ferrie hydroxide or to insoluble basic 

ferric sulphates. 

•According to the extent to which organic 

acids are present iron may be carried in solution as salts of these acids. It. is not impossible that such organic salts as iron formate, 

iron butyrate, iron lactate, or iron· citrate may 

occur in iron-bearing waters. Aschan 3 is of 

the. opinion that great quantities of iron are 

carried in solution as soluble ferrohumates and 

ferrihumates a.nd that .humus. compounds are 

largely instrmpental in the formation of bog 

iron ore deposits,.being active both in the solution of iron compounds and in their subsequent 

precipitation. He believes that the dark color 

of streams that pass through· regions of abundant vegetation is largely. due to the presence 

of humus compounds. · 

Once the iron is reduced to a form in which 

it is soluble in water it may be taken into solution and carried a greater or less distance depending upon the change in composition suf. 

fered by the water. It. is generally suppqsed, 

probably with sufficient reason, that iron is 

·carried in solution mainly as ferrous bicarbonate and is kept in solution as long as the 

waters retain an abundance of C.:'trbon dioxide. 

Among the iron-bearing waters analyzed many 

have been found which contain no sulphate 

or other acid radicle besides the carbo11ate, 

thus showing conclusively that at least in 

these waters iron was carried as the soluble 

carbonate. It is quite possible, however, 

that· iron is carried to some extent also in 

other forms, perhaps as :ferrous or :ferric 

3 Aschan, Ossian, Die Bedeutung der wasseriOsllchen Humusstoffe fiir die Bildung der See und Sumpferze : Zeitscbr. 

prakt. Geologie, Jo.hrg. 15, p. 56, 190i. 

• 
• 

48 IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

· sulphate or as compounds of some of the 

organic acids. 

The waters of many streams, springs, and 

lakes contain much iron in solution, as has 

been shown by analysis, by the fact that flocculent precipitates of ferric hydroxides occur· in 

them, that iridescent films of limonite form 

O:t:l their surface~ and by the fact that objects with which they come in contact cOinmonly b'ecome coated with limonite. Thus, 

although it is undoubtedly. true that ferric 

oxide, which is soluble with great difficulty, 

forms in abundance by the oxidation of other 

iron compounds and along with alumina 

and other insoluble substances becomes concen.tr~ted in residual soHs, still it is certain 

that acids capable of taking and retaining 

iron salts in solution are abundantly present 

in soil waters and a large amount of iron is 

undoubtedly carried away by surface waters 

and redeposited elsewh~re. 

!J'YPES OF SEDIMENTARY IRON ORES AND IRON 

FOR)\IA TIONS. 

GENERAL FEATURES. 

Iron may be precipitated from natural solutions under ordinary conditions of sedimentation either by chemical or· by biologic agencies. The precipitates may occur in any one 

of the following forms: Ferric hydroxides, 

ferrous carbonate, ~1ydrous ferrous and ferric 

silicates b£ several kinds, iron phosphates, 

basic ferric sulphates, ferrous sulphide, and 

perhaps iron clisulphide. 

In the formation and accumulation of deposits of ferric hydroxide biologic agencies 

play a most important part, though chemical 

act!on is undoubtedly of great importance as 

well. Iron sulphide also may be formed either 

chemically or by the action of 1nicroorgani~ms. 

Ferrous carbonate and iron silicates, however, 

are not definitely known to be precipitated by 

organisq1s. They are probably chemical precipitates, the presence of organic matter being 

commonly an. important factor in their formation. Iron phosphates and basic ferric sulphates are chemical precipitates. 

Iron may be precipitated under many conclitions. Usually it is taken into solution by 

ground waters that contain carbon dioxide in 

their passage through soil and rock, and in 

general it remains in solution as long as the 

water retains an excess of carbon dioxide. 

Under ordinary conditions ground waters lose 

their carbon dioxide and become saturated 

with oxygen soon after they readi the surface, 

and the iron is deposited as ferric hydroxide. 

Iron bacteria are nearly always present under 

these conditions and not only aid in the precipitation but play an important part in the_ 

accumulation of the precipitated m.aterial. If 

the iron-bearing waters reach the surface in 

localities where abundant vegetation and decaying organic matter are present they may 

not become saturated with oxygen, but the 

solvent carbon dioxide may be taken up by the 

growing plants. In such localities the iron is 

predpitated as ferrous carbonate. If alkaline 

silicates are abundant in the water ferrous silicates may be formed. If phosphorus is present 

it is usually precipitated 'vith the iron. 

In localities where conditions are such that 

the iron is not chemically oxidized, when the 

iron-bearing waters_ come to the surface and 

when carbon diqxide is formed in sufficient 

abundance to retain the iron in solution, iron 

bacteria may be the agency in precipitation. 

Such conditions probably exist to some extent 

also in larger underground openings, such as 

caves and fissures, and un~ler these circmnstances. certain subsurface concentration deposits of brown iron ore 1nay be formed. \Vhen 

iron is carried in solution in the form of soluble humates or other salts of organic acids, 

iron..:precipitating bacteria may also play an 

important part in its deposition. 

The accumulation of iron precipitates usually takes place in quiet waters, such as bogs, 

1narshes, lakes, and lagoons. Often, however, 

deposition occurs where iron-bearing waters 

issue from the ground and where they usually 

flow quite rapidly in little streams and rivulets: Some of the iron precipitated under this 

condition is doubtless carried along 1nechanically as little flocculent masses and is finally 

deposited in quiet water, where it may accumulate. Much of it, however, is doubtless lost 

in the mas:3 of other sediments, so that only a 

relatively small proportion of the iron dissolved and carried in solution by ground waters 

is actually accumulated in the form of ironore deposits. 

Sedimentary iron ores and iron ores derived 

directly from iron-bearing sediments by concentration are of great importance commer-
GEOLOGIC IMPORTANCE OF IRON-DEPOSITING BACTERIA. 49 

cially. Deposits of this nature occur on nearly 

all the continents, ai1d probably more than 90 

per cent of the iron ore that is being produced 

at the present time is of thi,s type. Such ores 

consist of hernatite, limonite, or iron carbonate, 

the first two being by far the most important. 

DEPOSITS ORIGINALLY LAID DOWN MAINLY AS FERRIC 

HYDROXIDE. 

Ferric hydroxides or hydrated ferric oxides 

a.re probably the most important iron compounds that play a pa:r;t in processes of sedimentation. The follo,ving table shows the 

composition of ~nhydrous ferric oxide and of 

the ferric hydroxides which are known to occur in nature: 

Ohcn1-ioaZ composi.tion of ferric oxide and the ferric 

hydroxides that ocaur in nature. 

--------------1---------

Hematite pe~0 ) ••••••••••••••••••• 

Tm·gite (2li .1Iz~ ... · · · · · · · · · · · · G?ethi~e (Fe10 3 .H20 ............ · ... . Lunomte (214 e20 3 .3 · 20) ............ . Xa.nthosiderite (Fe20 3.2H20) ....... . Limnite (Fe20 3 .3H20) .............. . 

70.0 30.0 

66:3 28.4 

62.9 . 27.0 

59.8 25.7 

57.1 24.5 

52.3 22.4 

0.0 

5.3 

10. 1 

14.5 

18.4 

25.3 

Most of the deposits of bedded hematite, as 

well a·s deposits of bog ore and beds of brown 

iron qre, were probably originally la~d down 

in the form of limonite, associated with other 

:ferric hydroxides and ferrous carbonate and 

locally accompanied by minor quantities of 

other iron compounds, such as phosphate, 

silicates, or sulphide. The ferric hydroxides 

that are probably most abundantly associated 

with limonite in freshly deposited iron sediments are xanthosiderite and limnite, both of 

which have been found in bog ores of recent 

origin which also carry impurities such as organic acids, phosphoric acid, and clastic material. In older iron-ore beds the hydroxides 

that contain less water appear to be more commonly associated with limonite, and in many 

of them only slightly hydrated hematite is the 

most important constituent. Deposits which 

are composed mainly of a mixture of various 

ferric hydroxides are commonlJ. known as 

limonite or brown iron ore deposits. 

I-Iematite mid limonite of sedimentary origin 

are distributed in many parts of the world, and 

65629°-19---4 

one or both of them occur in many important 

iron-ore deposits and iron-bearing formations. 

Among deposits which are formed wholly or 

in part by ferric oxide oi: hydroxide of original sedimentary origin are the Clinton hematite beds of the eastern United States, the Wabana iron-ore beds of Newfoundland, the ironbearing formation of the Lake Superior region, 

the hematitic quartzite and associated bedded 

hematite of Minas Geraes, Brazil, the banded 

jasper and associated hematite of India, the 

extensive Jurassic oolitic limonite ores of Lorraine and Luxembourg, and the widely distributed bog and lake ores·. 

Beds· and lenses of iron ore of Clinton (Silurian) age occur in many parts of the Appalachian region in eastern United States, extending frmn New York as far south as Alabama.1 

The ores are interbedded with shale and sandstone. In some places only one bed is found, 

but in other places three or four beds occur 

one above the other and separated from each 

other by clastic sediments.·· In m~ny places 

lenses of clastic material occur within iron-ore 

beds. The iron-ore layers themselves range in 

thickness fron1 a few inches to 40 feet, and 

single beds may extend along the strike of the 

rocks for n1any miles. As n1ost of them. occur 

in a region of folded rocks they have attitudes 

ranging from horizontal to vertical. 

The Clinton ore beds are composed principally of three classes ~of ore-(1) oolitic, (2) 

fossil, and ( 3) finely granular or. textureless 

ore. By far the larger part of the ore beds is 

formed by oolites, but locally fossils are very 

abundant· in the ore beds, and in places may 

even form the principal part of them. Finely 

granular material is nearly everywhere present in small amount, and in places forms definite lenses within the oolitic or fossiliferous 

material. Locally ferruginous pebbles occur 

near the· base .of the ore beds. 

The ore is mainly ferric oxide and contains 

calcium carbonate and . silica as impurities. 

1 Burchard, E. F., Butts, Charles, and Eckel, E. C., Iron 

ores, fuels, and fluxes of the Birmingham district, Ala. : 

U. S. Geol. Survey Bull. 400, 1910. 

Burchard, E. F., Preliminary report on the red iron ores 

of east Tennessee, northeast Alabama, and northwest 

Georgia: U. S. Gcol. Survey Bull. 540, pp. 270-328, 1!)14; 

'l'he red iron orcs of Tennessee: Tennessee Geol. Survey Bull. 

16, 1913. 

Newland, D. H., and Hurtnagcl, C. A., Iron ores of the 

Clinton formatien in New York: New York State Mus. Bull. 

123, 1908. ' 
50 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

The vvater content of the hard ore. which has 

not suffered surface weathering is remarkably 

low, being on the average only about 0.5 per 

cent. Even in the weathered surface ore the 

water content averages only from 2 to 3 per 

cent. Roughly the composition of the hard 

unweathered ore is as follows: 

Composition of hard 1tnweathered Clinton iron ore. 

Fe2o~--------------------~------------------- 52 

CaCOa---------------r----------------------- 34 

Si02-------------------~--------------------- 10 

Al20s----------------------------------------- 3.5 

II20----------------------------------------- .5 

lJpon weathering the calcium carbonate is removed, causing a proportionate increase o-f the 

remaining constituents and commonly increasing the ferric oxide content to 70 per cent. 

There is an increase in water in the weathered 

ore because of hydration. 

The spherules in the Clinton oo-litic ore on 

being examined microscopically are seen to 

consist of ·a nucleus of quartz or· shell fragment around which are concentric alternate 

layers of hematite and silica or of hematite 

and calcite. Many spherules contain a green 

mineral, supposed to be an iron silicate, in the 

center. The matrix separating the spherules· 

is largely calcite and detrital quartz. 

Three principal hypotheses have been offered 

for the origin of the Clinton iron ore. The one 

most generally accepted is that the beds were 

originally laid down, together with the inclosing rocks, in much the. same form in which 

they now occur.1 The iron is supposed to have 

been precipitated as ferric hydroxide and later, 

owing to compression, to have been dehydrated. The oolites were probably formed immediately after deposition, while the ferric 

hydroxide was still in a flocculent form. The 

replacement of much of the calcium carbonate 

in the fossils present is believed ·to have taken 

place during the deposition. The second hypothesis is that the present hema:tite layers represent original beds of limestone, which have 

been replaced at some later period by iron. 

brought in hy percolating waters. By this 

hypothesis it is difficult to explain the regularity of the beds as well as the absence of similar 

1 Smyth, C. H., jr., On the Clinton iron ore: Am. Jour. 

Sci., 3d ser., vol. 43, p. 487, 1892. • 

replacen1ei?-t phenomena with reference to other 

limestone beds in the region. AccordinO' to the 

th!rd hypothesis 2 the ore beds were originally 

laid down as glauconite, which was . subse .. 

quently leached of some of its in1purities and 

oxidized to hematite. As evidence is given the 

fact that unaltered remnants of a green mineral, supposed to be an iron .silicate, occur in. 

some of the spherules composing the oolitic ore. 

The W abana iron ore 3 is found in beds 

which outcrop on Bell Island in Conception 

Bay in the eastern part of Newfoundland. The 

beds dip northwestward underneath the waters 

of the bay at angles that range from 8° to 10°. 

Many individual beds range in thickness frmn 

mere sea-ms to 30 feet or more. They are scattered through about 1,000 feet of strata, but 

they are more or less grouped into zones which· 

are separated by zones of barren rock. . The 

thickest one of the barren zones is 600 feet in 

thiclmess. Though the individual ore layers 

differ in thickness from place to place, the ore 

zones are very continuous. The inclosing rock$ 

are indurated sandstones, shales, and slates of 

Arenig t() Llandeilo age (Ordovician). 

The principal ore mineral is hematite, with 

which chamosite, an .aluminous ferrous silicate, 

is abundantly associated. Siderite forms a 

considerable proportion of the ore beds locally 

and quartz occurs as detrital fragments. Fossil fragments of shells, mainly brachiopods, 

consisting of calcium phosphate, occur throughout the ore and tubes of boring algae are very 

abundant. 

The great mass of the ore has an oolitic texture, being composed of fine. spherules of 

mixed hematite and chamosite, generally 

somewhat flattened parallel to the bedding. 

Microscopically the individual s·pherules are· 

seen to consist of alternate layers of hematite 

and chamosite arranged concentrically about a 

center which may be detrital quartz, a shell 

fragment, or chamosite. Locally the spherules 

may consist almost entirely of chamosite and 

elsewhere of hematite. The matrix between 

the spherules is generally chamosite, but hematite, quartz, or siderite may replace it in part 

or entire~y. 

2 1\fcC.allie, S. ·w., Report on the fossil iron ores of Georgia: 

Georgia Geol. Survey Bull. 17, 1908. 8 Hayes, A. D., "'abana iron ores of Newfoundland : Canada Geol. Survey, Dept. Mines, Mem. 78, 1915. 
GEOLOGIC IMPORTANCE OF IRON-DEPOSITING BACTERIA. 51 

The range in composition of the vVabana from the sideritic chert and ferrous silicate 

iron ores is as follows: rock, and the ·iron ore is· believed to have been 

derived from the hematitic and limonitic chert 

by the leaching and removal of silica under the 

Per cent. · fl 111 u~nce of meteoric waters. The iron-bearing Hemtltite ____ ·-------------------------------- 5Q-70 

Minera.l co1n1JosUion of ll'C£bana i1·on ores. 

Chamosite ___________________________________ 15-25 

Siderite_____________________________________ Q-50 

Cnlciunt phosp_hnte___________________________ 4-5 

Qunrt:r.______________________________________ Q-10 

Calcite______________________________________ o-1· · 

formation was, therefore, for the most part 

laid down originally as sediments that consolidated iJ?.to -sideritic chert, siderl.tic slate, and 

greenalite rock. In association with :these 

rocks, however, there were locally deposited 

Iri contrast to the Clinton ores and to the ·beds and lenses of original ferric oxide or hyoolitic limoni~ of northern France and south~ drated ferric oxide and silica which upon conern Gern1any described later, these o.~;es con- solidation form~d a rock very similar in all 

tain little or no calcium carbonate but instead respects to the hematitic and limonitic chert 

contain abunda:nt calcium phosphate. formed by the secondary alteration. of the 

The ores are supposed to be primary bedded sideritic chert and greenalite ~ock. In places 

deposits, originally laid clown with the inclos- layers of_ original relatively pure hematite ore 

ing clastic sediments in much_ the same form are found with these beds, which in their charin which they occur now, the hematite and acter and manner of_ origin probably resemble 

chamosite being deposited at the same time the Clinton ml.d 'Vabana iron ores. 

but perhaps under slightly different condi- In the State of Minas Geraes, in southeastern 

tions. The spherules are supposed to have re- Brazil, there are extensive .beds of so-called 

suited frmn the action of surface tension on the "itabirite," an iron oxide bearing quartzite, 

fine unconsolidated sediments. Boring algae that contains intercalated beds and lenses . of 

presumably played an important part in the ferruginous schist and of pure hematite. 2 The 

ore formation. Tubes of these organisms pene- itabirite in general is a thinly laminated rock 

trate both spherules and matrix and seem to that consists of alternating layers of quartz sand 

have thrived during the ore deposition.· It is and iron oxide. In places, however, these two 

thought that they 1nay be responsible :for part constituents are irregularly intermixed, forming 

of the oxidation to hematite. a granular rock. The"itabirite and associated 

In the Lake Superior region extensive beds iron ore and schist are interbedded with metaof iron-bearing formation of pre-Cambrian age morphosed sedimentary rocks of probable preare found, interlayered with meta.morphosed Cambrian age. The iron-bearing formation· 

clastic sediments such as slate and quartzite varies g1;eatly in thickness, being les,s than 20 

and with volcanic flow,s. 1 The beds have a feet thick in some parts of the region and more 

maximum thickness of 1,000 feet or more and than 4,000 feet thick ·in other parts. It is un~ 

in places are known to be con~inuous along the derlain by' a great thickness of sericitic quartzstrike for more than 200 miles. The iron-bear- ite which in turn overlies granite and gneiss. 

ing formation as expbsed consists mainly of A.t the· contact of the iron-bearing forn1ation 

hematitic and limonitic chert and slate and and quartzite is a thin layer of argillaceous 

iron ore. These rocks in many pla~es ·grade schist. Above the iron-bearing fonnation is 

downward at different depths along ·the bed- a schist bed of great thickness, which in .,the 

ding into sideritic chert and slate, or into upper part becomes quartzitic. In the lower 

greenalite rock, a ferrous silicate rock. Meta- ·part of this schist are local beds and lenses of 

morphosecl phases of the various types of the limestone and itabirite. In places beds of man-. 

iron-bearing formations which have been ganese ·ore also occur near the contact of the 

altered by igneous intrusions or regional cleformation occur locally. 

The hematitic and limonitic chert and slate 

were probnbly derived main~y by o~iclation 

1 Van Rise. C. R., aud Leith, C. K., ~rhe geology of the 

Lal<e Superior region : U. S. Geol. Survey Mon. 52, 1911. 

2 Leith, C. K., and Harder, E. C., The hematite ores of 

Brazil and a comparison with the hematite ores of Lake Superior: Econ. Geology, vol. 6, pp. 670-686, 1911. 

Harder, E. C., '.rhe " itabirite " iron ores of Brazil: Econ. 

Geology, vol. 9, pp. 101-111, 1914. 

Harder, E. C., and Chamberlin, R. T., The geology of ccn-. 

tral Minas Geraes, Brazil: Jour. Geology, vol. 23, pp. 341-

378, 385-424, 1915. 
52 IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

iron-bearing formation and the overlying 

schist. 

The iron content of the itabirite in general 

ranges between 30 and 50 per cent, and the interlayered iron ores range from· 50 to 70 

per cent in metallic iron. In fact the itabirite, with diminishing quartz, grades into· iron 

ore. ·Both hard and soft ores occur, the former 

being of very high grade and commonly averaging 69 to 70 per cent metallic iron and 

less than 0.02 per cent phosphorus for an 

entire deposit. High- grade hard- ore beds 

have a maximum thickness of 750 feet and a 

maximum length of 4,000 feet, but the lower 

grade soft ores :form. deposits several thousand 

feet in thickness and rrwre than 2 miles in 

length. 

The iron ores and. associated itabirite and 

schist are believed to be primary sediments. 

The iron 'vas probably deposited as ferric hydroxide by chemical and biological agencies 

at. the same time as the associated clastic 

·material. 

The Archean rocks of British India consist 

of a basement of gneisses and crystalline 

schists. These are overlain by what is known 

as the Dharwar series of metamorphosed sediments, consisting of conglomerate, quartzite, 

slate, phyllite, crystalline limestone, and different kinds of schist. BoJ;h of these series have 

suffered deformation and have been intruded 

by ·granitic and other rocks. The Dharwar 

series locally contains beds of iron-bearing 

rocks, such as banded ·hematitic and magnetitic 

jaspers and ferruginous quartzites and schists 

associated with beds and lenses of pure iron 

ore.1· Scattered areas of Dharwar rocks occur in many parts of the peninsula of India, 

and iron-ore deposits are found in them both 

in the north and south. 

·The iron-ore deposits range in size from 

mere sea1ns to great tabular lenses, some of. the 

largest of which are 300 feet in thickness and 

cover many acres. The ore is generally hard 

and massive, but locally where associated with 

slate or phyllite it is soft, laminated, and 

schistose. It consists of a mixture of. hematite and magnetite and contains as impurities 

1 Weld, C. M., The ancient sedimentary iron ores of British 

India: Econ. Geology, vol. 10, pp. 435-452, 1915. 

Holland, '.r. H., Geology of the neighborhood of Salem, 

Madras Presidency: Geol. Survey India Mem. 30, pt. 2, pp. 

103-168, 1901. 

quartz and chlorite or pale-green amphibole 

( griinerite). Some of the ore contains. as 

much as 68 per ·cent metallic iron and only 

about 2 or 3 per cent of impurities. As silica 

and amphibole increase the ore grades into 

hematitic and magnetitic quartzite and jasper. 

The ores are supposed to be original sediments that were precipitated chemically as 

ferric hydroxide and later metamorphosed to 

their present form. 

Beds of siliceous iron ore and associated ferruginous rocks similar to those of Brazil and 

India <JCCur in Dunderland, in the northern 

part of Norway. 

Jurassic limonite, or " 1pinette " ore, is of 

widespread distribution in· northern France 

and southern Germany, and is of great importance commercially. 2 The ore occurs as lenticular beds interlayered with shale, sandstone, 

and 1narl of Middle Jurassic (Dogger) age, not 

far above the underlying Lias marls. The 

seven principal ore beds vary in thickness, the. 

maximmn being 20 feet, and occur within a 

vertical distance of 75 to 150 feet. They are 

separated from one another by beds of marl 

and limestone. The sedimentary beds are 

n:early horizontal but have a very gentle dip 

to the west, and the iron-ore layers conform in 

structure with the sediments. 

The ore beds consist mainly of oolitic limonite, soft and earthy, different beds having different colors, such as gray, brown, red, green, 

and yellow. With the limonite occur .some calcite, siderite, secondary magnetite, and· iron 

silicates, mainly glauconite, but berthierine, 

chamosite, and thuringite also have ,been found. 

The spherules that make up the oolitic ore are 

about the size and shape of millet seed or 

smaller, and consist of :ferric hydroxide with a 

skeleton of silica. They an~ cemented by silica, 

lime, and clay shale. 

2 Einecke,· G., and Kohler, W., Die Elsenerzvorriite des 

Deutschen Reiches : The iron-ore resources of the world, 

p. 670, Stocl,holm Internat. Cong. Geol., 1910. 

Dondelinger, V. 1\L, Die Minette im Grossherzogtum Luxemburg: Idem, p. 43. 

Nicou, L., Les ressources de la France en minerals de 

fer : Idem, p. :?. 1 

Cayeux, L., Les minerals de fer oolithique de France, 1909. 

Kohlmann, W., 'Die Minetten~blagerungen des lotbringischen Jura : Stahl und Eisen, 1902, pp. 493-503 ; 554-570, 

1273-1287, 1340-1357.. . 

Van "'erwecke, L., Bemerkung ueber die Zusammensetzung und. Entstehung der lothringisch-luxemburgischen 

oolithischen Eisenerze : Zeitschr. prakt. Geologie, 1901, p. 

396. 
GEOLOGIC IMPORTANCE OF IRON-DEPOSITING BACTERIA. 53 

The oolitic limonite is of low grade and con-· 

tains abundant impurities. The range in composition of ore from different beds is as follows: 

Ra;nge in co1n1JOB·it-ion of J1t1·assio lhnonUe of li'ranoe 

and Gertnany. 

Per cent. 

Fe________________________________________ 34- 40 

8102-------------------------------------- . 7- 16 

AI20a-----------------------------------~-­

Cn0 --------------------------------------

2- 8 

6- 19 

1:' ----------------------------------------- o. 3-0. 7 

C02+ H20 --------------------------------- 14- 22 

. I-Iypotheses ha \•e been offered for the origin 

of . the Jurassic limonite similar to those advanced for the origin of the Clinton ores. It 

was forrnerly held that the ores were replacements of oolitic limestone beds, due to 

the action of iron-bearing waters. ~~ore recently, however, hypotheses have been adYancecl claiming that the ores were deposited as original iron-bearing sediments. Some 

investigators believe that the ore was originally deposited as oolitic ·siderite and that 

it has subsequently been oxidized in large 

part to limonite. Others, who have found 

iron silicates in the ore beds as well as silica 

in the ore spherules, claitn that, in part at least, 

th.e ore is an alteration product of original iron 

silicates, perhaps glauconite. Still.others hold 

that the beds were deposited essentially in their 

present form, mainly as limonite, btit with admixtures of iron carbonate and iron silicates. 

Bog iron ore is found in. many parts of the 

world .. It consists essentially of an earthy yellow to red or cbrk-brown mixture of ferric 

hydroxides, mainly limonite but with associated l:imnite and xanthosiderite. 'Vith these 

hydroxides occur some silicate, sulphate, and. 

locally carbonate of iron, besides organic rilatter and clastic material, such as sand and clay. 

BC?g iron ore is usually high in phosp~o~·us, 

which is present as the iron phosphate, .vivianite,t and ]ocal1y wad or bog manganese also is 

an abundant constituent. The organic matter 

consists of humus substances and of plant remains such as leaves and sticks, which may be ' . . . in part 01.; entirely replaced by hmon1te. 

Boo- iron ores are of two kinds-(1) those b 

formed in Jakes by water currents and known 

t Van Bemmelen, .T. M., Hoitsema, C., and Klobbie, E. A., 

Ueber dns Vorkommen, die Zusammensetzung nnd Bildung 

von Jmsennnhilufuugcn In und unter Mooren: Zeitschr. anorg. 

CIH•mle, Bnnd ~2, pp .. 313-379, 1700. 

as iake ores,2 and (2) those formed in place in 

still water and occun·ing either as surface 

· layers lying on soil or below a layer of porous 

surface soil and resting on clayey impervious 

subsoil. 

Lake ores have been· described from localities in Ontario and Quebec in Canada . and 

fron1 the eastern United States, as well as from 

Sweden and other places in northern Europe. 

The Canadian dep'osits, which are typical, consist mainly of layers of flat disldike or irregular concretions of ferric hydroxide that extend 

along the sho'l:es of lakes in which vegetation 

is abundant and into which streams carry 

iron-bearing water. 'The .layers may attain a · 

foot or two in thickness and are usually thickest at the w~ter's edge and thin out toward the 

lake, few concretions ·being found where the 

water is more than 2 feet deep. The concretions themselves range from less than an inch 

to a foot ·or more in diameter. They contain 

quartz grains as impurities and are apparently 

formed around sand grains as nuclei by the 

rolling action of waves and currents. In the 

lower portion of such a layer of concretions, 

broken concretions with soft limonite and sand 

usually occur, and with them a green ferrous 

salt, perhaps a silicate or a sulphate, is generally found. Locally instead of concretions a 

layer of soft or hard, yellow' porous, bedded 

limonite occurs in the shallow water, and in 

still other places Hmonite occurs as cement in 

sand. In the deeper water of the lakes into . 

which iron-bearing waters flow the distribution of the deposits is usually irregular, but 

in many places 6 to 8 feet. of ocherous, slimy 

inud occurs at the bottoms of the lakes. Iron 

carbonate is usually absent in lake ore , deposits. 

Th~ second type of bog ore usually forms in 

marshes, peat bogs, or other shallow surface 

depressions. These deposits may occur immediately at the surface but are more commonly 

found. below several feet of porous surface 

soil and in many places are mixed with humus 

or peat. They form horizontal tabular bodies, 

as a rule of small circumference and of no 

O'reat thickness. Some deposits have a piso- b 

litic texture, consisting of small spherules of 

2 Moore, E. J., The occurrence :!nd origin of some bog Iron 

deposits in the district of ~rhunder Bay, Ontario: Econ .. Geology, vol. 5, pp. 528-537, 1910. 
54 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

porous yellow ocher, the interstices of which 

are filled with hard brownish-black limonite; 

others consist of layers of concretions or nodules embedded in sand or sandy clay, and 

commonly contain much iron carbonate and 

vivianite; and still others form solid, thin, 

tabular bodies consisting of sand and clay 

impregn~ted and cemented by limonite. 

vVhere much peat is present irregular nests of 

bog ore that ~onsist almost entirely of white, 

amorphous. iron carbona"te are numerous. 1 

Such deposits are common in the Netherlands 

and northern Germany. 

Bog iron ores are distributed through many 

pads of the world but· are especially abundant in the glaciated northern regions of 

North America, Europe, and Asia. 2 In these 

regions percolating waters dissolve iron from 

the glacial drift, where it is abundantly present as magnetite as well as iron silicates. 

Shaler states that in the glacial drift in New 

England 1 to 3 per cent of magnetite is found. 

The iron may be carried in solution as soluble 

carbonate, as sulphate, or combined with organic acids, and may be precipitated chemically or. biologically. Chemical precipitation 

takes place either by removal of the solvents, 

by reaction with other materials in solution, 

or by oxidation. Biologic precipitation occurs through the action of microorganisms. 

Deposition usually takes place in small lakes 

or marshes, which are abundant in glaciated 

regions. The form in which the "iron is precipitated depends on a number of factors, such 

as the form in which the iron is being carried 

in solution, the ainou.nt of oxygen present, the 

amount of organic 1natter present, and -the 

presence of other materials in solution. 

. Usually the conditions are so varied, however, 

that a mixture of iron salts is deposited, including ferric hydroxides, iron silicates, iron 

phosphate, and in places iron carbonate, iron 

sulphate, or iron sulphide, and perhaps ferrihumates or basic ferric salts. The. deposition 

is described in more detail on pages 75-82. 

. Very few localities are known in which deposits· of ferric hydroxide are at present form1 Van Bemmelen, .T. M .. , Hoitsema, C., ana Klobbie, E. A., 

op. cit. 

2 Duke, C. L., The formation and distribution of bog iron 

ore deposits: Am. Jnst. Min. Eng. Bull., July, 1915, pp. 1420-

1436. ' 

Shaler, N. S., General account of the fresh-water morasses 

of the United States: U. S. Geol. Survey Tenth Ann. Rept., 

pt. 1, p. 305, 1890. 

·-ing in 1narine marshes, and it is supposed that 

the salts in solution in sea water interfere with 

the precipitation of ferric hydroxide. However, locally on the east coast of Brazil there 

are small areas of Tertiary n1arine sediments 

in which beds of sandy limonite are abundant, 

and in Huelva Bay, on the 'south coast of 

Spain, limonite is being deposited at present 

fron1 iron-bearing mine waters. The "red 

mud," a terrigenous oceanic deposit which occurs -locally on the borders of the continents ih 

place of the more widespread" blue mud," also 

contains considerable ferric hydroxide. 3 Such . 

deposits are forming along the coast of Brazil 

and in the Yellow Sea and are caused by 

abundant ocherous material being brought by 

the rivers to the ocean. Whether the preci pitation of ferric hydroxide in these localities 

occurs in the waters of the rivers before they 

reach the sea or in the marine waters it is not 

possible to say. 

l;>EPOSITS Ol;tiGINALLY LAID DOWN MAINLY AS 

, FERROUS CARBONATE. 

Probably next in in1portance to ferric hydroxide as an original iron-bearing sediment is 

ferrous carbonate (FeC03 ). This compound 

has a theoretical composition of iron protoxide 

62.1 per cent (Fe 48.2 per cent), and c:;trbon 

dioxide 37.9 per cent. 

Ores originally deposited mainly as iron 

carbonate include the clay ironstones and 

"black band " ores of the " Coal Measures " 

in both the United States and Europe, the 

oolitic siderite of the Jurassic in the Cleveland 

Hill~ and other parts of England, the cherty 

siderite and much of the he1natite in the great·· 

pre-Cambrian iron-bearing beds of the Lake 

Superior district, and possibly a considerable 

part of ·the Jurassic oolitic limonite of northern France and southern Germany already describeq. Besides these ores there are large deposits of iron carbonate which have usually 

been regarded as originating by the replacement of limestone but many of which may be 

of primary origin. They include the beds of 

iron carbonate near Bilbao and irr southern 

Spain, those of Erzberg in the Styrian Alps, 

and many others of minor· importance. 

Ironstone concretions and black-band ores 

of Carboniferous age occur in Ohio, Pennsyl3 Murray, J~, and· Hjort, J., The depth of the ocean, pp. 

161 et seq., 1912. 
GEOLOGIC IMPORTANCE O:F IRON-DEPOSITING BACTERIA. 55 

vania, West Virginia, and elsewhere in the 

eastern United States and also in Great Britain and parts of Germany. In the eastern 

United States ores of this nature are found 

principally in strata of lower Pennsylvanian 

age (Pottsville and. Allegheny), though scattered beds occur both above and below this 

horizon. The siderite beds, which vary somewhat in fol'ln and structure, are classed under 

four groups. The most importa_nt of these 

groups are the limestone ores, so called because they occur at or ne.ar the top of limestone strata. These beds range from a few 

inches to several feet in thickness and have a 

pockety character because of variations in 

thickness in short distances. 'Tihe ore is dense 

and close-grained and has a gray or bluishgray color. The second type of siderite ore is 

called blocl{ ore because it cleaves into blocks 

when mined. These beds are more persistent 

and of more uniform thickness than the beds 

of lin1estone ore but usually contain a considerable amount of sand as ~mpudty. The 

third group includes the concretionary or kidney ores. The ironstqne concretions; though 

not regularly bedded, occur at definite stratigraphic horizons as peculiar rqunded 1nasses 

scattered through zones of clay or shale 3 to .6 

feet thick. The fourth group, the black band 

ores, consist of iron carbonate with more or 

less intermixed bituminous and earthy matter. 

They occur as layers a few inches in thickness, interbedded with carbonaceous shale in 

zones 10 to 15 fee't in thickness. They are generally of higher grade than the other carbonate ores. '~There beds of . iron ·carbonate of 

any of these types are exposed to weathering. 

they are altered to limon.ite for varying dis-· 

tances fron1 the outcrop. 

In ·Greut Britain1 three types of ironstone 

are mentioned, of which two are importantthe black band ores, which are closely associated with coal sean1s, and the clay-band ores. 

Both types occur as beds or seams, lenslike in 

character and varying from a few inches to 

several feet in thickness. In central England 

there are a dozen or n1ore importa~t beds of 

black-band and clay-band ironstone in the Up-. 

per and. Lower Coal Measures. The third type 

1 Louis, H., 'J.'he iron resources of the United Kingdom of 

Grout Britain und Irclund: The iron-ore resources of the 

world, Cong. g~ol. tnternut., Stockholm, p. 637, 1910. 

of iron carbonate ore is the nodular ironstone 

that occurs in parts of Ireland. The average 

range in composition of iron c~1.rbonate ores of 

the Coal l\1easures of Great ;Britain is, iron 

26 to 35 per cent, silica 10 to 20 per cent, and 

phosphorus 0.5 to 1 per cent. 

These sedimentary iron mirbonate beds arc 

supposed to have been formed by chemical 

precipitation from iron-bearing waters under 

conditions where oxidation could not take 

place. The presence of coal beds and carbonaceous shales in ~ssociation with the ore indicates the presence of abundant vegetation at 

the time of deposition. The precipitation o£ 

iron carbonate probably o·ccurs in shallow la-

. goons or 1narshes along .the sea coast, and is 

due to the absorption by plants of the excess of 

carbon dioxide which held it in solution. Some 

of it n1ay have been precipitated as ferric 

hydroxide, which upon settling to the bottom 

and becoming mixed with decaying organic 

material, was reduced to ferrous carbonate. 

IGclney ores were not originally deposited as 

such, but represent later segregations of iron 

carbonate originally deposited with muds. 

Oolitic siderite beds of :Middle and Lower 

Jurassic age 2 are found in the Cleveland I-Iills 

and in N orthamptonshire, Lincolnshire, and 

elsewhere in the eastern part of England. The 

principal beds in the Cleveland Hills occur in 

the Middle Lias (Lower Jurassic); which consists of about 125 feet of nearly horizontal 

shale, sandstone, and ironstone. Four beds of. 

ironstone occur, and these range in thickness 

from 1 t to 12 feet and haye a combined average thiclmess of 16 feet. The main seam, 

which ranges in thickness from 6 to 12 feet, 

consists of impure bluish oolitic· siderite that 

averages iron 30 to 35 per cent, silica 6 to .12 

per cent, and phosphorus pentoxide (P 20 5 ) 1 

to 3 per cent. 

In Northamptonshire there is only one important bed of iron carbonate, which lies at 

the base of. the Lowe,r Oolite (Middle Jurassic). Its maximum thickness is 30 feet and 

its average thiclmess throughout the district 

is about 9 feet. It is siliceous siderite of gray, 

green, or blue color and is oxidized to sandy 

brown or yellow limonite where exposed to 

we~thering. . The ~iderite. averages in compo-

~Louis, H., op. cit., p. G30. 
56 IRON-DEPOSITING BACTERIA AND THEIR GhOLOGIC RELATIONS. 

sition from 30 to 35 per cent ·of iron, 12 to 14 

per cent of silica, and 0.5 to 1 per cent of 

phosphorus. 

The Lincolnshire ironstone bed occurs in the 

.middle of the Lower Lias (Lower Jurassic). 

The thickness ranges from 10 ·to 25 feet, and 

averages about 12 feet. It lies nearly horizontal and where known consists mainly of 

calcareous brown hematite, having been oxidized by weathering agencies. 

The oolitic siderites of England occur at approximately the same geologic horizons as the 

oolitic limonites of northern France and southern Germany, and this situation is somewhat 

suggestive of a similar origin. l-Iowever, the 

Jurassic ores of· England are mainly iron carbonate which is altered only at the surface to 

limonite, whereas the ores of France and Germany, where deep mining has taken p~ace, do 

not seem to alter their character markedly with 

depth. 

Probably the mo.st extensive beds of iron 

·carbonate known are those of the Lake Superior region already mentioned.1 Though 

the iron-bearing formation as exposed at present in this region consists almost entirely of 

oxidized rocks, such as hematitic and limonitic 

chert and slate and iron ore, these rocks have 

been found to grade downward into cherty 

iron carbonate and silicate in a sufficient number of places to make the phenomenon appea:r 

:fairly general. 

The iron-bearing formation in the Lake Silperior district is associated with basic· volcanic rocks of Archean age and with metamorphosed sediments and volcanic rocks of lower, 

middle, and upper Huronian age. The beds 

are of great thickness and longitudinal extent, those of the upper Huronian being most 

widespread. Iron-bearing rocks of Archean 

1 Van Hise, C. R., and Leith, C. K., The geology of the 

Lake Superior region : U. S. Geol. Survey Mon. 52, 1911. 

Irving, R. D., and Van Fiise, C. R., The Penokee ironbearing series of Michigan and Wisconsin: U. S. Geol. 

Survey Mon. 19, 1892. ,, 

Van Hise, C. R., Bayley, w:· S., and Smy.th, H. L., The 

·Marquette iron-bearing district of Michigan : U. S. Geol. 

Survey Mon. 28, 1897. 

Clements, .T. M., Smyth, H. L., and Bayley, W. S., The 

Crystal Falls iron-bearing district of Michigan : U. S. Geol. 

Survey Mon. 36, 1899. 

Clements, J. M., The Vermilion iron-bearing district of 

Minnesota : U. S. Geol. Survey Mon. 45, 1903. 

Bayley, W. S., 'J'he Menominee iron-bearing district of 

Michigan : U. S. Geol. Survey Mon. 46, 1904. 

Harder, E. C., and Johnston, A. W., Preliminary report on 

the geology of east-central Minnesota including the Cuyuna 

ir<?n-ore district : Minnesota Geol. Survey Bull. 15, 1918. 

and lower Huronian age are found only in the 

Vermilion district in northern Minnesota, and 

iron -bearing rocks of middle Huronian age 

are found only in the Marquette ·district in 

northern Michigan. The upper Huronian 

iron-bearing formation, however, is found 

throughout most of the Lake Superior district. 

The Archean iron-bearing formation is in-

'folded in I(eewatin greenstone, the relation 

between them indicating that the iron-bearing formation is the younger. In places, however, bands of the iron-bearing formation are 

interbedded with greenstone flows, indicating 

contemporaneous· origin. The lower IIuronian iron-bearing formation lies on conglomerate and is overlain by slate. It is of little importance. The middle Huronian iron-bearing 

formation is underlain by slate and overlain 

unconformn:bly by conglomerate arid quartzite. 

The upper Huronian iron-bearing formation 

is in general underlain by quartzite or graywacke and is overlain by a great thickness of 

quartzose, micaceous, chloritic, and carbonaceous slate with associated basic volcanic rocks. 

Extensive layers and lenses of iron-bearing 

formation entirely inclosed in the slate also 

occur in the upper Huronian, as in the Guyuna 

and Crystal Falls districts. 

The unaltered beds of the iron-bearing 

formation consist largely of cherty siderite, 

grayish white to gray or greenish gray in 

color. With the cherty siderite are interbedded, here and there, layers of sideritic slate 

of grayish or greenish color. The cherty siderite in detail consists of interlaminated dense, 

fine-grained chert and siderite, usually in very 

thin layers. The average composition of 

·cherty siderite is, iron 25 per cent and silica 40 

per cent .. 

In their general occtirrence and their- relation to the inclosing sediments the Lake Superior cherty and slaty siderite beds resemble 

other sedimentary iron carbonates. Because of 

this general similarity they were formerly regarded as having the same origin. More recently, however, on account of their great thickness and their conspicuous association with 

basic volcanic rocks, a hypothesis has been advanced that ascribes their origin, at least in 

part, to igneous agencies. 2 The iron is supposed to have been derived from basic' igneous 

2 Van Hise, C. R., and Leith, C. K., op. cit., pp. 499 et seq. 
. GEOLOGIC IMPORTANCE O:E' IRON -DEPOSITING BACTERIA. 57 

rocks, the eruption of which occurred at approximately the same time as the formation of 

the iron-bearing sediments. These eruptive 

rocks, which are rich in .iron, are now represented by greenstones, which occur at various. 

horizons from the Archean to the upper Huroni u.n. The iron, according to Van Rise 

and Leith, may have been derived from the 

eruptives in three ways: (1) A part n1ay have 

been derived through processes of weathering 

frmn ln.vas extruded on land areas. (2) Another part may have been given off by reactions 

between sea ''Vater and hot subaqueous eruptive rocks. (3) :Most of it, however, probably 

came from hot magmatic solutions that were 

squee.zed out of the lavas during solidification. 

The precipitation of the iron carbonate and 

silicate from solution is believed to have been 

the result of simple chemical reactions between 

ferrous solutions, alkaline silicates, and carbon dioxide. The deposition of t.he iron-bearing sediments took place in marine waters, the 

ferruginous materials being distributed· over 

large areas by currents. The conditions of 

deposition differed considerably in different 

parts of the district and in the different epochs, 

causing a great diversity in the occurrence of 

the iron-bearing sediments. 

The iron carbonate deposits of Bilbao, in 

northern Spain, are scattered over an area 

about 30 kilometers in length and 2 to 8 kilometers in width.1 They occur as irregular 

tabular masses in the upper part of a thick 

Cretaceous limestone overlain by calcareous 

shale. The masses ·are said to have a maximum thickness of 100 feet. Along the outcrop and for some distance in from the surface they are altered to hematite and limonite. 

The iron carbonate is supposed to have been 

formed by the replacement . of limestone by 

ir?on-bearing waters that percolated downward 

from the overlying shale. Their tabular shape 

and their occurrence at a definite horizon, 

:1 VIdal, L. 1\f., fil!sum6 des gisements de fer de l'Espagne: 

~!:he ll'On ot·e resources of the world, Con. geol. internat., 

Stocld10lm, p. 4!), lDlO. 

Allnnis, F. D., Notes on the iron-ore deposits of Bilbao, 

northern .Spain : Canadian Min. Inst. Jour., vol. 4, pp. 196-

204, 1901. 

Czyszlwwsld, 1\f. S., Exploration geologique de ln region 

ferrif~t·e de Bllbao-Somorl'Ostro, 187!). 

John, Die Elsenerzlagerstlitten von Bilbao und ihrer 

Bedeutung flit· die zuldlnftige Elsenversorgung Grossbritannlens und Deutschlands : Gli.ickauf, vol. 46, pp. 2002-2013, 

2045-2052, 1910. 

however, suggest the possibility of their direct 

sedimentary origin. 

The iron carbonate ore in northern Styria 

occurs in the so-called "graywacl{e zone/' a 

complex of Paleozoic rocks lying between the 

granite, schist, and gneiss of the central part 

of the eastern Alps and the Triassic sediments 

of the northern part.2 It is found over an area 

about 50 kilometers in length, east and west, as 

scattered deposits. 3 The principal ore bed occt1rs at Erzberg and has a maximum. thickness 

of 125 meters. Underlying it unconformably 

is the Sauberg limestone of Lower Devonian 

age, which consists of interlayered limestone 

and a!lkerite; The ankerite coinmonly passes 

over into siderite. Between the main ore bed 

and the limestone is a thin ·bed of dark sericitic schist. Overlying the ore bed unconformably are Lower Triassic rocks, which consist 

of first a conglomerate and then a grayishgreen sandstone, which passes upward into red 

vVerfener slates. The ore bed itself' consists of 

dense fine-grained siderite and here and there 

contains more coarsely crystalline siderite 

along fissures and fractures. Local interbedded layers of shale and limestone are found 

in it.· 

The generally accepted hypothesis for the 

origin of this ore is that it was formed by the 

metasomatic replacement of limestone. by iron 

brought in by percolating w~ters. The chief 

evidence cited is that small siderite deposits 

are irregularly distributed in the Sauberg limestone ·and that sulphides occur· in the ore beds. 

However, the well-developed bedding of the 

iron carbonate and the fact 'that fragments of 

ore occur in the basal Triassi~ conglomerate 

above the ore bed would indicate that at least 

the principal ore bed is of sedimentary origin,2 

though the siderite in the Sauberg limestone 

:niay be· a later replacement. 

DEPOSITS ORIGINALLY LAID DOWN MAINLY AS IRON 

SILICAT:E;S. 

Iron silicates of several kinds occur as sedi· 

ments, the most widespread probably being 

glauconite. This mineral has . no de-finite 

2 Singewald, .J. · T., jt·., The Erzberg in Styria : Eng. and 

Min. Jour., vol. 92, p. 22, 1!}11. 

• 3 Uhlig, V., Die Eisenerzvorriite Oesterreichs: The iron-ore 

·resources of the world, Cong. geol. internat., Stockholm, p. 

143, 1910. . 
58 IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

chemical composition but is essentially a hydrous silicate of iron and potassium with some 

alumina. When pure it probably has approximately the composition represented by 

the formula Fe"'l(Si20 6.aq.1 Alumina may 

· replace ·a . part of the iron. The iron is 

largely in the ferric form, but a variable 

though small amount of ferrous iron is always 

present. Glauconite is common in sedimentary 

rocks of many different ages but especially of 

the Cretaceous. It is usually more or less disseminated, but locally it forms pure beds and 

lenses. 

Another important iron silicate found in 

sediments is the hydrous ferrous or ferrosoferric silicate, greenalite, which occurs along 

with cherty siderite as an original constituent 

locally in the Lake Superior iron-bearing 

formation. 2 Greenalite has the composition 

FeSi03 .nH20 or Fe"' 2Fe" a (Si04 ) 3 .3H20. A 

part of the ferrous iron roay be replaced by 

magnesiUm; 

Besides these there are four other more or 

less related hydrous silicates of iron-thuringite, chamosite, berthierine, and ba valitewhich are quite widespread. Only the first of 

these has a definite chemical formula, which 

is as follows: 8Fe0.4 ( AlFe) 20 3.6Si02.9H20 

(silica, 22.8 per cent; alumina, 17.2 per cent; 

ferric oxide; 13.5 per cent; ferrous oxide, 36.3 

per cent; combined water, 10.2 per cent). The 

other three silicates differ from thuringite- in 

that they contain a higher percentage of iron 

protoxide, only a small percentage of alumina, 

and little or no ferric iron. 

Thuringite and chamosite are said to be the 

principal minerals in certain lenses of iron ore 

of Low~r Silurian age in Bohemia and ill Thuringia, Germany. Thuringite is olive-green in 

color and scaly, and chamosite is dark grayish 

green and either compact or oolitic. Chamosite is an abundant constit.uent of the vV abana 

iron ore of Newfoundland, in which it is asso-· 

ciated with compact and ooliti_c hematite. 

Berthierine occurs in northern France a,g a constituent of the Jurassic oolitic ores, associated 

1 Clarke, F. W'., The data of geochemistry, 3d ed.: U. S. 

Geol. Survey Bull. 616, p. 517, 1916. 

2 Leith, ·c. K., The Mesabi iron-bearing district of Minnesota: U. S. Geol. Survey Mon. 43, pp. 239 et seq., 1903 •. 

Van Hise, C. R., and Leith, C. K., The geology of the Lake 

Superior region : U. S. Geol. Survey Mon. 52, pp. 165, 521, 

1911. 

with limonite, siderite, and other minerals.3 

Bavalite is found in scattered deposits in Brittany, where it is interbedded with metamorphosed rocks. 4 . 

·Glauconite occurs as dark-green granules 

widely distributed in ~edimentary rocks and is 

also being deposited at the present time in 

many places on the ocean bottom. It forms 

a green granular sediment and is generally 

more or less mixed with other sedimentary Inaterial, especially fine sand and silt. The separate granules usually have the shape and size 

of foraminiferal shells, and many of them still 

have fragments of shells attached to the outside 

of them. Many also are distinct internal casts 

of Foraminifera. Very few glauconite grains 

exceed 1 millimeter in diameter. 

At the _present time glauconite is fanning 

most abundantly in comparatively shallow 

waters and near the mud line surrounding the 

continental shores j·ust beyond the limit o£ 

wave and current action. 5 The depth at which 

it commonly forms ranges between 100 and 

~00 fathoms, but in some places it forms at 

depths as great as 900 fathoms. The entrance 

of large rivers interferes with its formation. 

The common occurrence of glauconite inside 

shells of Foran1inifera has led to the belief that 

these organisms are concerned in its formation. 

The dead organisms a:re supposed to drop to 

the bottom, whereupon the shells become filled 

with fine mud which in the presence of the 

slilphates in sea water is acted upon by the de'" 

caying organic matter in the shell.6 The iron 

supposed to be contained in the mud is reduced 

to sui phide, and this afterward oxidizes to ferric hydroxide, setting free sulphuric acid. The 

sulphuric acid acts upon the alumina, causing 

it to be removed in solution and at the same 

time colloidal silica is set free. The colloidal 

silica reacts upon the ferric hydroxide and in 

the presence of pot.:'lssium salts, supposed to be 

derived from adjacent decomposing minerals, 

forms glauconite. Sediments with which glauconite is associated are said to contain invaris Clarke, F. W., The data of geochemistry, 3d ed.: U. S. 

Geol. Survey Bull. 616, pp. 516-518, 1916. 

4 Dana, E. S., System of mineralogy, p. 658, 1914. 

11 Murray, J., and. Rena.rd, A. F., OhaUenger Rept., Deep-sea 

deposits, p. 383, 1891. 

o Clarke, F. W., The data of geochemistry, 3d ed.: U. S. 

Geol. Survey Bull. 616, p. 135, 1916. 

Murray, J., and Renard, A. F., op. cit. 
GEOLOGIC IMPORTANCE OF IRON -DEPOSITING BACTERIA. 59 

ably abundant orthoclase, muscovite, and other 

minerals frOin which potassium may have been 

derived. Other materials commonly found 

'vith gh1uconi.te in greensand are quartz, hornblende, magnetite, augite, zircon, garnet, and 

varying amounts of calcareous matter derived 

from shells. 

Glauconite is disseminated in marine sediments of all geologic ages, forming strata 

which are known as greensand. In the Paleozoic rocks greensand is probably most abundant in Cambrian and Ordovician strata. 

Cambdan greensand is common in the northcentral U'nited States, where it is associated 

with siliceous limestone and fine calcareous 

sandstone beds. Ordovician (" Lower Silurian") greensand occurs in the Baltic provinces 

of Russia. In the l\1esozoic rocks glauconite is 

particularly abundant in the Cretaceous formations both in Europe and North· America. In 

England it occurs throughout the southern 

counties as well-defined beds generally interlayered with sand, marl, and clay. It is so 

abundant along certain zones that tJ:ey are 

known as greensand horizons. The principal 

greensand horizons are in the upper part of the 

Lower Cretaceous and in the lower part of the 

Upper Cretaceous. The principal chalk beds oc-

·cur above them in the Upper Cretaceous. In 

the Atlantic and Gulf coastal sediments of the 

United States greensand occurs in the Cretaceous and. in the overlying Eocene deposits. 1 

It is found more or less abundantly throughout the strata, being associated with coarse and 

fine sand, clay, and marl. Locally beds of pure 

glauconite occur. 

Below is shown- the range in composition of 

glauconite obtained from different localities. 2 

R(l,nuc in com.zJosU·ion ot glamconite front d·ifjerent 

localities. · 

The occurrence and character of the Lake 

Superior iron-beari1ig formation have already 

been described. Although cherty siderite is the 

principal rock in the unaltered iron-bearing 

formation, there are localities in the PenokeeGogebic district where a considerable amount 

of greenalite occurs with it, aloi1g certain horizons, and other localities, as in the l\1esabi district, where most of the formation is believed 

to have originally consisted of greenalite. 3 

Greenalite forms a clark-green, hard, cOinpact. rock with oolitic texture. The greenalite 

spP.erules have a n1aximmn diameter of a millimeter or more and in shape they vary from 

spherical to oval or elliptical. They differ 

from spherules of Clinton hematite and W abana ore in that they do not show concentric 

layering. They are usually homogeneous 

throughout and consist of green amorphous 

material which in places has a little siderite or 

chert or crystalline ferrous silicate intermixed. 

The 1natrix in which the spherules are embedded consists in places of chert and elsewhere of a light-greenish crystalline ferrous 

silicate, probably gr.linerite. 

Greenalite rock n1ay occur as beds of considerable thickness, but as a general rule it is 

thin bedded and is interlayered with thin beds 

of dense black ferruginous slate. Upon exposure to surface weathering the greenalite rock 

is altered to a ·peculiar granular, speckled, 

hematitic chert to which the name taconite has 

been given. 

The following shows the range in composition of greenalite frOin the l\1esabi district, 

Minn.4 

R(l,nge in com.zwsit-ion of green(l,lite f1'om Mesab·£ 

d·istrict, Minn. 

Si02----------------------------------· 

AJ208---------------------------------· 

8102-----------------------------------' 40. OOo-53. 61 Fe20s---------------------------------· 

Al20n---------------------------------· 6.62-13.00 Fe0 ----------------------------------· 

46. 12-61. 90 

. 37- 1. 09 

5.01-15.00 

10.28-30.93 

2.33- 5.35 

. oo-- . 2s . 75- 2. 50 

4.17-6.41 

1\fgO ________ . ________ ..,. ________________ _ 

CaO------------------------------~--- ll"e20n---------------------------------· 15. 16-23. 43 

11'e0 _____________________________ . _ _: __ . 1. 32-10. 17 

l\"' 0 95- 2 97 H 20---------------------------------· '.lg ---------------------------------- . . + CaO ________________ .:. _________________ . . 57- 1. 97 H 20 ---------------------------------

Nn~O---------------------------------- · 

42- 2· 

16 The.· chamosite ores of Bohemia are found in 

1(20----------------------------------- 3.49-9.54 

H20 _____________________________ -----· 4. 93-10. 32 the Brdagebirge, the principal deposits occur1 Clark, W. B., Origin and classification of the greensands 

of New Jersey: Jour. Geology, vol. 2, pp. 161-177, 1894.· 11 Clarke, :F'. W., op. cit., p. 518. 

3 Leith, C. K., The Mesabi iron·bearing district of Mione· 

sota: U. S. Geol. Survey Mon. 43, pp. 101 et seq., Hl03. 4 Idem, p. 108. 
60 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

ring in the region of N ucitz.1 · Beds of this 

ore are located at the base and near the top of 

a certain horizon in the Silurian known as 

horizon "D." 

The base of horizon "D" consists of graywacke and slate with sheets of diabase and diabase tuff and Iayers of iron ore which seem to 

be genetically related to the diabase. The iron 

ore is mainly oolitic. hematite, but oolitic ferI'ous silicate (mainly chamosite) is abundantly associated with it. It occurs in lenticular beds which range from a thin ·film to 18 

meters in thickness ~nd is widely distributed. 

Near the surface the chamosite is altered to 

limonite. 

In the. upper part of horizon " D " also 

several zqnes containing beds of iron ore occur. The rocks consist. mainly of graywacke 

and graywacke slate, the former containing 

light-colored quartzite layers. The ore beds 

are associated with the slates. They are lenticular in shape ~ndin places, as in the vicinity of Nucitz, reach a maximum thickness of 

22 meters. The ore is· oolitic dark-green or 

bluish-green ferrous silicate with a more or 

less sideritic or slaty matrix. At the surface 

it is altered to limonite. The beds are lensshaped and pinch out horizontally. 

Near Schmiedefeld, in the ·Thuringian Forest, widely distributed beds of ferrous silicate 

occur in rocks of Lower Silurian age. They 

extend over many square miles and are so constant that they are taken as horizon markers. 

The lower bed, which is unimportant, is found 

just above a Cambrian quartzite. and grayishgreen argillaceous schist and is over lain by a 

few meters of micaceous quartzite schist. This 

is overlain by the main ore bed, 15 to 20 meters 

thick,. above which are Lower Silurian ·clay 

slates. 2 The lower bed is only a few meters · 

thick and locally is represented by two layers. 

It contains much hematite, u_sually oolitic. 

The upper bed is extensive and consists of 

chamosite and thuringite, the former being 

predominant. The chamosite is silver-gray to 

black in color and shows oolitic texture. At 

1 Beyschlag, F., Kruscb, P., and Vogt, J. H. L., Die Lagerstatten der nutzbaren :Mineralien und Gesteine, Band 2, pp. 

528 et seq., 1913. 

Uhlig, V., Die Eisenerzvorriite Oesterreichs: The iron-ore 

resources of the world, Cong. geol. internat., Stockholm, pp. 

148 et seq., 1910. 2 Beyschlag, F., Krusch, P., and Vogt, J. H. L., op. cit._ 

Band 2, pp, 531 et seq. 

the surface it alters to limonite. The thuringite is olive to dark green in color and fine 

scaly, dense, · or oolitic in texture. A large 

quantity of iron carbonate occurs with the ferrous silicates. 

The association of chamosite with hematite 

in the Newfoundland oolitic iron-ore beds has 

been mentioned on page 50. 3 It is found in the 

spherules and in the interstices between the 

spherules· composing the ore beds and occurs 

also in the matrix of the clastic sediments that 

inclose the ore beds. In the leaner portions of 

the ore layers chamosite is abundant in the 

spherules and either occurs concentrically interlayered with hematite or forms entire 

spherules itself. In this form it is usually dense 

and amorphous. In the matrix between the 

spherules and in the inclosing clastic rocks the 

chamosite is nonoolitic and shows a micro .. 

crystalline or finely crystalline texture .. Occasionally it forms large tabular crystals. 

Hayes 4 gives the following recalculated 

average analyses of 'iV abana chamosite: 

Recalculated average analyses of Wabana charno8ite .fro·m, 

New.f.Jundland. 

Si03 •••••.••••••• _____ .••.••. 

Al203 ....................... . 

~iga_-_-.-~--·. -. ~::::::::::::::::: MgO ........................ . H20 ......................... . 

24.87 

19.45 

6. 66 

34.52 

3. 34 

11. 16 

23.23 

22. 85 

1.00 

38. 99 

3.25 

10. 68 

25.64 

19. 75 

39. 74 

2.98 

11. 89 

-The color of chamosite var.ies from light to 

deep green and occasionally has a grayish tint. 

Tubes, supposed to be those of boring algae, are 

abundant in the ore beds. Where these -tubes 

penetrate chamosite they ~re usually lined 

with a coating of hematite, which is believed 

to have resulted from the oxidation of the 

chamosite by th~ action of the algae. 

DEPOSITS ORIGINALLY LAID DOWN MAINLY AS IRON 

. SULPHIDE. 

Iron disulphide (FeS2 ; iron, 46.6 per cent; 

sulphur, 53.4 per c'ent) is abundant in sedimentary rocks, occurring both as disseminated 

specks and nodules and as beds and lenses. It 

is generally present as pyrite, but in some 

recent sediments the black iron disulphide, 

melnikowite, has been found also. Marcasite 

s Hayes, A. 0 .. op. cit., p. 26. 

' Idem, p. 62. 
GEOLOGIC IMPORTANCE OF IRON-DEPOSITING BACTERIA. 61 

more commonly occurs ·as a vein mineraL Ferrous sulphide (FeS) forn1s a constituent in 

some modern lacustrine and marine sediments. 

Lenses of crystalline pyrite, of probable 

sedimentary origin but more or less recrystallized, occur interbedded with metamorphic 

rocks such as slate, schist, and quartzite, in 

Spain, France, Italy, Austria, Norway, and 

many other parts of the world. Beds of oolitic 

pyrite occur in the Ordovician rocks of Newfoundland, and in the Devonian rocks of ''Testph alia, Germany. :Melnikowite has recently 

been described as occurring in "J\1iocene clays 

in southeastern Russia. 

J\1ore interesting probably than these, however, are the deposits of hydrous ferrous sulphide which characterize the black mud forming at present in the bottom of the Black Sea 

and neighboring limans and in bays on the 

island of Oesel, Gulf of Riga, and elsewhere~ 

Iron sulphide, some of ·which is probably in 

the ferrous form, also characterizes the "blue 

mud" deposited locally in the ocean bottom. 

In the Huelva region in southern Spain1 

lenses of pyrite occur in sedimentary rocks, 

mainly clay slate with some graywt1cke and 

limestone belonging to the Culm (Lower Carboniferous). The rocks are highly folded and 

faulted .and ha.ve steep dips. The lenses· have 

a maximum length of more than 1,100 mete~ 

and a maximmn width of 180 meters. They 

occur at different horizons in the Culm and 

most of then1 are said to be closely associated 

with intrusive sheets of porphyry. On account 

of this association the pyr.ite lenses are usually 

described as being epigenetic in origin and as 

having been formed by hot solutions from the 

porphyry magma. Their interlayering with 

the sediments, however, and close concordance 

with them in strike and dip make a sedimentary origin not impossible. The Huelva pyrite 

lenses are important copper bearers and contain also some lead, zinc, arsenic, and silver, 

the occurrence of which is taken as additional 

evidence for their epigenetic origin. 

At Agordo, in the Venetian Alps of northern Italy,2 lenses of pyrite, similar to those in 

the I:Iuelva region, occur interlayered with 

pre-Carboniferous metamorphosed argillaceous 

schist, usually not far from masses of intrusive 

quartz porphyry: The lenses have a maximum 

length of 550 meters and a maximum width of 

200 meters and show fine-grained texture and 

distinct layering. In metal content they resemble the Huelva pyrite lenses. Their origin 

must be· explained along similar lines. 

In the Carpathians at Szomolnok 3 pyrite 

lenses occur in folded. and metamorphosed 

sediments of the Culm, consisting of gra·phitic 

and chloritic schist and quartzitic sandstone. 

Intrusive diorite and porphyry occur in the 

schist. The pyrite lenses are found in distinct 

layers ~orresponding in· structu~e with the 

metamorphosed sediments. However, they are 

usually explained as being of epigenetic origin, 

resulting from the diorite intrusions. 

At Rammelsberg, near Goslar,4 on the northwestern border of the Harz Mountains in 

central Germany, a lens of pyrite occurs inter-· 

layered between two slate beds o£ Middle Devonian age, which stratigraphically overlie 

Lower Devonian coarse sandstone. The beds 

are folded into an overturned anticline of 

which the sandstone forms the center. The 

pyrite lens occurs ttn the lower limb of the 

anticline and has been folded with the inclosing slates, following the contortions of the 

slates closely. It generally ranges in thickness 

from 0.5 meter to 3 meters, and shows marked 

banding parallel t9 the lens, which in part is 

due to included thin laye:rs of slate. The principal minerals are pyrite, zinc blende, chalcopyrite, galena, and arsenopyrite in a gangue 

of barite. 

It is generally believed that the Ran~elsberg pyrite deposit is a contact vein formed by 

magmatic solutions. Recently, however, fossils of Goniatites have·been found in the pyrite 

bed, which has led to its reclassification by 

some authors as a sedimentary deposit. 5 

The oolitic pyrite bed in Westphalia occurs 

at Meggen on the Lenne. 6 By son1e authors it 

is con.sidered· as of sedimentary origin and by 

others as a later introduction. The bed consists of pyrite and barite and averages about 

10 feet in thickness. The pyrite occurs in fine 

8 Idem, pp. 329-331. 4 Lindgt·en, Waldemar, Mineral deposits, pp.. 606-610, 

1913. 

1 Be~·schlng-, F .. Krusch, P., and Vogt, J. H. L., Die Lager- 5 Beyscblag, F., Krusch, P., and Vogt, J. H. L., op. cit., 

stiltteu ~let· uut~bnt·eu Mlneralien und G.esteine, Band 1, pp .. Band 2, pp. 630-G37, l.D13. 

3l.l-323, 1010. 6 Stelzner, A. W., and Bergeat, A., Dle Erzlagersti.itten, 

:1 Idem, pp. 326-328. Baud 1,. pp. 339-342, 1904. 
62 IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

layers, distinctly stratified and in places oolitic. 

Underlying it are graywacke slates and overlying it is a bed of dense nodular iimestone; in 

part dolomitic, carrying inclusions of iron pyrite. Above the limestone are clay slates. The 

rocks are of Devonian age. 

The oolitic pyrite beds which are associated 

with the 'Vabana hematite beds of Newfoundland are probably the most typical sedimentary 

pyrite beds known.1 The pyrite-bearing zone 

is found just above one of the principal hematite beds (the Dominion bed), being separated 

fron1· it by ·1 to 10 feet of shale or sandstone. 

There are one to three beds of pyrite l'anging 

in thickness from an inch to a foot or more and 

separated by fissile black shale. The beds 

thicken, thin, and die out within short distances, btit the zone is persistent. Shale occurs 

above the pyrite beds. The pyrite nearly all 

has a distinct oolitic texture and together with 

the inclosing shale contains abundant grapto-

]ites and some brachiopods, showing its marine 

or1g1n. Associated with the pyrite spherules 

are nodules and small irregular bodies of pyrite. Quartz occurs both as fragments and as 

a matrix between pyrite spherules. 

In the southeastern part of Russia near 

N owo-U sensk in the Government of Samara, 

clays conta~nirig iron sulphide were encountered in drilling natural gas wells. 2 The succession of ·strata passed through in these borings is as follows :· 

Section penetrated in borings near Nowo-Usenslc, 

Samara, Russia. 

Post-Tertiary : Feet. 

Bro~ claY--------~------------------~~--- 150 

Clayey sand containing magnesium sulphate 

bearing .water ----------------·----------- 35 

Sanpy clay________________________________ 5 

Miocene: 

Brown clay, in part sandy, with layers of gas- bearing sand ____________________________ 115 

The Miocene brown clay is interesting in 

that it carries a black iron sulphide, melnikowite, which occurs finely disseminated through 

the clay, as well as in streaks and thin layer~. 

1 Hayes, A. 0., 'Vabana in:m ore of Newfoundland : Canada 

Geol. Survey 1\fem. 78, p. 15, 1915. 2 Doss, Bruno, Ueber die Natur und Zusammensetzung des 

in l\fiocaenen Tonen des Gouvernements Samara auftretenden Schwefeleisens: Neues Jahrb., Beilage Band 33, pp. 662-

713, 1912 ; Meh:iikowit, ein neues Eisenbisulphid und seine 

Bedeutung fiir .die Genesis der· Kieslagerstatten: Zeitschr. 

prakt. Geologie, Jahrg. 20, pp. 453-483, 1912. 

Particles of it are connnonly attached to fragnlents o£ fossil mollusks. As obtained from 

the bore holes the melnikowite was mainly in 

the form of dull, dense, compact fragments, 

generally with concentric structure. Associated with these fragments were found spherical, oval, grapelike, or kidney-sh~ped forms, 

the largest of which were 1 millimeter in diameter. The microscopic text~re ·of the 

melnikowite is finely crystalline and the color 

black. Analysis has shown it to be iron elisulphide (FeS2 ), but it differs from marcasite 

and pyrite in being strongly magnetic and in 

various other physical properties. 

The particles of melnikowite are somewhat 

impure, containing quartz and calcite grains, 

clay particles, or fine muscovite flakes. Much 

of the melnikowite also has associated with it 

particles and grains of finely crystalline pyrite, 

whose occurrence and gradation into melnikowite suggest strongly that the pyrite is a stable 

form into which the melnikowite is altering. 

Black muds containing abundant organic 

material and impregnated with colloidal hydrous ferrou!;) sulphide occur in many localities 

both in inclosed seas and in gulfs and bays connected with the open ocean.3 Among the bestknown localities are the eastern Mediterranean 

Sea., Black Sea, Sea of ·Azov, Caspian Sea, 

Dead Sea, Aral Sea, and other inclosed bodies of 

~ater in southeastern Europe and western Asia. 

Similar muds, however, also occur around Oesel 

Island and elsewhere in the Gulf of Riga, at 

several localities in the southern Baltic Sea., 

around the mouths of the Elbe and the Weser, 

and along the Nether lands coast in the North. 

Sea, as well as locally on the coast of Scotland. 

M~ny sulphur springs throughout Europe contain black muds that carry ferrous· sulphide, 

and the "blue mud" of the ocean bottom n.long 

the edg~s of the continents is also characterized 

by iron sulphide, part of which is doubtless in 

the ferrous forin. 

The "blue mud" of the ocean bottom 1s blue 

or slate-colored, but the upper layer in contact 

with the water is oxidized to red or brown. 

The blue color is due to the presence of organic 

matter and sulphide of iron in a fine state of 

division. It has t~e smell of sulphureted hydrogen. The depth at which it occurs ranges 

from 125 to 2,800 fathoms. "Blue mud" cona Doss, Bruno, Neues Jnhrb., Beilage Band 33, pp. 689 et 

seq., 1912. (Numerous references cited.) 
() 

GEOLOGIC IMPORTANCE OF IRON -DEPOSITING -BACTERIA. 63 

tains, besides terrigenous clastic material, 

abundant remains of Foraminifera, Radiolaria, diatoms, sponge spicules, and fragments 

of mollusk and echinoderm shells. 

The "blue muds" surround nearly all the 

continents and occur in inclosed seas like the 

Mediterranean, and even in the Arctic Ocean. 

They occupy the largest area of the terrigenous ocen nic deposits.1 

The following table shows the range in composition of the principal constituents of blue 

mud: 

Rango rn co1nposUion of tho twincipa.l consti.t,uents of 

blno nMul. 

8102---------------------------------- 59.54-64.20 

il1208--------------------------------~- 13.55-19.42 

Fe20s--------------------------------- 7.15-11.23 Loss. on ignition2_______________________ 4. 92- 6. ~4 

Small amounts of soda, potash, lime, and 

magnesia are also present. 

Recent studies of ·muds from the bottom of 

the Black Sea and neighboring limans 8 as 

well as from other inclosed seas of southeastern Russil1>, have shown that they contain an 

abundance of ferrous sulphide. As indicated 

by the dredgings two kinds· of mud exist in the 

Black Sea at depths of 300 to 717 fathoms. 

One type is a sticky black .mud containing hydrous ferrous sulphide (FeS.ni-12 0) presum- · 

ably as a gel. The other type is a less dense 

blt~e mud containing pelagic diatoms, a smaller 

quantity of ferrous sulphide, and concretions 

of iron disulphide. The blue mud is believed 

to underlie the black mud, and its existence 

proves that iron disulphide undoubtedly occurs at least locally in unconsolidated ferrous 

sulphide bearing muds. 

In some of the limans and shallow la.kes of 

southern R.ussia ferro_us sulphide generally occurs as an intermixed paste or as lmnps and 

concretions in black mud, or ~s coatin~ of 

other substances, but it is also found with moist 

black shore muds and sands. 

The limans bordering the Black Sea are shallow, salty lagoons separated fron1 the open 

11\fm·r·ny, .T., and Renard, A. F., Challenger Rept., Deep-sea 

deposits, pp. 22!) et seq., 18!)1. 

l\furrny, .T., and Hjort, .T., The depth of the ocean, pp, 161 

ct: seq., 1!H2. . 

D Organic mutter, sulphur, etc. 

s Andr·nssow, N., r~a mer noire: Cong. g~ol. internut., Guide 

des cxc., 7° aess., Excursion 29, p. 7, 1897, cited by Hayes, 

A. 0., op. cit., p. DO. 

water by low, narrow bars.4 The bottoms of 

these lagoons are covered .with a tough, black 

mud which owes its color to an abundance of. 

ferrous sulphide. The mud is plastic and 

doughy, has a strong odor of hydrogen sulphide, 

and gives an alkaline reaction. It consists of 

clay particles, fine sand, and shells, which are 

impregnated with and held together by colloidal, hydrated ferrous sulphide and abundantly mixed with decomposing organic material derived from both plants and animals. The 

liman n1ud is used for healing ·purposes on ·account ·of its content of hydrogen sulphide, but 

when exposed to the air the ferrous sulphide 

oxidizes and the mud takes on a gray color. 

However, upon being reimmersed in brine it is 

again reduced, owing to the action of reducing 

bacteria, which are present abundantly. 

Doss's explanation 5 or' the origin of sedimentary deposits of iron sulphide is as follows: 

Iron is dissolved from iron-bearing minerals 

and carried in solution as soluble ferrous carbonate (Fe(C08 ) 2 ) by surface waterS to inclosed bays or lagoons in which decaying organic matter is abundai1t. I-Iere the iron is precipitated, either directly· as black colloidal hydrated :ferrous sulphide by reaction with hydrogen sulphide liberated by bacterja from the 

decaying organic matter, or as ferric hydroxide 

by iron bacteria. Ferric hydroxide under reducing conditions and in the presence of hydrogen sulphide is changed to hydrated ferrous 

sulphide. By loss of water and the addition of 

sulphur, which occurs as free sulphur in the 

mud, the hydrated ferrous sulphide is changed 

tomelnikowite (FeS2 ). Th~melnikowitealters 

gradually to pyrite and the inclosing mud becomes hardened and cemented to clay and shale. 

·Where iron sulphide was o:r;iginally mixed with 

the mud it _was later disseminated through the 

resulting rocks, but where more or less pure deposits occurred tliey resulted in -t]?.e formation 

of beds and lenses of pyrite. . Later metamorphism may cause the recrystallization of the 

pyrite lenses and alteration of the inclosing 

rocks to slate and schist. Thus· all stages occur 

between the black ferrous sulphide muds :forming in many inclosed basins and the recrystal- · 

" Omellanski, W., Dcr Krel.slauf des Schwefels, in F. Lafar's Hnndbuch der technischen Mycologic, Band 3, pp. 222-

223, 1904-1!)06. 5 Doss, Bruno, Zeitschr. prakt. Geologie, .Tahrg. 20, pp. 

460-461, Hl12. 
64 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

lize9- lenses of pyrite interbedded with slates 

and schists. 

Many_ of the pyrite lenses in schists and 

other n1etamorphic rock, such as the deposits 

at Huelva and those of Agordo and Szomolnok, have been fairly definitely shown to be 

relate~, at least in part, to igneous intrusions. 

The igneous rocks may have caused the formation of the entire deposits or they may simply 

have caused the recrystalHzation of original 

lenses of iron sulphide and the introduction 

into them of their content of silver, lead, ·zinc, 

copper, .and other n1etals. It n1ust be remembered that deposits of iron sulphide are forming abundantly at the present time in association with argillaceous sediments, which upon 

n1etamorphism would yield just such rocks as 

those in which we find the lenses of pyrite 

containing copper, lead, and zinc sulphides. 

The facts that these lenses are distinctly conformable to the bedding of the rocks in which 

they occur, that many of theE1 exhibit banding 

parallel to the bedding of the associated rocks, 

and also that many are far removed frmn igneous intrusions, are strong points in favor of 

their original sedimentary origin. The reason 

why only a few deposits of iron sulphide that 

are clearly of sedimentary origin, such as those 

of Russia and Newfoundland, have been described in the literature can perhaps be sought 

in their relative unimportance con1mercially, 

which is due to their lack of precious or semiprecious metals. 

FORMATION OF SEDIMENTARY IRON-BEARING DEPOSITS. 

DEPOSITION OF IRON :BY MECHANICAL PROCESSES. 

There are certain iron-ore deposits which 

have been formed almost entirely by mechanical processes. To this type belong the black 

sands, whic"tl consist of magnetite or hematite 

sand mixed with particles of other hard, heavy 

minerals, such as garnet, zircon, ilmenite, 

rutile, quartz, and chromite. 

The processes which are most active in the 

formation of black sands are disintegration 

and transportation. The rocks that contain 

disseminated iron minerals upon being subjected to disintegration without much decomposition release the separate mineral pa.rticles, 

which are then ·carried away. by streams and 

finally sorted by currents and waves according 

·to their density. Black sands 1nay form on the 

seashore or on the shores of rivers or lakes. 

Their specific gravity prevents the particles 

from being carried very far from shore, though 

moderately swift flowing streams may carry 

thmn some distance, along with other coarse 

clastic material, and deposit them in their 

deltas. 

In general black sand deposits are very impure on account of the admixture of non ironhearing clastic particles. In n1any places also 

they are very high in titanium owing to the 

presence of abundant ilmenite. Deposits of 

1nagnetite sands are forri1ing at the present · 

time along the sea coast and along the larger 

rivers in Washington, Oregon, and California. 

Deposits of hen1atite sand are forming along 

~treams in Minas Geraes, Brazil, the materials 

being derived from the disintegration of the 

extensive beds of hematite-bearing quartzite 

that occur in that region. Though most of the 

lmown black sand deposits are of recent origin, 

older beds of a similar character are met with 

locally, such as the black sand beds in Upper 

Cretaceous rocks in northwestern Montana.1 

Other iron-ore deposits that are formed 

largely by mechanical processes are the detrital 

talus deposits, consisting of blocks and fragments of ore, which comn1only lie.on slopes below outcropping cliffs of iron ore. They are 

generally designated by the name of· rubble ore. 

Such deposits may become cemented by the filling of the spaces between the fragments and 

thus result in clastic breccias. To this type 

belong the "canga" ores .of Brazil, which are. 

drived from and associated with the bedded 

hematite. oSome fragmental varieties of laterite 

which occur in India in association with the 

Dharwar iron-bearing sediments may also be 

classed with thi3 type. 

DEPOSITION OF IRON BY CHEMICAL PROCESSES. 

FORMATION OF DEPOSITS OF FERRIC HYDROXIDE. 

Ferric hydroxides 1nay be precipitated either 

from organic or inorganic. iron solutions, the 

reaction being accompanied by hydrolysis in 

ferric compounds and by oxidation with hy1 Stebinger, Eugene, Titaniferous magnetite beds on t'!le 

Blacldeet Indian Reservation, Mont.: U. S. Geol. Sur:vey 

Bull. 540, pp. 329-337, 1914. 

() 
GEOLOGIC IMPORTANCE OF IRON-DEPOSITING BACTERIA. 65 

drolysis in ferrous compounds. The ferric 

hydroxides form a gradationaJ series in° which 

iron, in the form. of Fe20 3, is associated with 

\Yater. This water (meaning "water above 

105° C.") ranges from a few per cent, as in 

hydrated hematite, to an unknown upper limit, 

perhaps more than 30 per cent. These amounts 

of "water" probably range through all the 

possible varieties of combinations, as with most 

other hydrated oxides, from. hydroxyl groups 

to firndy held hygroscopic moisture. In general the series of ferric hydroxides is probably 

analogous to the various .hydrated forms of 

silica. A large number of ferric hydroxides 

ha "'re been prepared or are found in nature as 

minerals, but the exact composition of many 

of these is uncertain.1 

l\1uch work was done on the constitution of 

ferric hydroxides during the nineteenth century, of which the most important was that of 

l\1uck,2 Tomassi,3 van Bemmelen,4 and Ruff~5 

Muck first and Tommasi later, by chemical 

precipitation from iron solutions, obtained two· 

different classes of ferric hydroxides, the red 

hydroxides and the yellow hydroxides. The 

red hydroxides are obtaiped by precipitation 

from ferric salts with alkalies, whereas the 

yellow hydroxides are. obtained by the oxidation of moist ferrous hydroxide or of ferrous 

carbonate. By drying freshly prepared precipitates of ferric hydroxide at different temperatures Tommasi obtained the following 

compounds, which he regarded a~ definite hydroxides: 

Yellow hydroxides: 

Fe~(OH)o _______ Forms b~low 70° C. 

Fe~ ( OH) ~o _____ .li'orms between 70° and ·105° C. 

~i.,t:'~(OHhO _____ .Forrns between 105° and 150° C. 

H('tl hydroxides: 

Fe~(OH)o _______ Not obtained. 

Fe2 (Oil) .o _____ Ji'orms below 50° C .. 

li'e2(0Hh02-----Forms between 50° and 92° C. 

Upon further heating of the red hydroxides 

a brown nnhydrous ferric oxide having a 

1 RoHCO<', FT. :m., and Schorl<'mmer, C., A treatise on chemiAtl'y, vol. 2, pp. 11!)7 rt: seq., 1!)13. 

D Muck, Zeltschr. Chemic, 2d ser., vol. 4, p. 41, 1868. 

C'lt!'d by Roscoe, H. F:., and Schorlemmer, C., op. cl_t., p. 1222. 

a 'l'ommnHI, D., Ulcet·che sulle formole di costitutione del 

compost! fet·rici; rnrtc prlmn, Idmti ferric!, Florence, 1879. 

Al~o HC'e D<'nf·Hche cll('m. 0<'sell. Her., vol. 12, pp. 1929, 2::134, 

lR7!). . 

• Van BcmnwlPn, J. l\I., Rec. trnv. chhn., vol. 7, pp. 36-

llfl, 1889. 

n Hull', 0., Ud.>et· das Elsenoxyd und seln Uydrnte: 

Deutsche chem. Q(•SC'll. )3er., vol. 34, pp. 3417 et seq., 1901. 

6[)629°-19-5 

specific gravity of 5.1 was produced, but the 

'anhydrous ferric oxide resulting from heating 

the yellow hydroxides was red9-ish yellow in 

color and had a specific gravity of 3.95. Tommasi concluded from these data that there exist 

t.wo distinct series of ferric hydroxides with 

different properties. 

Van Bemmelen in his experiments with colloids showed that red ferric hydroxides are 

really colloidal substances without any definite 

chemical composition, the amot~nt of water retained by them being dependent on the 

aqueous vapor pressure in the atmosphere·, with 

w h1ch they are in equilibrium. Only at high 

temper~~tures are they converted to anhydrous 

ferric oxide. He believed that the red hydroxides do not differ in any essential way 

from the yeUow hydroxides and that the latter 

also are colloids jn perhaps a little more stable 

and concentrated form. 

If these conclusions are correct it is difficult 

to understand under what conditions various 

stable ferric hydroxides found in nature are 

formed, and further how deposits of anhydrous or slightly hydrated ferric oxide are 

formed so abundantly under natural" conditions when in the laboratory ·high temperatures 

are necessary for their formation. 

Realizing the discrepancies between the conclusions of Tommasi and Van Bemmelen, Ruff 

took up the study o£" the ferric hydroxides. 

His first experiments were performed with red 

colloidal ferric hydroxide under ordinary conditions of pressure but with varying temperature. They confirmed more or less the work 

of Van Bemme1en. He found also that the 

freshly precipitated red ferric hydroxide, 

when. allo·wed to stand for several years at 

ordinary temperatures, gradually lost water 

bi1t before becoming entirely anhydrous began 

to take on water again and after 10 or 15 years 

changed to the normal.sta ble ferric hydroxide, · 

2Fe2 0 3 .3H2 0. 

The second series of experiments of Ruff was 

perfonned with ferric hydroxide under varying pressures of about .5,000 atmospheres. By 

raising the temperature under these conditions 

of pressure he found that the colloidal reel ferric hydroxides became converted into definite 

hydroxides all ·:found in nature,· the particular 

hydroxide formed depending on the temperatures. Between 30° and 42.5 ° C. the colloid 
66 IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

. changed to a yellow granular powder having series being transformed into the hydroxides 

the water content and specific gravity. of lin1o- of an~ther series by the elimination of water. 

nite (2Fe20 3.3H20), between 42.5° and 62.5° C. Hydroxides of iron of various kinds, thereit became yellowish red and took on the prop- fore, may be formed by precipitation with alerties of goethite (Fe20 3.H20), and above kalies or by simple oxidation and hydrolysis 

62.5° C. it became bl.·ick-red and had the com- frmn different iron compounds. Thus, soluposition of turgite (2Fe 20 3.H2 0). )luff did tions of ferric chloride and ferric nitrate, when 

not obtain the anhydrous oxide, hematite, at treated with sodium, potassium, or ammonium 

high pressures below a temperature of 150° C. hydroxides, give precipitates of red colloidal 

The yellow hydroxide, when treated under sim- ferric hydroxide. Solutions of ferrous salts 

ilar conditions with a range of temperature when treated with alkaline hydroxides give 

from 40° to 7'0° C., behaved like a stable com- precipitates of light bluish-green ferrous bypound and did not alter in c.ontent of water. droxide, which upon oxidation changes to yelThe suggestion is made that this material may low ferric hydroxide. Yellow ferric hydroxide 

be represented in nature by the mineral xantho- is also formed by oxjdation and hydration of 

siderite (Fe2 0 3.2H2 0). · ferrous carbonate and in the rusting of metalRuff concludes from these data (1) that red lie iron. Freshly precipitated iron rust concolloidal ferric hydroxide under ordinary con- sists chiefly of ferric hydroxide but usually 

ditions is a colloid of indefinite cmnposition, contains considerable quantities of ferrous bybut that under high pressure and rising tern- droxide and ferrous carbonate. 2 When dried 

perature it may change· in a short time to and exposed to atmospheric oxidation it soon 

various definite hydroxides; (2) that yellow loses its ferrous iron and consists entirely of 

ferric hydroxide is very probably a definite ·ferric hydroxide, with the approximate comchemical compound that contains various pqsition 2Fe2

0 3

.3H20. 

a1nounts of adsorbed water; ( 3) that under In some solutions of iron salts, such as ferordinary conditions of temperature and pres- rous or ferric sulphs.te 1 as well as certain iron 

sure the red colloidal ferric hydroxide is slowly salts of organic acids, iron may be precipitated 

. dehydrated and changed to anhydrous ferric by oxidation and hydrolysis (for the ferrous 

oxide, but at the same time water is taken up salts) or by hydrolysis alone (for the ferric 

by the anhydrous oxide and a change occurs to ·salts) not as hydroxide, but in the form of basic 

the stable ferric hydroxide, limonite; ( 4) that salts. "Then a ferric sulphate solution is 

. pure anhydro~s ferric oxide does not form treated .with an excess of alkali, as ammonimn 

from ferric hydroxides except 11nder excep- hydroxide, :ferric hydroxide is· precipitated. 

tional conditions of temperature or· pressure. 'Vhen, however, the precipitation is incomplete 

Nicol~rdot,1 by whmn the most recent work various basic ferric sulphates are fonned. The 

has been done on ferric hydroxides,' has. come san1e is true when a solution of ferric sulphate 

to the conclusion that six modifications of fer- is boiled or when a solution of ferrous sulphateric hydroxide exist which are all polymers qf is allowed to oxidize in the air: Among' the 

the simplest hydroxide. They all differ in com.mon basic ferric sulphates thus formed 

chemical and physical properties .and in tfie which are said to exist is FeS04 (OI-l) .7H20, 

content of water. Two of the hydroxides, ·which is decomposed by water to form the in-

(Fe203)1 (Hz0)1.5-z and (FezOa)l (H20)1-1.5' are soluble salt Fe~S04 ( OH) 4 .5H2 0. Several o:f 

brown and are derived from the normal _ses- the basic sulphates occur as n1inerals, being 

quioxide Fe20 3, whereas the other four; all formed by the oxidation of iron sulphicles.3 

opalescent and yellow in color, are derived Among these are vitriol ocher (FeS04 (0H) 4 • 

from the. two anhydrides of Fe2(0H)o- 2Fe(OH) 3H 20), copiapite (Fe2(S04 ) 3. 

Fe20(0H) 4 and Fe20 2 (0H) 2• Each of these Fe2(S04 ) 2 (0H) 2.10H20), and fibroferrite 

substances forms a series of hydroxides with (2Fe2 (S04 ) 2(0H2 .Fe2S04 (0H) 4 .24I-l20). 

variable water content, the. hydroxides of one 

1 Nicolardot, M. P :, Recherches sur le sesquloxyde de fer : 

Annales chimie et physique, 8th ser., vol. 6, p. 334-393, 

1905. 

2 Moody, G. T., The rusting of iron': Chern. Soc. Jour., 

vol. 89, pp. 720 et seq., 1906. 

a Roscoe, H. E., and Schorlemmer, C., op. cit., pp. 1214 

et seq. 
GEOLOGIC IMPORTANCE OF IRON-DEPOSITING BACTERIA .. 6'7 

Pickering/ who has done some work on the Fe2 (C2H 3 0 2 ) 2 (0H) 4+2Fe20 3 •

4 I-Ierz 5 found. 

constitution of basic ferric sulphate, states that that the basic ferric acetate,' FeC2H 30 2 (Oil) 2, 

011ly one basic ferric sulphate exists and that is precipitated from solutions of pure ferric 

it has the formula Fe2 (S04 ) 3 .5Fe20 3 .wH20, in acetate (Fe(C2H 3 0 2 ) 3 ) when heated for 10 

which w 1'anges from 8 to 40. The n1olecular hours or more a~ a temperature of 44° C., and 

weight ranges from 1,341.34 to 1,916.10, accord- also fron1 impure ferric acetate solutions when 

ing to the amount of wn,ter present. allowed to stand at ordinary temperature or 

Tho reason for these varying results is prob- when boiled for a short time. Under the }atably to be found in the fact that the precipi- ter coi1ditions no precipitation occurred from 

tate which .. fonns varies with the nature of pure solutions. This basic ferri~ acetate is a 

the solution, the temperature, and the manner fine yellow colloidal precipitate. Often ferric 

of precipitation. It proba.bly consists of a hydroxide (Fe(OH) 3 ) is Sttid to form with it 

mixture of one or more of th'e p·ossible ferric .as small, brown, shining crystals. 

hydroxides with one or n1ore basic ferric A solution of iron oxalate upon treatment 

sulphates and the proportion of each present 'Yith alkalies also gives a. brownish-red flocvaries under different conditions of precip- culent precipi.tate, which is probably a 1nixture 

itation. 2 of ferric hydroxides and basic ferric oxalates. 

1\1ixcd precipitates of all degrees of oxida- An iron oxalate solution when boiled leaves a 

tion and hydration probably form under di£- yellowish-brown salt with the .composition 

ferent coiH1ition.s, the degree of complexity Fe 2 ( C2 0 4 ) 3 .18Fe (OI-l) 3 , but when the solution 

Vftrying with the treatment. Thus simple boil- is only heated to 100° C. the precipitate is 

ing would result in the formation of a larger Fe2 (C2 0 4 )a.2Fe(OH) 3+4H20, showing an inproportion of basic.ferric sulphates, and treat- crease of Fe(OII) 3 ·with the increase in temment with alkalies would result in the £orn1a- perature.6 

tion of larger amounts of ferric hydroxides. Iron lactate upo'n treatment. w'ith alkalies 

11he further hydrolysis of basic ferric sul- gives a flocculent brownish-black precipitate, 

phates results i ri the formation of the stable doubtless a ,mixture of ferric hydroxides and 

ferric hydroxide, linionite. · basic ferric lactates. 

Several of the iron salts of organic acids, Comparatively little work has been done 

such as iron acetate, iron oxalate, and iron lac- heretofore on the. constitution of basic ferric 

tate, give precipi~ates of flocculent basic salts. compounds precipitated from solutions of orThe precipittttion results from simple oxida- ganic iron salts and very little definite intion, heating, or treatment with alkalies. formation is available with regard to these 

A solution of iron acetate, when treated with compounds. In general the precipitates 

alkalies or. when evaporated or boiied, gives a forined are probably of indefinite composition, 

red ifocculent precipitate, consisting probably due to the. variable content of water and to the 

of a mixture of ferric hydroxides and basic varying amounts ·of ferric hydroxides mixed 

ferric acetates. The amount of ferric hy- with them. As in the precipitation from soludroxiclc present in the precipitate increases with tions of ferrous and ferric sulphate the precipitemperaturc, with the strength of the precipi-. tates which form in~ solutions of organic iron 

tant, nnd with the time allowed for precipita- salts vary in composition according to the contion. "\.Yhen a solution of iron acetate is boiled· 'clitions of precipitation.2 I£ precipitation takes. 

in the 1n:esence of alkn:Iine acetates, ferric by- place through the agency of a strong alkali, 

droxide rather than bnsic ferric acetate is said such as sodium hydroxide (N nOl-I), more ferto be precipitated.8 A number of basic ferrie 

acetates have· been described, among which 

are Fe(C2l-I3 0:J (0~1) , Fe(C2H 30 2 ) 20I-I,ancl 

1 rtcl{et·ing, S. W., On the constitution of molecular compound!'! ; the molecular weight of basic ferric sulphate: 

Chem. Soc .. Tom·., vol. 4B, pp. 182 et seq., 1883. 2 Hunter, W. II. (Dcptntment of Ch'emistry, University of 

MinnC'Sotn), IH~rsonnl communication. . 8 Betlstcin, li'., ITnndbuch der organiscben Chemie, Auflage 

3, Bnnd 1, pp. 405-406, 1893. 

4 Scheurer-Kestner, 1\I. A., Sur quelques nouvelles comblnaisons du fer et sur l'atomiclte de cet element: :-:ioc. 

cbim. Paris Bull., vol. 5, pp. 342-352, 1863; 1\:Iemolre sur 

nne nouvelle clnsse de scls de fer, et sur la nnt:ui·e he:xa.-

tomique du ferrlcum : Annales chimlc et physique, 3d ser., 

vol. 63, pp. 422-447, 1861. · 

u Herz, W., Ueber den Yerlauf der Zersetzung des Ferrlacetats : Zeitschr. anorg. Chemic, Band 20, pp. 16-20. 

1899. 

0 Beilsteln, F., Ha.ndbuch der organlscben Chemic, Auflage 

3, Band 1, p. 644, 1893. 
68 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

ric hydroxide is liable to be intermixed with 

the ba~ic ferric salts than if a weaker alkali, 

such as ammonium hydroxide (NH4 0H), is. 

responsible for the precipitation. Likewise 

the reaction with a weak alkali would result 

in the formation of relatively more ferric hydroxide than would result from simple boiling. 

It seem.s probable that more than one basi_c 

cmnpound of each of the organic iron salts may 

exist. Thus there are probably several basic 

ferric acetates or basic ferric oxalat.es and these 

vary in quantity relatively to each other and to 

the ferric hydroxides in precipitates formed 

under different conditions. Care must be 

taken, however, in, drawing conclusions frmp. 

analyses of precipitates; because even if but 

one ferric hydroxide anclbut one basic salt' of 

a given organic acid '\vere present, their changing ratiosl under varying conditions might 

counterfeit the presence of other compounds in 

these mixtures. 

In solutions of organic iron salts o~ oxyacids, such as iron citrate, iron tartrate, or iron 

malate, basic ferric salts do not precipitate, 

because in these salts the iron forms part of an 

"inner complex salt." This is tru'e also of 

salts of many of the acids which 9ccur in the 

" composite" called humic acid, and is .the 

reason ,.Vhy such salts may be carried in solution for long periods. · 

In the formation of sedimentary iron-bearing deposits in nature the precipitation of 

ferric hydroxide is mainly from ferrous solutions .and occurs when these solutions come in 

contact with the oxygen of the · atmo$phere. 

The precipitation may result chemically from 

oxidation alone, but as a rule iron bacteria aid 

in the reaction. To some extent ferric hydroxide is also probably precipitated from ferric solutions which in nature are mainly solutions of organic salts, and here also iron precipi-

. tating bacteria may aid in the deposition. ' 

·The hydroxide precipitated from solutions of 

· ferrous salts is generally the stable yellow ferric hydroxide of fairly defin~te chemical composition, whereas that pr~cipitatecl from ferric solutions is generally the red colloidal hydroxide, which, however, in time may change 

to the stable hydroxide, 2Fe20 3.3H\l0, as 

shown by Ruff. 1 

1 Ruff, 0_., op. cit. 

The most common form in which iron occurs in solution in natural waters is as ferrous 

bicarbonate, but ferrous or ferric sulphates 

probably occur, as well as salts of organic 

acids, which have generally been included under the terms ferrohumates and ferrihumates. 

Ferrous bicarbonate may be derived from 

many different iron minerals. It is taken into 

solution through the agency of carbonic acid 

(H2C03 ) and retained in solution by excess 

carbon dioxide. Such solutions may remain in 

circulation underground for long periods and 

eventually come to the surface as iron springs 

or seepages and may be carried by streams 

to lakes or lagoons. Upon the removal of 

the excess carbon dioxide and exposure to the 

atmospheric oxygen, oxidation and hydration 

take place according to .the ·following reaction: 2 

4FeC03 -f-3II20+20=2Fe20 3 .3fl2 0+4C0 2 

This reaction may perhaps be better stated 

in two steps, thus : 

FeC03+H2 0=Fe ( OH) 2+C02 

4Fe (OH) 2+20:-2Fe2 0 3.3H20+H2 0 

The flocculent yellowish-brown precipitate of 

ferric hydroxide (2Fe2 0 3 .3H20) that is formed 

dr<;>ps to the bottom, where it accumulates or 

where a part or all of it may become mixed 

with mud containing organic matter and be reconverted to ferrous carbonate. A part of the 

yellowish-brown precipitate may co.nsist of 

iron in the more hydrated forms, such as 

Fe20 3.2H20 and Fe2 0 3.3H20. In this way the 

mixture of various ferric hydroxides and of 

ferrous carbonate in bog o'res is accounted for. 

The iro·n sulphide and jron sulphate locally 

present in the deposits n1ay be formed by the 

action of H 2S, given off by the decaying organic matter, on ferrous carbonate or by precipitation from iron su~phate solutions. 

Iron sulphate is present in solution in Ineteoric waters owing to the decomposition of sulphides of iron or to the action of sulphuric acid 

on other iron minerals. The ir'on present in 

this form may be precipitated by simple oxidation as a, mixture of ferric hydroxides and 

basic ferrio sulphates, or by reaction with cal-. 

2 Van Hise, C. R., .A. treatise on metamorphism: U. S. 

Geol. Survey Mon. 47, p. 826, 1904. 
GEOLOGIC IMPORTANCE OF IRON-DEPOSITING BACTERIA. 69 

cium carbonate present in solutions as ferrous carbonate, which then may be oxidized to 

li monitc. Van Ilise says that basic ferric sulphate may be precipitated from ferrous sulphate solution according to the following reaction: 1 

12FeS04+G+ (x+9)H2 0= 

Fe2 (804 ) 3.5Fe20 3.wl-I20+9l-I2S04 

In reality, however,· the reactions which take 

placo ure probably much more complex and. the 

result :is a mixture of compounds rather than 

a singlo basic salt. 

The reaction between ferrous sulphate and 

calcium carbonate to form ferrous carbonate 

is as follows : 2 

FeS04+CnC03=CaS04+FeC03 

The calcium sulphate is deposited as gypsum, CnSO.l.2l-I20, and the ferrous carl?onate 

nuty be oxidized--to ferric hydroxide according 

to the reaction given above. In the presence of 

abundant oxygen the bvo reactions might occur almost simultaneously thus·: 

FeS04CaCOa +If2

0 +02Fe20 3 .3H20-i-CaS04 • 

2H20+C0 

If ferric sulphate is present in solution the 

precipitat,on of ferric hydroxides may occur 

thus: · 

Fe2(S04)scaCOa + H202Fe20 3 .3I-I20 + CaS04. 

. 2H20+C0 

The occurrence of iron in solution in natural 

waters as salts of organic acids has recej. ved 

but little study, nnd the literature with reference to it is largely speculative. It is commonly supposed that the iron is in the form of 

soluble salts of certain little-known soil acids 

termed humic acids. It does. not seen1 impossible, however, that it may also be carried as 

snits of other organic acids known to be present 

in the soil, such ns formic acid, lactic acid, 

butyric acid, citric acid, or tartaric acid. 

The iron which is present in solution in the· 

fonn of organic salts upon precipitation. is 

probably largely thrown down as ferric hydroxide together with various insoluble or1 Vnn [J'if;e, C. R., op. cit., p. 826. 

~ l\Toot·e, JU. J., The occm~rcnce and origin of bog iron deposits in the distt·lct of '£hunder Bay, Ontario: Econ. Geology, YOl. 4, p. 535, 1910. 

ganic ferric compounds, which, however, in a 

comparatively short time will also change to 

ferric hydroxide. According to Aschan,s' who 

has studied this subject; the principal organic 

iron salts occurring in natural waters are salts 

of humic acids, such as ferrohmnates and ferrihumates. He believ~s that humic acids are the 

principal constituents of the soluble dCI·ivatives of humus, which he calls humus hydrosols 

(gels in colloidal solution). Humus hydrosols 

are of unknown and variable composition and 

are supposed to contain; besides humic acids, 

various other soil substances such as humat~s 

of different composition. They a,re believed to 

play an important part in the decomposition of 

rocks and n1inerals, as well as in the precipitation of such substances as iron and aluminumThe humus hydrosols are the materials ·which 

impart the deep-brown color to streams and 

lakes in regions of abundant vegetation. By 

decomposition they change to carbon dioxide 

and ammonia. 

Aschan found that if ferric salts were pres~ 

ent within certain narrow limits of concentration, in waters containing humus hydrosols, 

insoluble ferrihumates were deposited but 

that above or below this concentration only 

soluble salts were formed. He found also that 

i£ ferrous salts instead of ferric salts were 

present, no precipitation took place, soluble 

ferrohumates being formed, which, however, 

if present in the proper concentration might 

by oxidation change to insoluble ferrihumate$. 

The action of humus hydrosols in the formation of lake and bog iron ores is supposed 

by Aschan to be· as follows : 'Vhen the sol uble humus substances are taken into solutio:1 

by ground waters some of the hqmic acids in 

them immediately begin to react chemically 021 

the m~neral constituents of the rocks through 

which the waters percolate and form soluble 

humates of different bases, among them iron. 

These humates are suppo$ed to form food for 

microorganisms and the microorganisms are 

believed to aid substa:ntially in rock decay. 

Besides aiding in the decay of rocks humus 

hydrosols are believed .to aid in the precipitation of iron and other substances from 

solution. When ferric or ferrous salts are in 

8 .t\schan, Ossian,, Die Bedeutung der wasserloslichen Humusstoffe (Humussole) fiir die Bildung der See- und Sumpferze: Zeltschr. prakt. Geologie, Jahrg. 15, pp. 56-62. 1!)07. 
70 IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

solution in water containing ·humus hydrosols ferrihumates or ferrohumates are formed. 

Ferrbhumates are soluble, but under certain 

conditions of concentration and oxygen content insoluble ferrihumates are formed and 

these are precipitated directly. The soluble 

ferrihumates and ferrohumates may have their 

organic portion utilized as food by microorganisms and the ferric hydroxide is then pre~ 

cipitated. Thus insoluble ferrihumates and 

ferric hydroxide are believed to occur together 

in lake and bog iron ores, and this is supposed to ·explain the presence of organic carbon in th~se ores. , · 

Sj·ogren 1 believes that the principal agents 

for the solution of iron in nature are sulphuric 

acid, carbon dioxide, and organic acids. Sulphuric acid is formed by the decomposition of 

sulphides, and carbon dioxide and organic acids 

are formed mainly from decomposing organic 

1natter. The decomposition of organic matter in the absence of oxygen results in the 

formation of hydrocarbon combinations such 

as humus, which when acted upon by ammonia 

or alkalies yield humic acids. This action 

withdraws oxygen from surrounding mineral 

·compounds, in this matter reducing ferric oxide 

to ferrous oxide, which then forms soluble douI:He salts with ammonia a·nd humic acids. These 

double salts may be further ~hanged to ferrous carbonate and this substance may be. oxi-

. dized to ferric hydroxide by the removal of 

carbon dioxide in the presence of oxygen. The 

iron, however, may also ·be precipitated directly from humic acid solutions. From sulphate solutions iron 1nay be precipitated as 

basic ·ferric sulphate, which, according to 

Sjogren, is changed to ferric hydroxide by the 

. action of ammonium or alkaline carbonates or 

by humus. From a mixture of humic acid and. 

iron sulphate solutions iron may be precipitated as ferric hydroxide by 'the action of ammonia. 

According to Beck 2 iron may also be precipitated from iron sulphate solutions by ·the 

addition of ammonium humate, which he 

states is always present in the brown waters 

1 Sjogren, II., Ueber .die Entstehung der schwedischen 

Eisenerzlager : Geol. Furen. Stockholm Forb. 13, p. 373, 

1891. Reviewed by R. Scheibe in Zeitschr. prakt. Geologie, 

1893, pp. 434-437. . ' 

. 2 Beck, R., The nature of ore deposits, '\?ol. 1, pp. 101-103, 

translated by W. II. Weed, 1905'. 

of peaty regions. The precipitate formed is 

ferric oxide and later ferric hydroxide. 

The opinions concerning the precipitation of 

ferric hydroxide from natural iron-bearing 

waters have been summarized above. Some of 

these opinions are largely speculative as to pos-

. sible reactions which may take place under 

conditions such as are fottnd in nature, but 

others are base;d on well-known ·chemical phenomena. Though many of the reactions mentioned in connection with the precipitation of 

ins~luble iron compounds from solutions of 

iron sulphate and organic iron ·salts probably 

occur, there is little doubt that far more important than these processes is the direct precipitation from ferrous bicarbonate solutions, 

·whether through simple oxidation and hydrolysis or through the action of iron-depositing 

bacteria. The nature of the action of the bacteria in the dep.osition of ferric hydroxide is 

dis_cussed at' length in a subsequent section. 

The precipitation of ferric hydroxide from 

ferrous bicarbonate solutions takes place almost immediately after the iron-bearing waters reach· the surface, where they become saturated with oxygen and lose their carbon elioxide. This accounts for the yellowish-brown 

ocherous scums, which occur around all springs 

and seepages of iron-bearing waters. !-lowever, there is no doubt that iron is also carried 

in solution by surface streams whose. waters 

are apparently rich in oxygen. In this manner iron in solution reaches lakes, lagoons, and 

marshes, where it is precipitated and forms bog 

and lake ores. In what form the iron is carried under these conditions it is difficult to say. 

Perhaps enough carbon dioxide occurs in these 

waters to permit the carrying of appreciable 

amounts of iron as 'ferrous bicarbonate, or perhaps the iron is carried in the form of organic 

iron .salts. The equilibrium between the solvent carbon · dioxide and the ferrous bicarbonate in solution is a subject which requires 

more thorough investigation. 

Besides the iron which is carried in solution 

by surface streams probably a considerable 

amount of light flocculent ferric hydroxide, 

which has been formed where the iron-bearing 

. soluti~ns first reach the surface, is· carried 

in suspension by the current and is deposited 

when quiet water is reached. 
GEOLOGIC IMPORTANCE OF IRON -DEPOSITING BACTERIA. 71 

The dehydration of iron deposits from their 

original form as ferric hydroxide to the final 

form. of slightly hydrated ferric oxide is a 

slow process and results froin several conditions. 

According to Ruff/ as already stated, the 

red colloidal ferric hydroxide suffers gradual 

dehydration and becon1es anhydrous ferric 

oxide. The anhydrous oxide, however, in the 

pr·esence of moisture becomes hydrated again 

nncl alters to the stable form, limonite, and rema:ins in this form. Other investigators, however, report that ferric hydroxide left for sev·-

eral years under water at ordinary temperatures became dehydrated and crystalline.2 

Spring 8 says that ferric hydroxide spontaneously loses its water if the iron is not combined 

chemically with some other substance. The' 

yellow color would thus indicate the presence 

of nlumina, lime, or magnesia. He believes 

that limonite is not a stable hydroxide and' will 

give up its water when not in. equilibrium with 

other .oxides present. . 

Pressure has in some places been an important factor in the dehydration of iron-bearing 

deposits and in other places heat and pressure 

both luwe been active. In some deposits the 

pressure may have been due simply to deep 

burial, but in other dep.osits deformational 

earth movements have been an added factor. 

It seems reasonable to suppose that long periods of time, aided by pressure due to deep 

bnl'ial, might result in at least a partial dehydration of iron-bearing deposits. 

Various· impurities besides iron. salts are 

commonly precipitated with ferric ·hydroxide 

from solntion, such as silica, ph'osphates, alumina, and manganese oxides. Silicic acid may 

be carried in solution in the colloidal forn1 or 

us nllmline sil:icates.4 The alkaline silicates are 

uctecl upon by carbon dioxide in solution and 

silica is thrown down. Colloidal silicic· acid is 

deposited by evaporation. Phosphorus, probably carried in solution in the fonn of soll.Jblo phosphates, may be precipitated either as 

1 Huff, 0., op. cit. 

l.l Wlttstelu, Vlerteljnhresschrlft fUr Pharmacle, Band 1, 

p. 277. Cited by Moore, K .T., op. cit., p. 537. 8 Spl'ing, W., Uebl'r die elsenhaltlgen li'arbstoffe sedimentlt•·en B•·dbodl'n und Uber den wahrsehelnllcben Ursprung der 

roth<'n li'<'lsen : Nenes .Tahrb., 1809, Band 1, pp. 47-62. 

' Sjogren, II., op. cit. 

calcium phosphate or as iron phosphate. Manganese, which may be present in solution in 

. considerable amount, is thrown down upon 

oxidation as a mixture of .manganese oxides. 

Some alumina also is probably precipitated 

·witl~ the ferric hydroxide, and, as previously 

stated, gypsum is thrown down with bog ores 

by the reaction of ferrous sulphate with calcium carbonate. 

}'ORl\fATION OF DEPOSITS 01' }'ERROUS CARBONATE. 

Ferrous carbonate is knmvn to occur in two 

forms-the insoluble carbonate (FeC0 8 ) and 

the soluble carbonate or bicarbonate (hypothetical formula, Fe(HC03 ) 2 ). The insoluble 

carbonate occurs oniy in the solid form and is 

either crystalline or fine grained and amorphous. It is made in the l.aboratory by precipitating a solution · .of green vitriol 

(FeS04 .7H20) with sodium bicarbonate and 

heating the mixture for 12 to 36 hours at a 

temperature of 150° C. 5 In this manner microscopic rhombohedra of ferrous carbonate 

(FeC03 ) are formed. vVhen a cold solution 

of pure ferrous Slllphate is treated with sodium 

carbonate, a floccul.ent ~vhite precipitate of ferrous carbonate is formed, which becomes dirty 

g1-:een in color on exposure to air, due to the 

n bsorption of OAjTgen and the evolution ·of 

carbon dioxide, and soon changes to ferric hydroxide. .If the precipitate is washed in the 

absence of oxyg~n it may be obtained pure and 

colorless, but usually it takes the form of a 

gray powder, which oxidizes readily to ferric 

oxide on exposure to air. 

Ferrous bicarbo~ate occurs in many natural 

waters,. being taken into solution by the action 

of carbon dioxide on ferrous carbonate. It is 

not known in the dry state, for on precipitation in the absence of oxygen h change~ to in- . 

soluble ferrous carbonate (FeC08 ) and in the 

presence o£ oxygen it is precipitated as ferric 

hydroxide. 

The supposition that iron is carried in solution in natural waters principally as the bicarbonate, or at least as a soluble carbonate, is 

probably fairly well founded, because abundant iron· is found in many places in solution 

5 Roscoe, H. E., and Sehorlcminer; C., A treatise on chemistry, vol. 2, p. 1247, 1913. 
.. 

72 IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

in waters in which there is no other acid radicle present except the bicarbonate. F~rrous 

bicarbonate remains in solution for ~n Indefi-. 

nite len oth of time as long as the waters carry b ·' 

an excess of carbon dioxide in the free state. 

As soon, however, as ~aters become depleted 

of free carbon dioxide precipitation in one of 

the various forms already mentioned will take 

place, the particular form dep~1_1~ing on the 

conditions· under which depositiOn occurs. 

.vVhen abundant oxygen is present precipitation will occti.r in the form of ferric hydroxide. vVhen no oxygen is present ·and at the 

same time carbon dioxide is re:r~oved preci pittl.tion occurs in the £orn1 of iron· carbonate. 

This form of ·precipitation takes place in 

marshes or shallow bodies of water where vegetation and decaying organic matter are abundant. The free carbon dioxide is supposed to 

be removed in part by diffusion and in part 

through absorption by plants, and at the same 

time the waters are depleted of their oxygen by 

decayin<Y or<Yanic matter. Even if part of the b b £ . iron is precipitated in the first place as erne 

hyd~·o~ide, that substance would probably be 

reduced and altered to carbonate on becOining mixed with nmds rich in organic. matter. 

The deposition of ferrous carbonate In bogs, 

therefore, is very similar to that of bog-ore deposits of ferric hydroxide, except that un~er 

these conditions the abundance of decaying 

organic matter results in the pr~cipitate remaining in the ferrous form or being changed 

to the ferrous form. 

I£ the iron is 'thr'own down as ferric hydroxide and sinks to the bottom it may become 

mixed with more or less organic matter as well 

as fine clastic sediments, and thus a considerable 

thickness of material n1ay be built up. 1 The 

reducin<Y action of the organic matter in the 

muds ;hich changes the ferric hydroxide to 

ferrous carbonat~ · is due to the removal of 

oxygen required for the oxidation of carbon 

compounds. As such places are below the 

level of ground water the conditions for the 

oxidation are imperfect, owing to the scarcity 

of free oxygen. The carbon, therefore, takes 

part of its oxygen from the. ferric hydroxide, 

reducin<Y it to ferrous hydroxide, which ~eacts b . 

with carbon dioxide to form ferrous carbonate. 

1 Van Rise, C. R., op. cit., p. 827. 

The reaction, on the assumption that carbon is 

the reducing a~ent, is as follows: 

{ 

2Fe20 3.3H20+C=4FeO+C02+3HzO 

4Fe0+4C02=4FeC0 3 

From ferrous sulphate solutions ferrous 

carbonate n1ay be precipitated by calcimn carbonate2 according to the reaction: 

FeS04+CaC03=FeCOa+CaS04 

In the absence of oxygen and free carbon dioxide the ferrous carbonate thus formed will 

be precipitated along with the calcium sulphate. . 

According to Van Rise and Leith, 3 ferrous 

silicate which has been precipitated from ferrous sulphate or other iron solutions by alkaline silicates, as explained elsewhere (p. 73), 

may, in the presence of abundant carbon dioxide, be partly or entirely changed to £errot1s 

carbonate, according to the following reaction: 

In the ·presence of excess carbon dioxide the 

ferrous carbonate will go into solution but may 

become deposited by the removal of free carbon 

dioxide. 

Various impurities may be precipitated 

with ferrous carbonate, such as calcium carb_onate, n1agnesium carbonate, and. manganese 

carbonate.~ 0£ these in1purities calcium carbonate, which is almost invariably present in 

·solution in iron:.bearing waters·, is by far the 

most impo;rtant. J\1agnesium carbonate, however, is commonly present and manganese carbonate may be conspicuous locally. Silica also 

· occurs abundantly in many places with ferrous 

carbonate. It n1ay be deposited in the form of 

clastic grains along with cla3r and other materials, but generally it is in the amorphous form 

as chert, and in that form it may be either a 

chemical precipitate or it may be derived from 

2 Moore, E. J ., The occurrence and origin of some bog iron 

deposits in the district of Thunder Bay, Ontario: Econ. Geology, vol. 5, pp. 528-037, 1910. · 

s Van Hise, C. R., and Leith, C. K., The geology of the 

Lake Superior region : U. S. Geo1. Survey Mon. 52, p. 526, 

1911. 

4 Vogt, J. H. L., Marmor und Eisenerze von Dunderland: 

Bildung der EUsenerzlager : Dunderlandsdalens jernmalmfelt, 

1894, p. 106. Reviewed in Zeitschr. prakt. Geologic; 1895, 

pp. 37-39: 
GEOLOGIC IMPORTANCE OF IRON-DEPOSITING BACTERIA. 73 

the casts of minute siliceous organisms living 

in the water. Phosphorus probably remains 

in solution under conditions which cause precipitation of iron carbonate. · 

l~OU:MA'l'ION OF J)I~POSITS 01!' IUON SILICATE. 

Various iron silicates, such as amphibole, 

pyroxene, biotite, garnet, epidote, olivine, and 

chlorite, which occur in igneous and metan 10rphic rocks have already been mentioned. 

Most of them are complex silic.ates containing 

iron, aluminum, magnesium, calcium, and other 

elements. Besides these there are a number o:f secondary hydrous iron silicates which 

:form under ordjnary conditions of sedimentation, such as glauconite, greenalite, thuringite, 

chamosite, berthierine, and bavalite. The occurrence and association of these have also 

been described. 

silicic acid ·used was produced from alkaline 

silicates by treatment with hydrochloric acid, 

so that the solutions contained sodium chloride 

as well. They thus resembled sea. water, in 

which the deposition of greenalite is b.elieved . 

to have taken place. Van Rise and Leith 

come to substantially the :following conclusions 

concerning the formation of iron silicates: 3 

1. A solution of :ferrous salt when boiled 

with silicic acid prepared as above stated [by 

neutralizing sodium silicate or water glass 

(Na20.3Si02 ) with hydrochloric aCid] produces (in the absence of air) no precipitate, 

showing that silicic acid and a :ferrous salt do 

· not react to :for1n :ferrous silicate. 

2. Ferrous sulphate reacts directly with solutions of silicates of the alkalies, producing a 

granular precipitate corresponding in composition to the water glass used in the precipitation. Thus: 

In o~·dinary sedimentary iron-bearing deposits, such as bog ores, :ferrous silicates are 

stated by Van IIise to be formed by reaction 

between colloidal silica and ferrous com- The precipitate formed in this manner is 

pounds.l When ferric hydroxide is precipi- compose~ of ferrous silicate and free silica. 

tated in the presence of abundant organic mat-. vVhen the relative proportions of alkali and 

ter and becomes mixed with it in the mud it silica are varied in the water glass the amount 

is reduced to ferrous oxide, as already ex- of silica precipitated with the ferrous silic.ate 

plained. Van I-Iise says that if under these also varies. !'£ a ~oluble magnesium salt is 

circumstances abundant colloidal silica is pres- present it will be precipitated with the iron as 

ent it may unite with the :ferrous oxide and magnesiunt ::;ilicate. The :ferrous silicates proform ferrous silicate, generally more or less duced were as follows: (1) Fe0.3Si02 , 

hydrated. ·The :formation of hydrous ferrous :formed fro1n hot or cold solutions with :fersilicate under these conditions,o rather than rous salt jn excess, (2) Fe0.5Si02 , formed 

ferrous carbonate, is said to be probably de-:- from cold :solutions with water glass in excess, 

pendent on the law of mass action. 1 It ·and (~) l~:e0.10Si0 , formed fro~ hot soluseems to be extremely questionable, howev.er, tions with water glass · in excess. ''Then 

whether :ferrous silicate is ever formed in this Fe0.3Si02 is boiled with water silica is taken 

manner. into solution and the precipitate which remains 

Van 1-Iise and Leith 2 give a discussion of approaches· FeQ.Si02 in composition. IIowthe formation of iron silicate from iron solu- ever, this composition is not reached, :for the 

tions by the action of alkaline silicates on· fer- iron oxidizes, rendering the remaining silica 

rous salts. The ii·on silicate greenalite soluble. If allowed to stand and dry, out of 

(Fe(J\fg) O.Si02.ni-I20), of the Lake Superior contact with the air, the, hydrous ferrous siliiron-bearing formations, is supposed to have cates also gradually lose water. 

been thus precipitated. ' 3. The :ferrous silicates require neutral or 

Various laboratory experiments '\Yere per- slightly alkaline conditions for precipitation. 

:formed to show the reactions between silicic They are soluble in acids or strong a.lkalies. 

acid or alkaline silicates and iron salts. The 4. In the presence of oxygen varying amounts 

1 Vnn Illsc, C. n., A treatise on metamorphism : U. S. Geol. of :ferri9 oxide form with the ferrous silicate .. Sun•cy 1\:lon. 47, p. 827, 1004. · 

:~ Van llise, C. R., nnd Leith, C. K., op. cit., pp. 521-526. s Idem, p. 521. 
IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

5. Ferrous silicates may be precipitated by alkaline silicates from ·various :f.errous salts, such 

as ferrous sulphate, ferrous bicarbonate, and 

ferrous chloride. The reaction for ferrous 

chloride would be 

6. In the presence of an excess of carbon dioxide ferrous silicate may be changed to ferrous carbonate . 

. The precipitates of. hydrous ferrous silicates 

formed as described above are flocculent and of 

a green color. According to Van Rise and 

Leith they develop on settling a granular 

texture similar to the greenalite occurring 

in the Lake Superior iron formation. This 

phenomenon is stated to be due probably to the 

surface tension between the precipitate and 

the liquid. r 

The commonly quoted hypothesis of the 

formation of the iron silicate glauconite is 

that of Murray and Renard which has al· 

ready been mentioned.1 According to this 

hypothesis the iron silicate is not precjpitated 

as such but is formed by secondary processes. 

Shells of dead organisms, 'mainly Foraminif· 

era, drop to the bottom and become filled 

with fine mud containing ~ron. This mud is 

acted upon by the organic matter of the organism in the presence of sulphatesin the sea 

water resulting in the reduction o£ the iron 

present in the n1ud to sulphide. This sulphide 

later oxidizes to ferric hydroxide setting· free 

sulphuric acid, which removes the aluinina in 

solution and sets free colloidal silica. The 

colloidal s~lica i:1 turn reacts· upon the hy· 

droxide, and in the presence of. potassium salts, 

derived from other minerals, forms glauconite. 

FORMATION OF DhPOSITS OF IRON SULPHIDE. 

Sulphides of iro:a may be precipitated from 

either organic or inorganic solutions of iron 

saits by simple chemical reaction with other 

constituents in solution or with materials in 

contact with the solutions. Precipitation 

may also take p.Etee by the reduction of iron 

sulphate i~ solution through the action of organic matter, bacteria, or other reducing agent; 

l.l\iurray, J., and Renard, A. F., Challenger Rept., Deep-sea 

deposits, p. 383, 1891. 

Clarke, F. W., The data of geochemistry, 3d ed.: U. S. 

Geol. Survey Bull. 616, p. 516, 1916. 

or by the action of hydrogen sulphide, liberated from decaying organic n1atter, on iron 

carbonate or other iron salts in solution. 

The following are the principal sulphides of 

iron: 2 

Formula. 

Ferrous sulphide, troilite____________________ FeS 

Magnetic iron sulphide, pyrrhotite ___________ Fe11S12 

Ferric sulphide-'-:---------------------------- Fe2Sa 

Iron disulphide, pyrite, marcasite, and melnikowite ________________ ~----------------- FeSz 

Ferrous sulphide, or iron monosulphide, occurs in ~ature as a constituent of certain sediments containing abundant organic matter and 

laid down under strongly reducing conditions. 

Such deposits occur in the Black Sea and elsewhere and have already been described. Ferrous sulphide is also found as the mineral troilite, a constituent of some n1eteorites. It is 

easily formed in the laboratory 2 by the direct 

union of the elements iron and sulphur, (1) 

by burning iron in sulphur vapor, (2) by 

heating iron filings and sulphur together in 

a red hot crucible, or ( 3) by stirring a whitehot iron rod in molten sulphur. In this manner ferrous sulphide forms as a yellowish crystalline metallic substance. 'Vhen iron filings 

and sulphur are mixed with water and rubbed 

to a paste, black ferrous sulphide is produced 

with the evolution of heat. It is also. formed 

a~ a black ap:10rphous mass by the action of 

ammonium sulphide on solutions of ferrous 

salts or by the reduction of ferric oxide or its 

salts in the presence of sulphates and decorriposing organic matter. Ferrous sulphide may 

also be formed by action of hydrogen sulphide, 

liberated from decaying organic matter, on iron 

carbonate or other iron salts in solution. 

Magnetic iron sulphide is a. mixture of the 

monosulphide and the sesquisulphide of iron. 

It occurs abundantly in metalliferous veins as 

the mineral pyrrhotite. It does not :form 

under ordinary conditions of sedim~ntation 

but is a product of hot magmatic solutions. 

Ferric sulphide is not known to occur in 

nature.· In the laboratory 2 it is produced .by 

the action of ammonium ·sulphide on solutions 

of ferric salts in an excess of alkali. 'Vhen 

the ferric salt is in excess a mixture of ferrous 

sulphide· and sulphur is formed. Ferric sul2 Roscoe, II. E., and Schorlemmer, C., Treatise on chemistry, vol. 2, pp. 1232-1236, 1913. 
GEOLOGIC IMPORTANCE OF IRON-DEPOSITING BACTERIA. 75 

phide is formed also by the action ·of hydr~­

gen sulphide on ferric hydroxide in the presence of traces of ·ammonia. It may be formed 

dry by gently heating sulphur· and iron together or by the action of hydrogen sulphide 

on ferric oxide at a t~mperature not above 

100° C. vVhen thus formed the material is a 

yellow nonmagnetic mass. 

Disulphide of iron occurs abundantly in 

nature as the minerals pyrite and marcasite 

and locally o as melnikowite. 1 Pyrite forms 

beds and lenses interlayered with sedimentary 

und rnetamorphic rocks and occurs disseminated or as concretions in sedimentary rocks, 

such ns shale, limestone; and quartzite. It is 

also abundantly disseminated through igneous 

rocks and occurs in association with metalliferous ore deposits, both in those of magmatic 

origin and those of meteoric origin. In general it is one of the n1ost widespread iron minerals nnd occurs in rocks of various kinds. 

Marcasite occurs in metalliferous veins. It is 

not n.s common as pyrite. 

Iron disulphide is said to be formed in nature by the action of organic matter on water 

which contains iron sulphate in solution and 

generally occurs as spherical, botryoidal, or 

stalactitic masses. It also is common in peat 

and coal, replacing organic matter and taking the form of roots, wood, etc. 2 

In the laboratory iron disulphide is formed 

by heating ferrous sulphide with sulphur or 

by passing hydrogen sulphide over oxides or 

chlorides of iron heated to . redness. · It is 

formed also as yellow crystalline pyrites when 

carbon bisulphide vapor acts upon heated ferric. oxide; when a mixture of ferric oxide, sulphur, and salammoniac is heated ,slowly above 

the volatilization temperature of salammoniac; or when ferric chloride is heated with 

phosphorus pentasulphide. · 

Van I-Iise 8 says that iron disulphide may be 

formed in sedimentary iron-bearing deposits 

by the reduction of basic ferric sulphate, 

which, as has been explained, results from the 

oxidation of ferrous sulphate solutions and 

may be deposited together with ferric hydroxide in the bottoms of lagoons. The reduction 

is clue to decaying organic ma:tter, which re1 Doss, Bl'tmo, Zeitschr. prnkt. Geologie, Jnhrg .. 20, pp. 

45~-4R~, 1012. 2 Roscoe, H. E., nnd Schorlemmer, C., op. cit., p. 1234. 

u Vnn Hise, C. R., op. cit., p. 828. · 

·quires abundant oxygen and takes part of it 

from the basic ferric sulphate, which is thus· 

reduced to disulphide of iron. As there is 

nwre -iron present than is required for combination with the sulphur·, it is believed that 

the excess iron may combine with carbon dioxide or perhaps with silica and form ferrous carl;>onate or ferrous silicate. 

Much of the iron sulphide occurring in sedimentary rocks has doubtless been formed by 

chemical processes, but .the chemical action is 

for the most part the result of the decompo-

'sition of organic matter by bacteria. DecOinposing organic matter may cause the formation of iron sulphide (1) by the direct reduction of iron sulphate in solution, owing to the 

removal of oxygen by the oxidation of carbon, 

or (2) by the action of hydrogen sulphide, produced· during the decomposition, on various 

iron salts in solution. Much of the iron sulphide also is deposited directly by th~ bacteria 

which have the power of reducing iron sulphates to sulphide and which have already 

been described. 

As bacteria are largely re~onsible for the 

deposition of iron sulphide in nature, the dis-

.Cllssion of this subject is therefore taken up in 

connection with the biologic deposition of 

iron. 

DEPOSITION OF IRON BY BIOLOGIC AGENCIES. 

l!'ORl\IATION OF DEPOSITS OF FERRIC HYDROXIDE. 

As bacterial processes are becoming better 

understood their relations to various phenomena in geology are f?und to be of increasing 

importance. Not only do they aid 'in the decomposition of rocks, as has already been 

shown, but they are important factors in the 

formation of certain rock. and mineral deposits, 

notably those of ca~cium carbonate, calcium 

phosphate/ . ferric hydroxide, and iron sulphide. 

Drew,5 1Cellerman, Vaughan, and others who 

have recently investigated modern calcium 

carbonate deposits of the sea bottom have come 

4 Blackwelder, Eliot, The geologic r6le of phosphorus : Am. 

Jour. Sci .. , 4th ser., vol. 42, pp. 285-208, 1016: 

G Drew, G. H., On the precipitation of calcium carbonate 

by inarlne bacteria A.nd on the action of . denltrif.ying bacteria in tropical anu temperate seas : Carnegie Ins.t. Washington, Dept. 1\fa.rlne Biology, Papers from Tortugas Laboratory, vol. 5, pp. 7-45, 1914. 
76 illON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

to the conclusion that bacterial processes have 

played an important part in the formation of 

the vast beds of marine, nonfossiliferous limestone of various geologic ages. 

The. generally accepted hypothesis :for the 

formation of nonfossiliferous limestones. has 

been that they were formed as chemical precipitates, the precipitation being ascribed to 

the action of ammonium cat.'bonate, an end 

product of the decomposition of nitrogenous 

organic· matter, on calcium sulphate present 

in sea water; according to the following equation: 1 

.(NH4) 2COa+CaS04=CaOOa+ (NH4) 2 804 

J?ecay-producing bacteria are of great importance in this process, for it is due largely 

to their activity that ammonia is produced, 

and this unites with carbon dioxide in solution 

to form ammonium carbonate. 

Drew in his recent work has shown that 

widely distributed marine denitrifying bacteria 

are also of great iinporta11ce in the precipitation ,)f calcium carbonate. He claims that 

these bacteria have largely caused the extensive accumulations of chalky mud in the vicinity of the Bahamas and the Florida l(eys 

which are being formed at the present time, 

and that they also play an important part in 

the cementation of fragments of coral an'd 

shells into coralline rock. He suggests that 

bacterial action has been an important factor 

in ·the past in the formation of chalks and 

limestones of different geologic ages. 

The principal denitrifying bacterium active 

in this precipitation is.a minute, actively Inotile bacillus with rounded ends, named B acteriwm calcis by Drew but found by l(ellerman to have a single polar flagellum and to 

belong to the genus Pseudomonas. 2 It is a 

facultative anaerobe and has the power of reducing nitrates to nitrites. The nitrites thus 

formed gradually disappear with the formation of some ammonia but without. the perceptible formation of free nitrogen. 

1 Murray, J., and Hjort, J., The depth of the .ocean, 1912. 

Murray, J., and Irvine, ·n., On coral re()fS and other carbonate of lime formations in modern seas : Roy. Soc. Edinburgh Proc., vol. 17. 1889. 2 Vaughan, T: W., (}eologlcal investigations in the Bahamas and southern Florida : Carnegie Inst. Washington, Ann. 

Rept. Dept. Marine Biology, Yearbook 13, pp. 227-233, 1915. 

The principal cultur~ medium used by Drew 

in the laboratory for preparing cultures of 

this organism consisted of calcium malate ( <;>r 

calcium acetate), potassium nitrate, sodimn 

phosphate, and sea water. Agar and gelatin 

were used in conjunction with these salts in 

the preparation of solid media. In these artificial media the reduction of the nitrates begins in a very short time and is accompanied 

·by the precipitation of calcium carbonate. 

Drew states that the pl:ecipitlltion of calci mn carbonate by these bacteria is in part 

caused by the greater alkalinity of the solution 

which results from the breaking down of nitrates and setting free of the bases durino- the . 0 

process of denitrification but is probably due in 

part also to the dire~t breaking up of calcium 

salts (chiefly of organic acids), the calcimn 

then uniting with carbon dioxide to form calciunl carbonate. 

l(ellerman and Sn1ith,3 who have recently 

further studied the activity of the nlicroorganisms that precipitate calcium carbonate, believe that the precipitation may take place in 

any of the following ways: 

1. The reduction of nitrates results in the 

£orn1ation of nitrites and finally of ammonia, 

which unites with the carbon dioxide present to 

form ammonium carbonate, and this reacts 

upon ca1cium sulphate to form calcium carbonate according to the equation already given. 

Ammonia may also be·formed by the decomposition of protein. 

2. Ammonia itself may react on calcium bicarbonate present in the sea water and precipitate calcium carbonate according to the 

following equation: 

Ca (HC03 ) 2+2NH4 0H= 

CaCOa+ (NH4 )' 2COa+2H20 

3. The bacteria feed on organic acids and as 

far as calcium salts of organic acids are present 

in sea water these are broken up and the calcium unites with free carbon dioxide and ·is 

precipitated as calcium carbonate. For this 

process denitrifying organisms also may be 

necessary. 

3 Kellerman, K. F., and Smith, N. R., Bacterial preciplta· · 

tion of calcium carbonate: Washington Acad. Sci. Jour., vo1. 

4, No. 14, pp. 400-402, 1914. 
GEOLOGIC IMPORTANCE 'OF IRON-DEPOSITING BACTERIA. 77 

Vaughan 1 states that the deposits of calcareous oolite in Florida and the Bahamas 

have probably resulted f1;om bacterial activity. 

The calcium carbonate, which is precipitated 

in a finely divided state, largely ·as aragonite, 

forms spherulites, which by accretion or by 

accumu]at:ion around various nuclei build up 

oolitic grains, and these gradually accumulate 

to form beds. 

The formation of the deposits of calcium 

carbonate thus outlined shows considerable 

analogy to the precipitation of iron compounds 

by bacterial action, which is briefly summarized in the following paragraphs. 

O:f the various accumulations of iron compounds in nature due to processes of sedimentation, biologic agencies are known to be 

import"ant only in the deposition of those of 

ferric hydroxide and ferrous sulphide. Indirectly, however, microorganisms may be of 

importance in the deposition of ferrous carbonate and ferrous silicate as well. · 

That biologic processes are important in the 

formation of iron-ore deposits is no new idea. 

It was first· advanced by Ehrenberg eighty 

y.ea.rs ago and since th~n it has been reiterated 

at various times by observers who have had 

occasion to study the so-ca~led iron bacteria. 

The facts regarding the activity of these organisms in the precipit~tion of ferric hydroxide, however, .have been treated in geologic 

literature only in a very general way and in 

many reports only vague references are made 

to them. 

It is now well known that not only ironprecipitating bacteria but various· other i:r;-onprecipitating organisms exist, some belonging 

to the algae and fungi and .others belonging 

to the protozoa. 'Vhether the tern1 "ironprecipitating organisms" is really applicable 

to many of the forms is still an open question. 

It .is not definitely known whether certain of 

the organisms actually aid in the precipitation 

of iron compounds or whether they .simply act 

as gatherers of iron compounds precipitated 

by chemical processes. It is certain, however, 

that many of the forms do aid in the precipi1 Vaughan, T. W., Preliminary remarks on the geology of 

the Rnhnmns, with spcclnl reference to the origin of the 

Hahnmun unll Flot·ldlan oolites: Curncgic Inst. Washington·, 

Dept. Marine Biology, Papers from Tortugas Laboratory, vol. 

5, pp. 40-54, 1914. 

tation, among thmn being certain of the iron 

thread bacteria. which precipitate ferric 

hydroxide frmn ferrous bicarbonate solutions, 

the 'various microorganisms which precipitate 

ferric hydroxide and basic ferric salts from 

solutions of certai~ organic iron salts, and the 

sulphate-reducing and hydrogen sulphide 

forming microorganisnls, which pre.cipitate 

fe~Tous sulphide from ·iroi1-bearing solutions. 

In the formation of fen~ous carbonate and ferrous silicate deposits organic material is of importance to the extent that its c}eca.y results in 

the reduction to the ferrous form or the retention i:Q. the ferrous form of any iron compounds 

present. In promoting this decomposition 

bacteria are of importance. The. precipitation 

of such ferrous compounds .in the form of ·ferrous carbonate or .ferrous silicate n1ay take 

place by the absorption of solvent carbon dioxide by plants, by rapid diffusion of carbon 

dioxide,· or by reaction of the ferrous compounds with alkaline silicates. 

. The activities of bacteria in depositing ferric 

hydroxide have been described quite fully in 

the foregoing pages, so that only a general 

statement concerning them is necessary. According to present know ledge it may be said 

that, as regards physiologic activities, three 

principal varieties of these bacteria exis~ 

(1). those which precipitate ferric hydroxide 

from solutions of ferrous bicarbonate and use 

the carqon dioxide liberated and the energy 

produced during oxidation for their life p~ocesses, (2) those which do not require ferrous . 

bicarbonate for their life processes but which 

cause the. deposition of ferric hydroxide when 

either inorganic or organic iron salts are 

present, and (3) those which attack organic 

iron salts, using the organic acid radicle as 

food· and precipitating ferric hydroxide, or 

basic ferric salts, which are gradually changed 

to ferric l}.ydroxide. These organisms can ·not 

utilize inorganic iron $alts. 

The first group has at least one represeniati ve and this is a very common and very important form~Spirophyllum ferruginewm. It 

is probable, however, that Gallionella ferruginea, which is a near relative of Spirophyllum, also belongs to this group, as well as 

other so-called iron bacteria whose physiology 
78 IRON -DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

has not yet been studied in detail. Lieske1 has 

shown that Spi'l·ophyllum ferruginewm will 

not grow in media in which fen~ous bicarbon-

. ate is not present, and that other iron salts can 

not take the place of ferrous bicarbonate in 

culture media for Spirophyllum. He f~:mnd 

also that the smaller the amount of organic 

material present in_ the solutions the better is 

its grow'th. In solutions containing an abundance of carbon dioxide but in which organic 

matter was entirely absent, Spirophyllum ferrugine'IJ)')n was found to grow profusely. The 

culture · solutions for Spiroph1Jllum which 

Lieske u9ed contained metallic iron and carbon 

dioxide for the formation of ferrous bicarbonate, and small amounts of ammonium and magnesium sulphates, potassium chloride, calcium 

nitrate, and potassium phosphate to supply 

other elen1ents required by the organisms for 

growth. 

In his experiments Lieske substituted other. 

metals, such as manganese, lead, zinc, tungsten, 

copper, etc., for iron, but found tha.t with none 

of these metals did growth take plac~. He attempted also to substitute ferric salts as well 

as other ferrous salts for ferrous bicarbonate 

but found that these did not induce any growth 

of Spirophyllum. However, he found that if 

ferrous bicarbonate were present in addition 

to some other iron salts\ the latter tlid not impair the growth. Atmospheric oxygen was 

found to be absolutely necessary for the growth 

of Spirophyllwm, and when oxygen was absent no growth took place. The optimum temperature was found to be 5° to 6° C., no growth 

taking place in solutions above 27° C. 

From these results it was concluded that 

Spirophyllwm f~ttgineum will grow in entirely inorganic media, that it does not require organic carbon for food but will take 

its carbon from fer1:ous bicarbonate, and that 

besides carbon it requires iron and oxygen. It 

is difficult· to see why the organism finds it 

necessary to take carbon from· the ferrous bicarbonate rather than utilize the carbon dioxide in solution in the water, unless, as is probable, the oxidation of ferrous· carbonate is 

necessary as a source of energy. 

1 Lieske, R., Beltriige znr Kenntnis der Physiologie von 

Spirophyllum ferrugineum (Ellis) : Jahrb. wiss. Botanik, 

Band 49, 91-127, 1911 ; also Centmlbl. Bakteriologie, Abt. 

~. Band 31, pp. 296~298, 1911. 

The physiology of Or·enothriw polyspora, 

Olonothrix f'usca, and SiderocaJJSa treubii has 

not been thoroughly studied, and the exact conditions under which these organisms thriveare 

not known. Orenothrix polyspora grows abundantly in pure well waters, ·which, besides calcium and magnesium carbonates and a small 

amount of· iron, contain few impurities. These 

conditions are very similar to those under 

which Spiroplbyllum and GaUionella thrive 

and would seem to indicate that Orenothrim 

requires very little if any organic matter. 

Orenothriw polyspora apparently does not 

grow profusely in· marsh w:;tters, where abundant organic matter ·is present. · Olonothriw 

fitsca resmnbles Orenothriw in its occurrence. 

Siderocapsa, on the other hand, more nearly 

resembles Leptothriw in its habits, occurring 

in marshes attached to living or dead vegetable matter and, like L.eptotkriw, probably 

requires organic matter for growth. 

Of the second group of iron-precipitating 

bacteria the principal fonns are Leptothriw 

ochracea ( 0 hlamydothr·iw ochracea) , and 

Oladothriw dichotoma. Leptothrix ochracea 

occurs abundantly in i'ron-bearing waters of 

iron springs and marshes, and Oladoth'rix 

dichotoma is a common soil organism, apparently being but little influenced in its distribution by the presence of iron compounds. 

While the occurrence of Leptothrix ochracea 

in nature is· undoubtedly controlled to a large 

extent by the presence of iron salts, it has been 

shown by :.Molisch 2 that in the laboratory 

LeptothTix will thrive abundantly on iron-free 

culture. media consisting of distilled water with 

1 to 2 per cent peptone. If iron is present in 

the cillture solutions, however, Leptothrix will 

show better development and will deposit ferric hydroxide in its sheath. It has a great affinity for manganese compounds as well, and 

if manganese salts are present it will deposit 

hydrated manganese oxide in its sheath. 

The form in which the iron or manganese 

occurs apparently makes little difference in the 

development of Leptothrix. In the natural 

waters in which Leptothrix grows the ir.on is 

probably largely in solution as ferrous bicarbonate with perhaps subordinate amounts as 

terrous sulphate and organic iron salts. In the 

laboratory l\1olisch used mainly orga~ic salts . . 2 Molisch, Hans, Die Eisenbakterien, p. 45, 1910. 
GEOLOGIC IMPORTANCE OF IRON-DEPOSITING BACTERIA. 79 

of iron and manganese, such as iron ammo-· various basic organic iron .salts. After prenium citrate, iron ammonimn tartrate, and cipitation, however, ba;cterial activity probably 

manganpeptone, and obtained profuse growth. conti1iues, and ·as a result more and more. of 

Like S7Jirophyllwm jerrugineu1n, Leptothri'J'J the organic. acid radicie is doubtless removed 

oclw·acca is an aerobic organism, but unlike from the precipitate until finally only ferric 

Svi1·ophyllu1n it requires organic matter as a hydroxide is left. 

source of carbon. l\1olisch states that he has The importance of this group of organisms 

never been able to cultivate it in a medium free in the formation of iron-ore deposits of course 

fro1~l organic matter. The optimum tempera- depends entirely upon the extent to which orture fo:r the growth of Leptoth1ix och.ra:cea··is ganic compounds of iron, such as humates, are 

23° to 25° C., and the temperature limits are carried in solution in natural waters. Some in5o to 4:0° C. vestigators believe that large a~nounts are carOladoth1Wn diclwtoma. is a widespread soil ried in this way, but others believe that the 

organism, occurring in association with Strep- amounts thus carried are insignificant and that 

tothrix, Actinomycetes, and other thread bac- practically all the iron in soh1t'ion in natural 

teria. It grows abundantly on most of the waters is in the form of ferrous bicarbonate. 

ordinary culture media used for soil bacteria, From observations regarding the conditions 

and if iron is present in them it will deposit under which iron is retained in solution in 

ferric hydroxide on its sheath. natural waters, notably the fact that surface 

The third group of organisms probably in- waters, which are apparently saturated with 

eludes numerous species, nearly all of which oxygen and carry little carbon dioxide, comare lower bacterial forms. These bacteria use monly contain appreciable quantities of iron, 

the acid radicle of organic iton salts as a it seems reasonable to believe that iron is carsource of food, and this results in the· precipi- ried in other forms besides that of bicarbonate. 

tat:ion of ferric hydroxide or basic ferric salts. 'Vhat these forms are will have to be deterMany of the forms probably atta:ck only one or mined by further work including careful analytwo organic salts, perhaps iron Gitrate, iron. ses of iron-bearing waters. It 'is extremely 

tartrate, or iron malate, but others may be able difficult to detect organic iron salts when presto usc a la.i-go number of organic iron salts, in- ent in such small quantities as would occur in 

eluding salts of soil acids, s1:1ch as humates. natural 'vaters. 

At present very little definite information is .As both chemical and· biologic processes of 

n.t hand concerning the importance of this various kinds are admittedly active in the preprocess in nature, and even in the laboratory cipitation of ferric hydroxide, the question as 

this phenomenon hns been studied only in a to which process is predominant in the formavery general way. It is quite possible that tion of sedimentary iron-ore deposits and ironmany of the already well-know1i soil bacteria bearing formations inust be solved largely by 

have the power of thus precipitating. insolu- field evidence. As many of the present deble ferric compounds from solution from one posits of iron carbonate were probably originor more organic iron salts. I have isolated ally laid down as ferric hydroxide and were 

severn! forms which actively precipitate h1- subsequently reduced, this question not- only 

soluble ferric salts from .solutions of ferric 

concerns . the present deposits of ferric oxide arnmon:ium citrate and have cultivated them but many of the deposits 9f ferrous carbonate 

on solid media. I have also succeeded in cans- and _perhaps of ferrous silicate as well. ing precipitation of insoluble ferric salts by From the ~eologist's point of view, the im- microorganisms from 'iron oxalate, ir0n lac- ._, tate, and other orga~lic iron salts but have not portant things to be considered with reference 

yet been successful in growing any of the pre- to bacteria that ·deposit ferric hydroxide are 

cipitants of these organic iron salts on solid as follows: (1) Their distribution,. whether 

me dm. . widespread or limited,· (2) the importance of 

It seems probable that the insoluble ferric their activity in natural iron-bearing waters, 

compounds precipitated. as' a result of this a.s compared with simple oxidation; (3) the. 

activity are mixtures of ferric hydroxides and conditions under which they are active; (4) 

I 
0 

80 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

the part which they have played in the formation of iron-ore deposits in the past. 

It has been repeatedly mentioned that iron 

thread bacteria are found practically wherever 

iron-bearing waters occur, whether stagnant 

or flowing. Some varieties' are more abundant 

in iron springs, wells, and. mines, where the 

water is relatively pure, but others are comn1on in marshes and lagoons where organic 

matter is abui}.dant. I have examined ocherous 

scums deposited from iron-bearing waters from 

. many different localities and have almost invariably found that they consisted mainly of 

sheaths of iron thread bacteria associated locally with granular and colloidal ferric hydroxide. In fact, I have examined only one 

specimen of ocherous scum in which I did not 

find bacterial remains. This was obtained 

frmn the hot springs near Ainsworth, British 

Columbia, and was sent to me by Mr. A. D. 

vVheeler, who says that the temperature of 

the spring is 112°· F. The material is yellowish brown in color and in the dry state is a 

fine powder. Under the microscope it is seen 

to consist of minute rounded granules, some 

spherical, some elongated, and some irregular 

in shape. The granules are light-colored, semitransparent, but with a dark border as though 

they might be hollow casts. 

One of the most common forms found, and 

one which occurs in relatively pure surface 

as well as underground waters, is Spirophyllum. I have found this form in nearly all the 

iron springs which I have examined and also 

in- the waters of several mines and in ironbearing well waters. It may occur in pure 

culture or it may be associated with any of the 

other forms of iron thread bacteria. Gallionella is not so common as Spirophyll1JJtrrb, and I 

have found it only in Inines, where it is common-ly· associated with Spirophyllum and 

Leptothrix. 

Leptothriw is almost as widespread as SpirophyUwm and usually is the predominant form 

where it is found. It is common in iron 

springs and marshes, where in 1nany places it 

forms large yellowish-brown gelatinous masses. 

At one locality I found it in a mine occurring 

in gelatinous masses on the sides and bottoms 

of drifts near openings where iron-bearing 

waters issued. With it occurred also Grtllionella and Spirophyllum. This occurrence of 

iron thread bacteria in mine drifts at depths 

as great as 300 feet and probably n1uch deeper 

is extremely interesting and to my know ledge 

has not been mentioned in the literature. It 

opens the interesting possibility tl;lat not only 

may these bacteria be instrumental in the 

formation of surface b_og ores, but they may 

play a part in the formation of certain underground deposits of .. limonite such as those 

which occur in the Appalachian region. 

Orenothrix and Olonothriw occur more 

rarely than the other iron thread bacteria. I 

have found Orenothriw only in well water that 

has passed through city distributing pipes. 

Molisch, however, states that in Europe it has 

been found also in surface waters that contain 

iron. Olonothriw is said to live under the same 

conditions as Orenothriw. I know of its occurrence only on the walls of certain underground. 

aqueducts that conduct water· frmn lakes to 

city reservoirs. 

Though the work concerning the dist~ibution of iron thread bacteria has perhaps not 

yet been as extensive as might be ·wished, it 

has been sufficient to indicate that wherever 

accumulations of ferric hydroxide occur at 

the present time under normal conditions they 

·are largely due to the action of iron thread 

bacteria. 

To what extent"" the lower iron-precipitating 

bacteria present in soil and natural ";aters 

are instrumental in the formation of deposits 

of, ferric hydroxide it is as yet impossible to 

say. These organisms do not leave residues 

that are readily identifiable, as are those left 

by thread bacteria, and besides it is not known 

to what extent iron is carried in solution in 

forms that could be utilized by them. In many 

of the iron scums much granular and colloidal 

.ferric hydroxide is associated with the casts of 

i~on thread bacteria, and it is possible that this 

material may in part have resulted from the 

action of the lower bacterial types. At any 

rate it is of considerable interest to note tbat 

these organisms are almost universally present 

in soil and natural water. 

The abundant occurrence of iron thread bacteria on articles of ~etallic iron that are· rusting under water is also interesting. It shows 

that these organisms are readily distributed in 

nature and are not confined to certain places 

where iron-bearing waters . are constantly 
GEOLOGIC IMPORTANCE OF IRON-DEPOSITING BACTERIA. 81 

present. I have seen Spi1·ophyllum attached 

to iron articles that were rustin·g in small temporary pools of water in localities where it was 

very difficult to account for its presence unless 

it hnd been carried by non iron-bearing waters 

for long distances. Generally when such pools 

of water dry up porous tubercles of iron rust 

are formed on the s·urface of the metallic iron. 

These tubercles may be several inches in diameter nt the base and consist largely of dried 

casts of iron thread bacteria. See fig. 13 and 

Pl. IX, B.) 

Th~ question as to the relative importance of 

microorganisms· and simple oxidation in the 

precipitation of ferric hydroxide under natural· 

conditions is a difficult one to answer. I have 

allowed samples of water that contain natural 

ferrous bicarbonate in solution to stand in vessels so that the iron present was precipitated. 

an~ forn1ed a deposit at the bottom. Upon examinn.tion this deposit was found to consist of 

a mixture of casts of iron thread· bacteria and 

grtu~ular ferric hydroxide, the grn.nular :ferric 

hydroxide being somewhat more abundant. 

The granular material probably resulted from 

direct oxidation, although there is a possibility 

thnt lower forms of iron-precipitatinD- bacteria 

nssisted. I-Iowever, even though sim;le oxidatiOn may be more effective in the precipitation 

of ferric hydroxide from ferrous bicarbonate 

solutions, the :fact that deposits of the precipitnte found in nature are made up largely of 

bacterial remains indicates the importance of 

microorganisms in the accumulation if not in 

the precipitation of the ferric hydroxide. 

Other questions 'vhich arise are what pei·-

centnge of the iron is carried in other forms· 

besides that of ferrous bicarbonate~ and what is 

the relative importance of organisms and simple oxidation in the precipitation of ferric hydroxide from such iron solutions. By present 

analytical methods it is practically impossibl~ 

to tell ordinarily in what form the bases are 

carried in solution.· It has been the common 

practice to combine certain bases with certain 

acid radicles without reference to the most 

probable combinations of salts present. Not 

only is it difficult, however, to determine. in 

what manner different bases and acid radicles 

are combined, but also to determine the presence of small quantities of certain acid radicles ' 65629°-1~6 

especially those of organic salts, in solution. 

Iron may not all be present in solution as ferrous bicarbonate or ferrous sulphate but may 

occur in forms which resist oxidation for a 

long time or may even require special conditions for any precipitation at all to take place. 

The conditi9ns under which iron bacteria 

are active in nature seem to be ex~remely varied. They thrive in surface as well as in 

underground waters and in stagnant as well 

as in running waters. Temperature also~ 

within moderate limits, seems to have little effect on the growth of iron-depositing bacteria, 

although most of them seem to prefer cold 

waters to warm waters. In the hot spring near 

Ainsworth, British Columbia, having a ·temperature of 112° F., there are apparently no 

remains of iron-depositing bacteria present in 

the ocherous deposits, but in ordinary iron 

springs both Leptothriw and Sjnrophyllum 

thrive during the winter as well as durino- the b 

summer, and Orenothrix is present in city 

water pipes. th~oughout the year. Lieske 

states that the optimum temperature for Spirophyllwm is 5o to 6° C.1 I·have found 9° to 10° 

C. to ?~ a common temperature in iron springs 

conta1n1ng growths of iron-depositing bacteria. 

The amount of iron required in solution for · 

most iron-depositing bacteria seems to be extremely small. Orenothrim is abundant in the 

water of the city supply of . Madison, vVis., . 

which contains only 1.8 parts of ferric oxide 

(Fe203 ) per million, and Leptothrix was 

found to grow profusely in iron spring water 

contai~i~g 5.2 parts of ferric oxi~e (Fe2 0 3 ) 

per mllhon. The latter an1ount of iron imparts a strong iron taste to the water but I . ' have found both Leptothriw and Spirophylwm in water in which the iron present was 

ha.rdly noticeable to the taste. · 

The amount of organic matter in solution is 

somewhat of a limiting factor in the growth 

of iron-depositing bacteria. Some forms, like 

Leptothriw, require a certain amount of organic carbon present, but other forms such 

as Spi?·ophyllum, thrive best in water c;ntain- · 

ing little or no organic carbon. It is probable, 

a.] so, that other n1aterials in solution, such as certain inorganic salts, affect the growth of irondepositing bacteria. Iron-depositing thread 

bacteria have never been found ih sea water and 

1 Lieske, R., op. clt. 
82 IRON-DEPOSITING .BACTERIA AND THEIR GEOLOGIC RELATIONS. 

probably do not occur there. on ~c~ount of the 

· high percentage of certain inorganic salts 

present. . 

The question as to what part iron-deposit-. 

ing bacteria have played in the formation of 

iron-ore deposits in the past can not be settled by. direct field evidence, for bacterial remains are comparatively short-lived in ocherous accumulations of iron oxide, and the slightest metamorphism will completely obliterate 

all traces of them. Schorler 1 has shown that 

even in the ferric hydroxid~ crusts forming inside of water pipes in cities which use ironbearing waters, the form of the bacterial remains composing them is preserved only for a 

comparatively short time in· the outer. layers 

of the crust and the inside layers consist of 

compact limonite from which all traces of bacterial forms have vanished.· 

In some of. the recent bog iron. ore deposits, 

however, casts of the organisms are still to be 

seen, although there are niany in which not a 

trace of them remains. Thus out of 61 specimens of bog ore examined by Molisch2 he 

found only four which showed abundant remains of iron thread bacteria. It is probable· 

that much of the granular ferric hydroxide 

which composes bog iron ore was originally in 

the form of casts of thread bacteria, but doubtless also. much of·it is chemically precipitated 

material, which has perhaps formed in quiet 

waters· or which has had a chance to accumulate because of becoming attached to baoterial 

threads or other objects. Perhaps a part of 

this granular material may have--been precipitated by lower bacteria as well, such as Sidero-

·capsa and ot4er forms already described, and 

thus would probably be indistinguishable from 

the chemically precipitated material. 

Both chemical and biologic processes seem 

to have been important in the formation of 

iron-ore deposits in the past, and the question 

as to which has predominated in the formation 

of any particular deposit must be solved by a 

study of the conditions at the tim·e of deposition. The method of attac;k involves a study 

not only of the sedimentation, but of climate, 

depth of water, relation to land areas, nature 

t Schorler B., Die Rostbildungen i'ii. den Wasserleitungsrohren : Centralbl. ·Bakteriologie, Abt. 2, ·Band 15, pp. 564-

568, 1906. 2 ·Molisch. Hans. Die Eisenbakterl~n, pp. 59-65, Jena, 1910. 

of ·currents, nature of materials carried in solution, and many other £_actors. It is only 

through a complete study of ~II th!3 conditions 

involved that a conclusion may be a,rrived at 

as to the most probable manner of deposition 

of any individual deposit. 

FORMATION OF DEPOSITS OF FERROUS SULPHIDE. 

The deposition of ferrous sulphide. usually 

takes place i?- inclosed or partly inclosed bodies 

. of water in which decaying organic matter is 

abundant. The organic matter is decomposed 

largely by the action of microorganisms, and 

during. the decomposition hydrogen sulphide, 

·ammonia, hydrogen, methane, and other gases 

are liberated. Iron salts are probably brought 

in by streams from surrounding regions. Under strongly reducing conditions and in the 

_presence of hydrogen sulphide these become 

converted to hydrous ferrous sulphi~e and _are 

precipitated .. 

In the formation of deposits of ferrous sulphide, under ordinary conditions of sedimentation, the ferrous sulphide may be precipitated 

from iron-bearing solutions directly by thereduction of iron sulphates, sulphites, or thiosulphates by microorganisms, or it may be precipi.tated by the action of hydrogen sulphide 

on ferrous salts in solution, the hydrogen sulphide. being formed by bacterial action either 

from. decaying sulphu~-bearing organic matter, from salts of sulphurous or sulphuric acid 

by reduction, or from free sulphur by. reduction.3 The precipitation of ferrous sulphide 

occurs under reducing conditions and usually 

in the presence of abundant decaying organic 

matter. The action is therefore largely dependent on the presence of various reducing 

and decay-producing organisms. 

Besides forming as a direct·precipitate from 

ferrous solutions, ferrous sulphide may be 

formed by the reduction of originally precipitated ferric hydroxide under the action of decaying organic matter in the presence of sulphates. 

I have already discussed the precipitation of 

ferrous sulphide in some detail, so that it will 

not be necessary to state more than the essentials of the process here. Probably the most 

.a Omellanski, W., Der Krelslauf des ScJiwefels, in F. La· 

far's Handbuch der technischen 1.\:lycologie, Band 3, pp. 211,1- · 

220, 1904-5. 
GEOLOGIC IMPORTANCE OF IRON -DEPOSITING BACTERIA. 83 

interesting of th~ microorganisms concerned 

in this activity are those which reduce various 

salts of sulphurous and sulphuric acid and 

which are known to be widely distributed in 

nnture. T'hey live under anaerobic conditions 

and obtain oxygen, whigh they require for the 

oxidation of carbon within their cells, from 

sulphates, sulphites, and thiosulphates, with 

the result that tll!ese comp·ounds are reduced to 

sulphides. Fertous sulphide may thus be directly formed by the reduction of iron sulphate. 

vVhen sulphides of other metals, such as calcium or magnesium, are formed in. an analogous manner, they m~y be. further acted 

upon by carbon dioxide in the presence of 

water and changed to cai·bonates and hydrogen st1lphicle. The hydrogen sulphide, may 

then react .on ferrous salts present in the water, 

especially ferrous bicarbonate, and precipitate 

ferrous sulphide. The equation for this reaction has already been given. 

Hydrogen sulphide is abundantly produced 

by the decay of sulphur-bearing proteins. The 

power to form hydrogen sulphide from proteins during decomposition is common to all putrefying bacteria, of which there are innumerable varieties and. which are abundant everywhere. The precipitation of ferrous sulphide 

(FeS) through the activity of these organisms becomes merely a· question of the presence 

of dead organic matter and of iron salts in 

solution. 

The reduction. of sulphur to hydrogen sulphide takes place in the presence of deCOJ?lpOS-

.ing organic matter. It is probably due to. secondary processes that result from various reactions which take place under these conditions. The hydrogen sulphide thus formed 

will precipitate ferrous sulphide from ferrous 

solutions which may be present. 

The production of hydrogen sulphide 

through the action of bacteria is important and 

widespread.1 In the presence of abundant 

hydrogen sulphide in the water and the resultnut decrease of oxygen the higher organisms 

frequently disappear entirely and the organisms which thrive in abunclan~e ar~ infusoria, radiolnria, oscillaria, diatoms, 0 hroococcus, and abundant bacteria such as sulphur bacterin and various anaerobes. Of these the sui~ 

phur bacteria are esp~ciapy interesting, as they 

1 Omel~anskl, W., op. clt., pp. 220-224, 1904-1906 .. 

oxidize hydrogen sulphide to free sulphur a.n'd 

sulphates and in this manner obtain energy 

for their life processes. This action is analogous. to the oxidation of ferrous carbonate t~ 

ferric hydroxide by some iron thread bacteria. 

In the W eissowo salt sea in the Charkow 

go_vernment, Russia, N adson found the following ~ontent of hydrogen sulphide per liter of. 

water: 1 

Content of hydrogen S1tlphide, in cu.bic centimeters per 

liter of water, from Wei.ssowo salt sea, Russia. 

Depth of 16 meters---------------.----------:... 5. 91 Dept~ of 18 meters_________________________ 88. 31 

Depth of 18.7 meters __________ _: ______________ 184. 96 

According to Lebedinzeff the Russian deepsea· expedition of 1891 found throughout the 

Black Sea at depths below 200 to 400 met~rs 

an increasing amount of hydrogen sulphide in 

solution. 2 

Content of hydrogen sulphide, i.n C1tbic centinteters 

per liter, of water from the.Black Sea. 

I>epth of.213 meters __________________________ 0.33. 

])epth of 427 meters----------'----------------- 2. ·22 

])epth of 2,026 meters _____ _: ___________________ 5. 55 

])epth of 2,528 meters (bottom)---------------- 6. 55 

This high content of hydrogen sulphide is 

typical of the Black Sea and does not extend 

into the Sea of Marmora or the ~{editerranean. 

Its presence is clue·· to the action of anaerobic 

bacteria on organic matter in the presence of 

sulphates of the sea water. Sulphate and thiosulphate reducers have also been found in 

Black Sea muds. ·According to Andrussow, 8 

the presence of hydrogen sulphide in the water 

of the Black Sea is clue to the fact that. on account of t~1e rapidly increasing density of the 

water with depth only the upper 170 meters 

have circulating currents, the· rest ·being sta-

. tionary. This is not true of other seas where 

oxygen is carried to depths arid the hydrogen 

sulphide formed is soon oxidized by sulphur 

bacteria to sulphates or reacts with iron salts. 

present, causing the precipitation of ferrous 

sulphide. 

The precipitated ferrous sulphide usually 

does not form pure deposits but becomes more 

2 Lebedlnzeff, A., Soc. naturalistes Odessa Travaux, Band 

16, 1891. Cited by Omelianski, W., op. cit. 8 Andrussow, N., Acad. sci. St.-Petersbourg Mem., Band 

1, p. 1, 1894. Cited by Omelianski, W., op. cit. 
84 IRON-DEPOSITING BACTERIA AND THEIR GEOLOGIC RELATIONS. 

or less mixed with fine clastic material and 

organic matter and forms a black mud. The 

black mud of the limans that occur along the 

shores of the Black Sea · and elsewhere in 

southeastern Russia . upon exposure to oxygen turns gray, due to the oxidation of ferrous 

sulphide, but upon being again~ covered with 

brine black spots appear and soon the whole 

mass becomes black, being again reduced to 

ferrous sulphide tlu;ough the activity of organisms which are able to live in concentrated 

salt solutions. These organisms liberate hy-· 

drogen sulphide and also ammonia and amino 

bases. Under the influence of hydrogen sulphide in alkaline solution ferrous sulphide is 

precipitated from the iron· salts present as a 

black, colloidal, plastic, hydrous deposit, 

which impregnates the muddy mass of organic 

and clastic .material. 

·The gray oxidized liman mud when sterilized keeps indefinitely .. However, upon be-· 

ing covered with water and reinoculated with 

fresh mud, with stream water, or with pure 

cultures of sulphate-reducing bacteria it again· 

takes on a black color. This shows that living 

·organisms are responsible for the reduction. 

It has been shown also that at the same time 

that hydrated ferrous sulphide gel separates 

out in muds silica gel freque·ntly separates out 

and forms thin films (less than 4 micra in 

thickness) around finely divided particles of 

hydrated ferrous sulphide gel, thus producing· 

minute grains.1 The granular texture thus 

produced is often characteristic of ·ferrous sulphide deposits. 

BIBLIOGRAPHY. 

ADLER, OscAR, Ueber Eisenbakterien und ihrer Beziehun·g zu den therapeutisch verwendeten natlirlichen Eisenwassern : Centralbl. Bakteriologie, 

Abt. 2, Band 11, pp. 215-219, 277-278, 1903-4. 

ANnRussow, N., VorUiufiger Bericht tiber die naturwisse~schaftlichen Ergebnisse der Tiefseeuntersuchungen im Schwarzen M~ere: Imp. russk. 

geog. Obschch. Izvestia, vol. 26, pp. 400-402, 

1890. 

·--- Contribution a la question de l'origine de l'hydrogene sulfure des eaux de la Mer Noire: Idem, 

vol. 28, p. 370, 1892. --- Sur la fermentation hydrosulfureuse llans les 

· eaux de la Mer Noire: Acad. sci. St.-Petersbourg 

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pp. 156, 217, 317, 437, 1915. 

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und Spaltalgen), p. 36, Leipzig, 1882. 

INDEX. 

Page. 

Acetate, baste ferric, precipitation of.:_____________ 67 

Ac:ctic ferml'ntntlon, pt·oc:css of- __________ --------- 45-4G 

Acids, occul"i·cnce of, In solls nntl watet·s------------ 45, 4U 

ot·lgln of, in soils and waters------------------ 45-46 

Aclmowlcdgments for aid------------------------- 7-8 

Action, method of, by h·on-dcposltlng bacterin ______ 5, 11-13 

Adlct·, Oscnr, cnltlvnt:lon of h·on-dcposlting bacteria by 10 

Algnc, dl'posltlon of ferric hydt·oxldc by ____ ..:._______ 11 

Anthophy8l~, OCCUl'I'CnCC OL----------------------'.0. 10 

Aschan, Ossian, work of, on organic salts of iron ____ 60-70 

Austria, Carpa.thlun Mountains, pyrite in__________ 61 

Bacilltts 11£. '1, nctlvltles oL----------------------- 13 

discovery of--------------------------------- 9 

JJaotorittm oalois, denltt·lfylng action of_____________ 76· 

Bnslc ferric acetate, precipitation oL--------------- 67 

Bnslc ferric oxalates, precipitation oL-------------- 67 

Basic fert·ic lactates, precipitation oL--------·----- 67 

Bavallte, oeeurrcnce oL-------------------------- 58 

Bedc, n., wo•·lc of, on the precipitation of iron orcs--- 70 

BcrlfJll~toa, activities of--------------------------- 44 

Bcljcrlnck, M., work of, on sulphate-reducing bacteria_ 42, 43 

Bet·tlllerlnc, occurrence oL----------------------- 58 

Blhllogt·nphy ------------------------------------ 84-85 

Blll.mo, Spain, Iron C:IH'bonatc deposits of__________ 57 

Blnclc hnnd Iron ores, nnturc und occm·rencc of- _____ 54-55 

Black muds, ferrous sulphide in ____________________ 61, 62 

Hinck snnds, nature nntl ol'igin oL_________________ 64 

Blnck Sen, bydt·ogen sulphide In water of__________ 83 

Iron In niud' of----------------------~------- 61,63 

"Blue mud," lt·on sulphides 111-----------~----- 61, 62-63 

Bog Iron ore, deposition of _______ .:_______________ 18 

nntm·e nnd ol'lgin oL------------------------ 53-54 

remains of bacterin in________________________ 82 

Bohcmln, chnmosltc orcs in _______________________ 50-60 

Bridgewater Cunni, Lnneasbirc, England, baclllus ft·om 

water of---------------------------- 39-40 

Brown, J'nmes Cn.mpbell, theory of, concerning .irondepositing bacterin__________________ 12 

Bn1ssllowsky, worlc of, on sulpha_te-reduciug bacterin._ 42 

Cnngn o•·es, origin oL _________________________ _._ 64 

Cat·bohydmtes, decomposition of-______ :_ ___________ 45-46 

Cnt·bon dioxide, origin oL----'-----------------·--- 45 

Carbonate of Iron, deposits of natmc and origin oL_ 54-57 

occurrence of, In pent bogs-------------------- 54 

Carbonic acid, action of, on it·on __________________ 46-47 

Cellulose, decomposition oL---------------------- 46 

Chamosite, natu•·c and oeem·•·encc oL ___________ 58, 59-GO 

occun·cnce of, In Wabana it·on ore _____________ 50, 51 

Chemical processes, deposition of Iron by _______ 64-75, 81 

Chla.tnyflothrlw fcrruginoa.. Soc aa:niunclla fm·ruginca .. 

ochracea Mlguln. See Lepidothriw ochracea 

KUtzlng. 

sidcrOlHtB, holdfust of------------------------ .20 

Claclothrtw llichotoma., habit of _______________ 9-10, 78-70 

occurt·enee · oL _________ :_____________________ 10 

Clay h·onstone, nutm·e and occurrence oL----'----- 54-56 

Cllnton iron ore, nnhirc and origin oL _____________ 49-50 

Olo1tothrlw fttsoa, dlstl'lbutlon of_ _____ ._____________ 80 

habit of--------------------------------·-- 9-10, 78 

Cohn, F. J., theory of, concerning Iron-depositing bacterin------------------------------- 11 

Collection of bacteria, method of__________________ 14 

Conidia, cxternnl, existence oL-------------------- 11 

production nnd germination ot_ ______________ 8, 15-llJ 

Page. 

Cm~tidlothriaJ, features of--~---------------------- 11, 21 

Coplaplte, origin of______________________________ GG 

Crawford, W. G., ·analyses by ______ 7 ______ 14, 16, 18, 33, 3::>· 

Crcnothriw polyspora Cohn, coating of, with ferric' 

hydroxide-------------------------- 16. 

collection and cultivation oL _________________ 14-15 

distribution of---------..,.-------------------- SO habit of _____________________________ .:_ ____ · 9, 78, 81 

occurrence 0!------------------------------- 13-14 

photomicrographs of ------------·---------- 14:, 15, 16 

portions of threads of, plate showing___________ 14 

reproduction of ______________________________ 15-16 

size. and structure of_________________________ 15 

staining of--------------------------------- 16 

Cultivation of iron-depositing bacteria _________ l4-15, 18-19 

preparation of solutions for_ _________________ 42-43 

salts used In________________________________ 30 use of plates for _____________________________ 34-35 

Cultures of bacteria, lceeping of___________________ 18 

Decomposition of iron-bearing minerals, process of_ __ 

Deposition of iron by bacteria _______________ ------

by chemical processes------------------------ by mechanical processes _____________________ _ 

D<>velopment of iron-depositing bacterin, time required 

for-------------------~----..:.------- Dhll.war rocks, iron ore in _________________________ _ Distribution of Iron-depositing bacteria ____________ _ 

Disulphlde of iron, formation oL~---------------­ Doss, Bruno, explanation by, of the origin of iron sulphides in sedimentary deposits ________ _ 

Drew, G. H., work of, on the· precipitation of calcium carbonate---------------------

Dunderland, Norway, iron ore In __________________ _ 

Ehrenberg, C. G., discovery of bacterial deposition of 

iron by ---------------------------- Ellls, David, work of, on the mode of a~tlon of Irondepositing bacteria ------------------ Experiments on precipitation of Iron by bacterin ____ _ 

45-48 

75-84 

64-75 

64 

26 

52 

79-80 

75 

63-64 

75-76 

52 

7 

12 

31-44 

Fats, decomposition of___________________________ 46 

Federal mine, near Hazel Green, Wis., Gallionell(l) and 

SpirophyZltm-, in __________________ 22, 24-25 

ocherous gelatinous scum from, photomicrographs of _________________________________ 10,22 

Ferric ammonium citrate, absence of iron-depositing 

bacteria !rom precipitates from ________ 32-33 

cultures in which sterilization has prevented precipitation from, plate showing_________ 32 

cultures in which ferric hydroxide bas been precipitated from, plates showing_~------ 27, 32 

precipitation. of Iron from, by bacteria ____ 31-36, 36-37 

use of In culture media----------------------- 30 

Ferric chloride solutions, attempts to make cul'l:ures of 

bacteria In ______ _:___________________ 40 

Ferric citrate, precipitation of iron from by bacteria_ 36, 37 

Ferric hydr.oxide, dehydration of___________________ 71 

deposition of, by bacteria __________ , ___ 8, 31-40, 77-82 

by chemical processes ____________________ 64-71 

from ground waters ____________________ 48, 40-54 

Ferric hyrlroxides, red and yellow, preparation of____ 65 

Ferric oxalate, precipitation of iron from, by bacterin_ 36, 37 

Ferric sulphate, oxidation of______________________ 69 

Ferric sulphates, basic, formation of _______________ GG4i7 

87 
88 INDEX. 

Page. 

Ferric sulphide, synthesis oL-------------·-------- 74-75 

Ferrohumates and ferrihumates, origin oL....: ________ 69-70 

Ferrous ammonium sulphate solutions, attempts to 

make bacterial cultures in_____________ 39 

Ferrous bicarbonate, origin and oxidation oL_ GS, 70, 71-72 

solutions of, attempts to make cultures of bacteria in _______________ ;..____________ 40 

Ferrous carbonate, deposition oL ___________________ 71-73 

impurities precipitated with ___________________ 72-73 

Ferrous sulphate, oxidation oL ___________________ 68-69 

solutions of, attempts to make cultures of bacteria 

in--------------------------------- 39 

Ferrous sulphide, deposition oL __________ 40-,l4, 74, 82-84 

occurrence of_______________________________ 61 

Fibroferrite, origin of____________________________ 66 

Flagellates, deposltion of ferric hydroxide by------- 11 

·Fred, E. B., acknowledgment to___________________ 8 

Fungi, deposition of ferric hydroxide by ____ _:-7 ______ 11 

Gallionella ferruginea Ehrenberg, activities oL______ 77 

description oL ______________________________ 23-24 

distribution oL ______ :.________________________ 80 

habit oL-------------------------~---.:._____ 10 occurrence of ________________________________ 22-23 

reproduction of______________________________ 24 

Geologic importance of iron-depositing bacteria ______ 44-84 

Glauconite, composition and occurrence of_.,. ________ 57-59 

formation oL ____________________ _:__________ 74 

Great Britain, iron carbonate deposits in __________ 54-56 

Greenalite, composition and occurrence oL _________ 58-59 

Greensand, distribution oL-----·------------------ 59 

Growth of bacteria, conditions r:equired for __________ 81-82 

ll aplobacteria, classification oL __________________ _ 

Hastings, E. G., acknowledgment to ______________ _ 8 

8 

Hay extract, bacteria in, precipitation of iron by____ 31 

Hematite, deposition oL-------------------------- 49-54 

Hillcrest mine, Cuyuna iron range, Minn., Spiro- .phyllum in ________________________ _ 

Humus, decomposition oL _______________________ _ 

Humus hydrosols, nature and action oL------------ . Hunter, W. H., acknowledgment to _______________ _ 

Hydrog;en sulphide, action of, in producing ferrous 

26 

46 

69-70 

8 

sulphide____________________________ 41 

oxidation oL _______________________ .________ 44 

production of, by bacteria ____________ 29, 30-31, 41, 83 

India, iron-ore deposits· in ______________ ~ _____ :_ __ _ 

Inorganic iron solutions, precipitation of iron from __ _ 

Investigation, scope oL-------.,-------------------

Iron, distrib~tion of, in the earth's crusL------,---

soluble salts of, carriage of, by water---------- formation of_ __________________________ _ 

Iron acetate, precipitation of iron from, by bacteria __ 

52 

38-40 

7 

44-45 

46-47 

47 

36,37 

Iron albuminate, precipitation of iron from, by 

bacteria---------------------------- 36, 37 

Iron bars, Spirophyllttm in tubercles on ____________ 26-27 

!l'on-depositing bacteria, classification of-___________ 8-11 

lower, activities oL-------------------------· 29-30 

Iron lactate, precipitation of iron from, by bacteria __ 36, 37 

Iron ores, types oL------------------'------------ 48-49 

Itabirite, nature and occurrence oL ______________ 51-52 

. Italy, northern, pyrite in------------------------ 61 

Jasper Peak, near Soudan, Minn., Spirophyllum at__ 25, 26 

Judson mine, Alpha, Mich.. ocherous scum from, 

photoniicrographs oL________________ 23 

SpirophyllUtn in ________ ~-------------------- 25 

Keeping of bacteria______________________________ 18 

Kellerman, K. F., and Smith, N. R., work of, on the 

precipitation of calcium carbonate_____ 7H 

Kennedy niine, Cuyuna district, Minn., Leptothrix~ 

Spi,rophyllum, and Gallionella in ___ 17-18, 22 

material from, photoroJcrogra.phs of __ ..• --------- 18 

Lactates, basic ferric, precipitl\tion of _____________ _ 

Lake Kegonsa, Wis., spring near, analysis of water 

Page. 

07 

from------------------r------------ 16 

spring near, LeptothriaJ in _________ -----------· 16-17 

ocherous scum on, photomicrogmphs of_____ 17 

precipitation of iron by bacteria in water 

from------------------------------ 31-32 

Lake Mendota, precipitation of iron by bacteria in 

water from --·----------------------- Lake ores, nature and origin of ___________________ _ 

Lake Superior iron region, iron carbonate deposits in_ 

ore of, nature an~ origin oL ___ ~--------------

Laterite, fragmental, mechanical deposition oL ____ _ 

Leith, C. ·K., acknowledgment to __________________ _ 

Van Hise, C. R., and, work of, on the formation of 

31,32 

53-54 

56-57 

. 51 

64 

8 

it·on silicateR.------------·----------- 73-74 

Leptotlwirc oclwacea Ki.itzing, cultivation oL ________ 18-19 

description of _______________________________ 19-21 

distribution of -------------------~-------·--- SO 

habit of __ ~--------------------------- 10,78-79,81 mode of action of _________________________ 11-12, 13 

occurrence of _______________________________ 16-19 

reproduction of----------------------------- 21 

Lleske, Rudolf, cultivation of Spirophyllu-rn by------- 27 

theory of, concerning iron-depositing bacteria ___ .12-13 

Limans, ferrous sulphide deposited in mud of _____ 61, 63, 84 

Limestones, deposition of _________________________ 75-77 

L!monite, Jurassic, of France and Germany, nature and 

origin of ___________________________ 52-53 

powder of, from tubercle of iron rust, photomicrograph of---------------------------

Lower iron-depositing bacteria, activities of ________ _ forms of __________________________________ _ 

habit of ___________________________________ _ 

photomicrographs oL _______________________ _ 

26 

80 

34-35 

79 

3~ 

Madison, Wis., city water, analysis of ____________ .;..__ 14 

bacteria in, precipitation of iron by ____________ 31,32 

CrenothriaJ poly81W1Y~ in, photomicrographs oL 14, 15, 16 

Gallionella_. Spi.rophyllttm, and CrenothriaJ in ____ 22-23 

Spirophyllum terrugineU1n in, photomicrograph of ________________________________ _ 

Magnetic iron sulphide, formation of ______________ _ 

Manganese acetate -solution, development of mold in __ 

Manganese citrate solution, development of mold in __ _ Marcasite, occurrence oL _______________________ _ origin of __________________________________ _ 

Marshes, bog iron ore deposits in __________________ _ 

Mechanical processes, deposition of iron by _________ _ 

. 1l.l egalothrirc. discophora, habit oL _________________ _ 

Melnikowite, occurrence oL ______________________ _ 

origin of-----------------------------------

Microspira aestuarii, isolation oL ________________ _ 

Middleburg, Va., Lept'othrix and Spiroplli!Jllum in 

22 

74 

36,37 

36,37 

60-G1 

75 

53-54 

6!' 

10 

61,62 

75 

42 

-spring near_________________________ 17 

Migula, W., classification of iron bacteria by________ 8-9 

Minas Geraes, Brazil, itabirite in, nature and origin of_ 51-52 

Minerals, iron-bearing, decomposition oL ___________ 45-48 

Minette ore, nature and occurrence of ______________ 52-53 

Molds, development of, in precipitates from solutions 

of iron salts--------------------- 33, 37, 39 

Mollsch, Hans, cultivation of Leptothrix by _____ .____ 19 

theory of, concerning iron-depo·siting bacteria____ 12 

Montfort, W. F., cultivation of Leptothrirc by________ 19 

Mtick, -, work of, on ferric hydroxides____________ 65 

Mumford, E. M., discovery of Bacillus M. 7 by ____ 13, 39-40 

work of, on the mode of action of iron-depositing bacteria-----------------~------- 13 

Murray, J., and Renard, A. F., on the formation of 

glauconite-------------------------- 74 

Newfoundland, pyrite in-------------------------- 62 

Wabana iron ore of ____________________ 50-51,58,60 

Nicolardot, M. P., work of, .on. ferrie ilydroxides____ 66 

Nitrogen, conversion of, to soluble nitrates__________ 46 

Nodofolium terrugineun", habit oL________________ 11 
INDEX. 89 

Not·wny, Dunderlt1nd district, iron ore in-----------

Nowo-Usenf:k, Russin, pyrite near ________ . ________ _ 

Page. 

52 

62 

Ohio, ironstone and black-band ore deposits in ______ 54-5ti 

Organic iron solutions, pt·ecipltntion of Iron from, 

by bactet·ia ________________ 36-38, 67-68, 6!) 

Ot·~nnlc matter, decaying, formation of hydrogen 

sulphide from---------------~------- . decnylng, t'eductlon of iron compounds by __ :.. __ _ 

sulphate-t·educlng bncteria present in _____ _ 

Oxidation of hydrogen sulphide by bactel'in _______ _ 

Oxy~en, pt·ecipltatlon of ferric hydroxide in nbsence of 

41 

47 

29 

44 

33 

l'ennln~ton mine, Spirophynu1n In _____________ ;.. ___ 26-27 

1'«-nnsylvnnlu, ironstone nnd black-band ore tle-

. posits 111---------------~----------- 54-55 

l''hystology, general, of iron-depositing bacterin _____ 11-13 

g(•net·nl, of sulplmte-t·edudn~ bactt~rln---------- 4:{-44 

Plclterlng, S. W., work of, on basic ferric ·sulphate__ (17 

P.lntl's, cultivution of iron-depositin~ bacteria on __ 34-35, 38 

l'recipltntlon of iron b.v hncterln, experiments on ____ 31-44 

Proteus vulf}aris, sulphate-reducing action oL_______ 30 

l't·otein, decomposition oL_______________________ 4(i 

formation or hydro~ren sulphide ft•om ___________ 41, 83 

Pt·otozon, deposition of fet'l'ic hydroxide by_________ 11 

P1wrulomonas denltrifylng action of--------------- 76 

Pyrite, distribution oL--------------------------- 60-62 origin or____________________________________ 75 

l'yl'l'hotite, ot·lgltt of ___________ .:._________________ 74 

ltnmmclsberg, Oet·muny, pyt·ite nL-----------------

lttwsome, l!'. L., preface bY------------------------

" Red mud," deposition oL------------------------

Jlpmalns of bacteria, rapid perishing oL ___________ _ 

RPnard, A. F., Mm·ray, .T., and, on the formation 

61 

5 

54 

82 

of ghtuconlte-----------------------:... 74 

Hl'pt·oduction of hncterla, methods of __________ 8, 11, 21-22 

no('lts, decay of, promoted by bacteritL-------------· 4G 

Howe mine, Cuyuna iron range, Minn., Lcptothrim in springs at _______________________ _ 

.Cuyunu it~on runge, Minn., Spirophyllum In ____ _ 

Hubble ot·e, ot·lgin oL----------------------------

17 

2G 

64· 

ltutf, 0., wot·lt of, on ferric hydroxides------------- G5-(i6 

Itusslu, Nowo Usensk, pyl'ite near _______________ _ G2 

Page. 

StJirophyllum terrugineum Ellis,. activities oL ______ 77-78 

classification oL ____________________________ 28-29 

cultivation of _____________________ ---------- 27 

description of _______________________________ 27-28 

distribution of------------------------------ 80, 81 habit of _________________________________ 10-11, 13 

occurrence of ____________________________ 17,24-27 

. photomicrograph of__________________________ 2:! 

reproduction of______________________________ 28 

Spores, formation of, in bacteria__________________ 8 

See also Conidia. 

St.at:ch, decomposition of _________________________ 45-4G 

Sterilization, effect of, In preventing precipitation_ 32, 37-38 

effect of, in preventing precipitation, plate showing________________________________ 32 

Styrla, iron cat:bonate deposits In__________________ 57 

Sulphate-reducing bacteria, activities of_ __ 29, 30-31, 41-44 

Sulphates of iron, reduction oL-------------------- 82 

Sulphides of iron, deposits of, nature and distribution of _________________________________ 6Q-64 

· formation of, by chemical processes ____________ 74-75 

Sulphur bacteria, activities of _______________ 44, 46, 83-84 

classification of_____________________________ 8, 9 

~'hiobacteria. See Sulphur bacteria. 

Thiosulphates, reduction of, hy bacteda_~--------·--- 41-44 

Thiothri:c, activities of-------------------------- 44 

Thuringite, composition and occurrence of __________ 58, 60 

Thwaites, F. T., acknowlcdgtitent to _______________ . 8 

Tomassi, D., work of, on ferric hydroxides_________ 65 

Trichobacteria, classification of------------------- 8-11 

Troll1te, occurrence oL----------·---------------- 74 

Uglow, ,V. L., .acknowledgment to _________________ _ 

Underground occurrences of iron-depositing bacterin_ 

Vacuum, precipitation of ferric hydroxide in ________ _ 

Van Bemmelen, .T. M., work of, on ferric hydroxides __ 

Van Delden, -,work of, on sulphate-reducing bacterin. 

Vnn Rise, C. R., and Leith, C. K., work of, on the formation of iron sili.cates _____________ _ 

Vnughan, T. ,V., on the precipitation of .:;alclum. cat·-

honate-----------------------------

Vermillion Lake, l\Unn., ocherous scum from Iron 

spt•ing near, photomicrogrnph of_ _____ _ 

8 

25 

33 

65 

42 

78-74 

77 

26 

l'dtot·IN, B., work of, on deposition of iron crusts in 

watt>t' pipes-------------------------

Scum, ocherous, in hon spt'ing, near Lnke Kegonsa, 

· Vermilion ore district, 1\:Iinn., Spirop1111Jllum In ______ _ 

2:{ V,iurio hydrosulfurcus, isolation of ________________ _ 25-26 

42 

30 

66 Wis., phomlci'Ographs of ____________ _ 

Sltlerlte, nature and origin of_ __ .. _________________ _ 

occurrence of, 111 Wabaun. iron ore ____________ _ 

Ni(tm·oc(IJJ8lt tnHtbH, activities of __________________ _ 

llnblt of------------------------------------

8illen.teR of lt·on, deposits of, nature and origin oL __ _ 

17 

54-57 

50 

2!l,82 

H,78 

57-60 

7:{-74 

sulphate-reducing- action of----------,---------

Vltrlol ocher, origin._ of~--------------------------

"\\'abana Iron ore, nature and origin of_ ____________ _ 

Water pipes, Iron, deposition of ferric hydroxide in __ _ 

'Vaters, natural, iron-depositing hncterin in ________ _ 

, 'Velssowo salt sea, Russia; hy(lrogcn sulphide in ____ _ 

West Virginia, ironstone and black-band ore deposits 

50-51 

23 

29-31 

83 

pt·eclpitntion of----------------------- 7 ------

Seo also Glauconite, Greenallte, etc. In --------------------------------- 54-55 SjUgrcn, IT .•. wot•k of, on tlte prt:'cipitntion of iron ores_ 

Smith, N. H., 1\:Pllet·mnn, K. F., and, work of, on the 

70 WPstphalia, Prussia, pj·l'itc in-------------.------- 61-62 

Wheeler, A. D., acknowledgment to ____ .____________ 8 

prl.'clpltatlon of calcium cariJonate:____ 7•3 

Rolls, bnctt.•t·ln In, pt·eclpltntion of iron by ___ 29-:n, ::12, :36-38 

Winogradsky, S., cultivation of Lcptot1wi:v by _______ 18-19 

Spnln Huelva region, pyrite Itt ________ ------------ ()1 

. theory of, concerning iron depositing bacterin __ 11-12 

Spi1·il~1t1n dcsulturica?~s, Isolation oL--------------- 42 Zopf, '"'. ... ,tl'IPOJ'Y of, coneerning h·on tlt:'posltlng 

sulphate-reducing action ot------------------- 30 bacteria----------------------------

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