THn AMERICAN M INERALOGISTJOURNAL

Vol. 23

OF THE MINERALOGICALSOCIETY OF AMERICANOVEMBER, 1938

No. 11MINERALOGY OF THREE SULPHATE DEPOSITS
OF NORTHERN CHILE*
Moss'
Menr C. BaNov, HaraardUniaersity,Combri'd'ge,
CoNrnNrs

page* Based on a thesis submitted to the Division of Geological Sciences, Harvard Univerof Philossity, in 1938, in partial fulfillment of the requirements for the degree of Doctor
oPhY'
669

670

, MARK C. BANDVAssrRecr

This paper gives the results of a study of the mineralogy of Chuquicamata,euerena,and Alcaparrosa, three sulphate deposits near calama, in Northern chile. The sulphate andchloride minerals, their description, their paragenesis, and the geochemistry of their formation, are the primary interest of the paper. The minerals described were collected by
the author in 1935.
Seventy-six minerals were identified and studied. Eighteen of these minerals are known
only from northern chile and twelve are known only from these three deposits. An attempt has been made to clear up some of the varietal na:nes and doubtful species that havebeen described from these mines. Seven new well-defined mineral species were discovered
during the research-antofagastite, bandylite, leightonite, ungemachite, and lindgrenite
have been described elsewhere; metasideronatrite and parabutlerite are described here.
For all of these. complete crystallographic, optical, and chemical data were secured. rmportant new crystallographic data are presented for the minerals szomolnokite, pickeringite, rhomboclase, botryogen, lapparentite and natrojarosite. New *+ay data were obtained on three minerals and new optical data on sixteen, and nine new chemical analyses
are presented.
PART

I. GEOLOGYANDPARAGENESIS

INrnooucrroN
A detailed study of the mineralogy of Chuquicamata, euetena and.
Alcaparrosa in Northern chile forms the basis of this paper. The writer
worked for five years at Chuquicamata and had ample opportunity to
study the deposits in the field. rn 1935 he returned to chile in behalf ofHarvard University and the United States National Museum and spenr
four months collecting minerals throughout northern and central chile.
Extensive suites of specimenswere collected from these three deposits
and later v/ere studied in the laboratories of Harvard university andthe united states National Museum. The sulphate minerals of these
deposits are the primary interest of this paper.
The writer wishes to acknowledge the financial assistancegiven him
by the Department of Mineralogy, Harvard University, and the UnitedStates National Museum, which made this study possible. He received
unstinted aid and advice from Professor Charles Palache, Dr. W. F.
Foshag, Mr. E. F. Henderson and Dr. M. A. peacock, and it is a pleasure
to acknowledge this. The writer wishes to mention particularly the aid
given by Dr. Harry Berman, whose guidance and unfailing interest in
this study contributed in great part to its present form and value.
Geography.Northern Chile is usually divided into three broad topographic and geographic divisions-the Coast Range, the Central Valley
and the Cordillera Real. The Coast Range rises abruptly from the
Pacific ocean on the west and reaches elevations of over 1,500 meters.
The central valley to the east of the coast Range is a relatively shanow
and broad valley from 50 to 100 kilometers wide. The western slopes of

S(JLPHATE DEPOSITS OF NORTHERN CHILE
the Cordillera

ReaI form the eastern side of the Central Valley'

67I
This

('t
)
(

J

r_1\

"--l
Ar
Frc. 1. Key Map of Northern Chile showing relative locations of
Chuquicamata, Quetena and Alcaparrosa Mines'

miles). Both of these cities are on the coast. The only other city of any
size in the Province is Calama, a small city about equidistant from thethree deposits.All these d.epositsare reachedby auto roads from Calama;
Chuquicamata 12 miles to the north, Quetena 5 miles to the west' andAlcaparrosa 18 miles to the south'
The deposits lie in the northeast portion of the Atacama Desert on thewest slopes of the Cordillera Real, 100 miles west of the crest of thisrange.

672

MAKK C. BANDYClimate. Northern Chile, particularly the Atacama Desert, is prob_
ably one of the driest areas on the earth. These deposits, on the edge ofthe desert, receive an hour or so of light rain once or possibly twice ayear. The average rainfall varies slightly in the three deposits; Chu_
quicamata, the highest and farthest to the east, receivesthe greatest
annual amount, less than 5 mm.; and Alcaparrosa, the lowest and theone farthest to the west, has a fall of about 1 mm. a year. There is reallyno "average rainfall" as years may pass when no rain falls. At Alcaparrosa a pile of several"tons of coquimbite and other sulphates has been
exposed to surface weathering for over sixteen years, yet today, on theoutside of the pile, only about a quarter of an inch has been dissolved
and a crust of secondary sulphates formed. under this crust the original
sulphates are still fresh and bright. rn the central valley there were six
rains during the Nineteenth century and there have been two rains
during the present century.
The evaporation factor is large and probably there is a precipitation
deficiency. Salt crusts at or near the surface are common over much ofnorthern chile and are probably the result of this precipitation deficiency. Fifty miles to the east of these deposits enough iain fails to
support a scattered vegetation during a part of almost every year.
The light rainfall and rapid evaporation in the vicinity of these deposits has allowed the formation of a great variety of water-soluble
sulphates, some in large and pure masses,as well as the famous nitratedeposits farther to the west in the Central Valley.
Local ropography. As stated before, these deposits lie in the western
foothills of the cordillera Real, several thousand feet above the floor of
the great central Valley to the west. The dominant topographic featuresin the vicinity of the deposits are the two great nathotithic peaks ofchuquicamata and Limon verde with the valrey of the Rio Loa between
them. The deposit at chuquicamata lies in the batholith, near theeastern edge. Alcaparrosa lies to the west of the Limon verde batholith.
The area is one of mature topography as a whole. The hils have moderate to steep slopes and narrow ridges with alluvium-covered lower
reaches. Undrained basins are common, usually occupied by salt plains
or salars. Remnants of old salars that have been tapped by tributariesof the Rio Loa are uncommon but can be found.
Geomorphology.Volcanism probably began in Northern chile in thelate Triassic. Following this volcanism there was a slow subsidenceanda long period of sedimentation, first of the playa-lake type and then inshallow inland seas during the Jurassic and early cretaceous. During
the cretaceous, the sea retreated and at the close of the Mesozoic or
beginning of the Tertiary folding began and this ushered in the present

SULPHATEDEPOSITS OF NORTHEKN CEILE

673

cycle. Accompanying the folding was strong volcanism and batholithic
intrusion on a grand scale.
The coast range, which follows the present coast line of northern Chile,
was probably formed at the close of the Cretaceous. At the beginningof the Pliocene when the general uplift of the Andes began, the Cordillera
to the east was raised to its present heights and the coast range was certainly elevated several thousand feet. The Central Valley of Chile,which consists of several valleys or basins with very low divides, wasprobably formed during this period. The beginning of the period of
uplift was marked by erosion of the older rocks under semi-arid conditions with torrential deposition of the debris in thick beds of conglomerates in the broad valleys. Contemporaneous with the uplift, active volcanism was renewed and has continued down to the present, but is probably diminishing. Thick beds of andesitic ash were deposited at thistime throughout the Cordillera; some of this material was later washeddown into the Central Valley. The conglomeratesand ash beds depositedfrom the middle Tertiary through the Pliocene are now subjected toerosion and in these beds the present drainage has cut youthful canyons.
The present arid climate probably began in the Pliocene or early Pleistocene and is probably increasing in aridity.
Gpor-ocv on CnueurcAMATA,Curr,B
Chuquicamata lies on the west slope of a low ridge that disappears
under the alluvium of the valley of the Rio Loa, to the south. To thewest of the deposit, across a broad shallow valley, is a hill about 1,300
feet high, the main mass of the Chuquicamata batholith. This batholith
has an areal extent of about 80 square miles with a north-south axis.
The Chuquicamata ore deposit is roughly pear shaped in horizontal
section with the wider portion to the north. Its dimensions are approximately 2 miles by 0.7 mile.
History. The first mining in the vicinity vras carried on by the aborigines on the gold deposit at the north of the present mine. Recent efforts
to find gold, even in traces or colors in this area, have been fruitless. The
copper veins were also worked by the aborigines and may have been
exploited by the Spaniards. Foreign capital came into the district about
1879 and active mining of the veins on the eastern edge of the deposit
continued until about 1920. In 1915 active open-pit mining on a large
scale with steam shovels began.
Outline of Geologi.cHistory. The geology of the Chuquicamata deposit
has been describedby Taylorr and only a brief outline will be given here:
1 Taylor: Copper Resources of the World, 16th Int. GeoI. Cong., vol.II,

1935.

pp. 473484,

674

MARK C. BANDY

1. Intrusion of the granodiorite batholith into the Jurassic shales,
probably at the close of the Mesozoic.
2. Fracturing along a fissure on the west side of the deposit followedby the flow of solutions along this fracture and the alteration of the
granodiorite to the east of the fracture. Orthoclase and perthite phenocrysts formed in the granodiorite, replacing the salic minerals and possibly some of the femic minerals, although fresh biotite occurs as inclusions in the phenocrysts.
3. Fracturing within the area of the present ore body followed byheavy silicification along the major fractures. With the silicification,
hematite and magnetite may have been introduced to the east of thedeposit, while pyrite, chalcopyrite, bornite, and molybdenite were introduced into the central and northwest portions. To the northwest theseminerals were introduced with a carbonate gangue. Gold may have been
introduced at this time in an area of intense silicification to the north.
4. Accompanying and following the silicification there was sericitization of the granodiorite along the central fissures,decreasingin intensity
to the east and west, being most intense between the central and west
fissures.Orthoclase phenocrysts were not sericitized except in areasnear
the fi.ssures.
5. Probably a renewal of crushing and shearing along the principal
fissuresfollowed by the main period of copper mineralization, namely,
pyrite, enargite, and covellite. During this period the veins along thenortheast side formed.
6. A period of oxidation and leaching during the middle Tertiary withsecondary enrichment and the development of a leached capping overthe deposit. The erosion of the iron veins to the east resulted in the formation of iron conglomeratesor itabirite.
7. Pliocene uplift with the introduction of an arid climate. Slightmovements in the deposit developed flat, rolling fractures.
8. Erosion and oxidation from the Pliocene to the present. A fluctuating water table with very limited rainfall has resulted in the dissemination of the enriched zones formed during the previous stage. The
many iron and copper sulphates and other supergene oxide minerals
were formed at this time.
Goorocv oF QuETENA,Cutr-n
The Quetena deposit lies to the west of Calama, Chile, near the crestof a steep hill that strikes about north-south. The ridge terminates
abruptly at the Rio Salvador, and at its highest point it is about 1,300
feet above the level of the river. It receives about the same amount ofrain as Chuquicamata. The deposit was mined for its oxidized copper

SULPHATE DEPOSITS OF NORTHERN CHILE

675

ores by an open pit, measuring about 125 feet by 40 feet by 25 feet deep
(Fig. 2); notwithstanding this small extent, it exhibits a highly complex
mineral assemblageshown in Table I B. It is the type locality for two
new mineral species,antofagastite and bandylite; five mineral varieties,
quetenite, salvadorite, rubrite, kubeite, and cuprocopiapite, as well astype crystals of pickeringite and co-type crystals of halotrichite.
This deposit is also referred to in older literature as Mina Salvadora.

Chile.Scale1 inch:'3 mile'
Frc. 2. SketchMap of Mina Quetena,
Contourinterval-25 ft.
Hi.story. A few prospect pits were sunk on the deposit before 1890 but
the actual mining records are not available today. Minerals from thedeposit appeared in d.escriptionsin Germany about 1890' It was wellknown that a small tonnage of low-grade ore existed there, but it was
not until about 1916 that it was actively worked. Mr. Green obtained
the property and transported.the ore to the banks of the Rio Salvador,
where a small leaching plant was erected. Mining was carried on forseveral years, after which the property was abandoned due to the decline
in the price of copper after the World War. In 1935 an unsuccessfulattempt was mad.e to operate the property. The estimated total prod.uction of the property is about 10,000 tons, and the present positive
reserve of low-grade ore is about 10 tons.
structwre. Quetena occupiesa stockwork ol qtattz veins in a seriesof
lava flows or possiblv intrusives at the contact with a seriesof Jurassic

676

MARR C. BANDV(Bajocian) cherty limestones. The stockwork is irregular in shape, atype of structure called "rebosadero" by the Chilean miners. The quartz
veins vary in width up to ten inches or more. The history of the fracturing is not known and no age can be definitely ascribed to either theflows or the mineralization.
Geologi.c
History. About a half mile to the north of Quetena, an igneousplug of red granodiorite forms the hill known as Cerro Quetena. This
plug is probably connected genetically with the Limon Verde batholith.
The rock is a normal granodiorite with occasionalareas of micropegmatite. The flows about Quetena are probably not related to this plug, as
evidencepoints to their being much older.
The history of the fracturing is not known, but early quartz was introduced into the fractures and crystals grew normal to the walls withwell-developed terminations projecting into vugs along the course of theveins. Following the qtrartz, abundant pyrite and small amounts ofcopper were introduced. No primary copper minerals were observed by
the writer. The centers of the veins, in the capping, are now occupied
by a limonite boxwork after pyrite, and copper evidently was not present
in sufficient quantity to modify this boxwork. The rock is little altered
at a distance from the veins except from supergeneagents.
The mineralization probably dates back to the late Mesozoic, while
there is little evidence to support an earlier date. The deposit was probably strongly oxidized during the middle Tertiary with the formation ofa rich chalcocite zone. The copper and iron sulphates have formed since
the Pliocene. Undoubtedly a considerable amount of leached capping
has been eroded from the deposit.
A discussion of the geochemistry of the deposit is given under thesection on Paragenesis.
Gnor,ocy oF ALCAPARRosA,
CrrrLEThe mine Alcaparrosa lies on the west side of Cerro Alcaparrosa, about
3 kilometers southwest of the station of Cerritos Bayos on the railroad
from Antofagasta to LaPaz, Bolivia. This deposit should not be confusedwith the more famous sulphate deposit of the same name at Tierra
Amarilla, near Copiap6, Chile. The property is reached by an auto roadfrom Cerritos Bayos. It is near the base of the hill, a peak that dominates the landscape in this vicinity. The deposits consist of a series ofveins and lensesof varying strikes and dips.
History. There are a number of small, massive isolated sulphate deposits at this property that have been mined over a long period. The
deposit is remarkable in the total absenceof copper, a feature that distinguishes it from any similar pyritic deposit in northern Chile known

SULPEATE DEPOSITS OF NORTEERN CEILE

677

to the writer. Due to the total absenceof any other metal, the deposit
has had a very limited value. The first work is reported to have been
carried on in about 1875.Minerals from the deposit began to be describedin Germany about 1880.
The sulphates were first mined for their sulphuric acid content- Inclined pits were sunk on the veins and roemerite and coquimbite weresought as the more favorable minerals. When dissolved in water, roemerite yields free acid, while solutions of coquimbite, when heated, yieldfree acid through precipitation of iron oxide. These acid solutions wereused in leaching copper and silver ores. The large amount of iron in thesolutions which would precipitate with the greatest of ease was a great
drawback to their use. Mining ceasedin the late nineties and was resumed about 1917 but ceased again about 1920. The area may haveproduced 20,000tons of sulphates. There may be 5,000 tons of sulphates
still available in the present workings and an unknown amount in undeveloped veins. However, of the material in sight, much is in the formof basic sulphates which have little or no value as a source of acid.
This deposit is the type locality for amarantite and hohmannite, forcrystals of metavoltine, and for the orthorhombic form of butlerite,
parabutlerite. It has yielded an undetermined mineral related to thealums, describedin this paper.
GeologicHistory. The sulphates occur in flows near the base of Cerro
Alcaparrosa. The writer believes the deposits to be no older than the
Pliocene. They represent oxidized portions of pyritic masses formed
close to the surface that have later been subjected to oxidation underincreasingly arid conditions. Since Pliocene times erosion has not been
great and there has been slight downward migration of the iron andsulphur.
The geochemistry of the deposit is discussedin detail under the section
on Paragenesis.
PanaGeNBSts
The paragenesisof the oxide minerals in these three deposits will be
discussed under two headings-sequence of Deposition and Geochemistry.
SequenceoJ Deposition The sequenceof deposition of minerals formedin the oxide zone of ore deposits has been hard to establish. The opaqueminerals have been studied intensively, but the far greater number of
nonopaque minerals have received little attention. Statements of depositional sequence of these oxide minerals are rare in the literatureof ore deposits. Such sequencesare established with difficulty. Physicalconditions, as well as the chemical composition of the meteoric solutions

678

MARK C. BANDI/

passing downward through a deposit, change rapidly from time to timeand from place to place. The change in the composition of the solutions
may be periodic and give rise to repeateddeposition of a certain sequencewith complete or partial solution or replacement of the older minerals.
There are many factors that may cause oxide minerals to be deposited:among them are degree of saturation, change in alkalinity, loss of volatile gases,changein temperature, change in pH. Meteoric waters passing
downward dissolve the more soluble minerals or salts first and the lesssoluble salts later, and unless reactions take place in the solutions theseminerals will be redeposited at lower levels. Minerals formed at one
time may, at a later time, be wholly or partially redissolved and thefortuitous presence or absence of some other mineral may completelychange the character of the next generation of minerals. Oxygen plays
an important role, and the availability of this element in the more open
channelsas contrasted with the solid country rock may give rise to two
different groups of minerals deposited from otherwise identical solutions.
In most mining districts, water, one of the essential agents of oxidation, is supplied at more or less regular intervals in sufficient quantity
to prevent the water throughout the deposit from becoming uniform incomposition for any appreciable period of time. With a more or lessconstant supply of water, these meteoric solutions rarely build up a
uniform concentration of either acids or basesover any appreciable areaof the deposit. There is always an abundance of the solvent, and thesoluble minerals are rapidly transported to the ground water reservoir.
Only the relatively insoluble oxide minerals are left in the supergenezone. As a result, most ore deposits have a relatively limited number ofminerals in the supergenezone, minerals that will form from very dilute
solutions and once formed are relatively stable, for example, hydrous
iron oxide.
fn northern Chile, conditions are exceptionally favorable for the formation of sulphates, chlorides and oxides from concentrated solutions
and from solutions that maintain a uniform composition over long
periods of time. fn the three deposits consideredin this study, the watertable is far below the surface and the primary sulphide horizon, with the
exception of portions of Chuquicamata. Rains capable of adding anappreciable amount of water to the deposit, that is, a sufficient amountto even moisten the entire oxide zone, only occur once in a decade as arule, During the intervening periods the sulphates form from concentrated solutions and then, once formed, change very slowly. There canbe no question but that many of the sulphates form from older sulphates
through reactions taking place in moist air and not by precipitationfrom aqueous solutions.

SULPHATE DEPOSITS OF NORTHERN CHILE

679

As a case in point showing the difference between the character ofdeposition of sulphate minerals from concentrated solutions, with essential stability between the solid and liquid phases, and sulphates deposited from supersaturated solutions where no stability exists between
the two phases, the famous sulphate deposit of Mina Alcaparrosa at
Tierra Amarilla, Chile, might be mentioned. This deposit on the banksof the Rio Copiap6 receives periodic rains but in scant quantity, as arule insufficient to penetrate far into the older sulphates. The original
sulphide was pyrite in large echelon lenses.Under more moist conditions
than those existing today, the pyrite was oxidized to a number of ironsulphates. The sulphat.eswere present to within a few feet of the surface

.

5

cn

.

Frc. 3. Sketch of a specimen of zoned sulphates from Quetena, showing
distribution of the minerals Dresent.

1. Pyrite and szomolnokite
2. PyriLe and halotrichite
3. Copiapite
4. Jarosite
5. Parabutlerite

6. Alums
7. Pisanite, var. salvadorite
8. Botryogen, var. quetenite
9. Copiapite and botryogen
10. Altered country rock

680

MAKK C. BANDVand when the deposit was mined a few pillars of the original sulphates
were left which are exposed on four sides and have dried out aimost
completely. As a result, when rain falls on these pillars the water rapidly
becomessaturated and supersaturatedand then redepositsthe sulphates.
The solutions penetrate only a few inches into the pillars and their effectis relatively limited. During the dry periods that follow the rains, thepillars dry rapidly and there is little bulk efiect from the rain such as
would exist if the deposit was a large unit, exposedonly on the surface.
The efiect of the deposition from supersaturated solutions is to form acrust of fine-grained sulphates on the pillars, sulphates composed.of
normal and basic varieties deposited simultaneously. underneath thissurface crust is a more or less solid mass of basic sulphates that show
essentially definite sequenceof deposition or formation. These original
sulphates were formed under conditions of relative stability, and thispermitted the formation of large massesof single mineral species.
Since the sulphates of the deposits here described are derived from
pyrite, the general sequenceas here given begins with that mineral. In
a zonedalteration of a pyrite nodule (Fig. 3), the outer portion is altered
f.rst, and, as the alteration proceedsinwards, the sulphate already produced undergoessuccessivechangesin composition, again from the outerrim inward. The sequencefrom pyrite is given, therefore, by the minerals
from the pyrite core outward with the outermost mineral the last toform. This last mineral is in the terminology of this paper the ,,late,,mineral, where pyrite is the "early.,, This treatment has led to certain
relationships that appear to be ambiguous. Pickeringite and halotrichite,
as well as fibroferrite, appear as recent effiorescentminerals on the wallsof openings in these deposits, forming after all other minerals. yet bothare early minerals, especially halotrichite, which is a normal hydrous
ferrous aluminum sulphate. The early crystals of halotrichite often contain inclusions of unoxidized pieces of pyrite. The recent formation ofthese minerals is probably due to their solubility and a wid.edepositional
range from solutions that are not in stable relationships.
Under average conditions the sulphates and chlorides form in thefollowing order, as determined in this stud.y.
Snqurxcr ol SupnncnNpHronous Sur,pqarnsaNo Cnr,orrors
Late

Hydrous oxides (limonite)
Hydrous basic salts
Hydrous basic salts

small percentage of HzO
large percentage of HzO

Hydrous normal salts
Hydrous normal salts

large percentage of HzO
small percentage of HzO

681

SULPHATE DEPOSITS OF NORTHEKN CEILE

Earl,yHydrous acid salts
Hydrous acid salts

Iarge percentage of HzO
small percentage of HzO

The above generalized sequenceis based, primarily, on a study ofthe pure hydrous iron sulphates. Departures from this sequence arecommon, but the "k"y" minerals in all deposits studied follow this sequence as a rule. t'Key" minerals are those minerals that appear frequently in all parts of a given deposit and in difierent deposits and towhich associated minerals can be referred on the basis of sequenceof
formation. The presenceof sodium, calcium, potassium, and magnesiumin the sulphates has an efiect on the generalizedsequence,but this could
not be evaluated in this study and no definite conclusionswere reached.
Additional studies need to be made upon either single veins in similar
deposits or upon deposits with a relatively simple and limited mineral
assemblage.As seen in the following table, normal hydrous sulphates
carrying one of these elements may form with basic iron and copper
sulphates. It is realized, of course, that the sequencerelationships ofthese minerals as here determined may be in error and that all sulphates
do not follow the sequenceoutlined above.
Table I representsan attempt to bring together a number of individual
sequencedeterminations. Single specimens or suites of specimensgive
definite relationships. Key minerals in different groups were correlated
and the intermediate minerals were fitted together as closely as the data
permitted. The following tabulation of some sequencerelationships at
Quetena illustrates the difficulties and limitations of the method used'
Acru.Lr, SequaNcns
Copiapite

Copiapite
Coquimbite

Conrureroo Sneurrcas
Copiapite
Voltaite
Coquimbite
Quenstedtite

Roemerite
Halotrichite

Szomolnokite
Chalcocite
PyriteSzomolnokite
PyriteCopiapite
Voltaite
Coquimbite
Quenstedtite
Roemerite
Halotrichite
Szomolnokite
Chalcocite
PyriteIn Table I more than one seqluenceis given for Chuquicamata and Quetena. In these deposits it was difficult to determine the relationships
between the different occurrences, and it was thought better to give
separatelists rather than to try to combine them all into one list on too
little data regarding interrelationships. The paragenetic associationsof

682

MAKK C. BANDY

these minerals will be discussedin the following section on geochemistry,
and more fully under the individual species.
T,qnrnI. MrNBnll Srqurxco et Cruqurcnr,rra, QunroNa,lNo Ar,clpennos.a.,Crnr,nA. Cnuqurcau.LraazI

SuppncnNr Sulpmons
Chalcocite
Covellite
BorniteChalcopyrite
Pnru.a.nvMrxnner,sLate Covelhte
Enargite
Fracturing
BorniteChalcopyrite
PyriteFracturingSupnncnNn Oxvcnr-BrenrNc
Northeast SectionArea of Heavy Pyrite
Veins
Late Limonite
KaliniteNatrojarosite
Natroalunite
Antlerite
Cuprocopiapite
Picromerite
Parabutlerite
Amarantite
Hohmannite
Copiapite
Fibroferrite(Tamarugite)
Aluminite
Metasideronatrite
Metavoltine
Ferrinatrite

PyriteFracturing
Magnetite
Earl,y Hematite
Eorfu

Mrrnrnrs

Central and Western
Sections

Limonite
GypsumCupriteMolybdic ocher
SulphurNatrojarosite
Picromerite
Antlerite
Lindgrenite
Natroalunite
Natrochalcite
Atacamite
Leightonite
Turquois
BloediteKroehnkite
Chalcanthite

Tamarugite
Coquimbite
Roemerite
Halotrichite

45
Supnncnxa OxycnN-Brarcwc Mrxnnar,s (Cont.)
SoutheastArea

East Side, Weakly Sulphatic

Opal
ChrysocollaAzuriteMalachite
Atacamite

Brochantite
Tenorite-manganite-Iimonite
CupriteNative Copper

6Pane,cnNBsrs Nor

Esranl,rsnro

Sphalerite
Tetrahedrite
Soda Niter
Mirabilite
Thenardite
Cerussite
Chenevixite
Pisanite
CalciteMagnesite
HaliteUlexite683

ST]LPEATE DEPOSITS OF NORTHERN CHILE
Tasr-n I (Continuetl)

B. Qunrnwl
T
Late

C. Ar,clleltosa
1z

Fibroferrite
Pickeringite
Chalcanthite

Brochantite

Jarosite
Metavoltine
Ferrinatrite
Pickeringite
Botryogen, var.
Quetenite, Rubrite
Kalinite
Chalcanthite(?)
Cuprocopiapite
Parabutlerite
Amarantite
Hohmannite
Copiapite
Pisanite, var.
Salvadorite
Bloedite
Voltaite
Coquimbite

GypsumAluniteAtacamite
Bandylite
Antofagastite

Late

FibroferritePickeringite
Jarosite
Iron-Pickeringite(Aromite?)
BotryogenPicromerite
Parabutlerite
Copiapite
Metavoltine
Ferrinatrite
Pickeringite
Lapparentite(Coquimbite)

Quenstedtite
Coquimbite
Roemerite
Halotrichite
Rhomboclase (?)
Eailry Szomolnokile

Orrencf ed f if c

Early

Roemerite
Halotrichite
Szomolnokite

PyriteChalcocite
PyritePenncnsrsrs Nor
Esranr,rsrml
Mirabilite
SodaNiter
Thenardite
AluniteVoltaite
Mendozitez3
P.q,ucpNrsrs Not
Esr.q.silsmn
Kroehnkite
Anhydrite
Picromerite

Geochemistry.The oxidation of pyrite is the basal mechanism in theformation of the sulphates found in these deposits. Enargite furnishedcopper and a small amount of sulphur at Chuquicamata, and some unknown mineral furnished copper for the copper sulphates at Quetena,
but in all three deposits pyrite was the main source of the sulphates. In
recent years the oxidation of pyrite has been extensively studied both

6U

MARK C. BANDY

in the field and in the laboratory, although the laboratory experiments
have not been as successfulin furnishing data as was hoped for.
More progress has been made and more definite conclusions reachedin the study of the various oxide systems, in particular CuO-SOe-HzO
and Fe2O3-SO3-H2O.
The former system was studied most successfully
by Posnjak and Tunell.2 The latter system was studied by Posnjak
and Merwin and others.s These works are not in entire agreement andthe work of Posnjak and Merwin is here taken as the best available.
The geochemistry of the oxidation at Alcaparrosa where no copper isinvolved and at Chuquicamata where copper is an important constituent
will be discussedin detail, while the oxidation at Quetena will be consideredin relation to these two deposits.
Oxidation at Alcaparrosa, Chile
There are two types of oxidation at Alcaparrosa, or what might becalled "two lines of descent,t' one involving iron sulphates, or sulphates
carrying iron, the other involving non-ferrous sulphates, principally
alums. For comparison with the work on the system FesOrSOrH2O
the two lines will be discussed separately.
In one of the inclined pits at Alcaparrosa a complete seriesof sulphates
from the surface to fresh pyrite was exposed. This series is describedhere in detail to give a picture of the deposit. The different pits on theproperty show difierent minerals, but the relationships are, in general,
the same. The section from the surface to the bottom is as follows:
1. Alluvium,1-4 feet.
2. Mirabilite alteredto thenarditewith associatednitrates,8 inches.Spotty andvariable in thickness. Probably not genetically related to the pyrite deposits.
3. A white pulverulent mixture of several minerals, mostly alums with some g;4)sum,
variable in thickness, usually in pockets.
4. A hard to pulverulent brown manto of jarosite and iron oxide, 1 to over 6 inches
thick.
5. In isolated areas, brown to orange parabutlerite. Evidently an alteration productof the underlying copiapite. At the bottom this layer becomes distinctly fibrous in character witl the general appearance of fibroferrite. Average, 8 inches thick.
6. A layer of variable thickness of greenish-yellow to brown copiapite. The crystals
are minute in size as a rule. Large, megascopic, brilliant yellow crystals are developed only
2 Posnjak and TunelJ,, Am. Jour. Sc., vol. 18, p. t,1929.
sPosnjak and Merwin, Jour. Ano. Chem. Soc., vol.44, p. 1965, 1922; Merwin andPosnjak, Arn. Minerd., vol.22,pp. 567,lg37 .
Cameron and Robinson, Jour. Phys. Chem., vol. ll, p. 641, 1907.
Wirth and Bakke, Zeits. anorg. Chern., vol.87, p. 13,1914.
Scharizer, Zeits. Krist., vol. 43, p. 125, 1907; vol. 46, p. 432, 1909; vol. 52, p. 385,
1913,etc.
Baskerville and Cameron, J our. P hy s. C hem., vol. 3g, p. 7 69, 1935.

SULPEATEDEPOSITSOF NORTEERN

CEILE

685

where country rock occurs. A feature of this layer is the occurrence in the copiapite ofcoarse, bladed, pale bluish-white, milky pseudomorphs of coquimbite after quenstedtite.
The copiapite is the younger mineral and the crystals show little evidence of replacementby the copiapite. Thickness,0-12 inches.
7. A massive layer of light purple, finely crystalline coquimbite. The upper contact
with the copiapite is sharp, as a rule. The layer grades downward into the lower bed.
Thickness, 2-10 inches.
8. A massive layer of dark purple and reddish purple coquimbite and roemerite, intimately associated. The roemerite is replaced by the coquimbite. crystals and crystal
druses are abundant. Associated with the coquimbite, in vugs, are crystals of lapparentite,
pickeringite, quenstedtite and pseudomorphs of coquimbite after quenstedtite. Large
crystals of coquimbite, up to t inch, occur in the more massive replaced quenstedtite. At
tle bottom of the horizon rounded masses of bright yellow roemerite appear. Thickness,
3-20 inches.
9. A layer of variable composition. At the top is massive coquimbite with round, isolated areas of szomolnokite and pyrite, surrounded by a layer of roemerite. The coquimbite
grades downward into massive reddish-brown roemerite with rounded areas of yellow roemerite. The same round areas of szomolnokite and pyrite occur in the roemerite as weII
as in the coquimbite. These areas may vary from a fraction of an inch to several inches indiameter. Thickness from 3 inches to 2 feet.
10. A layer of unknown thickness but certainly up to two and a half feet thick of colorless and faintly brownish-purple rhomboclase and intimately associated szomolnokite withbright angular pieces of pyrite scattered through the minerals. where the pyrite is mostabundant the szomolnokite increases in abundance in relation to rhomboclase. The contact between the upper bed of roemerite and the rhomboclase-szomolnokite is line-sharp
and apparently plane. There is no apparent change in texture as one passesfrom the colorIess rhomboclase to the reddish-brown roemerite.

From this section the following sequencecan be more or less definitely
established.
Sneunncr II

Snqurucn I
Mirabilite-soda niterAlums-gypsum
KFes(SOa)z(oH)oJarosite
Parabutlerite Fer(SO4)r(OH)r.4HrO
Fer(Sor)r(oH)2. 16H2o
Copiapite
Quenstedtite Fez(SOr)s'10Hro
Lapparentite Ah(SOtr(OH)r'gHrO
Pickeringite MgAlz(SOr)r.24H:O
Coquimbite Fez(SOr)s.9HrO
Quenstedtite Fer(SO4)s.10HrO
Roemerite
Fe".Fe2"'(SOr)r.14HzO

Basic
Basic
Basic
NormalBasic
NormalNormalNorrnalNormalRoemerite
Rhomboclase Fer(SOtB'HzSOr'8HzO Acid

Szomolnokite
PyriteFeSOr'HuO
FeSzNormalSzomolnokite
PyriteIt is at once apparent that in the sequenceoutlined above the otherwise orderly change from acid or normal sulphates to later basic sul-

686

MAKK C, BANDY

phates and from ferrous to ferro-ferric to ferric sulphates is interrupted
by rhomboclase. If the field occurrence is taken at its face value, wehave (Sequence II) a normal ferrous sulphate, szomolnokite, altering
to an acid ferric sulphate, rhomboclase, and this in turn altering to anormal ferro-ferric sulphate, roemerite. In the other case (SequenceI)
we have a normal ferrous sulphate altering to a normal ferro-ferric sulphate, and this in turn to normal and then basic ferric sulphates. It isbelieved that some localized circumstance, explained in a later section,
caused the formation of rhomboclase in the place it now occupiesin thedeposit.
No study has been made of either of the systems FeO-SOa-HzOor
FeO-FezOa-SO3-H2O,
but Posnjak and Merwina have studied the system
FezOe-SOa-HzO
from 50 degreesto 200 degrees.They obtained rhomboclase, copiapite and monoclinic butlerite among the artificial minerals
formed at the lower temperatures. The minerals obtained and the solutions from which they formed at 50 degreesare tabulated below.
Mrnnner,

Lreurn Pnasn
Weight Per Cent

Rhomboclase
copiapite
Butlerite

Fe:os
0.09- 5.55
t6.78-21.00
21.00 20.13

Soe
55.3+33.96
30.72-28.2
28.2 -27 .18

Hro
44.57-60.49
52.50-50.8
50.8 -52 .69

So3/FezOr
6.15-6.1
1.8 -1 .3
1 .3

Also within the range studied, the various classes of iron sulphates
were obtained from liquids of the composition noted below.
Lrquro Pnasn
Weight Per Cent
FezOs
Acid
NormalBasic

0 . 0 0 -5 . s 5
8 .5 G 1 67. 8
1 6 . 7 80- . 1 4SO:
75.37-33.96
32.52-30.72
30.72- 0.39

HrO
24.56-60.49
58.92-52,50
52.50-9947

SO3/FerO3
Inf. -6.1
3.8 -1.8
1.8 -2.8

It is observed from these data that sulphuric acid content is the dominating factor in the type of sulphate formed. It is also noteworthy thatmany of the sulphates so abundant in nature were not obtained in thesestudies, coquimbite for example.
Scharizer and others have obtained a number of artificial salts that
correspond to natural minerals in various experiments. Some of these
data, in compositional ratios, are given here for comparison with natural
4 Op. ci.t.

SULPHATE DEPOSITS OF NORTEERN CEILE

687

sequencerelations of the minerals and for comparison with the data ofPosnjak and Merwin given above.
Szomolnokite
Copiapite and coquimbite
Coquimbite and rhomboclase
Copiapite
Rhomboclase

weight per cent
HzOlSOs:2 ' 186-7.935
SOs:H2O: 1:3 .47:30.886
FerOs:
FezOr: SOa:HzO: 1 : 6. 69: 55.776
Fezoa: SOs: HzC: l : 6. 45: 41.947
FIzO/So3:3.744-3.6647

There are some additional data, mostly by Scharizer, but there isserious doubt as to whether his solutions reached equilibrium. The data
are, therefore, of little value in this connection and are not quoted here,
although his findings check the sequencesdetermined in these deposits.
This might be expected, as manv of these natural sulphates formed fromsolutions that had not reached a state of equilibrium with the solid
phases.
From the foregoing data it is apparent that acid, normal and basic
salts are deposited in this order from solutions that are more and more
dilute and from solutions in which the acid content decreasesin proportion to the iron, although in the very dilute solutions the actual ratio
increasesa little.
The writer offers the following explanation for the formation of rhomboclaseat Alcaparrosa. It is believed to be later than the roemerite andszomolnokite with which it is associated, and to be a sulphate derived
from the oxidation of these two minerals. The szomolnokite formed firstfrom the oxidation of the pyrite under conditions of limited water andoxygen. It was then partially oxidized under similar conditions toroemerite. At some subsequent period, while this process of oxidation
was still going on, probably after it was well advanced, suficient mois'
ture appeared in the deposit to allow the formation of a water table,
and this probably maintained a given horizon for some time in thebottom of the deposit. The water contained a high percentage of salts
and was relatively strongly acid. In this water, sufficient oxygen waspresent, and was added from time to time, to oxidize the roemerite andpart of the szomolnokite to the acid sulphate rhomboclase. An origin of
this nature would. explain the more or less horizontal, exceptionallysharp contact between the roemerite and rhomboclase-szomolnokite
mixture. It would also explain the complete oxidation of the roemerite,a readily soluble sulphate, and the partial oxidation of the ferrous sul5 Kenrick, Jour. Phys. Chem., vol. 12, p. 699, 19O8.
6 Wirth and Bal<ke, Zeils. anorg. Chem., vol. 87, p. 40,1914.
7 Scharizer,Doelter, 4 pt. 2,572,1929.

688

MARK C. BANDY

phate szomolnokite, which is lesssoluble and would require more oxygen
and acid to oxidize it to an acid ferric sulphate.
The relationships of coquimbite and quenstedtite are noteworthy.
These minerals have the composition:
Quenstedtite
Coquimbite

Fez(SOr)g.l0HzO
Feg(SOa)a.9HzO

According to the general sequence relationships of the sulphates, coquimbite would be expected to form first and then be followed by quenstedtite. The relationship is, in general, in agreement with this sequence,but there is a marked overlap of the period of the two minerars. As aresult there appear to be two ages of quenstedtite, one replaced bycoquimbite and one later. The dull, pale blue, milky pseudomorphsprobably formed as quenstedtite at the same time as coquimbite was forming.
The coquimbite had the power to replace the quenstedtite rrnder certain
conditions, while the reverse replacement was apparently difficult or
impossible. The coquimbite would form from the more acid and moreconcentrated solutions, and after a rain or some influx of water into thedeposit the first solutions would be diluted and quenstedtite would form
and as the solutions became more acid and more concentrated the depositional range for coquimbite would be reached and it would. form
and at the same time replace the older quenstedtite. This type of deposition went on during the latter half of the coquimbite period. The
small amount of crystallized quenstedtite may have formed along withlapparentite and pickeringite. The formation of these minerals will be
discussedlater but the conclusionsreached will be applicable, probably,to the formation of crystals of quenstedtite that have not been replacedby coquimbite. Theoretically, a point is reached in the deposition ofsulphates from a solution where the solid phase is not readily soruble
and minerals are deposited from solutions that are less and less concentrated. rf this is true, quenstedtite would have a period of formation
later than coquimbite and the crystals of this mineral may have formedin this manner, from more dilute solutions.
All of the basic iron sulphates are later than the normal sulphates.
The relationship of copiapite and later parabutlerite is definite in boththe hand specimen and in the field. The natural occurrence coincides
exactly with the data obtained on artificial systems. At the contact ofparabutlerite and copiapite much of the parabutlerite retains the platy,
radiating structure of the copiapite, from which it is derived.
The conditions of formation of the non-ferrous sulphates cannot betreated with the same assuranceas the pure iron sulphates. rn the fierd
their volume is much lessin these deposits and their occurrenceis spotty.

SULPHATEDEPOSITS OF NORTHEAN CEILE

689

Minerals that are compound sulphates of iron and some other element
are more abundant, but they shed little light on the sequenceof thenon-ferrous sulphates. Potassium and sodium may appear in theseminerals along with the iron but there is no consistent relationship.
Jarosite is definitely a late mineral. This is a potash-iron sulphate andat Alcaparrosa occurs above the parabutlerite. Other near-surface compound sulphates carrying iron are:Botryogen
Metavoltine

MgrFer(SOn)r(OH)2- I4IJIO(K,Na)rFer(SOr)r.8HzO

Botryogen is abundant in one of the pits as a late mineral, later thancopiapite with which it is associated.The only other associatedminerals
are kalinite and mendozite, potassium and sodium alums. Metavoltine
occurs in rather definite, narrow relationships. It occurs near the surface
associatedwith copiapite and various alums, both of which are younger
minerals.
From these associationsit is evident that the alums, normal sulphates,
are late minerals. Associated with the lapparentite, a basic sulphate,
are pickeringite and iron sulphates.
Late Copiapite
Pickeringite
Lapparentite
Quenstedtite
Eorly Coquimbite

l6HrO
Fe4(SO4)6(OH)2.
MgAlz(SOr)r.24HzO
Alr(SO{)r(OH)r.gHrO
10HrO
Fer(SO4)a.
Fez(SOr)s.9HzO

It is difficult to explain the formation of a basic aluminum sulphate preceded and followed by normal sulphates. However, the lapparentite ispresent in a very limited quantity. In other areas of the deposit, near thesurface, lapparentite is a later mineral and follows and is followed byalums. However, the writer is rigorously following the sequencedeterminations on individual specimens;and, while in the deposit, in general,
there is as much evidence that lapparentite is a late mineral as an earlyone, in this caseit is definitely followed by pickeringite, a mineral closely
related in composition to the alums.
As stated above, the alums are late minerals, all of them being normal
sulphates and forping later than basic iron sulphates. Much of thepickeringite is in the form of radiating acicular crystals growing on othercrystals in vugs and veins. The last mineral to form in present openings,
covering the walls of many of the pits as an efflorescenceis the basic
ferric sulphate fibroferrite, Fe2(SOa)r(OH)r.9HrO. This mineral ofiers
the key to certain anomalous minerals, especially those present in minor
quantities, which form under conditions of limited hydration. With no690

MARK C, BANDV

water present in liquid form it is possible for them to form throughout
the deposit. As in the case of lapparantite and pickeringite, on coquimbite, in the bottom of the deposit, the minerals may have altered fromearlier formed minerals but a short time previous to removal arld are now
in association with early minerals and in zones beneath minerald thatare much older. At Chuquicamata we find fibroferrite associated withamarantite, hohmannite and botryogen where it has formed earlier thanany of these minerals from acid, aqueous solutions. Likewise we find it
as an effiorescenceof very recent origin in vugs, etc., the product ofhydration.
The conclusion reached is that minerals of this type can form in any
opening when sufficient water vapor is present. These hair-like forms
grow out from the walls or from the support by addition of material tothe bottom of the crystal, that is, the point of support of the crystal.
The writer has observed the formation of fibroferrite at Quetena in thismanner after a moist period, and specimens of metavoltine, copiapite
and rhomboclase began to develop fibroferrite on their surfaces after
exposurein Iaboratories in the United States for a few months.
The problem of the sequenceof the non-ferrous sulphates must beleft open. Where the minerals contain both iron and some other base,isolated sequencerelationships can be determined at Alcaparrosa, butwith the pure non-ferrous sulphates a consecutive sequencecannot be
determined in relation to the iron sulphates. Most of them are later than
the iron minerals. Since the non-metallic elements are obtained fromthe country rock, reactions between the sulphate solutions and the wallrock would probably tend to dilute the solutions, and variations in theintensity of reactions and degrees of dilution might account for thevariations in the sequenceof formation found in this study.
Oxidation and Enrichment at Chuquicamata, Chile
At Chuquicamata and to a less degree at the two smaller sulphate
deposits, the oxidation of the ore has resulted in a rather wide distribution of the valuable metals and, as a rule, no sharp horizons of demarcation between leached capping, enriched zone and primary sulphides
exist. The rapidity of oxidation of the pyrite-enargite veins was roughly
proportional to the ratio of pyrite to enargite. In the massive enargite
veins to the northeast, oxidation was slow, and many veins show enargite
near the surface, while in the area of disseminated enargite and in areasof abundant pyrite the zone of oxidation is much deeper and oxidationmust have been much more rapid. While similar minerals have formed
in almost all areas,especially the common and abundant minerals, someof the rarer minerals are limited to definite areas at Chuquicamata, andSULPHATE DEPOSITS OF NORTHEKN CHILE

691

these rarer minerals ofier much information regarding the conditionsof formation of associated minerals.
In all cases, the first product of enrichment was chalcocite. This
mineral occurs throughout the deposit but is most widely distributed
through the porous sericitic rock along the western edge. In the central
area of the deposit, rare occurrencesof supergene(?)chalcopyrite older
than chalcocite occur in massive chalcocite. This chalcopyrite is in theform of rounded, scattered grains.
Much of the chalcocite, probably most of it, formed through reactionsof copper sulphate and pyrite and is found today very intimately associated with this sulphide. It has been estimated8that it would be necessary to crush the Chuquicamata ore to four microns in order to release
enough chalcocite to make a 90/s recovery by flotation, and obtain a
65/6 copper concentrate.
Along the east side of the deposit, in the area to the northwest and in
the vein zone northeast of the present pit, cuprite formed intimately
associatedwith native copper. Associated with these minerals along theeast side is tenorite and manganeseoxides forming a "copper pitch ore."
No satisfactory reaction can be given for the formation of this minor
occurrence. Whatever the cause, the one feature evident in the field isthat these oxide minerals and the native copper formed in an environment that was less acid than that of the great bulk of the supergene
minerals. Most writers believe that native copper and cuprite form fromessentially neutral or alkaline solutions. In the northwest the cuprite
formed from veins carrying primary carbonates.
Another occurrence of native copper and minor cuprite intimately
associated with specularite has been discovered by drilling along theeastern edge of the deposit. The shape and extent of this deposit were
not delineated but the mass is essentially tabular, elongated parallel tothe length of the main deposit. A feature of the occurrenceis the intimate
association of specularite and native copper with minor cuprite in cubic
crystals. Some iron oxide is present but is not abundant. More detailed
knowledge of the occurrence is necessary before the origin can be established. It may represent the formation of cuprite and copper after
chalcocite through the action of ferric sulphate in a neutral environmentor the specularite may be involved in the origin.
Cuprite forms after and from native copper at Chuquicamata. Characteristically the copper occurs as small to minute grains scattered throughthe cuprite, or, as mentioned above, the cuprite occurs as crystals on
native copper. The massivecuprite occurs as kernels or veins surroundedby "copper pitch" and this, in turn, by chrysocolla and opal. Along the
8 Bandy,Privatereport,1931.SeeTaylor,op.cil.

692

MAKK C. BANDY

extreme eastern side of the deposit the "copper pitch" occurs in puremasses,round to tabular in shape. Some of the round massesare threefeet in diameter. The ore is black with pitch-like luster in the center andgrades to a soft dark brown mass on the border. This material is discussedunder the name "Copper Pitch." Cuprite is also present as a late
supergenemineral, pseudomorphic after antlerite. This will be discussed
later.
In the bulk of the deposit at Chuquicamata the hypogene sulphides
were deposited as small veins and disseminations through the "quattzsericite," "normal rock" and to a minor degree in the "transition rock"types. These sulphides have weathered deeply except in areas of intensequartz flooding. In this part of the deposit the sequencerelationships
are clearer, and some of the oxidation reactions are more obvious thanaround the outer fringe.
The difficulty of oxidizing enargite is well known. The reason for the
deep alteration at Chuquicamata is believed to be due to the disseminated character of the enargite as mentioned above, and to the abundance of associated pyrite. The latter mineral furnished the necessaryiron (ferric?) sulphate, which could attack the small and isolated grains
and small veins of enargite more effectively than large massive veins.
It would appear that ferric sulphate rather than ferrous sulphate is
involved in the oxidation of enargite with the formation of arsenate
minerals. While arsenate minerals are not unknown at Chuquicamata,on the whole they may be considered as rather rare. There are a few
isolated areas where chenevixite occurs. The weathering of the greatmass of enargite at Chuquicamata has released a large quantity ofarsenic, and whether this arsenic was carried away during the Tertiary
period in solution or was fixed in the outcrops during this period as somearsenate mineral and then removed by the post-Pliocene erosion cannot
be determined.
With the oxidation of the enargite, pyrite and minor covellite, thecopper was carried downward and deposited from acid sulphate solutions
on other pyrite and enargite as chalcocite. The replacement proceeded
inwardly, and bladed enargite structures are preserved in some of thesupergene chalcocite. This supergene chalcocite was later altered tooxide minerals. As a rule, the first mineral to form from the chalcocite
and pyrite is chalcanthite, and in near-surface areas chalcanthite andkroehnkite, CuNar(SO+)2.2H2O. Field evidence indicates that kroehnkite formed from lessacid solutions than chalcanthite. With an adequate
supply of water these minerals would go into solution and pass downward as copper sulphate in ferric sulphate solutions. Upon encounteringST]LPEATE DEPOSITS OF NORTHEKN CEILE

chalcocite, free from pyrite or with only minor amounts, covellite mightform first from the chalcocite and, in turn, alter to antlerite. Many
sections of chalcocite show a band of coarsely bladed covellite between
the antlerite and the chalcocite. The band of covellite advances into thechalcocite as the antlerite vein widens.
The excessof sulphuric acid developed during the formation of antlerite and the ready oxidation of ferrous sulphate probably is the reasonfor
the general absenceof cuprite and native copper at Chuquicamata, asboth of these agents readily attack those minerals. Studies of artificial
minerals have shown that antlerite forms from relatively concentrated
solutions. Some of the free acid is removed by the attack on ever-present

additional water, sufficient to cause solution, such solutions would beconcentrated after a very short migration, and minerals, antlerite inthis case,.would precipitate from the concentrated solution.
The formation of antlerite, Cu3(SOa)(OH)r, at Chuquicamata andother Chilean deposits, and of brochantite, Cua(SOa)(OH)o,at almost
every other basic copper sulphate deposit the world over (except at theAntler Mine in Arizona, the type locatity) may be explained by the
special conditions of acidity of the solutions at Chuquicamata' The
characteristic feature of almost all the Chilean deposits is the presenceof abundant soluble sulphates throughout the deposits with an excess
of available acid. Specimensfrom these mines, when placed in water,
will usually yield a solution containing free acid. By analogy, water
entering these deposits would soon contain free sulphuric acid which
would attack less soluble salts and in this manner rapidly increase theamount of material in solution. It is well known that the presence of
limestone in a deposit tends to retard migration of sulphates through theremoval of free acid from the solutions in the deposit and in fixing thesulphates as insoluble or difficultly soluble minerals. fn contrast, at
Chuquicamata little acid. is removed in this manner; instead it forms
soluble salts and much of the acid is read.ily available by resolution in

694

MARK C, BANDV

content of both base and acid, except in rare or isolated cases.Tunelland Posnjakeworked with a portion of the system FerOs-CuO-SOa-HzO
and their data support this theory. They found that brochantite formed
from dilute solutions, solutions with a concentration less than,
CuO
0.61

SO,
0.64

HzO
98.75

Antlerite formed from solutions with a concentration greater than.

CuO
5.01

SOt

5.22

HrO
89.77

The antlerite is the end point in the copper enrichment at Chuquicamata. After forming, it is removed and carried downward in solutions
containing iron sulphates with the precipitation of iron oxide either as a
hydrate mineral or as hematite. The boxwork of the iron oxide after
antlerite is believed to be characteristic of the mineral, and certainly theiron oxide itself is. ft is known locally as "maroon oxide" and has avery distinctive deep red color and texture. Whatever the intermediate
composition of the "maroon oxide" pseudomorphic after antlerite is,during the oxidation process,it changeseventually to a brown limonite
which is stable.
Some of the ore at Chuquicamata shows the rare relationship ofcuprite replacing antlerite. The pseudomorphs retain the fibrous structure of the antlerite in minutiae. The chemistry of this replacement is
not clear. It probably results from the reduction of the antlerite by
fetrous sulphate with a delicate balance in the proportion of ferrous
sulphate to antlerite. These pseudomorphs occur only on the easternside of the ore body in areas of low acidity.*
Four other minerals of uncommon or rare, but genetically significant
occurrence at Chuquicamata are chrysocolla, brochantite, azurite andmalachite. Chrysocolla is rare in the southeastern section of the deposit.
It is confined to the "low acid" areas. The writer has found brochantite(identified optically) in this same area associatedwith gypsum. ft aho
occurs in the northwest area associated with gypsum. As pointed out
earlier, the study of artificial minerals showed that brochantite forms
from more dilute solutions than antlerite, and one would expect to findmore dilute solutions in these areas.
Malachite and azurite occur in an outlying vein to the south of thedeposit. The gangue of the ore is coarse, bladed specularite and minor
eTunellandPosnjak,.I.phys.Chem.,
vol.35,p. 929,I93I.

+ By "low acidity" the writer refers toareas characterized byoxide minerals
and few
or no sulphates. At Chuquicamata low acidity areas are "more or less coincident with theTransition Rock type."

SULPHATE DEPOSITS OF NORTHEKN CHILE

695

magnetite. Chrysocolla is an abundant mineral in this vein. The amountof malachite and later aztrite is insignificant in proportion to othercopper minerals, but signifi.cantin indicating the environment of deposition of these and associatedminerals. The carbon dioxide in these minerals was probably derived from a small amount of carbonate gangue inthe vein. It should be noted. that gypsum is a near-surface mineral at
Chuquicamata and is a most abundant mineral in the fringe of thedeposit and in the alluvium about the mine. The bulk of the gypsum
was not derived from the ore deposit, however.
Atacamite was an abundant mineral at chuquicamata in the earlyyears of the mine. This basic copper chloride, 6u*Qlr(OH)e, formed fromthe action of surfacewaters, charged with sodium chloride, on the soluble
copper salts. The mineral is practically limited to the upper 70 feet ofthe deposit. It is more abundant in the "low acid" areas.
The massive iron sulphate veins in the northeast area of the mineshould be mentioned briefly. The pyrite is oxidized first to halotrichite,
FeAh(SO+)n.24HzO, and then in successive steps to f.broferrite,
9HzO, hohmannite, Fer(SOr)z(OH)z' 7HzO, amarantite,
Fez(SOa)z(OH)zFez(Sor)r(OH)z' 6}ilzo,botryogen,MsFe (SODr(oH)' 7HrO' and jarosite,
KFer(SOc)z(OH)0,with an introduction of AhOa, MgO, etc. The age
relationships of botryogen are not clear. This mineral may be earlier
than amarantite.
In other veins, probably veins that contained less primary pyrite or
smaller veins,possibly areasof unusually strong disseminationof pyrite,
metasideronatrite and metavoltine in intimate association, fibroferrite,
ungemachite and clino-ungemachite and alums occuf. These veins are
not associatedwith the fibroferrite-amarantite veins and apparently thechemical or physical conditions of formation of the two associations
were different. Almost all the minerals in these veins are soda-iron sulphates or soda-rich equivalents of potash-iron sulphates.The sequenceis,
Alums (soda)
Ungemachite
Metasideronatrite
Ferrinatrite
Early Metavoltine

Lote

NazAlz(Sor)r
NaoKz(SO+)n
NarFe:(SOr)r(OH):
Na4Fe2(SO4)b
(K, Na)rFer(SOt4

24H2o
8HrO
3HrO
7H2O
7H2O

The alums are principally mendozite with a very small amount ofkalinite, the potash alum.
This association representsan important feature of many deposits ofnorthern chile and especially of chuquicamata. In this deposit, potassium sulphates are rare although the host rock is potash-rich. when
the sulphates were formed, there was evidently an abundant source of696

MARK C. BANDY

sodium that was taken up by the solutions moving down from the surface
through the deposit. In every case, soda-rich minerals formed, such as
natrojarosite, ungemachite, clino-ungemachite, or compound sodium
sulphates such as those mentioned above. Corresponding potassium
minerals did not form, while the sodium minerals mentioned above, as
well as bloedite, mirabilite, kroehnkite and natrochalcite (the latterknown only from this deposit) are common. This might well be called a"sodium province."
Two sourcesof the sodium can be postulated. One source is the sodium
removed from the granodiorite during sericitization and orthoclasization.
This sodium might have been carried upward to some horizon above thepresent deposit and there deposited as a sodium salt, possibly natroalunite, that would break down readily under weathering conditions.
The one important point against this source is the presenceof kroehnkite, metasideronatrite and metavoltine in other Chilean deposits. The
second source is the abundant soluble sodium minerals in the alluvium
over almost all of northern Chile. These minerals include halite, soda
niter, mirabilite, and thenardite, salts believed by the writer to be of
volcanic origin. All of these minerals occur about the deposit at Chuquicamata today and have certainly been present since the volcanism of
the Pliocene and probably since the early Tertiary. The writer has foundlenses of nitrates, chlorides and borates in early Jurassic beds in thisvicinity. Any circulating ground water would carry sodium in considerable quantity, and rain falling on the surface over the deposit would becharged with this element. On encountering iron and copper minerals
or solutions of iron and copper sulphates, the sodium would form compound sulphates with these elements. The preponderance of sodium
minerals in the oxide zones of ore deposits in northern Chile has neverbeen sufficiently stressed.This second source of sodium seemsthe more
likely.
Oxidation at Quetena, Chile
A study of the oxidation at Quetena adds little to the data obtained
from Alcaparrosa and Chuquicamata. At the surface, near the contact
with the limestone, float pieces of limestone are being replaced by brochantite and gypsum. These minerals occur in shells about the limestone.
The association-carbonate, gypsum and brochantite-is similar to thatat Chuquicamata. The basic hydrous copper chloride, atacamite, occurs
at the surface and gives way in depth to bandylite and this mineral, in
turn, to the normal chloride, antofagastite. The sequenceof formation is,
Late
Early

Atacamite
Bandylite
Antofagastite

Basic
NormalNormalST]LPHATE DEPOSITS OF NORTHEKN CHILE697

If chlorides and sulphates follow the same general sequencein oxidation,
can it be true that other classesof minerals follow it also? The carbonates
do at Chuquicamata in the one specimen of malachite with later azrrite
examined by the writer. Both are basic carbonates, but malachite is themore hydrous. However, this relationship between malachite and azurite
is not universal, as one mineral is later than the other in one deposit, andthe reverseis true in other deposits.An outstanding example of malachiteaf.ter azurite is found in the fine specimensfrom Tsumeb. It should be
noted, however, that the Tsumeb ores are in a limestone and dolomite
gangue and would not be entirely"comparable to occurrenceslike Chuquicamata. At Tsumeb, as at many mines, azurite does form after someof the malachite. At Bisbee, malachite is both earlier and later thanazurite, but the great bulk of the azarite is apparently later than thegreater amount of the malachite. This samerelationship is true at Chessy,
France. At Clifton-Morenci, Lindgrenlo states that azurite "is often thelatest mineral formed." Lindgren also states that malachite follows
brochantite at Clifton-Morenci, an identical relationship to that foundat Chuquicamata. From these data the writer believes that the tendency
for the carbonates to follow the general sequence of the sulphates isprobable. Carbonates are most abundant, of course, in deposits in limestone. The sulphate sequenceis established from deposits in a countryrock that does not react to any appreciable extent with the oxidizing
solutions.
No data are available for considering the other classesof minerals'
The oxides, phosphates, arsenates,vanadates, etc., offer an interesting
field of study in this connection.
An excellent example of the sequence relationships at Quetena isafiorded by the specimenshown in Figure 3. The central core is composedof a mass of individual crystals of halotrichite, szomolnokite and pyrite.
The minerals of the succeeding bands and the mineral sequence aretabulated below.
Late Pickeringite
Limonite
Pisanite
Botryogen
Jarosite with alternating bands of copiapite
Parabutlerite
Copiapite
Halotrichite
Szomolnokite
Eail.y Pyite
10Lindgren, U. S. Geol.Suraey,Pro!. Papu 43, p. 118, 1905.

NormalNormal
Basic
Basrp
Basic
Basic
NormalNormaI698

MAKK C. BANDY

It is to be noted that normal cupriferous minerals, such as pisanite,form after basic pure iron sulphates. This occurrenceof copper minerals
after iron minerals checks the work done by Tunell and Posnjaku on thesystem FerOr-CuO-SOr-HrO, since they show that when there is any
appreciable concentration of iron in the solution, that is, FezO3present
in quantities greater than 0.01/6, iron sulphates rather than copper
sulphates form. A solution with the following composition:
FezOs
CUO
SOa
HrO

0.22%
0.9+
t.61
97.20

formed a precipitate of FezO:.HzOand 3FezOa.4SOr.9HzO.
f t is evident
that the copper is held in soluticn until the iron content falls to a trace,and then copper salts begin to form. In some parts of Quetena, cuprocopiapite formed by replacing copiapite, but only after copiapite, parabutlerite and jarosite had been formed. The same relationship is true
at Chuquicamata.
PART II. DBSCRIPTIVEMINERALOGY
The minerals are described under the same classification and in thesame serial order as in Dana's "System of Mineralogy," sixth edition.
Several new minerals are described and these are placed in serial order.
The minerals, fully described, are treated in the following order:
Crystallography
Forms
Structure Ce'll
Habit
Twinning
Cleavage
Physical Properties
Optical Properties
Composition
D-.-^-.^^^+:^^

bil:;""*;.

Sequence

References

Some speciesare described and discussedas a group as well. An attempt
has been made to clear up some of the doubtful speciesthat have comefrom the area described as well as speciesthat are directly related to thisstudy from other areas.
Minerals that are of slight importance to the study and minerals uponwhich no new data have been obtained are treated briefly. Minerals seen
tt Op. ei.t.

SULPHATE DEPOSITSOF NORTHERNCHILE

699

only as essentialconstituents of the local country rocks are not included'
Most of the new minerals describedherein have been given names except
where it was felt that they were not as yet adequately described'
An alphabetical list of the minerals d.escribedor discussedis givenin the index.
NerrvB Er.BlrBNts
SulPhur
A few veinlets of sulphur were observedin the field in a small specimen
at chuquicamata. During the detailed study of the chuquicamata suite,
a number of magnificent, although minute, crystals of sulphur were
found in one specimen. The specimen contained abundant dehydrated
pisanite, chalcanthite, rare crystals of kroehnkite, sulphur and cuboid
natrojarosite in twinned crystals. The minerals are named in the orderof their formation. The sulphur crystals were essentially spherical inshape and covered with faces. One crystal, less than a millimeter indiameter, was measured and. found to have 120 faces' Two crystals
showed 26 of the 34 known forms for sulphur. The known forms notobservedwere: (210) (120) (023) (337) (335) (553) (551) (344)'
Ungemachl* described similar crystals from the sulphate deposit at
Alcaparrosa, Tierra Amarilla, Chile. These crystals were found on
roemerite associatedwith lapparentite. Sixteen forms were observed.
The origin of the sulphur is an unsolved problem' Sulphur in ore deposits has been reported fot u few mining camps of the Western United
Stut"t, Monte Poni, Sardinia, and Mexico. Sulphur has also been reported from the Wheatley Mine, Pennsylvania. With the exception ofTierra Amarilla and Chuquicamata, all the ore deposits that have sulphur in the supergene zoneare lead deposits. The origin of the sulphurin the Chilean deposits probably involves difierent processesthan thosethat were active in the lead deposits. In Chile the sulphur was probably
formed by the action of chlorides or hydrochloric acid on acid sulphates'
Hydrochloric acid will precipitate sulphur from solutions of acid sodium
sulphate.
RnlBtnNcB. 1 Ungemach, M. H., Bull,. Soc.Fran. Min., vot.58, p' 97, 1935'

CoPPerNative copper is rare at Chuquicamata as a natural mineral and is
not known at Quetena. At ChuquicamaLa it occurs as residuals in cuprite and as small slugs or irregular massesin the southeast section oflhe deposit. The latter occurrence is in a somewhat tabular but illdefined zone where the copper is associated with cuprite and much
* References are given at the end of each species.

700

MARK C. BANDY

specularite. The area was encountered during churn-drill prospecting
and little is known regarding it. rt is possible that the copper has resulted
from the reaction between specularite and copper sulphate solutions withthe result that iron sulphate formed and copper was precipitated. This
assumesthat the copper is supergene.As far as known, it occurs onlyin the transition rock, in an area where sulphates give way to silicates,oxides, and chlorides. Possibly some reaction involving chloride solutions may have given rise to the native copper.
rn many of the old mines that have been worked to the water level,
fluctuations of the water-table level have flooded the lower workings at
difierent times. The waters are acid and charged with copper, and now
all the available iron left in the mines has been replaced by spongy
massesof native copper.
Gold.
Gold is reputed to have occurred in quantity to the north of thepresent open pit at Chuquicamata. Repeated panning and assaying of
the gravel and crushed qvartz from this area has failed to reveal evena color. Nevertheless, old workings of the indigenes extend to depths ofmore than 75 feet. Their only interest could have been gold. There area few spotty occurrencesof gold along narrow fractures to the west of
Chuquicamata but not in commercial quantities
Surpnrnns aNo Sur,puo-Sar,rs
Molybd.enite
MoS2 Hexagonal
Molybdenite occurs in plates and crystals at Chuquicamata in thenorthwest area, associated with primary chalcopyrite and bornite. ft
formed earlier than either of these sulphides.
' As the open-pit mining extended
to the west, the appearanceof molybdenum in the ores and solutions at chuquicamata caused a great dealof trouble in the mill. The molybdenum acted as a catalytic agent andprevented the precipitation of copper in the electrolytic plant. Thousands of mine samples were assayed for molybdenum, and the metal
was found to be limited roughly to the western half of the deposit. The
actual mode of its occurrence was not known, but it was believed to bepresent as "molybdic ocher." rn 1932 the writerl recognized that the
molybdenum was associatedwith narrow interlacing quartzveins on thewestern side of the deposit. These veins formed a rock type that had
been mapped as "lacing veinlets.,, A number of assays of tle vein material proved it to be comparatively high in molybd.enum. The study

SULPHATE DEPOSITS OF NORTHERN CEILE701

of about a hundred polished sections of these veins failed to give any
positive proof of the exact state of the molybdenum in the veins, as all
were oxidized and the amount of molybdenum present was usually lessthanO.5/6. OnIy occasionalspecks of a dark gray mineral gave any hintof the original mineral. The gray mineral had a hardness of four andgave etch tests that do not agree with any known mineral' The writerbelieves the mineral to be an iron-molybdenum sulphide.
RBlenrNcB.

1 Private report, 1932. SeeTaylot, op. cit.

Chal,cocite
CurS Orthorhombic
Chalcocite is widespread at Chuquicamata and rare at Quetena. At
the former mine it occurs as a supergenemineral to depths of over 2,000
feet, replacing pyrite and enargite. There is evidence of chalcocite zones
formed at different elevations at Chuquicamata and, while some may
have existed in pre-Tertiary times, the more distinct zones were formedin Tertiary times. Chalcocite occurs in all forms from disseminatedgrains to pure veins of massive sulphide up to eight inches wide. "Sooty"
chalcocite is common on exposed surfaces in the abandoned mines, but
most of this is a mixture of covellite and chalcocite. Much of the massive
chalcocite is very pure, yielding less than 0.5/6 impurities upon analysis.
No crystals have been observed.
The sequencerelationships are shown in Table I.
Sphalerite
ZnS Isometric
Sphalerite has been reported by Berkey and Kerrl in the veins of theoutlying mines. The writer has never been able to definitely identify
this mineral at Chuquicamata.
Ralrtrrtcn. 1Privatereport,1931.SeeTaylor,op.cit.
Covellite
CuS Hexagonal
Covellite is both a hypogene and supergenemineral at Chuquicamata
and is rare as a supergenemineral in "sooty" chalcocite at Quetena. At
Chuquicamata the hypogene covellite is latter than enargite in formation and was introdu..d follo*ing, or during, a period of fracturing.
Much of it, especiallyin the outlying veins, shows apparent deformation,
but this may be due to replacement of deformed enargite. The hypogene
form is never in coarseblades as in much of the supergenematerial. It is
widespread as both a hypogene and supergene mineral, but is neverabundant. The sequencerelationships are,

702

MARK C. BANDY
Supergene

Late

Sulphates, etc.
Covellite
Chalcocite
Chalcopyrite
Covellite
Enargite

Hypogene
Eaily

BorniteCusFeSaIsometricBornite occurs at Chuquicamata as a rare mineral except in isolated
points in the outlying fringe of veins at the north and east of the deposit.
In these veins it occurs as a hypogene mineral replacing chalcopyrite.
Subsequentto its formation, fracturing occurred and enargite was introduced, which replaced both the bornite and chalcopyrite. As a supergene
mineral, bornite is very rare at Chuquicamata. It has been observed insmall, sharp cubes associatedwith chalcocite. The age relationships ofthe supergenemineral are not known.
Chalcopyrite
CuFeSzTetragonal
Chalcopyrite is rare at Chuquicamata as both a hypogene and supergene mineral. It has been mentioned by almost everyone who has written
about Chuquicamata as an important ore mineral. Actually, the hypogene variety is confined to the outer fringe of veins. ft is most abundantin the northwest area, but it also occurs in veins to the north and eastof the deposit, associated with bornite. It is very rare as a supergene
mineral associatedwith chalcocite. The sequencerelationships are,Supergene

Late

Hypogene

Chalcocite, etc.
Chalcopyrite
Enargite, etc,
BorniteChalcopyrite
Molybdenite
PyritePyriteFeSz

Isometric

Pyrite is an abundant mineral at all three deposits. At Chuquicamata
it occurs in grains and crystals up to one-half inch on the edge. The best
crystals are found in vugs in the pyrite roots of the enargite veins. rrere
small brilliant cubes occur with euhedral quartz in a massive quartzpyrite gangue.
There are several ages of pyrite at Chuquicamata, probably three andST]LPHATEDEPOSITSOF NORTEERNCHILE

703

possibly four, two or three of the pyrite periods preceding the copper
were
iulphides. Some of the massive pyrite veins of the northeast area
weathering'corirparatively free fro- coppei mineralization and, uponmisleading term as many writers have pointed out'
ArsenoPYrite
FeAsS Orthorhombic

satisfaction.
Tetrahedrite
CuaSbSeIsometric
Tetrahedrite was reported by Berkey and Kerr in a private report'of a1931, in ores from the Panizo Vein. The writer has found specks
buttetrahedrite
be
may
this
and
veins,
gray mineral in other outlyingshowsmineralunidentified
This
identified.
it has never been definitely
the following age relationshiPs,
HYPogene

Late

Earl'yEnargiteUnknown (tetrahedrite?)
BorniteChalcoPYrite

Enargite
CusAsSaOrthorhombic

704

MARK C. BANDY

only the common forms. The coarsest enargite found at chuquicamata
comesfrom the lower levels of veins farthest to the east.
Enargite replaces pyrite, bornite and chalcopyrite and is in turn replaced by covellite and supergene sulphides and sulphates. There is a
closeparallel in the occurrence of enargite at chuquicamata and Butte,Montana. In both camps the enargite occupies the central area, andchalcopyrite and bornite occur outside the main mass of the enargite.
Haroros
Halite and other chlorides are common in the soil throughout northern
chile. rn the vicinity of these three deposits and especially at chuquicamata where alluvium is more abundant, halite, gypsum and nitrates
are found in disseminated grains, crystals and lenses. These minerals
occur in the alluvium at varying depths up to several meters but usuallyless than a meter. There are more or less continuous openings at these
depths that are lined with crystals and crystalline aggregates.The openings are roughly tabular in shape, very irregular and rarely over a footthick' rn walking over the ground, these openings give a faint drum-likesound. The origin of these salts is believed to be volcanic and the openings are probably due to solution and possibly to some extent to bucklingof the superincumbent material by crystallization of the salts.
Halite
NaCl Isometric
Halite occurs widespread in the surface material about these deposits.
Tt occurs in grains, crystals and aggregatesand is found in the deposits
themselves as well. The halite has been the source of the chlorine thathas combined with copper to form atacamite and. other chrorides soabundant in these deposits. Alcaparrosa is an exception in that only
halite has been identified from there.
Band,ylite
CuBzOg CuClz.4HzO
This mineral is one of a number of new species first found by thewriter in chile, and later studied by him and others at Harvard university and the U. S. National Museum.l
Crystallography:
Tetragonal,
ditetragonal-dipyramidal,
a:c:
1:0.9070.Forms: c(001), a(010), m(tl}), d(012), e(023),/(011),
9(021),o(ll2), p01D, qQ21). Common forms: c, p, g, ar. Structure cell, os 6.13,
cs 5.54, contains CuBrOn.CuCh.4HzO. Habit often tabular (001), fre_quently irregular with large pyramidal development. Cleavage (001)perfect and easy, producing ttrin flexible plates. H:2+. G:2.g10. Color
deep blue with greenish tights. streak pale blue to white. uniaxial negative, co7.691,e 1.641.Pleochroismin blue with co)e.

705

SULPHATE DEPOSITS OF NORTEERN CHILE
ANAI,YSIS OT Bexon:rt
n
I
.5498
34.94
0.05

Cu
CaO

Mso

J

35.74

0.05
0.40

NazO
KzO
FegOa
CI
BOa
CO,
HrO
Insol.

none

0.35
19.47
23.35
0.05
19.60
1. 8 4

.27r5

19.94
24.08

1 .0888

20.24

.5490

100.00100.10Total

1. Mina Quetena, near Calama, Chile. Analyst, W. F. Foshag.
2. Molecular ratios.
3. Calculated composition for CuB:Or' CuClz' 4HzO.

Occurrence:Occurs near the surfaceat Mina Quetena, west of Calama,
Chile, associatedwith antofagastite and atacamite on rusty qloattz.
Am. Mineral.,vol. 23,p. 85,1938.
Rrrnnrrqce.1PalacheandFoshag,
Antof agastiter
CuClz'2HzO
The natural occurrence of this common laboratory product was firstfound by the writer.
Orthorhombic,dipyrami dal, a: b : c : 0.9117 : I: 0.4631.1Forms:2c(001),
D(010),o(100), m(tl}), t(520), q(103), r(101), r(301), p(llt). Common
forms: b, m, t. Structure cell: ao 7.38, bo 8.04, co 3.72, contains Cu2Cl4'4H2O.3 Crystals commonly curved. Cleavage m(ll}) perfect, c(001)good. Brittle. Fracture conchoidal.H:2+. G:2.4. Color bluish green to
greenish blue with sometimes a yellowish tinge.
g r e e n ,F : c :Biaxial positive, 2Y:75", r1a1 u:b:1.646:bright::
1.685 olive green, 7 1.745:pale blue.
Analysis
Cu
FezOs
CaO
CI
HzO
Insol.

1.
3 6 .8 90.20
0 .1 5
0.04
40.68
20.81
0.95

Total

99.72

Mso

z.

37.22

4t.52
2r.26
100.001. Mina Quetena, Calama, Antofagasta, Chile. W. F. Foshag, analyst.
2. Composition for CuCIz.2HzO.

706

MAKK C. BANDY

Occurrence:Found near the surface at Mina Quetena, west of Calama,
Chile, associated with bandylite and atacamite. These chlorides occur
in a leached zone above the massive iron sulphates.
Copper chlorides are rare in nature, atacamite and the rare chloride
nantokite being the only ones known heretofore. As stated above, atQuetena this new chloride is associated with atacamite and the newcopper borate-chloride bandylite. Antofagastite was the first mineral
to form, followed by bandylite, with atacamite last. In the mine theseminerals are associated with heavily iron-stained vuggy quartz veins'
Antofagastite extends to the greatest depths, while abundant atacamite
occurs within a foot of the surface and decreasesin amount with depth.
The sequencerelationships of the three minerals are very clear in thefield.
Rrrennscns. 1 Palache and Foshag, Am. Minerol., vol.23, p. 85, 1938.
2 Forms (100) (103) (101) on artificial crystals only. See Grcth, Chem. Kr'ist., vol. l,p.238,1906.
3 lfarker, Zei'ts. Krist., vol. 93, p. 136, 1936.

Atacamite
CuClz'3Cu(OH)z
Orthorhombic, dipyrami dal-2 / m 2/ m 2/ m, a : b : c : 0.6617: 1 : 0.7535,1
p o 2q or2o : 1 .1 3 8 7: 0 . 7 5 3 5: 1 .
New
Forms
370
012
0 . r 1. 2

No. of
Crystals
31
I

32"37',
038000

90'00',
1930
7627

553
232
143

2
2
2

5634
47 07
2t 14

66 t9
58 12
4715

Measured
6p

Calculated
6p32"56',

90'00'

000
000

2039
7626

s6 30+
45 13
20 42

66 r7
58 04
47 02

Much of the atacamite at Chuquicamata and all the atacamite at
Quetena occurs in long acicular crystals or in crystalline mats and radiating rosettes of prismatic crystals. A common habit at Chuquicamata
is tabular, enormously extended o" {OtO}. Strong vicinal development
sometimes gives the crystals an axe-like shape.
Occurrence: At Chuquicamata atacamite is limited to the upper one
hundred feet of the deposit. While erratic in its distribution, it is mostcommonly found, in quantity, in the upper portions of the more massive
sulphide veins. It occurs in a pulverent maroon-colored iron-oxide matrix in the axe-like crystals and less commonly in matted masses ofminute prismatic crystals. As a rule it occurs in areas that might beSULPHATE DEPOSITS OF NORTHERN CHILE

707

called "low acid" as contrasted with the sulphate-rich or "high acid"areas; certainly it forms in areas of too low acidity to produce antlerite.
The place of atacamite in the general sequenceis not clear, but its
relations to a few associatedminerals are definite. A common association
is kroehnkite-atacamite-natrochalcite, named in order of formation fromoldest to youngest. Kroehnkite is a normal hydrous mineral, while theother two are basic. The relationship of atacamite to the two otherminerals is very intimate and there is considerableoverlap in the periodsof formation, with distinctly separate periods for kroehnkite and natrochalcite. Veinlets of atacamite cut turquois at Chuquicamata and crystals occur on crystals of leightonite. It ,is commonly associated withchrysocolla and is always the earlier mineral.
At Quetena atacamite occurs with antofagastite and bandylite and is
the youngest mineral of the three. It is limited to the upper twenty feetof the deposit now exposed.In all of these associationsatacamite agrees
with the general sequence outlined in Table I, but the gaps between
some of the associatedminerals may be so great that it is impossible tosay with certainty that it always confortrs to this sequence.
Bull. Soc.Mi'n.France,vol. 34, p. 148'1911'
Rrrnnnxcn. l Ungemach,
OxrrBsOPal
SiOz'zHzO Amorphous
Opal occurs at Chuquicamata only in association with chrysocolla'
It apparently results from the lack of sufficient copper to form chrysocolla, as it occurs coating this mineral and grades into it. This relationship might be expectedfrom the composition of the two minerals.
Cupri.te
CuzO Isometric, Plagiohedral
Cuprite occurs in a number of associationsat Chuquicamata. Fibrous
cuprite occurs after antlerite. The cuprite preserves the structure of theantlerite even to the chatoyance. Massive and crystalline cuprite occur
after native copper. The crystals are simple cubes showing small octahedral and dodecahedralfaces. The massive cuprite replacescopper andis commonly associatedwith "copper pitch." Cuprite is a rare mineral
at Chuquicamata, occurring in the "low acid" areas about the central
part of the deposit. It is most common along the east-central and southeast areas and in the northwest area. Fine specimenshave been obtained
from the veins outside the deposit to the northeast.

708

MARK C. BANDY"Copper Pitch"
This is a translation of an old German term of doubtful value. rt has
been used at chuquicamata to describea pitch-like occurrenceof copperand manganese oxides. For a time the material was called crednerite
becausean analysis showed it to contain about forty per cent of copperand manganesein equal amounts. It occurs in round massesup to threefeet in diameter and in veins along the east side of the deposit. rt varies
widely in composition and grades in color and luster from a pitchy blackin the center to a dull pulverent brown mass on the edges. Cracks
through it are commonly coated with antlerite crystals. polished sections of the material showed it to consist of varying proportions oftenorite, melaconite, pyrolusite and manganite. There is some chrysocolla associatedwith it as well as some opal (?). These minerals would
account for the silica content of some specimens. The material also
occurs in veins where it may have cuprite associated.The copper pitch
always forms a shell about the cuprite. No attempt was made to differentiate this material farther. Hausmannite may be present, but theidentification was questionable.
Hematite
FerOaRhombohedral
Hematite occurs along the eastern side of the deposit and in scatteredveins and lensesthroughout the batholith, near the roof. In the deposit
it is more or less coincident with the transition rock type. ft occurs in
specular masses,sometimes as breccia filling. No measurable crystals
were observed. It was probably introduced before the copper mineralization and was followed by magnetite. With associated magnetite it
forms a seriesof lensesand iregular veins to the northeast of the present
pit at Chuquicamata which appear to be a continuation of the moredisseminated hematite in the deposit proper. The only alteration
definitely associated'with these lenses is a small amount of irregularly
distributed epidotization. Hematite is earlier than magnetite and allstages of replacement of hematite by magnetite can be observed. At
Quetena, hematite occurs in small pure massesin the flows about thepir.
Magnetite
FeFezOl fsometric
Magnetite may occur in small, almost pure massesat Chuquicamata,but in general it is a rare mineral, pseudomorphic after hematite. No
crystals have ever been observed.

SULPEATE DEPOSITS OF NORTHERN CHILE

709" Lirnonite"
Fezos.nHzO Amorphous
Under the term ttlimonite" a number of iron oxides at Chuquicamata
may be mentioned here. It is possible, in the field to difierentiate thetype of iron oxide formed through the oxidation of pyrite, high-grade
copper ore, hematite, etc. These are given various names referring to thecolor of the oxide. The exact nature of these oxides has never been
determined.
Many beautiful specimens of iridescent limonite have come from
Chuquicamat&, some in delicate imitative shapes of considerable
beauty. An unusual form of iridescent limonite is that formed after
gypsum. The gypsum commonly weathers to stringy stalactitic masses,
and when this material is replaced by limonite it results in very striking
and beautiful materia-.
CAnsoNA.rBs
Dol,omite
CaMg(CO)z Rhombohedral
The veins in the northwest area carry some carbonate as a gangue.
The material is very fine grained and it has never been definitely determined. An analysis showed it to consist of calcium and magnesium carbonate in somewhat varying proportions, the variability being too greatfor dolomite. It is probably a mixture of dolomite and calcite. Due tothe rarity of magnesite in ore veins, it is doubtful if it is a mixture ofmagnesite and calcite.
Cerussite
PbCOa Orthorhombic
Cerussite is the only lead mineral that has ever been identified at
Chuquicamata. Lead minerals are unknown in the other deposits. The
cerussiteoccurs in rare pockets in the central northwest area of the mine.
The crystals range in size up to three millimeters and are associated witl
antlerite in fibrous masses.The antlerite is later than the cerussite. Dueto the deep etching, the crystals were not measured.
Malachite
Cuz(COa)(oH)z Monoclinic
Malachite is rare at Chuquicamata. One specimen was found in thesoutheast area of tle deposit where the fibrous malachite was later thanassociated brochantite and earlier than associated'azurite. Malachite,
as well as all the other carbonates with the exception of cerussite,occurs
in areas of "low acidity."7r0

MAKR C. BANDY

AzuriteCus(COs)(OH)r Monoclinic
Azurite occurs as a late mineral in the Mina Flor de Bosque at
Chuquicamata. The associated minerals and the sequencerelationships
ate,
Late

Chrvsocolla

A"iit"

Earl,ySupergene

Malachite
Brochantite

HlpogeneSpecularite

Srr-rc.qrps
The rock-forming silicates will not be considered here. Only the unusual silicates, tourmaline and chrysocolla, will be mentioned.
Tourmaline(Na,Ca)R3(Al,Fe)683Si6O27(OH,F)r
Rhombohedral, hemimorphic
Tourmaline occurs in two forms at Chuquicamata. It is common near
the roof of the batholith to the west of the deposit in minute radiatingneedles filling cracks in the granodiorite. Some of the minor veins ofcopper near the central part of the batholith, also near the roof, carry
tourmaline as a vein mineral. Some of these veins are quite large, but
the mineralization is weak and spotty.
To the north and west of the deposit in the country rock about thebatholith, pegmatites of albite-tourmaline-titanite occur. The tourmaline
is black to deep blue and replaces the albite. Rough crystals four inches
in diameter can be found. The indices of the tourmaline are,co-dark brownish green-1.667
e-light reddish brown-1.638
These indices would indicate a tourmaline with an iron oxide content of
about 13/6.r
1Ward,Am.Mineral.,vol. 16,p. 145,1931.
RnrBneNcB.
Chrysocoll,a
CuSiOa.2HrO(?) Cryptocrystalline
There are evidently a number of minerals that have been called chrysocolla and are hard to distinguish. There are at least three difierent minerals in the "chrysocolla" at Chuquicamata with difierent optical properties. It would be impossible to separate them and they never occur pure.
These are all included here under the term chrysocolla.

SULPEATE DEPOSITSOF NORTHERNCHILE

7II

The chrysocolla occurs in botryoidal, cyrptocrystalline massesin theextreme southeast portion of the deposit. The area is a "low acid" oneand the most commonly associated mineral is atacamite, an earlier
mineral. In some of the open vugs the chrysocolla grades into opal'
SPheneCaTiSiOr Monoclinic
sphene occursin the tourmaline-albite-titanite pegmatites to the northof the d.epositat Chuquicamata. It is in small, brilliant cinnamon-brown
crystals iounded and etched. It would' appear that the sequencein thepegmatite was,
Late
Eaily

Tourmaline
Titanite
AlbiteAnsBN'trBs-PnosPnlrBs
Chenevixite
HrO
CurFez(AsO4)r(OH)4'

well be expected to occur in abundance and variety'
Rnr.BnaNcn. 1 An analysis by the chemist of the Company showed a similarity
lished analyses of chenevixite.

with pub'Turquois
CuO' 3AbOs' 2PzOt'gHzO Triclinic
Turquois was first identified at Chuquicamata in 1931 by the writer'
areas
It is rather common but is characteristically associatedwith the

Antofagasta in beads.

712

MAKK C. BANDV

RnrnnrNcns. l Pogue, Mem. Nal. Ac. Sci., vol. 12, 1915.
2 Boman, Antiquites de Ia
Region Andine de la Republique Argentine et du desertd'Atacama, 1902, p. 766.

NrrnarBs
Sod.aNiter
NaNOa Rhombohedral
Soda niter occurs in massive aggregates in the upper portion of thedeposit at chuquicamata and in the alluvium surrounding all threedeposits.Associated minerals are atacamite, bloedite and altered mirabilite. No sequencerelationships can be given for these minerars. The soda
niter is certainly earlier than the bloedite in specimensexamined.by thewriter. The mineral is believed to be of volcanic origin.
Bonerps
UlexiteNaCaBsOe.SHzO Monoclinic

Sur,pnaros
Thenardite
NaaSOeOrthorhombic
Thenardite occurs at chuquicamata and Alcaparrosa as an arteration
product of mirabilite. rt has never been observed at
euetena. The mineral occurs as a fine-grained white powder. rn northern chile this mineraloccurs in beds on the east side of the Central Valley, near Iquique. Many
writers have noted it from this district. The total volume of the mineralis small' rt is always alate, near-surface mineral, pseudomorphic after
mirabilite.
Anhyd.rite
CaSOnOrthorhombic
Anhydrite occurs in the alluvium about Chuquicamata and, rarely at
Quetena, associated with gypsum, halite and soda niter. ft is not acommon mineral, although it occurs in thick beds in the valley of the
Rio Loa in the vicinity of these deposits.

SULPHATE DEPOSITS OF NORTEERN CHILE/ lJ

Brochantite(oH)6orthorhombic
Cur(SOr)Brochantite is a comparatively rare mineral in the ore at Chuquicamata and Quetena. For many years the main ore mineral at Chuquicamata was called brochantite, but various people have studied the orein laboratories and it has been recognized for some time that antleriteand not brochantite is the main ore-mineral. Brochantite occurs about
the borders of tle deposit in areas where the minerals formed from dilute
solutions carrying a relatively small percentage of acid. Associated minerals are gypsum and chrysocolla. As stated before, brochantite is anearly mineral, earlier than the rare malachite with which it may be associated. Another occurrenceat Chuicamata is in the veins of the northwest
area. These veins carry primary carbonatesin the gangue. Brochantite islater than gypsum at Quetena.
Antlerite
CugSOr(OH)r Orthorhombic
It has been known for some time that the main ore mineral at Chuquicamata was not brochantite but antlerite.l The crystallography of antlerite has been studied by Professor Palache and the orientation changed
from that of Ungemach2 to conform to the orientation of brochantite
and atacamite. Several new forms were observed on the crystals from
Chuquicamata by Ungemach. Besides occurring as implanted crystals,
antlerite forms well-defined cross-fibre veins cutting silicified rock.
Antlerite is the last step in the copper mineralization at Chuquicamata and a late mineral in the supergenesequence.Its place in the sequence may be seen in Table I A2 and A,3. The vertical range of themineral is great, ranging to depths of 1,000 feet. It usually forms as anoxidation product of chalcocite and covellite.
Several minerals have been described from Chile under different
names that are actually varities of antlerite. Stelznerites and heterobrochantite4 belong here.
RBrntrrcns. l AndriethandMartens,Am. Mineral.,vol. 1O,p. 16l, 1925.
2Ungemach,Bul'|,.Soc.Mi.n.,vol.47, p. l, 1924.
3Thadeeff,Zeils.Krist., vol. 31,p. 2+2,1899.
a Buttgenbach,Bultr.Soc.Geol.Bel,g.,
vol.41, B 164,1926.
Mirabilite
NazSO+.10HrO Monoclinic
Mirabilite is common but spotty in occurrence in the upper portionof the deposit at Chuquicamata. It has not been observed at depths

714

MARK C. BANDI/

greater than 60 feet, although it probably extends deeper than this. It
has not been observed at Alcaparrosa and was only identified from its
alteration product, a dehydration form, thenardite. The water in mirabilite is loosely held and goes off at 32.4"C.r In the arid climate of the
Atacama desert, freshly broken surfaces of mirabilite have been studied
and it was found that it required twenty secondsfor a film of dull white
thenardite, Na2SOa,to form over the mirabilite.
Mirabilite is dificult to place in the sequenceat Chuquicamata andAlcaparrosa. At the former it is associatedonly with bloedite and occurs
in the upper portions of the deposit. It is probably a late mineral andformed after the soluble iron sulphates had moved downward to lower
levels. At Chuquicamata it occurs exclusively in the sericitic rock along
the western side of the deposit. At Alcaparrosa it occurs with soda niternear the surface.
Rrrennrygp.1Wuite,Zeits.phys.Chem.,vol. 86,p. 249,1914.
Szomolnokite
FeSOr.HzO
This mineral was first observed in 1891 by Krenner,l who named itfrom the type locality, Szomolnok, Hungary. Mackintosh2 had, however,in 1889 analyzed an impure sample of the same mineral from Chile, but
did not name it. In 1903 Scharizersanalyzed pure szomolnokite associated with roemerite from Chile and erroneously named it "ferropallidite." In 1928Krenner's posthumous paper by Zimanyia gave an analysis of material from the type locality, and a crystallographic discussion.
Schallerslater studied crystals from Utah and found that his data did
not check well with Krenner's. The writer and others in the Harvard
laboratory have again investigated the crystallography of this mineral,and have corrected Krenner's work. ft was found that the positive andnegative quadrants of Krenner are reversed from their proper position.
Accordingly, Krenner's crystal has been redrawn ( Fig. 4a), and a crystalof the Alcaparrosa szomolnokite with a very difierent habit is also given(Fig. ab). This unusual habit, tabular (111), is very much like that oflazulite from Grave's Mountain, Georgia.
Since the habit of the crystals was so unusual it was thought at firstthat they were triclinic. Ifowever, the decisivemeasurementwhich estabIished the true symmetry of the crystal was made by Professor Palache,
who measured a crystal with [010] polar, that is, in the position of thesecond permutation. As neither pinacoid was present, the adjustment
was made by using two pairs of faces of the forms (111) and (111).

SULPHATE DEPOSITS OF NORTEEKN CHILE/tJ

Frc. 4. Crystals of Szomolnokite.

The following table gives some of the measured and calculated values
for the more prominent forms found in this study.
Calculated

Measured

No. ofUbservatrons

o

p

a

p

m(rrO)
t(0r2)s(113)

3
3
22

46"43'
118-45 3190'00'
42 tO
40 3546057',131
JJ;

g0'00'
42 08
40 44i.

*(Ir2)p(rrr)q(I11)

20
28
28-45 555230
6e 2r+
69 06-45 585227

47 02+-46 19+692r+,r orm4702+-46 19+

-4J

69 06

An angle table for the specieshas been prepared by Professor Palache.
In this table the new forms found by Dr. Schaller, as yet unpublished,
are given, with his permission,* as well as the new forms found in the
Harvard laboratory.
Monoclinic ; ptismatic-2 f m
a:b:c:0.9344:1:1.8085
0:91'22t',
P:88"37i'?o:4o:ro:1.9356:1.8080:1
r z :p 2 : q 2 : 0. 5 5 3 1: 1 . 0 7 0 61:?o':1.9184, qo':1 8085, xo':0.0240* The anglesof this table agreewell with those observedby Schaller.Personalcommunication.

716

MARK C. BANDY

Forms
b+ 010rn 110tl ol2

6
0"00,
46 57
1 31

90000,
90 00
42 08

62
0000'
0 00
88 37+

ux 023s f13
rl TI2

1 08+-45 35+-45 585020
40 44+
5227

8837+
r2r 36+13305

nl 223p 1ll
q Irl-46 08147 02+-46 19+@ 07
6e zri.
6906

L4l 27zl T37
utl 131-r7 52],1942

s9 a9+
S009+

p

pz:B

C
90000,
88 59+
42 07

A
90000,
43 03
88 59

39 4t

50 19

6249+
s633+

41 44+
s4W+

8e07+
1s212+

27 14+
r52 10j.

s3 04+
s0 23
49 49i

61 07
68 21
70 06

14108
46 46+
1s2 30+

rcA02
27 t4+

53 03

2r s6

39 36

10110+
7036* New forms, Schaller.
tNew forms, Bandy.

0000,
46 57
47 53

7es0+

14515

Habit: Pyramidal crystals, commonly distorted, tabular parallel to(111); parallel growth common.
Twinning: Twinning common, but twin laws not determined in thisstudy.
Physical Properties: Fracture conchoidal, brittle. G:3.05. H:2+.
Luster vitreous. Color, light shadesof yellow, blue, red, brown, colorless.
Optical Properties:,t,o : 1. 5 9 1

F:r.azs
t:1.663

Positive
Y:b
X 1\c: -26"
2V:80"/>r, shong

Composition: hydrous ferrous sulphate, FeSOr. HzO.
Pyrognostics: B.B. light brown. Closed tube, yields acid water andblack residue. Slowly soluble in water, yields brown solution.
Occurrence: Commonly associated with pyrite. Rare at euetena.
szomolnokite apparently forms under arid conditions from solutions ofhigh acid content and of high concentration. At Quetena it is intimately
associatedwith halotrichite, a mineral to which it apparently alters. At
Alcaparrosa it alters to roemerite and to rhomboclase. It is apparently
the first mineral to form upon oxidation of pyrite, where there is noabundance of oxygen. With abundant oxygenated water, pyrite probably alters first to rhomboclase.
Relation to Kieserite: The new axial ratio here given for szomolnokite
shows its close relationship to the corresponding magnesium mineral,kieserite.

SIILPEATEa

Kieserite
Szomolnokite

0.91470.9344DEPOSITS OF NORTEERN CHILE

bcP
|
1

1.74451.8085gr"A7',
91 23

The crystals of kieserite are similar to those of szomolnokite from thetype locality. The optical orientation in the two minerals is likewisesimilar. No intermediate compositions have been recorded, however.
RttrneNcns. 1 Krenner, Ak. Ertesiti),Builapest,vol. 2, p. 96, 1891.
2 Mackintosh,Am. Iour. Scl., vol.38, p. 245, 1889.
3 Scharizer,Zeits.Krist., vol.37, p. 547, 1903.
a Zinanyi, Centralb.Min., A, p. 268, 1928.
5 W. T. Schaller,[/. S. Geol.Swztey,unpublished.

Gypsarn
CaSOr.2HzO
Gypsum is a common mineral in the alluvium about these deposits
and occurs within the deposits themselves to some extent. In the
alluvium the gypsum occurs in beds up to a. foot or more in thickness.
The beds are usually made up of fibrous gypsum, although rarely crystals
have been found. In some of the old mines about the Chuquicamata
deposit the walls of the workings may be coated with gypsum in curved
forms. Commonly at Chuquicamata the gypsum is stained deep blue bycopper sulphate. In the alluvium much of the gypsum is stained red withiron oxide.
The only sequencerelationship that could be established showed thegypsum to be earlier than either antlerite or brochantite. Further to theeaSt, in the Cerros de Sal, beds of coarse crystals of gypsum several
yards thick overlie a thick bed of halite.
Epsomite
MgSOa'7HzO
Epsomite occurs associatedwith other salts in the alluvium about thedeposits. Further to the west, beds of epsomite four to eight inches thick
are associatedwith pickeringite. About the deposits the epsomite is inwhite pulverent masses,commonly fibrous.
M elanterite
FeSOr'7HzO
Melanterite has been reported from Alcaparrosal associatedwith roemerite. This mineral was not encountered in this study, and there is apossibility that Frenzel confused fibroferrite with melanterite.
RnlnnNco.

1 Frenzel, Min. Mitt., vol. ll, p.221, 189O.

718

MARK C. BANDY

Pisante (Sohadorite)(Cu,Fe)SOa'7HzO
The material described from Quetenal and called solztad.orite
difrers in
no important respect from pisanite, the iron-copper member of themelanterite group.2 The following analyses show about a per cent more
copper than that found in the original pisanite.
FeO
CuO
SO:
HrO

1
8.49
18.77
2 7. 8 744 65

2
9 .5 91 7. 5 7
28.16
44.3t

Total

99.78

99.63

1. BIue ttsalvadorite." 2. Green ,,salvadorite.,, l-2Hen,

analyst.

Pisanite is a late mineral at Quetena forming, as a rule, after the ironsulphates have crystallized. This sequence is conformable with dataobtained from the studies of the formation of artificial sulphates.
RnrnnBxcns. rHerz, Zeits. Krist., vol. 17, p. 26, 1896 gave a prism measurement of
48"16', which is the complementary angle for the prism angle of pisanite.
2 Powder photographs of melanterite and pisanite are notsimilar and a series probably
does not exist between the two minerals. Boothite is the pure copper member of thegroup.

Chalcanthite
CUSO+.5HzO
Chalcanthite is abundant at Chuquicamata and uncommon at Quetena today, although in years past it was an important ore mineral. At
Chuquicamata it occurs in cross-fibre veins up to two inches wide. Occasionally vugs lined with crystals of chalcanthite are found, and small
crystals are not rare in the north area of the deposit. A number of thesecrystals were measured and two new forms were observed.*
Measured
6pe(l2l)

h(-122)52"25t-ts3 30

Calculated
Q

59"28'

52"28',

23 49-1.5333p

No. ofFaces

59'19',

1

2s 53+

l

Chalcanthite occurs as both an early and a late mineral. At Chuquicamata one of the first sulphates to form from chalcocite is chalcanthite,
closely followed in time by kroehnkite. It is apparent that these sulphates do not form from solutions carrying a high percentage of iron
* Elements of Tutton in theorientation of Kupfer.

SALPHATE DEPOSITSOF NORTHEENCEILE

719

sulphate, and thus form after much of the iron sulphate has been precipitaGd. It occursin the upper portions of the "mixed ore" zoneat Chuquicarnata,a zonecarrying both chalcocite and sulphates. Chalcanthite has
not been definitely identified at Quetena, due to the diffrculty of separating it from pisanite.
Bloedite
MgNaz(SOr)z' AIIzO Monoclinic
Bloedite is a common mineral at Chuquicamata and rare at the otherdeposits. At Chuquicamata it occurs most abundantly in the southwest
area of the deposit and is limited to the upper 75 feet. It is usually infibrous or granular veins and crusts. Crystals of good quality have neverbeen observed. The common associatedmineral is mirabilite or its dehydration product thenardite. Soda niter has been found with it, and atacamite is not rare in this association. It is often replaced by kroehnkite
and leightonite. The age relationships with mirabilite and soda niter are
not clear, but it is probably later than mirabilite. At Quetena it was observed in a crust, replaced by jarosite and replacing voltaite andcoquimbite.
P'icrornerite
A mineral identified as picromerite on the basis of optical properties
occurs in all three deposits. The indices of the material from Quetena, : 1 . 4 6 4 , 1 : I . 4 7 1 ; r ) a ; 2 V l a r g e .T h e i n d i c e sv a r i e d
w e r e :d : 1 . 4 6 2 P
in the other deposits.
Picromerite occurs in white crusts of glistening crystals. It has the appearance of a mineral that has resulted from dehydration. There areseveral other white minerals of similar appearance found in these deposits, and some show minute and complex twinning.
At Chuquicamata this mineral is rather widespread, occurring mostcommonly with hohmannite, also with metavoltine and metasideronatrite. At Quetena it is commonly associatedwith botryogen and at AIcaparrosa with alums and massive pickeringite.
Leightoni.te
K2Ca2Cu(SOD4'2H2OThis mineral, long known to the geologicalstaff at Chuquicamata, hasbeen recently described by Palache.l The following abstract of its properties is taken from his PaPer.

720

MARK C. BANDVPseudo-orthorhombic ( triclinic)a : b : c : 0 . 7 0 4 3 : 1 : 0 . 4 5 7 91 p o i q o t r o : 0 . 6 5 0 0 : 0 . 4 5 7 g1:
Forms
,
a
n

010
100
130

6
0"00,
90 00
25 19+

tn
d
e

110
03r
701

54 50+
000
90 00

s3s6+
3301+

'p

rrl

q

131

54 50;
2s 19+

38 29
56 39

p

90"00'
90 00
90 00
90 00

The crystals are too poor for details of the triclinic form elements to be
determined, but the nature of the lamellar twinning and optical properties make it certain that leightonite is triclinic. Twinning is piobably
parallel to (010) and (100) of the triclinic setting.
Peacock2was able to show that by a new setting of the triclinic mineralpolyhalite, a homologue of leightonite, a close parallelism in the formof the two minerals became evident:
Polyhalite K2CarMc(SO4)
r 2HzO
Triclinic: a ib:c: 0. 7176 i 1:0.465Z
a:91"39', A:9O"O6t,,t =91"53,
Leightonite KsCazCu(SOa)r.
2HrO
Pseudo-orthorhombic: a : D:c: 0 . 7043: | :0 . 457g
a:90", 0:90', z:90.
Habit: Prismatic in flattened blades[001] the crystals commonry
showing some curvature of macrodomefaces,producing an hourglass-likeappearance. rt aho forms cross-fibre veins up to one-half inch in widthwith kroehnkite and bloedite. The crystals reach a maximum length of 1
centimeter, generally much smaller.
Physical properties: No cleavage. Glassy fracture. H:3. G:2.95.
(Berman).
Optical properties: (Berman) Color faintly blue to bluish green,transparent.
z(Na)o : 1. 5 7 8 1
B: t.s87i all + .002
z : 1. 5 9 5 J

Biaxial negative
2Y:65or)a fairly strong
Extinction about 2o to
Y on sectionsparallel to (010)SULPEATE

721

DEPOSITS OF NORTEERN CHILE

Chemical composition:
ANar,vsnssv F. A. GoNrmn
Calculated for
the Formula
KzCazCu(SOr)r'2HzO

1. Crystals

2. Massive

CuO
KzO
NazO
CaO
SOs
HzO

rt.97
13.93
0.56
J. /I

1 1. 2 4t3.62
0.98
1 7. 5 0
5 0 .7 5
5.98

t7 .44
49.92
5.62

TotaI

99.91

100.07100.00

18.41
49.33

12.36
14.66

Occurrence: As bladed crystals on fractured rock surfaces and incross-fibreveins. The following notbs on the distribution of leightonite in
the mine at Chuquicamata are taken from a letter written by O. W.
Jarrell, a geologist on the mine staff. Leightonite occurs quite abundantly
on the east and west sidesof the open pit near the south end. It is limited
to within about fifty yards of the original surface, below which it is notfound. Thus it is nowhere found in the center of the present pit. Minerals
found with it are chiefly atacamite and kroehnkite, never antlerite. It
was found only under conditions of low acidity and hence is found generally in borderland material, never in rich ore.
Name: Leightonite is named in honor of Dr. Tomas Leighton, Professor of Mineralogy at the University of Santiago, Chile.
RnrnnrNcns.l Palache,
Am.Mineral.rvol.23,
p. 34,1938.
2Peacock,
Am. Mineral,.,vol. 23, p. 38, 1938.
Aruu euo Har,ornrcurrE GRoUPS
These groups are considered together becauseof their chemical similarity. The so-calledisometric alums are usually inverted to lower symmetry forms, and the crystals now found are therefore pseudomorphs.
Isometric

Kalinite
Mendozite
Mineral42

KzAb(SOr)r.24HzO
NarAlr(Sor)r.24Hzo
Unknown

Monoclinic

Tamarugite
Pickeringite
Halotrichite

NazAlz(SOr)r.12HzO
MeAIr(Sor)r.22Hro
FeAlz(SOr)r.22HrO

Kali.nit e (P otash AI um)
The mineral from Chuquicamata identified here as kalinite is isotropic
with a refractive index of 1.455 and was not found in crystals. No biaxial

722

MAKK C. BANDV

material was identified as kalinite or potash alum. This mineral is oneof the few potash-bearing minerals to be found at Chuquicamata. It
occurs there as a late mineral, later than natrojarosite and other ironsulphates. It is confined to the upper fifty feet of the deposit.
The mineral is much more abundant at Quetena. There it occurs withpisanite and jarosite. It forms both earlier and later than jarosite but islater than other copper and iron sulphates. Kalinite from there is always
biaxial and varies somewhat from the indices given.l
RnrnnnNcB. 1 Larsen and Berman, Bull. 848, U. S. GeoI. Suroey.

Mendozite (Soda Alum)
NazAh(SOa)
L.24H2O
At Alcaparrosa and Chuquicamata, mendozite occurs in some abundance,and it is common at Quetena.In all of these places it is not isotropic,l and the white plates appear under the microscope as complex
twins. The following optical data were obtained:
A:1.466, y:1.472,X:b, Z A twin plane:40o
Biaxial negative
Mendozile is a late mineral in the sequenceand occurs after alunogen,with which it is easily confused. The sequenceat Alcaparrosa is,
Late

Early

Fibroferrite
Mineral 42
Tamarugite
Mendozite
Pickeringite
Copiapite
Metavoltine

The mineral occurs throughout the deposit but no crystals wereobserved.
RnrnnrNcrs.
refraction.

1 Dana (p. 951) states that the mineral often exhibits anomalous double

Mineral 42This mineral occurs at Alcaparrosa as tiny brilliant yellow, transparent
crystals with well-developedfacesconformable with isometric symmetry,
but an optical examination revealed an inversion, so that the crystals
are now made up of anisotropic aggregates.The forms found include thecube, dodecahedron, trapezohedron, and the octahedron, the latter inexcellent faces.
H:2+.G:1.80.
O n l y t h e m e a n r e f r a c t i v ei n d e x ( 1 . 5 8 3t o 1 . 5 8 8 )w a s
determined, since the biaxial segments were too small to make a com-

723

SULPHATE DEPOSITSOF NORTHERNCHILE

plete optical study possible.The axial angle is large, and abnormal interference colors were visible.
The mineral occurs along the contact of tamarugite and the iron sulphates, metavoltine and copiapite. If it is an alum, it may be a soda-ironmember.
The sequenceis,
Lote

Earl'yFibroferrite
Mineral 42
Tamarugite
Mendozite

Tomarugite.I2H2oNazAIz(SOa)+
Tamarugite was originally described from northern Chile,l and later
again analyzed from Chile.2 The mineral has been analyzed from St.
Bartholomew,3 Grotto del Zolfoa and GascogneRiver, Australia.s Since
the agreement between the analyses is good, the species seems wellestablished.6
ANALYSES

NazO
CaO
AIzOs
SOo
CI
HzO

1
9.04
0.20
14.48
45.66
0.12
3 0 .8 6

99.36
Total
1. fquique, Northern Chile. Schulze,anal.r

a

8.64

8 .8 6

14.66
45.48
0.48
31.40

14.58
45.70
30.86

100.66100.002. Grotto deIZoIto, Cap Miseno. Zambonini, anal.a fncludes lJZ/swater.
3. Theoretical composition f or NarAlr(SOa) a' l2}IzO.

hygroscoplc

The optical properties determined on material from the three depositsof this study are slightly variable and differ somewhat from the values
given in the literature.T One set of observations gives:
Biaxial positive 2Y :60"
a : I . 4 8 8 , A : I . 4 9 1 , - y: 1 . 5 0 0
Tamarugite occurs associatedwith various alums and is always a latemineral, usually later than the alums.
l Schulze, Verh. Naturw. Deutsch. Ver. Sonti,ago, vol. 2, p. 56, 1889.
Roronntcns.
2 Domeyko, 11[ilxsTslbigio;'2ndApp., p. 30, 1883.
3 Cleve, SoenskaVet. Ak. Eand'l'ingor, vol. 9, p. 12, 1870'

724

MARK C. BANDYa Zambonini, Ac. Sc.Napoli, Renil., Dec. 1907.
6 SimpsonJ . Roy. Soc.WesternAus!,ralia,vol. 9, p. 62, 1923.
6 The specieshas been omitted from recent editions of Ford's Dana Textbook of
Mineralogy.
z Larsenand Berman,BuLl..848,IJ.S. GeoI.Sun.
Pickeringi.te

MgAh(SOr)r'22H2O
Hitherto nothing was known with certainty as to the crystallographyof this mineral. The data contained in the following tables are therefore
new and are based on the measurement of many crystals. These were
slender needles (Fig. 5) and the terminal faces were excessively small,but the data are well established and the crystal setting is confirmed byan fr-rav studv.

Frc. 5. Crystal of Pickeringite.
Tarr,o 1. Ar.rcr,nTlsre-Prcrox.ulortr
Monoclinice : b: r : 0 . 8 6 5 5: 1: 0 .2 5 5 1
9:96"33i'
p:83o26'
Poi qo:r s: O.2948:0 . 2534| |12:P2iq2:3.9459:I . 1638: I
po':0.2967, qo':0.2551, oo': 0. 1150

725

STJLPHATE DEPOSITS OF NORTEERN CHILE

o

O2

P2:B

A

b 010
4 100
nx llo0'00'
90 00
49 18+

90'00'
90 00
90 00

0000'
000

0000'
90 00
49 r8i

90000'
83 26+
85 02

90'00'
0 00
40 41Ltn 210?c, 011
* 021

63 26
24 16
1242

9000
1538
2736+

000
8326+
8326+

63 26
75 46+
63 07i

84 08+
14 rs+
26 s2+

26 s4
83 38+
84 09

y 031
z 041
d tOl

833
626
90 00

s744
4s 4s+
2222+

8s26+
8326+
6737i-

s245+
44 36+
90 00

37 t4L,45 23i
1549

84 +7
85 24
67 37+

e

301
D 101
E 301

90 00
-90 00-90 00

4509
1028
3747

445r
10028
r2747

90 00
90 00
90 00

38 3s+
17 0r+
44 20+

44 sr
10028
r2747

p 111
q 221
P T11

58 13
s4 14+-s5 27+

2sso+
4107+
r7 23+

6737i2544r
10018

76 43"
67 24
7s s4i20 32+
35 58
21 50

68 15
5745
c)959

o 22r

-4s oe+-45 2r+

J t2r

3854

65 17
58 50
64 44i.

39 42i52 t6
29 3r+

11305
r2r 36+69 51+

s 331
131
F 121
G 131
H
L

I

TA 1

2tr
231

2rl
23r
K 24r
311
32r

t
R 311

32r
V 42r

34 58

11534

47 26+
33 15

r27 46+67 37+
67 37i
10018
10018

5443
63 20,

38 14;-rs 2rh

40 .59;28 26+
38 11+

sr 12+

99rrt

s301+

40 08

98 12+-10 0670rri
4247+

46 0r+
36 58+
46 t2

10018
54 4r
54 4r

44 53
78 r4is8 01

47 31
30 52+
41 57+

97 15
s5 32
60 38i-61 56

2828
4204
48 25

11534
1 1 53 4
11534

7702+
5223
47 22+

34 23
4549
5r 27+

65 08
69 12
10831

46 02i"48 2s+
39 12+
42 sr+
49 53+

44 5r
44 5r
r27 46+12746i13659

7948

3e +2+
42 s9
45 29
48 26+
55 51;

45 45+
48 09+
12654+
r24 37
r33 40i,

2816+-19 36-32 oo+-25 07754s+
6305-71 47-s6 38+-64 32+

70r2+
7836
68 02
70 48i7r s3+

Table 2 gives the details concerning the distribution of forms on theeleven crystals measured, and shows the prominence of the various
forms.

MARR C. BANDV
Tesrn 2, ColrsnllrroNs oN Ptcrmrxcrrr
r234567891011
b0l0xxxxx
o100xx
mll0
x
x
x
x

x

n2l0
w0lI
tc02l

x
x

x

x

x

x

x
x

x

x

x
x

x

x

yO3Txxxxxx
z04lx
dl0lxxxx
e30lxxxx
DT01
E301

x

x
x

plllxxxx
q227xxxxx
PIll
x

I

x

Q22l
s33l
fl2lxxxx

gl3lxxxxxxx
FI21
GT31

x
x

H-r41
i2llxxxxx
i23lxxxxxxxx
I2l1
J23t
K24l

x

x
x

x
x

x

x
x

x

x

x

x
x

x
x

x
a

x

x

X

r3llxsxxx
t32lxxxxxx
R311
x
T32l
VAI

x
x

I

x
x

x

x

x

x
x

x

Structurecell: SpacegroupP 2f m; on 20.8,bo24.2,co6.17,;p:95"+.
ggHzO.
astbnics:0.860:I :0.255;containsMgaAla(SOn)ro.
Habit: In long aciculartufts; as a felted mass,and as closelypacked
cross-fibreveinlets.Also massive.

727

SULPEATE DEPOSITSOF NORTHEKNCEILE

Physical properties: Cleavage (010) poor. Fracture conchoidal. Brittle.
H:1+. G:L73. Luster vitreous. Color white to yellow, sometimes
brown.
Optical properties : Biaxial negative,o*:y:6
2y:60",24c:*36.,
1.475; 0N,: 1.480; T : N"1.483

Chemistry: A hydrous magnesium aluminum sulphate MgAh(SOa)r
'22H2O corresponding to the iron compound halotrichite. The following
is an analysis of the material used in this study.
PrcronrNcrrn(analysisby F. A. Gonyer)
Alzog
MgO
CaO
HzO*
Sos
Insol.

12.30
4.35
0.09
44.66
37 '84
0.50

Total

99.74

Relation of pickeringite to halotrichite: The two minerals form aseriesaccording to the formula(Mg, Fe)Ab ( SO4)4.22HzO
with analyses showing an apparently complete gradation between
magnesium and iron. The following table shows their similarities in otler
respects.
Cnysrelr,oonepgv
Ratio
0.8655:1:0.255J
F:96"33i'
0 .845: 1:0. 254
0:100.6o

X-Ray
an20.8,bs24.2
co6.17
ao20.5, bo24.2
c o6 . ! 7

Pickeringite
Halotrichite

Pickeringite

OprrcsaBl2YOrientation
1.475
1.480
1.483

60"

Halotrichite

1.480

35o

1.486

1.490

Zy\c:36"
Y:D
ZA.c:38"
Y:b

Occurrence: Pickeringite forms snow-white tufts of fibers on massive
jarosite, toget"her with chalcanthite and fibroferrite, as one of the lastminerals to form at Quetena.

MAKK C. BANDY

Halotrichite
FeAlz(SOa)a.
22HzO
Terminated crystals of halotrichite have never been found. Ifowever,
the matefial of this study was in sufficiently distinct crystals for therequirements of an *-ray study with the Weissenberggoniometer. The
crystallograpny here given, as well as the optical properties, and ananalysis are new data for the species,and establish its close relationshipto pickeringite, the magnesium member of the series.
Crystallography: Prism measurements on the needle-like crystals
yielded forms and angles as follows:
Forms
b

010

I 250
m ll0

Measured

Calculated

No' of

6p6pFaces
0"00'
90000,

0000'

90"00,

19

2443
49 18

2412
48 20

9000
90 00

4
38

9000
90 00

The calculated angle is derived from the x-ray data given below.
Structure cell: Monoclinic; oo: 20.47, bo:24.24, cs:$.167; S:199.6o
I I " . a : b : c : 0 . 8 4 5 : l : 0 . 2 5 4 . C o n t a i n s F e e A l s ( S o a ) r868.H 2 O .
Habit: Prismatic [001];commonforms b m;verticalzone striated [001];
crystals commonly acicular in radiating or matted aggregates, larger
crystals commonly hollow [001].
Cleavage:(010) poor.
Physical properties: Fracture conchoidal, brittle. G:1.895. H:1+.
Luster, vitreous; silky in fibrous aggregates.Colorless to light green.
Optical properties:z(Na)a:1.480

P:r.486
t:l .490

Negative

2V:35'
r>0, medium
ZAc:38" Y:bComposition: An analysis on material used for the optical and r-ray
study was made by F. A. Gonyer, as follows:
Alzos
FezOs
FeO
HrO+
so3
CuO
Insol.

10.26
0.65
7 .28
43.33
37.28
0.66
0.93

Total

100.39This is in good agreement with the formula.

729

STJLPEATE DEPOSITS OF NORTHERN CHILE

Pyrognostics:Closed tube yields abundant acid water; B.B. decrepitates. Readily soluble in water and acids.
Occurrence: Occurs at all three deposits intimately associated with
pyrite, szomolnokite and other iron sulphates.
Halotrichite is an early mineral, apparently forming directly from
pyrite by action of solutions carrying aluminum sulphate. Occurs as analteration product of szomolnokite. Apparently the presenceor absenceof aluminum sulphate determines whether szomolnokite or halotrichite
forms. It occurs at Chuquicamata in crystals up to one-sixteenth of aninch thick in a groundmass of pyrite, sericite and aluminum sulphate.
C. Klauerr found that halotrichite only formed in iron aluminum sulphate solutions that contained an excessof sulphuric acid and, when theexcessacid failed, precipitation ceased.The natural associationspoint
to an excessof sulphuric acid at the time of formation of this mineral.
Rrrnnnxcn.1Klauer,Ann.J. Photm.,vol. 14,p. 261,1835.
C oquimbite and P orocoquimbite
Fez(SOa)r'9HzO
Coquimbite was first describedfrom Chile,l where it is more abundant
than in other described occurrences. Recently an exhaustive crystallographic study was made by Ungemach2 on material from the type
locality, with the conclusion that the mineral represents dimorphous
forms, for one of which, the hexagonal form, the name coquimbite isretained, and the other, the rhombohedral modification, is called paracoquimbite. These two forms have been verified by the writer.
Analyses of the material of this study, are as follows:
l-e2OB
CuO
CaO
SOs
HsO
Insol.
Total

1
27.5
2.8
1.5
39.9
28.4

23
28.71

28.s

42.3r
28.82

42.8
28.7

0.40
100.1

r00.24

1. Chuquicamata. Bert Carter, Chile Exploration Co., analyst. Inchrdes SiOz, AlzOs'
MgO trace.
2. Alcaparrosa. Deep amethystine color. E. P. Henderson, U. S. National Museum,
analyst.
3. Theoretical for Fez(SOr)a 9I{sO.

Coquimbite is not a common mineral at Chuquicamata. It has been
observed in several specimens,but it apparently disappears rapidly in
depth.

730

MARK C. BANDYBoth coquimbite and paracoquimbite occur at Quetena, coquimbite
being the more common in the specimensstudied. It is commonly associated with voltaite, a later mineral. ft is less commonly associatedwith szomolnokite, roemerite and quenstedtite. Both szomolnokite androemerite are earlier minerals and the relationships with quenstedtite
are not clear. The latter mineral appears to be the later. The coquimbite is always light in color.
Both coquimbite and paracoquimbite are abundant at Alcaparrosa,
the rhombohedral modification, paracoquimbite, greatly predominating.
The mineral ranges in color from a pale violet to a deep amethystine.
Crystals up to three-quarters of an inch in size are present.
The sequencerelationships of the mineral are given below,
Lote

Lapparentite

Eail,yQuenstedtite
Coquimbite
Roemerite
Szomolnokite

An attempt was made to determine which modification was the earlier,the hexagonal or the rhombohedral. The data is conflicting but it isbelieved by the writer that the hexagonal coquimbite is the earlier form.
RnronrNcrs.r Rose,Pogg.Ann.,vol.27,p. 31O,1833.
2 Ungemach,
Bultr.Soc.Min.,vol.58,p. 165,1935.
Kroehnkite
NazCu(soa)2.2H2oKroehnkite is a common mineral in northern and central Chile and arare mineral elsewherein the world. In portions of the deposit at Chuquicamata it constitutes an ore mineral. Crystals are common, and it
also forms cross-fibreveins. The largest crystal found measuresone-halfby one-quarter by three and one-quarter inches. The crystallography ofkroehnkite in its present form was first establishedr after a study of
crystals from Chuquicamata. In this study the following forms wereobserved:a b m h e d q s vLr.
In the oxidation of chalcocite in the northern portion of the ore deposit
at Chuquicamata, chalcanthite is usually the first sulphate to form.
This is followed by kroehnkite, and antlerite replaces the kroehnkite.
Along the western side of the ore body, kroehnkite is characteristicallyassociated with atacamite and natrochalcite. The deposition of purekroehnkite was followed by the simultaneous deposition of kroehnkite
and acicular atacamite. Toward the end of this period of deposition,atacamite began to crystallize in pyramidal crystals and continued toSULPHATE DEPOSITS OF NORTHERN CHILE

7sr

form beyond the period of the kroehnkite. Natrochalcite forms crusts
over these minerals and is definitely later. fn the southern part of thedeposit early bloedite is commonly replaced by kroehnkite.
RuennNcn. 1 Palache and Warren, Am. f our. Scd., vol. 24, p. 342, l9O41,Zeits. Krist.,
vol. 45, p. 529, 1908.

N atrochalcite
NazCu+(SO+)
4(OH),' 2HrO
Natrochalcite is a rare mineral found only at Chuquicamata, inbeautiful bright emerald-green crystals. The mineral was describedin 1908.1ft was limited to the upper portions of the deposit and in recent
years has become increasingly rare. The mineral occurs coating cracks
in the altered country rock or as crystalline crusts on kroehnkite andatacamite. Rarely it occurs in vugs in fibrous kroehnkite.
The paragenesiswas incompletely determined in this study. A definite
sequencewas,
LateNatrochalcite
Atacamite
Kroebnkite

Early

No minerals were found coating the natrochalcite and nothing can besaid regarding minerals that are later.
Ralnnnxcn. 1 Palache and Warren, Am. Jour. Scz'., vol. 24, p. 342, 1908; Zeits. Krist.,
vol.45,p. S29,lgDS.Theformulagivenaboveisacorrectionofthatintheoriginalpaper.

Ferrinatrite
NaaFe(SOn)a.3H2O
The mineral ferrinatrite was first described by Mackintosh.l Later thecomposition was verified by Genth2 and Frenzel.s Recently a mineral
was found in Chile and named leucoglaucite by Ungemach,aon the basisof a chemical analysis of a very small sample. In all other respects themineral matches ferrinatrite closely. The mineral collected by the writeris similar in its physical properties to these two previously describedminerals but differs from both chemically. The formulae derived fromthe analysesare:(1) Ferrinatrite(2) Leucoglaucite(3) Ferrinatrite-Bandy

NagFe(SOa)a'3HrO
H Fe(SOdz'2HzO
7H2O
Na4Fer(SO4)b'Since four analyses in good agreement have been made of ferrinatrite,
the first of these formulae is the best established, on chemical grounds.
Further, the three minerals are admittedly hexagonal, so that fromstructural considerationsthe first is also most likely since two molecular

732

MARK C. BANDY

weights of the first formula would give the proper number of atoms andmolecular groups to distribute in hexagonal space groups. On the basisof symmetry the last formula is least suitable.
The following table lists chemical analyses and physical properties of
the three minerals under consideration.
Ferrinatrite
Bandy

Ferrinatrite
123
18.34
0.40

NazO
K:O
CaO
FezOa
Al2os
SOa
H:O
InsoI.

17.23
0.43
50.25
tr.t4
2.00

Total

99.79

G

456

19.95
tr.
0.22
t7.30

20.22

20.06

19.92
0.40

1 7. 6 9

16.91

19.00

28.06

51.30
11.89

50.85
11.90

51.29
11.50

49.75
15.13
0.30

56.97
15.02

100.66100.6699.76

100.54100.05)2.s47
12.s78

2.61

2.57

2.52+

0.55278

1.557
1.615
0.5582

1.559*
t.627+
0.5589@

1. 5 5 8e.L OIJ

aic

Leucoglaucite+ Determined on type material
kindly sent by Professor Ungemach.
1. Ferrinatrite. Mackintosh, analyst.r
2. Ferrinatrite. Genth, analyst.2
3, Ferrinatrite. Frenzel, analyst.g
4. Ferrinatrite. Scharizer, analyst.s
5. Ferrinatrite-Bandy. E. P. Henderson, analyst. Unpublished.
6. Leucoglaucite. Ungemach, analyst.a

Physical properties: The Chuquicamata ferrinatrite has G 2.57,H 2\.
Fracture splintery; fibers brittle. Cleavage {1010} perfect. Color paleamethystine.
Habit: Prismatic to fibrous [0001], deeply striated. Often in parallel
growths. Common forms: b(ll1}), .1G}TD.
Occurrence: As fibrous crusts associated with metasideronatrite andmetavoltine at Chuquicamata. The former shows some evidence of
replacing ferrinatrite and pseudomorphs have been observed. Metasideronatrite may be changed to ferrinatrite by treating with a solution
containing an excessof sodium sulphate and sulphuric acid. This may
account for the overlapping of the sequenceof these two minerals since
they seem to alter, one to the other, with ease,in both directions.

SULPHATE DEPOSITS OF NORTEEKN CALIN/JJ

RrrnnnNcns. 1 Mackintosh,Am. Jour. Scl., vol.38, p. 243, 1889.
2 Genth, Zects.Krist., vol. 18, p. 586, 1891.
3 Frenzel,Zei,ts.Krist., vol. 18, p. 596, 1891.
a Ungemach,Bull,.Soc.Mi.n.,vol.58, p.97, 1935.
5 Scharizer,
Zei.ts.Krist., vol.4l, p.412, t906.
Scharizer,in Doelter, 4ft1, 582,1929.
M etasideronatrite
NarFez(SO+)4(OH) 2' 3HrO
This mineral is newly described here. It differs from sideronatrite
only in having less water, and consequently higher refractive indicesand higher density. The relation between the two is shown below:
Stnnnox.q.tntrn
Mntestnnnoxetntlp. 3Hzo Na4Fer(So4)4'(oH),' 6HrO
Na4Fer(So4)4(oH)z
2.21.32.+6FormulaGa

I . .)4.t7

1. 5 7 5
1.634

1 .508
1.525
1. 5 8 6

2V

60'

58'

Metasideronatrite can be produced from sideronatdte by dehydration
over sulphuric acid. Whether the Chuquicamata material has gone
through a dehydration is not certain, but no evidence of alteration isvisitrle in the specimens,which are fresh, the cleavageflakes being quitetransparent.
The minerals urusi.ter and bartholornire2are apparently related to theminerals here discussed,but the data are so meager that a decision concerning their nature cannot be reached.
Since this speciesis named here for the first time a complete description is given.
dipyramidal-Z/ m 2/ m 2/ m
Orthorhombic;
Crystallography::1
p o : r o i r s : O . 2 5 7: 09. 1 1 8 7
p2:q2:8.4246:2.1877:l12:

a i b: c : 0 . 4 5 7I : 1 : 0 .1 1 8 7
pr:o.457 1: 3. 8598: 1
Qt:.h:
Forms

Q

p: C

6t

pr: A

Qz

P2--B

b 010
m ll0
e OIr

0'00'
65 26
000

90'00'
90 00
644

90'00'
90 00
646

90'00'
24 34
9000

0"00'
9000

0'00'
65 26
ggr+rlForms

No. of
faces

b 010
m ll0
e 011

10
2l
z

Measuredo0"00'
62048'.-67"59',
89 49 -89 s8

p

90'00'
90 00
6"44',-6"48',

734

MARK C. BANDY

Habit: Prismatic [001] crystals rare; usually in coarseto fine crystalline
aggregates.
C l e a v a g e :{ 1 0 0 } { 0 1 0 } p e r f e c t , { 0 0 1 } e m i n e n t .
Physical properties: Fracture, fibrous; G:2.46; H:2.5.
Luster,silky. Color golden yellow to straw yellow.
Opticalproperties::1.543a: a:colorless
0: b: light yellow : 1.575
yellow: I .634
z: c: brownish

Positive
2V:60"
r)2, strong

Chemistry : Basic hydrous sodium-iron sulphate, Na+Fez(SOe)+(OH)2.
3H2O.
Arar,vsrsev E. P. Ilrlronnsow
Fesoe
NarO
KzO
soa
HrO
fnsol.

22.90
17.56
.26
48.66
9.75
.60

Total

99.73

Mol. Ratios
.t+34
1.00
.2832
I oo
.0028
.6077
4.23
.5411
3.77

fnsoluble in cold water. Soluble in boiling water with decomposition;solublein dilute acids.
Pyrognostics: B.B. gives strong soda flame, colors bead dark brown.
Closed tube yields abundant acid water. Insoluble in cold water.
Occurrence: At Chuquicamata intimately associatedwith metavoltine,less commonly with ferrinatrite, ungemachite, alums and natrojarosite.
Rrmnrrrrcns.1 Frenzel,Min. Mitt., vol. 2, p. I33, IB7g.
2 Cleve,Ah. Stochhobn,
vol.9, Nov. 1870.
Roemerite
Fe2'l/Fe//(SO4)4- I4H2O
The crystallography of roemerite has been variously interpreted. The
final satisfactory setting of this triclinic mineral is that of Wolfe.l No
crystals were encountered in this study, but roemerite is an abundant
mineral at Alcaparrosa where it is associated with szomolnokite andrhomboclase ,during an early phase of pyrite oxidation. The following
optical propertieswere determinedon fresh material: a : I.526, A : 1.564,
r : 1 . 5 7 5 ;2 V : 5 0 " ; r ) z : e x t r e m e .

SULPHATE DEPOSITS OF NORTHERN CEILE/JJ

No analysis of material was made as the mineral commonly showed
incipient alteration to coquimbite. The color was most intense and themineral was purest in narrow halos about areas of pyrite and szomolnokite. In the change from roemerite to coquimbite the amounts of ironand oxygen remain the same, sulphur is added and water decreasesinamount. At Quetena and Chuquicamata roemerite is a relatively raremineral compared to coquimbite with which it is closely associated.
RnlnnnNcn.I Wolfe,Am. Mineral.,voI.22,p. 736,1937.
Metaaoltine?
The writer has not been able to definitely identify the mineral here
described. It approaches most closely the originally described metavoltine,l with, however, important difierences. The mineral referred tometavoltine by Zambonini2 is probably not really that species,nor is it
related to the mineral here described. The artificial products of Scharizers and Gossnel are undoubtedly of the same composition as Zambonini's mineral, but they are not metavoltine.
The crystallography of the material from Chuquicamata is containedin the following table:
Hexagonal; dipyramidal-6/m
po:1.4517
c:2.5143..
r ormsNo. of-Haces6pc 0001o 10T0b tt20

12
3
1

0o00'
30 00

0"00'
90 00
90 00

Calculated
6p
0"00'
90 00
0000'
30 00
90 00

.p r0lr
I 202r

000
000
000

55 26
7100
7840

000
000
000

55 26
7100
80 14

000

8315

000

83 27

c

4041

1
1
1

e

6061

I

Measured

Habit: In aggregatesof six-sidedplates and scales;common forms: o o;crystals very rare; parallel growth [0001] common.
Cleavage: {0001} perfect
Physical properties: Fracture, rough and interrupted, plates slightly
flexibleG; : 2 . 5 , 2 . 5 3 , 2 . 3 9 6H
. :2+.F:5.
L u s t e rv i t r e o u st o o i l l - .
Optical properties: Color olive green to greenish brown.
<,r(brown)e (pale greenishyellow)

f .Ss#f .Sso
I.572-1.574

Negative

736

MARK C. BANDY

Chemistry: In order to show the relation of the Chuquicamata mineral to metavoltine, as described, and to Zambonini's mineral, as wellas the artificial material, a table of chemical analyses is given below:
ANlrvsBs

ol Mnrevor.rrNB

l2
FezOa
FeO
KzO
NazO
SOt
HzO

21 20
2.92
9.87
4.65
46.90
14.58

Total
G

100.12
2.53

21 03
21.49
42.98
14.35
99.85

eNo Rrlerno
345
23.3t

MrNnn.qr.s
22.03

2 1. 5 1

4.69
8 .1 5
45.42
17.83

21.22

2t.44

43.84
2r.91

42.86
t4.49

99.56
25

100.002 396

100.33

1. Metavoltine. Blaas, analyst.l Persia.
2. Metavoltine? Zambonini, analyst 2 Vesuvius.
3. Metavoltine? Henderson, analyst (Unpublished). Chuquicamata.
4. Artificial. Scharizer, analyst.s
5. Artiicial. Gossner.a

The analyses given above indicate the following formulae:(1) Metavoltine, Blaas(2) Metavoltine? Zambonini(3) Metavoltine? Henderson

K4Na3(Fe"Fe "6') (SOru' 16HrO
K1sFe6'/' (SOa)1r(OH)4'16HrO
K2Na6I'e6"'(SO4)rr(OH),' 20HrO

Since the data at hand are not definite, no statement can be madeconcerning the validity of the formulae listed. Zambonini's material ismost probably correctly formulated, since several analyses of similar
artificial material are available.
General experiencein sodium and potassium salts indicates that little
isomorphism exists between them. Mixed crystals are usually notformed, so that the three substanceshere discussedrnay well be different
minerals.
Pyrognostics: Partially soluble in water and dilute acids. On heating,the aqueous solution yields reddish precipitate. In closed tube yields
water and forms black residue.
Occurrence: At Alcaparrosa metavoltine (?) occurs surrounded by ahalo of copiapite in veins of pickeringite. The age relationships are
metavoltine followed by copiapite with the pickeringite the younger
mineral.
At Quetena metavoltine (?) is intimately associated with metasideronatrite, but the mineral is so uncommon that the age relationship was
uncertain. Jarosite is later than the two minerals.

SULPHATE DEPOSITS OF NORTEEKN CHILElJl

Metavoltine (?) is almost always associated, more or less intimately
with metasideronatrite at Chuquicamata. The latter may occur without metavoltine, but in the writer's experience metavoltine (?) neveroccurs without associatedmetasideronatrite. With one exception, every
occurrenceappears to show the metavoltine (?) as the younger mineral.
In a single specimen the metasideronatrite is certainly the younger
mineral. Commonly associated with the two minerals are a number ofmembers of the alum group such as kalinite, pickeringite, tamarugite.
All of these minerals are normal sulphates and later than metavoltine (?)
and metasideronatrite. Other associated minerals that are later are
ungemachite and jarosite.
Rnlonnxces.r Blaas,Ak.Wien.Ber.,vol.87,p. 155,1883.
2Zambonini,
Atti,R. Acc.Napoli,8,13,1906.
3 Scharizer,
Zeits.Krist., vol. 58,p 424,1923.
a GossnerandArm, Zeits.Krist., vol 72,p. 205,1929.
Copiapite and' Cupr ocopiapi.te
Copiapite is common in all three of the deposits studied here, andof ten as very fine small crystals. These crystals were studied by Professor
Palache, who found the mineral to be triclinic, not orthorhombic ormonoclinic as it had been previously regarded. The same conclusion
regarding the symmetry of this mineral was simultaneously arrived atby Ungemach.l
Aws.ysns or Coprerur

No.

1.
3.
4.
5.
6.
8.
9.
10.
lt.
12.
l.t.
14.

15.
16.

so, l",o lx,'olltl*o1.550 28.95139.56128.60
1 546 3 0 . 7 51 3 9 . 2 8t 2 9 . 9 7
1 .545 2 9 . 9 8 | 3 9 6 8 I 3 0 . 4 5
1 . 5 4 3 2 s . 2 1| 3 8 4 4 | 2 7 . 7 6| . 1 6
4.01 1.0.+4
1. 5 4 1 2 s . 0 4 I 3 8 3 6 | 2 9 . 7 1.29
1 . 5 4 0 24.93 | 39.10 | 29 92 | .40.78
1 . 5 3 8 2 4 . 9 6| 3 7. 9 2 I 3 1. 5 1
3 .1 01 . 5 3 5 2 7. 4 4 | 3 9 . 4 7| 2 7. 8 4
.52
326
4.06
1 . 5 3 2 2 6 . 1 0| 3 8 . 3 7| 3 0 6 8
1. 5 3 1 2 1 . 9 1 1 3 8 . 8 7 1 3 3 . 3 3.94
I 530 2 6 . 2 51 3 9 . 2 41 2 8 . 3 2
r.0+
26.39t39.79t29.92
3.19
1 . 5 2 9 2 9 . 6 6| 3 9 . 8 r | 2 9 . 9 5.33
27.28 | 39 83 | 29.92
2 7 . 6 6| 4 1. 6 2 | 2 3 . 5 1

26.8 1J3.5 12e.0| .40

lnsol.

1.06

.3r
.52
3.62
. 3 1 5.43
3.49 1.24.52 1.96
I .16
Tr.
4.15 .01
.08
.48
.30
.30
.55
1.47 .21
2.7

7s8

MARK C. BANDY

1. Atacama Desert, Chile. W. F. Foshag, analyst; unpublished.
2. Artificial. Posnjak and Merwin, Jour. Am. Chem. Soc., vol.44, p. 1980, 1922.
3. Congo Mine, Perry Co., Ohio. Caughey, Am. Mineral,., vol. 3, p. 162, 1978.
4. Island Mountain, Calif. W. F. Foshag, analyst; unpublished.
5. Leona Heights, Calif. W. F. Foshag, analyst; unpublished.
6. Temple Rock, Utah. W. F. Foshag, analyst; unpublished.
7. Laird Post, B. C. Todd, analyst; Walker, [Jniv. Toronto Studies, Geol, Ser., vol. 14,
p.84,1922.
8. Blythe, Calif . W. F. Foshag, analyst;unpublished.
9. Capo d'Arco, Elba. Manasse, Proc. verb. S oc. T oscany, l9ll.
10. Vignera, EIba. Manasse, l9ll.
11. Las Vegas, N. Mex. W. F. Foshag, analyst; unpublished.
12. Santa Maria Mts., Calif. Schairer and Lawson, Arn. Minerol,., vol. 9, p. 242, 1924.
13. Copiapo, Chile. Manasse, l9ll.
14. Chuquicamata, Chile. F. A. Gonyer, analyst; unpublished.
15. Chuquicamata, Chile. Cuprocopiapite. F. A. Gonyer, analyst; unpublished.
16. Chuquicamata, Chile. B. W. Carter, analyst; unpublished.
On analyses 1,4, 5,6,8, 11-refractive indices by Larsen, Bull.679, U. S. Geol,.Swo.,7921.

An attempt to correlate the refractive index (B) with the variations incomposition of copiapites from Chile, and elsewhere,led to no conclusive
results. fn the following table is a list of analyses of copiapites, together
with measurementsof the B index. The writer is indebted to Dr. W. F.
Foshag for the privilege of publishing here the six analyses credited tohim.
Synthetic copiapite2yields a formula Fea(SOa)6(OH)z'16HzO.Analysesof natural copiapites vary considerably and the water content is frequently 18HrO. Analyses 7, 8, ll and 12 are in good agreement with theformulaMgFea(SOa)o(OH)2.19 or 2lIIzOg
The cuprocopiapite composition (anal. 16) is most closely represented by the formula
CuFea(SOr)s(OH)n. 1THrOor, using analysis 15, the formula may be written
CuFer(SOr)o(OH)r. 14IfrO
Occurrence: Copiapite is an abundant mineral in all three deposits.
ft is relatively most abundant at Alcaparrosa, where it occurs in thicklayers of clear, brilliant crystalline aggregates.ft may be used as a ((keymineral" in the sequencestudy, as it is one of the earliest basic minerals,with the possible exception of fibroferrite.
Cuprocopiapite is always associated with copiapite, commonly withparabutlerite, chalcanthite and jarosite. It is later than the first-men-

739

SULPEATE DEPOSITS OF NORTEERN CHILE

tioned two minerals and earlier than the last two. It is probably formedby the reaction between copiapite and sulphate solutions carrying copper. At Quetena it occurs in rounded masses,within massive iron sulphates, usually copiapite.
Rrlnnrxcns. 1Ungemach,Bull,.Soc.Mi.n.,vol.58,p. 97, 1935.
2PosnjakandMerwin,Jour.Am. Chem.Soc.,vol 44, p. 1965,1922.
3 Fromunpublished(1938).
resultsof M. Fleisher(1935)andM. A. PeacockQuenstedt'i.teFer(So4)a.10H2o Triclinic, pinacoidal
The crystal form of quenstedtite was first correctly established byUngemach,l whose data we use. One new form on quenstedtite was observed in this study,&[easuredCalculated

r.r 032a21"44+'

p29"r7+',

6
21o20'

p29"58',The mineral occurs in tabular crystals {010}. The color does not agreewith that given by Linck2 and Ungemach.l The material from Alcaparrosa is colorless to pale violet, differing from the "rose-lilas intense"
color of the Copiapo material.
The optical properties of the Alcaparrosa material are tabulated below(as obtained in a measured crystal oriented on the Fedorov stage).
6p
43"
45o
l2g"
43"
-138'
88o
"
Extinction
on (010)against[001]:30'.
a
p

-

z(Na)
1.547
1.566
1.594

Positive
2Y:7Oor(a strong;horizontal

Quenstedtite was only observed from Alcaparrosa. There it occurs
intimately associatedwith coquimbite and lapparantite. fn association
with coquimbite it shows a remarkable caseof replacement by alteration'
Most of the quenstedtite is altered to coquimbite. Apparently the latter
mineral forms earlier than quenstedtite but, due to the strong overlapping of their stability fields, both can form at essentially the same time.
Within the range of the overlapping fields the quenstedtite alters readily
to coquimbite through the loss of one molecule of water. Unaltered material occurs as crystal druses in the coquimbite and in rounded aggregates of minute crystals in copiapite.
Rnrnnewcos.1 Ungemach,
Bull. Soc.Franc.Min., vol.58,p. 97,1935,
2Linck,Zei,ts.
Krist.,vol.15,p. 11,1889.

740

MARK C. BANDY

Lapparentite
Alr(SODz(OH)29H2O Monoclinic
Lapparentite is a new mineral recently described by Ungemachl fromTierra Amarilla, Chile. This mineral was found at Alcaparrosa, near
Cerritos Bayos, thus adding a new locality. It occurs in colorlesstabular
crystals, rather difficult to tell from quenstedtite with which it is commonly associated.All of the forms observed by Ungemach were foundin this study with the exception of the base, and eight additional new
forms were observed. ft is to be noted that Ungemach found no orthodomes, and only the positive and negative unit orthodomes were observed in this study. The new forms are given below.
Calculated from
Ungemach's Ratio

Forms

No. of
Faces

140
150
160

4
3
4

39"53',
3407
3005

90'00'
90 00
90 00

6p
40"41'

90000'

343l
29 49

90 00
90 00

180
L.l2.O
101

2
2
2

23 32
1 61 5
89 42

90 00
90 00
42 34

23 16
16 00
90 00

90 00
90 00
42 27iT01
r-41(?)

r|-89 17-37 32

36 24
50 51

-90 00-37 4l

36 44
5040;

MeasuredopOptical properties: The optical properties for this species have notyet been recorded. Doctor Ungemach kindly furnished crystals of theoriginal material, and the optical properties were determined on this as
well as on crystals from the newer occurrencehere given.
Biaxial positive.
a:1.490
p:t.492

2V:55'+
Y:b
XAc:*5"z:1.504

At Alcaparrosa, lapparentite occurs in tabular crystals associatedwith
quenstedtite in vugs in coquimbite and with pickeringite. Quenstedtite
and coquimbite are earlier minerals, and pickeringite is later. Ilowever,some pickeringite appears to be earlier.
RnrnnrNcn.I Ungemach,Bull,.Soc.Fronc.Min., vol. 58,p. 209.1935.
Rhontboclase
HFe(SOa)z.4HzO
This new species, recently described from Szomolnok, Czecho-

74I

SULPHATE DEPOSITSOF NORTHERNCHILE

slovakia,l has been found by the writer at.Alcaparrosa. This marks thesecond occurrence. Since the material available for this study was ingood crystals, a complete redescription is here given. The crystallography has been amplified by a more complete form list and a more accurate
axial ratio. The refractive indices have been determined. Several otherphysical properties have been measured.
Crystallography:
Orthorhornbic ; dipyramidal
p o i Q s : r 6 : 1 . 6 8 0 :10 9 3 7 0 : 1
a:b:c:o 5577:1:0.9370
qr:n:fi:O.5577:0.5952:t
r2t?2:q2:l O672:1.7930:l

Forms

Calculated

No. ofMeasure-6pmentsdpOP0'00'
110"00' 90 00
10

c
b

001
010

s

120 4153

Measured
0o00'
90 00

x
x

x

3

4142

9000

60 51
000
6051

90 00
7502
1331

19
2
3

60 51
0000
6056

90 00
7513
1301

r ll4
6051
v lt3
6051
w 223 6051

2541
3240
5203

1
3
6

5810
5800
6045

2500
3100
5210

p lll
6051
q 22r 6051
u 241 4153

6232
7526
7846

10
5
2

6051
5800
4144

6232
7528
7840

Krenner's

Ktenner's
Forms

0000'

9000

m ll0
t o{t
n ll8

Krennet's
Measurements

58o36' 90 00'

x

6238

x

axial ratio isai b : c : 0.5695| I : 0.946+4.
All the forms observed by Krenner were also found by the writer. Additional forms are given in the table.
Habit: Tabular {001};base showsetch forms, common forms: b c m p'
Cleavage: {0011, perfect, { 110}, excellent.
Physical properties: Fracture conchoidal to fibrous, cleavagefolia are
flexible and polished. G:2.23. H:2. Luster pearly to subvitreous.
Colorless to gray.
Optical Properties:
a:[001]

9:[100]z(Na)1 .534

1.553
1.638

Negative

2Y:27"":[010]Pyrognostics: Slowly soluble in water. fnsoluble in NHrOH but forms
a brown coating over mineral (iron hydroxide ?). Soluble in acids. B.B.
decrepitates and fuses to a dark brown bead.

742

MARK C. BANDY

Occurrence: Rhomboclaseoccurs at Alcaparrosa, near Cerritos Bayos,
intimately associatedwith szomolnokite and roemerite. rt is believed tobe later than either of these minerals. The formation of this mineraland a detailed description of the mineral relationships has been given in
the section on geochemistry.
RrlnnnNcr. I Krenner,Central,bl.
Min., A, p.265, 1928.
Parabutlerite
Fe(SOa)(OH).2H2O
A basic hydrate of iron of this same composition has already been described as the mineral butleritel and as an artificial compound2 in thesystem FezOs-SOrH2O.However, the mineral here called parabutlerite
is orthorhombic, prismatic in habit; the artificial substance is presumably monoclinic;2the originally described butlerite has been erroneously
assignedto the orthorhombic system but is really triclinic.
Parabutlerite, both by its crystallography and optical properties asgiven later, is definitely orthorhombic. Butlerite has been re-examined
during this study, and the conclusion was reached that it is triclinic
because microscopic examination shows a twin plane in the position(100) of Lausen'sl orientation. The optical orientation within each individual is such that the most probable symmetry is triclinic.
The artificial compound is in diamond-shaped crystals with possible
twinning on (30T) and (203). This suggests the possibility that theartificial material may be the same as butlerite. Actual crystallographic
measurementsof the artificial substance were not included in the work
cited, but the ratio and forms were given.
The following table compares the modifications here discussed.
Taslr

Symmetry
Ratio

oF Coleegsorq

Parabutlerite
Orthorhombic
a:b:c:
O. 7 3 1 O : l : 0 . 7 2 1 8

Butlerite
Triclinic (pseudoorthorhombic)

Artificial
Monoclinic

0.9005:1:1.3606 0.858:1:1.358
9:7lo24l

a

1.598
1.663
r.l5t

1.604
1.674
1.731

G

2.55

2.548

-t \2

2+

1.588
t.678
r.749

SULPHATEDEPOSITS OF NORTHERN CHILE,*J

Frc. 6. Crystalof Parabutlerite.
The following full description of parabutlerite is given here since themineral is first named and described in this study.
Crystallography:
Orthorhombic;
bipyramidal-2/m 2/m 2/ma : bi c: O . 7 3 1 0; l : 0 . 72 1 8
q t : n :p t : O . 7 3 1 0 1: . 0 1 2 :81

po:Qo:ro:0.9874t0 .7218:I
rziPziqz:| '3855:1 ' 3680:I

O,
70"29+', 0o00'
36 10
000
90 00
90 00

pz:B
19"30+'
5350
70 09+

35 49
47 16+

90 00
90 00
90 00

90 00
90 00
90 00

61 34+
54 11
42 4s+

000
3s 4e+
19s0+

45 22
51 19
47 07

45 22
45 22
45 22

90 00
62 49
7536

Forms

6

L t40
m 110
s 012

19'30+'
53 50

90o00,
90 00

0 00

1950+

1eso+

f 034
e 0ll
s, 032

0 00
000
0 00

2825+
3549
47 L6+re r(1

d tOL

9000
s350
69ss+

4438
5044
4626

p rrr
r

212

p:C

6t

90"00'90 00

Pr:A

Habit: Prismatic [001] (Fig.6) common forms: m s e p; prism zone
striated [001].
Cleavage:{110} poor.
Physical Properties: Fracture conchoidal, brittle. G:2.55. H:2.5.
Luster, vitreous.
Optical Properties: Color light orange to Iight orange-brown.

C, BANDY

MARK

yellowa:fi:ps.le
p:c:greenish yellow
yellow
7:o:brownish

z(Na)
1.598
1.663
L737

Positive
2V:87"
r)z, moderate

Composition: Basic hydrous iron sulphate, Fe(SOa)(O}I)'2}IrO.
Analvsrs(Henderson, U. S. National

Museum)3

Molecular Ratios

Fesos

Per cent
39.21

soa
HrO
Insol.

39.15
22.OO
.23

Total

100.59.2455.4889|.2210

1.00
r.99
4.97

Pyrognostics:B.B. dark brownl closedtube, yields acid water;insoluble
in water, hot or cold, ammonia, soluble in dilute acids.
Occurrence:Occurs at Alcaparrosa near Cerritos Bayos in a bed about
8 inches thick above copiapite. It results from the alteration of copapite
and in part is pseudomorphic after copiapite. It also occurs with copiapite and jarosite at Quetena and Chuquicamata.
All of the field evidence points to the conclusion that parabutlerite
formed after copiapite. This evidence is conformable with the findingsof Posnjak and Merwin2 in their study of the system FerOa-SOr-HrO.At
50 degrees they fouird that these minerals formed from the following
solutions.
Couposrrror or Sor,urroN
weight per centFe(SOr)OH.2HzO
Copiapite

SOa/FezOa
2.55-2.69
2.7+-3.66

FezOa
17.9G20.13
20.70-16.78

HrO
SOs
22.96-27.r8 59.08-52.69
28.40-30.72 50.90-52.50

Jarosite is later than parabutlerite. The definitely established sequenceis:
Jarosite
Parabutlerite
Copiapite
Coquimbite
Much of the parabutlerite at Quetena and Chuquicamata is associated with copiapite and jarosite and shows the same sequence relationships as at Alcaparrosa. One specimen showed the parabutlerite as
having formed during the formation period of copiapite at Quetena.
Posnjak and Merwin obtained both the compound FezOr'2SO3.5H2O

745

SULPHATE DEPOSITS OF NORTHERN CHILE

and copiapite from a solution of the compositionFe2O3,2l'0; SO3,28'2;
H2O, 50.8.
RerrneNcns. l Lausen, Am. Mineral., vol. 13, p. 2O3, 1928'
2 Posnjak and Merwin, Jour. Am. Chem. Soc',vol.44, p. 1965,1922.
s lfenderson, U. S. National Museum, unpublished data on the material of this study.

AruenaNrrrB GnouP
3HrO' nH2O
Fez(SODz(OH)r'
Hohmannite
Castanite
Amarantite
Paposite
Metahohmannite

3H2o'4H2o
Fe:(Sor)z(oH)z'
SHro'SHroFer(so4)r(oH)r'Fez(SOa)z(OH)z'3HzO

The members of this group are brownish red basic hydrous iron sulphates, in one of which, amarantite, dehydration datal indicate thatthe water is given ofi in three stages. The three molecules most loosely
held go ofi below 100o,the next most loosely held above 100oand below
red.heat, and the hydroxyl at a higher temperature' The formulae are,accord.ingly,written to indicate these various kinds of water. On dehydration, when exposed to air, hohmannite apparently loses the four
loosely held molecules of water and forms what is here called metahohmannite. In this respect it differs from amarantite, which is much morestable under atmospheric conditions. At Chuquicamata a fresh surfaceof hohmannite alters on exposurein about twenty seconds.
Amarantite is characteristically found in radiating or matted acicular
crystals. Hohmannite may be distinguished by the rapidity of its alteration, and metahohmannite is always a powdery alteration product'
A comparison of the optical properties of these three minerals is
given below.
Hohmannite
1. 5 5 9
t.643
1. 6 5 5(-)40'/>2, extreme

a
{J
^l

2V
disp.
Pleochroism,.

"*l;,;lExtrnctlon

I X:verypaleyellow
j V:pale greenish yellow
I Z:dark\

greenish brown

I

|

"

Amarantite
1. 5 1 6
1.598
1.621
(-)30'
r <1)

Metahohmannite

colorlesspale yellow
reddish brown

pale yellow
reddish yellow
reddish brown

r.709
1.718
1.734
-l-

+7"

In addition to lhe three specieshere mentioned, two other minerals,
castanite2and paposite,2have been consideredauthentic speciesbelonging to this group.

746

MARK C. BANDY

most recently been made6 on the basis of its physical similarity tohohmannite. with the last opinion the writer is in agreement, having
arrived at this conclusion independently.

The original analysis, with 30 per cent of impurities, cannot be con_sidered as adequate proof of the validity of this mineral.
Hohmannite
Fer(soa)r(oH)2.3Hzo. 4Hzo
crystallography: Triclinic. No crystals of this mineral were available
for study.
optical properties: color, light amaranth-red to chestnut-brown.
Transparent to translucent.
X:very paleyellow
y:pale greenish
yellow
Z:dark greenish
brown

"jf:g
p:l.643
r:1.655

negative
2y:40"r)a extremewith only cleavagesfor orientation the optical orientation could not beworked out with any degree of certainty. The{010} cleavage yields aslightly ofi-center optical axis figure. rrohmannite can be distinguishedfrom amarantite by the extinction on {010}. fn hohmannite yniOOtl_23"; in amarantite yn [001]:47..
chemistry: The composition of this mineral is not well established.
The formula most suited to the analyses' is that given above. The socalled castanite is in good agreement with the formula.
Hohmannite is always intimately associated with chalcanthite andpicromerite. The chalcanthite is an earlier mineral and is believed to beformed from an earlier iron-chalcanthite (pisanite?). It is usually insmall, brilliant crystals showing a number of faces. Hohmannite is later
than both fibroferrite and copiapite and earlier than amarantite. As
stated before, it is an extremely unstable mineral, especially in a dry
atmosphere, and readily dehydrates to the four hydrate mineral (metahohmannite).

SULPEATEDEPOSITS OF NORTHEKN CHILE

Amarantile
Fez(SOr)z(OH)z.
3HzO.3HzO
Small crystals of excellent quality were available for the crystallographic and optical study. The triclinic character of the minerar was
confirmed. Two new forms were established, using the elements ofPenfield.
Crystallography: Triclinic
a:b:c:0.7692il:0.5739;a:95o39*,,g:90.23i,; "y:97"13,0.7484:0.5784: 1; I: 84.17,,rr: 88o53,;?s:Qo:ro:v: 82"42I,
p n:' 0 . 7 5 2 2 ,q s ' : 0 . 5 8 1 3r;o , : 0 . 0 0 6 9r,0 , : 0 . 1 0 0 4 .
New Forms:

320
301

Measured
6p59o56'
90000,
77 30
66 t7

Calculated
6p
57'05',
90000f

8011+

66 14+

These two forms are weak and not in good position so that they must be regarded as
uncertain.
Optical properties: Color, amaranth-red. Transparent.

a:colortess
B:pale yellow
z:reddish brown

rrr"

fr"

illt?

178" 68o I .598

Neeative
2V-:30.

Chemistry: Amarantite has the composition Fez(SOr)z(OH)z.3HzO.
3HzO. This composition is well established, although a recent analysis
indicated somewhat less water. This was perhaps due to some dehydration of the material which had been collected some fifty years before theanalysis was made.
Occurrence: Found in the oxidized portions of massive quartz-pyriteveins at chuquicamata and Quetena. Always found associated withhohmannite and usually with fibroferrite. Amarantite occurs along thewalls of small sulphate veins with the centers usually occupied byhohmannite and fibroferrite or in crystalline masseswithin the hohmannite. rt commonly forms in chalcanthite or pisanite and develops thecharacteristic acicular cystals in either medium. rt is less commonly associated with fibroferrite than is hohmannite. rt is clearly later than allthese minerals in period of formation. The only data on its sequence
relationships are derived from the statement by R. scharizerz that it islater in formation than copiapite. Scharizer worked with the system
FezOr-SOa-HzO
and found that when the ratio SOs/Fe2O3w&s less than
2.5 a mixture of copiapite and amarantite formed but with a ratio equal
to 2.5 only copiapite formed. Posnjak and Merwins working with the748

MARK C. BANDY

same system between the teniperatures 200oC. to 50oC. did not obtainany amarantite, and at 50ofound that copiapite formed with concentrations between 2.74 and 3.66,and below 2.69 no copiapite was formed.
There is some question regarding the state of equilibrium of Scharizer's
solutions. Posnjak and Merwin failed to find amarantite, fibroferrite andhohmannite. On the basis of these data can we assume that these threeminerals form from solutions not in eauilibrium?
Mrtohoh*)onnit,
Fez(SOr)z(OH)r.3H2OThis mineral is the dehydration product of hohmannite and has beenfound only as an orange powdery material in association with thatmineral. Analyses have been madee on this dehydrated substance, but
it has been heretofore unnamed.
The optical properties were first measured in the course of this study.
They are:a: l. fQp:pale yellow
9: 1 . 718:reddish yellow
t:l.734:reddish brown
The loss of about half the water (molecularly)
tive indices greatly over those of hohmannite.

has increased the refrac-

Rrrennxcns. 1 Scharizer,Zeits.Kri.st.,vol. 65, p. 335,1927.
2 Darapsky,N. Jb. Min., I, p.49, 1890.
3 Linck, in Hintze, vol. l, p. 4426, 1929.
a RogersAm. Mhreral.,vol. 16, p.396, 1931.The materialcalledcastaniteby Bandyand provedto be arnaranAm. Minerc!.,vol. 17, p.534,l932rhassincebeenre-examinedtite.
6 Ungemach,
Bull. Soc.Min., vol.58,p. 97, 1935.
e Analysison original material by Frenzel,Minn. Mitt., vol. 9, pp. 398 and 423, 1887;
alsoFrenzel,Min. Mitt., vol. 11, p. 215, 1890;Ungemach,1935.Analyseson "castanite"
by Darapsky, 1890,and Ungemach,1935.
7 Scharizer,in Doelter,4,2, 574,1929.
e Posnjakand Merwin, f our.Am. Chem.Soc.,vol. 44, p. 1965,1922e Mackintosh, 1889,and Ungemach,1935.
Fi.broJerrite
Fer(SO+)z(OH)r'gHrO
Fibroferrite was identified from physical and optical properties and
The color ranged fromfrom old.er analyses made at Chuquicamata.
greenish gray on fresh
a
silky
to
grayish white in eflorescent crusts

SULPHATE DEPOSITS OF NORTEERN CHILE

749

fractures of the massive mineral. The following optical properties were
determined on fresh material:
c-colorless
P-colorless
7-pale brownish yellow

n1.513
1. 5 3 5
1. 5 7 1

After a short exposure to air the mineral dehydrates into a soft incoherent mass of radiating fibers.
At Chuquicamata it is commonly associated with hohmannite andamararr-tite,being earlier than either of these minerals. In one of the more
massive occurrences, chalcanthite is a common associate but age relationships could not be determined. At Quetena it occurs as a lateeffiorescenceon the walls of workings and in cracks in some of the massive minerals.
V oltai.te
Voltaite was determined on the basis of optical properties. The
Alcaparrosa voltaite is leek-green in crushed fragments. It is isotropic
with an index of 1.608. Slight anisotropism was observed.
This is not an abundant mineral at Chuquicamata, being confinedto the areas of massive pyrite veins and commonly associated withcoquimbite. From field relations it appears to be earlier than metavoltine
although the minerals have not been observed intimately associated.
It is later than coquimbite. At Quetena it occurs massive in massivecoquimbite in the bottom of the pit. Its paragenetic relationships were
not clear. Voltaite occurs in small crystals at Alcaparrosa imbedded inpickeringite and alums.
Botryogen
MgFe"'(SOa)r(OH)' THrO
A number of minerals have been described and given speciesnamesthat have later been proved to belong to this species. There are two
reasons for this. The original and early descriptions of botryogen were
inaccurate and the descriptions and identifications of synonymous
specieswere either inaccurate or, in the caseof palacheite, more accurate
than the original description of botryogen proper.
During this study the writer has concluded that quetenite, rubrite,
idrizite, palacheite and the mineral called kubeite should all be included
under botryogen as synonyms. All of these minerals have been recognized as thus related by one writer or another. Positive identification canbe made on quetenite.

/5U

MARK C. BANDY

Crystallography:1

Monoclinic ; prismatic-Z f m
aib i c:0. 5893i | :0. 3996
F:100"01'p o :Q o : r o : o. 6 78 1: 0 . 3 9 3 51:
p: 79"59',
12:p2it12:1.4747:l .7232:lp st: 0. 6886,qo':0. 3996;*o,: 0. l7 66
Forms

6

p

ez

pz:B

b 010
a 700
e 270

0"00,
90 00
2613

90.00,
90 00
9000

0o00,
000

0000'
9000
26 t3

C
90'00,
7959
85 35+

A
90"00,
000
63 47

h
J
I

130
2sO
120

29s2+
s4 34+

9000
9000

0 00
0 00

2952+
34 s4+

8502
8420

4045

60 07;55 2s+

9000

000

4045

8329

4915

h 350
t 450
m ll0

4s 57+
s4 02+
s9 s2+

90 00
90 00
90 00

0 00
0 00
0 00

45 s7+
s4 02+
59 s2i82 4s
81 54+
8r 21

44 02+
35 s7+
30 07+

i 210
F 310
p 0ll

73+9
790s
23 50+

9000
9000
23 36

000
000
79 59

7349
7903
68 s1

8023
8010
21 29

161r
1057
80 41

s 021
P O3I
d 10r

1227+
823
90 00

39 18
5028
40 54

7959
7959
49 06

5148
4016
90 00

38 12
4944
30 53

8208+
8333
49 06

o 101
r lll
z 221

-90 0065 14
67 17+

27 04
43 s9
64 t3

11704
49 06
27 38

90 00
7s rr+
69 3s+

37 05
34 45+
55 03+

1r704
s1 11+
33 s0

n T7r
D 12t
u r3l

-51 58+
47 18
s5 sl

32 58+
49 4r
55 56

rI7 04
49 06
49 06

70 2s
58 52
47 49

41 16+
42 43+
50 30+

rri 2355 55
60 58+

w 74r
a I2r
q Ist

28 27
-32 ss+-23 0561 lt
43 2e+
s2 30

L9 06
rr7 04rL704

39 37
s+ s3i'43 08

56 4s+
49 27t56 57

65 rs+
nr 45+
10807+

r 17r
y 2rL

-1o 21-75 3570 s7+
ss 04+

rr7 04r47 rS

2r 52+
77 48

72 42+
67 48+

ss 45+
t4S r7+

crystals of botryogen were first described by Haidingerls and havebeen frequently studied by later workers. All the earry work sufferedfrom the poor quality of the crystals availabre. Eakrel, obtained thefirst reliable results on the material which he named palacheite but
which proved to be botryogen. rn this study excellent crystals of quetenite have been measured both by the author and by Dr. Berman, and75r

SULPHATE DEPOSITS OF NORTEERN CEILE

they have finally established its identity with botryogen. The results ofthese studies are contained in the table of forms observed by each, together with a column showing symbols of each known form in the newposition.
trakle

c 001
b 010
a 100

Borrovoceiv: Ossnnvrn FonMs.
Bandy
Berman
c

c

e 270
h

130

R

f 2so
I
,

120

I

I
h

350

m
i
F

2t0
310

450

m 170

n 0ll
o 021

d 20r
p lrr
s 121

nx

PalacheNew Symbol
oT01

e 270
h r30
f 2s0
I 120
h 350
t 450
m ll0
i 210
F 310

n
o
q 031

n llL
v I2l
q Ist

*. O7l
d

fr

tl L

d

d

tOl

p

p

p 01r

s

s
P I31

s 021
P 031
r lll

u 231
w 241

D 221
u
w

D l2l
w 131
w l4l

z

z

z

n
o

r

211

32t

221

Habit: Prismatic [001]; smaller crystals long prismatic, Iarge crystals
short prismatic; common forms o b m t n; vertical zone striated [001].
In the larger short crystals o is the dominant form, often striated [100].
Twinning: Not observed.
C l e a v a g e :{ 0 1 0 } p e r f e c t ; { 1 1 0 } g o o d .
Phvsical Properties: Fracture conchoidal and interrupted, brittle.

752

MAKK C. BANDY

G 2 . 1 0 , H 2 . 0 - 2 . 5 .L u s t e r v i t r e o u s .
Optical Properties: Color light to dark orange-red. Transparent totranslucent.
a:1.523
0: 1.530
t:1.582

X:b
Z1\c:

ll2"

colorless to pale brown
cinnamon browngolden yellow

Composition: MgFe",(SOr)z(OH). TH:O
Ar.rar,vsrsny HnNoBnsoN*

Biaxial positive
2Y:42"r)v strong

Turonnncer Couposrrrorl(Quetenite)
Fe:Or

19.73
9.40
38.45
32.00

Mgo
SOs
HrO

Total
100.18x U. S. National Museum.
Unpublished.

19.28
9 -64
Jd. JJ?? q?

100.00Difficultly soluble in water with precipitation of iron hydroxide. Soluble
in dilute acids.
Pyrognostics:B.B. brown to black. Exfoliates in flame. Closed tube,
yields copious water.
Occurrence: Botryogen is common at Chuquicamata intimately associated with hohmannite and amarantite. At Alcaparrosa it occurs near
the surface associatedwith copiapite in smaller veins. Botryogen is not
associatedwith the more massiveand purer occurrencesof iron sulphates.
Botryogen (quetenite) occurs at Quetena in large masses,characteristically in halos of coarse radiating crystals about a center of copiapite.
The crystals radiate outwardly from the copiapite core. Often thesenodules of copiapite-botryogen show rough cracks about the peripheries,
which often contain fibres of pickeringite. Massive veins of pickeringite
cut the botryogen in many cases.
The sequencerelationship that can be definitely established is,
Pickeringite
Botryogen
Parabutlerite
Amarantite
Hohmannite
Copiapite

MgAlz(SOa)r.22HrO
MggFez(Sor)r(oH),. 14Hro
Fe(SOa)(OH)2H:O
Fe(SOr)(oH)'3HzO
Fez(Sor)z(oH)2.THgo
Fer(SOr)s(OH)g16HrO

From these data it is apparent that the introduction of magnesia causes
a departure from the sequenceof the pure iron sulphates.The botryogen,while basic, is less basic than the parabutlerite and the pickeringite, thelast formed, is a normal sulphate.

753ST]LPHATE DEPOSITS OF NORTHERN CHILE

The relations of the various substances,all believed to be identicalwith botryogen, is brought out in the following table of analyses'
Rubrite answers the description of quetenite and, since it was identified from the analysis of an impure material, there can be little question
but that it belongs here.
The original analysis of quetenite from Quetena (Salvador Mine)5
was made on impure material, evidently a mixture of quetenite and someiron sulphate. Rubrite was described from the Rio Loa by Darapsky2
and earlier kubeite from the same locality and by the same writer'3
These are both impure mixtures of botryogen and other sulphates'
Analyses of these minerals as well as other analyses of this speciesare
quoted here for comparison. Quetenite was first recognized as a synonym of botryogen by Larsen and Bermana on the basis of similar opticalproperties. In the course of this investigation an analysis of typicalquetenite was made and it was found to be identical with botryogen.
Their crystallographic identity was also established.

Mso
FezOg
SOs
H:O
FeO
CaO
MnO
ZnO
AleOa
PzOu
Insol.
Total

MgO
FegOe
SOr
HzO
CaO
Fe(Mn)OAlzOs
Insol.
TotaI

ANer.vsnsor BornvocnN
t23456
5.69
7.3r 10.21
7.40
6.65
26.50
16.69 19.60 20.63
t8.73
3 7 . 6 4 3 7 . 0 0 3 7. 7 8 3 8 . 1 0 3 6 . 5 334.10 31.39 29.47 30.90
31.04
0.38
2.24
0 .5 32.9r
1.06
0. 4 4
1. 9 32.50
4.82
0. 2 70.30

0. 2 199.68

t00.7299.61

891011t213r+
9.40
9'35
5.gZ
19.73 19.51
22.70
38.45 33.37
37.37
32.28
32.00
34.01

100.00100.18

99.51

6.18
26.64
32.42
31.04

7
3. 5 9
20.50
40.95
30.82
4.12

2 . 730.11

98.41

102.53 99.r2

99.98

5.62
18.22
4 1' 1 5
27.64
4.10

7.8
19.3
36'4
33.7
0.1

4'51
8'70
33'94
40.80

9'95
19'81
39'48
30'76

3'01

abs'
2'7

99.84

100.0

3 ' 10
8'59
99.64

100.001-4. Botryogen, 1. Cleve,6 2. Hockauf, analyst.T 3 Mauzelius, anal'8 4' Ilngemach' anal'e
5-7. Botryogen? 5. Berzelius, ana1.106. Ungemach, anal.Lr7' Blaas, anal'D
8. Quetenite. Frenzel, anal.6 9. Quetenite. Ifenderson, U. S. Nat. Museum, unpublished
anal.

754

MARK C. BANDI/

10- Palacheite.Eakle, anal u
11. Rubrite. Darapsky, anal.2
12. Kubeite. Darapsky, anal.a
13. Idrizite. Schrauf,anal.la
14. Quetenite. Anal. of the chile Exploration co., chemical Laboratory. Through thecourtesyof O. W. Jarrell.
RnlnnrNcns. r The elementsand anglesof this table are derived from the observationsof Berman* on quetenite. They were very close to Eakle's13observationson botryogen(palacheite).Eakle's elementsgive an uns;rmmetricaldistribution of the forms and have
beenmodifed by Palacheaccordingto the transformationEakle+palache I0I/0T0/001.
2 Darapsky, N. fb. Mi,n., vol. l, p. 65,
1890.
3 Darapsky,N. fb. Min., vol. l, p. 163,1898.
a Larsenand Berman,Bull. &8, I/.S.G..S.,
1934.
5 Frenzel,M'in. Mitt., vol. ll, p. 2lT, 1890.
6 Cleve, Upsala Un. Arsskri,Jt,vol.22, 1862.
7 Hockauf, Zei.ts.Krist., vol. 12, p. 251, 1886.
8 Mauzelius,Geol,.
Far. Fdrh., voI.17, p. 311, 1g95.
e Ungemach,Bull. Soc.Fr. Mi.n.,
vol. 52, p.97, 1935.
10Berzelius,Afh. i.. Fys.,vol. 4, p.
302, 1815.
11Ungemach,Bull,. Soc.Fr. Mi,n., vol,'2g, p. 271, 1906.
D Blaas,Si,tzber.Wiener
Ak., I Abt., vol.8, pp.8Z, 161,1883.
13Eakle, Bull.. Univ. Cali.f., vol. 3, p.231, 1903.
la Schrauf,Jb. iI. geol.R. A. Wien, vol.
41, p. 379, 1891,
6 Haidinger, Pogg.,vol. 12, p. 491, 1828.
16Berman, Unpublisheddata on botryogen (quetenite).
AluniteAlunite occurs at Chuquicamata as a supergene vein mineral and in
the oxidized gossans of the larger pyrite veins. rt commonly shows thecharacteristic "hopper structure." rn veins associated with antlerite it isthe earlier mineral. rn the oxidized gossans it was only observed alteredto jarosite. The writer was never able to separate the mineral in order todetermine whether it was the potassium oisodium

variety of alunite.

Janosrrr Gnour
andnatrojarosite
are relatively common minerals in all of
Jarositethese deposits. They are late minerars as a rure and serve welr as kev
minerals for the later part of the mineral sequence.
J orosite
KFes(so4)r(oH)6Jarosite is common at Chuquicamata in fibrous and massive aggregates and in minute tabular crystals. It occurs throughout the deposit
but is most common in massive form in the central part. A micaceous
variety with the external appearance of argento-jarosite was known as

SULPHATE DEPOSITS OF NORTEERN CHILE

apatelitel locally. The jarosite at Chuquicamata carries a small but variable percentage of silver as a rule and argento-jarosite may be a raremineral of the deposit. All of the jarosite examined in this study waseither the potassium or sodium variety. A rare form of jarosite is avariety pseudomorphic after either alunite or natroalunite. The jarosite
has replaced the alunite, preserving the "hopper crystal', structure of
the original mineral. The jarosite shows an average index, n:1.816.
Jarosite occurs in minute crystals and crystalline and granular crystals
at Quetena and Alcaparrosa. The mineral has an index ru: 1.818 at both
places. The jarosite at Alcaparrosa commonly shows under the microscopea slight divergence of the optic axes.
Jarosite commonly forms at the end of the iron sulphate period andbefore the copper sulphate period. Reversals of this order were recorded
during the study, but the sequence relationships were not always
definite.
Rarer-BNcn. 1 Meillet, Ann. d.esM,ines, vol.3, p. 808, 1841.

N atr oj arosite
NaFe3(SO),(OH)6
The tiny brilliant cinnamon brown crystals of natrojarosite at Chuquicamata afiorded an opportunity to study the crystallography, andespecially the twinning of this species.An explanation of the previously
noted anomalous optical behavior is given, and other new data arehere presented.
Crystallography:
Orthorhombic(Pseudorhombohedral)

a:b:c:l .732:l:2.252
g:rti fu:lpo:Qo:rs:1.300:2.252:l. 73 2 : 0 . 7 6 9 : l

Forms
p:C
6
c 001
0"00'
m ll0*
60o00'
90 00
u l0l
9000
5226
* Noted only as a twin plane.
Form
a

l0l

r z :p 2 : q 2 : O. 4 4 4 : 0 . 5 7 7: l

et
0o00,
90 00
000
Measured
No. of Faces29

n:A
90.00,
60 00
3734

,k
90.00/
0 00
3734

Range
p

52"06'-52"57'

Habit: Commonly in cuboid trillings; common Iormsi c, u.
Twins: In trillings; twin plane (110).

Pz:B

90"00'
30 00
90 00

756

MARK C. BANDT/

LusterPhysical properties: Fracture conchoidal, brittle; H:3.
vitreous.
Optical properties: Color, cinnamon brown. Basal section divided into
three biaxial segments. Biaxial negative, 2V small; B:I.826. X:c;
Y:a.
The first observation that natrojarosite was not uniaxial, and that it
was made up of biaxial segments,was on material from Schlaggenwald.l
Later2 the same optical effects were noted on specimensfrom Buxton
Mine, North Dakota. The same effect, but less distinct, has been notedon other members of the jarosite group.3

Frc. 7. Sketch showing optical orientation in the orthorhombic
trillings of natrojarosite.

The optical orientation on the various segments is illustrated inFig. 7, where X emergessensibly normal to each of the (001) faces, thelatler being co-planesin the twin. The plane of the optic axes is parallel,in each case, to (100). Under these circumstances,the smaller 2V is, themore difficult it becomes to recognize t]ne segmentation of the twins,
for, if 2V:0, no birefringence would be noted and the twinning could
not be detected.und.er the microscope. The potassium members of thegroup have presumably a smaller 2V because the efiect is less marked
than in natrojarosite, and the Chuquicamata natrojarosite exhibits thetwinning best becauseit is the most sodic of any yet found'a
Chemistry: A basic sodium ferric sulphate, NaFe3(SOa)z(OH)0,withsmall amounts of potassium sometimes substituting for the sodium.

SULPEATE DEPOSITS OF NORTHERN CHILE

NazO
KrO
FezOa
SOs
HzO
Total

lJl

ANar-vsrssv F. A Gexven
Molecular Ratios
Per Cent
1X.091.091
5. 5 1
0 .1 5
3X.101.302
48.08
4X .108. +JJ
34.65
6X.110.659
1 1. 8 3
t00.22

Occurrence: The mineral was first described,5but not named, fromthe Buxton Mine, Lawrence County, North Dakota. Latero it was foundat Soda Springs Valley, Nevada, and at Cook's Peak, New Mexico, andwas given the name natrojarosite.
At Chuquicamata natrojarosite is associated with chalcanthite,kroehnkite and sulphur. It is a late mineral, forming after most of theiron sulphates and before most of the copper sulphates.
RBlnrcNcns.l Slavik,Zeits.Krdst.,vol. 39, p.297,1904,statedthat the natrojarosite
showed six segments in the basal section, and that the axial plane is (010). These data are
not in agreement with the writer's.
2 Cesaro, Bull, Ak. Roy. Bel'ge, 138, 1905.
3 Larsen and Berman, BulI, 848, U . S. Geol,.Suney, 1934.
aFor other analyses see Hillebrand and Penfield Am. J. Sc., vol. 14, p.2ll,
1902;
also Dana, System, Ap.IIL
6 Headden, Am. l. Sc., vol. 46, p.24, 1893.
6 Hillebrand and Penfield, Am. f . Sc., vol. 14, p.2lI,
1902.

Ungemachite
1OHgO
NaeKaFe(SO4)6.
This mineral, discovered in the course of this investigation, has been
described in detail by Peacock and Bandy in a recent paper.l The
following abstract of properties is taken from that paper.
Crystallography: Hexagonal, rhombohedral-3. a:c: l;2.2966, a:
6 2 "5 l | ' ; p o ir o: 2 . 6 5 t 9: 1 , ' y : 1 0 8 ' 1 5 * ' .
Forms: Numerous, the habit dominantly rhombohedralwith r(1011),
M(0112), p(1123), and the base c(0001).
Structure cell: Rhombohedral: oo: 10.84t 0.02A, co:24.82+ 0.03A.
10HrO.
ao:c0: l:2.290. Contains NaeIGFe(SOa)G.
Cleavage: Perfect, basal.
P h y s i c a lp r o p e r t i e s :H : 2 + . G : 2 . 2 8 7 * . 0 0 3 ( B e r m a n ) .
Optical properties: Colorless, transparent. Uniaxial negative. @:1 . 5 0 2 e, : 1 . 4 4 9 .
Chemical composition:

758

MARK C. BANDY
Ar.rar,vsrs sv F. A. GoNvBn
21.61
NazO
KzO
II.JJ
Fezoa
7. 6 9
40.23
SOg
HzO
16.69
tr.
NzOa
Insol.
2.07

99.64

TotaI

Composition as written above is not homologous with any known
natural or artificial salt.
Occurrence: Ungemachite occurs in granular vein fillings and lining
small vugs in massive jarosite and metasideronatrite. The mineral isvery scarce in the material collected. The name is in honor of the late
Henri Ungemach, mineralogist of Strasbourg.
RnlnnnNcr.

1 Peacock and Bandy, Am. Minerotr.,vol.23rp.314,

1938.

Clino-Ungemachite
Clino-ungemachitel is a monoclinic mineral closely similar in appearance and occurrence to ungemachite from which it was distinguishedonly by goniometric measurements.The divergenceof anglesfrom rhombohedral symmetry is slight, and it is presumed that the composition ofthis substance is close to that of ungemachite. But as only six minutecrystals were found its nature is still uncertain.
Rrlnnoxcn.

I Peacock and Bandy, Am. Minerol., vol.23, p. 314, 1938.

Mot vslarE
Li.ndgrenite
Cus(MoOa)z(OH)z
Lindgrenitel is monoclinic, holohedral. a: b : c : 0.5941: t : o.5124; 0 :92"12'. The crystals are green and transparent, tabular parallel to (010),
w h i c h i s a p e r f e c t c l e a v a g e .U n i t c e l l : a o : 8 . 4 5 , b o : 1 4 . 0 3 , c o : 7 . 4 4 ;. :4+. G:4.26. Biaxial negaB : 9 2 t " ; c o n t a i n i n gC u u ( M o O 4 ) 8 ( O H ) rH
tive;Z:b; X:6,:*7". a:I.930, 9:2.002, 7:2.020; 2Y:7t"; rta.
Analysis: CrO 40.62, MoO: 50.97, H2O 3.30, FerOr 1.43, Insol. 3.34;
Sum 99.66; giving the above formula. Soluble in HCI and in HNOa.
This unusual mineral, the first known molybdate of copper was colIected by the writer during his residence at Chuquicamata. It occurs
associatedwith antlerite and iron oxide in massive qrartz veins on thewestern side of the deposit. The mineral is rather common, although fine

759

SULPHATE DEPOSITS OF NORTHERN CHILE

crystallized specimensare rare. It occurs along the edges of the larger
qrartz veins. In this connection it is possibly significant that the molybdenum in the smaller "lacing veinlets" of. quarLz occurs along or near
the edges of the veins. Antlerite follows the lindgrenite and replaces it.
RnntnaNcn.

l Palache, Am. Mineral., vol. 20, p 484. 1935.

INpBx oF MTNERAL Specrps
Alunite....
Amarantite.
Anhydrite.
Antlerite.
Antofagastite.
Arsenopyrite.
Atacamite.
Azurite.

..

Page
754
747
712
7l3
705
703
706
710

Page

Halite. .
Halotrichite.
Hematite.
Hohmannite.

704
728
708

Jarosite.

754

Cerussite.....
Chalcanthite.....
Chalcocite.
...
Chalcopyrite.
Chenevixite.
Chrysocolla.
Clino-ungemachite..
Copiapite.. .. . ..
Copper.
CopperPitch.
Coquirnbite. . .
Covellite.
Cuprite.
Cuprocopiapite

Kalinite.
Kroehnkite.
704
719
702 Lapparentite.. ..
749 Leightonite.
713 Limonite.
Lindgrenite709
7 1 8 Magnetite . .. .
701 Malachite.
702 Melanterite. . .
711 Mendozite.
710 Metahohmannite. .. . .
758 Metasideronatrite. .
737 Metavoltine
699 Mirabilite .
708 Molybdenite
729
701
Natrochalcite.
707
Natrojarosite.
737

Dolomite

709

Bandylite.
Bloedite.....
BorniteBotryogen.
Brochantite

Enargite
Epsomite.
Ferrinatrite.
Fibroferrite.
Gold. . .
Gypsum.

..

..

.

703
717
731
748
700
7I7

t+o

.........

721
730
74O
719
709
758
708
709

7r7
722
748
/JJ

735
714
700
731
755

Opal...

707

Parabutlerite
Paracoquimbite
Pickeringite.
Picromerite
Pisanite.
Pyrite.....

742
729
724
719
718
7O2

Quenstedtite.

739

760

MARK C, BANDY

Rhomboclase
Roemerite.

740
734

SodaNiter
Sphalerite.
S p h e n e..... . .
Sulphur
Szomolnokite.

712
7OL
7ll
IIlexite.
699 Ungemachite.
714

Tamarugite..

723

Tetrahedrite.
Thenardite.
Tourmaline. . . .
Turquois.

VoItaite.

712

7r0
7tr
712
757
749