DEPARTMENT OF THE INTERIOR

BULLETIN

OF THE

UNITED STATES

GEOLOGICAL SURVEY

No. 13

A CRYSTALLOGRAPHIC STUDY OF THE THINOLITE OF 

LAKE LAHONTAN.

WASHINGTON

GOVERNMENT PRINTING OFFICE

1884

A.3DVBRTISBMBNT.

(Bulletin No. 12.)

The publications of the United States Geological Survey are issued in accordance with the statute 

approved March 3,1879, which declares that 

" The publications of the Geological Survey shall consist of the annual report of operations, geo-. 

logical and economic maps illustrating the resources and classifications of the lands, and reports upon 

general and economic geology and paleontology. The annual report of operations of the Geological 

Survey shall accompany the annual report of the Secretary o the Interior. AU special memoirs and 

reports of said Survey shall be issued in uniform quarto series if deemed necessary by the Director, 

but otherwise in ordinary octavos. Three thousand copies of each shall be p'ablished for scientific 

exchanges and for sale at the price of publication; and all literary and cartographic materials received 

in exchange shall be the property of the United States and form a part of the library of the organization. And the money resulting from the sale of such publications shall be covered into the Treasury of the United States." . On July 7, 1882, the following joint resolution, referring to all Government publications, was passed 

by Congress:

1 ' That whenever any document or report shall be ordered printed by Congress, there shall be printed, 

in addition to the number in each case stated; the " usual number " (1,900) of copies for binding and 

distribution among those entitled to receive them."

Under these general laws it will be seen that none of the Survey publications are furnished to it for 

gratuitous distribution. The 3,000 copies of the Annual^Beport are distributed through the documentrooms of Congress. The 1,900 copies of each of the publications are distributed to the officers, of the 

legislative and executive departments, and to stated depositories throughout the United States.

Except, therefore, in those cases where an extra number of any publication is supplied to this office by 

special resolution of Congress, as has been done in the case of the second, third, fourth and fifth Annual 

Beports, or where a number has been ordered for its use by the Secretary of the Interior, as in the case 

of "Williams's Mineral Eesources, the Survey has no copies of any of its publications for gratuitous distribution.

ANNUAL REPORTS.

Of the Annual Keports there have been already published:

X First Annual Eeport to the Hon. Carl Schnrz, by Clarence King. 1880. 8°. 79 pp. 1 map. A 

preliminary report describing plan of organization and publications. 

H. Eeport of the Director of the United States Geological Survey for 1880-'81, by J. W. Powell.

1882. 8°. Iv, 588 pp. 61 pi., 1 map. 

m. Third Annual Eeport of the United States Geological Survey, 1881-'82, by J. W. Powell.

1883. 8°. xviii, 564 pp. 67 pi. and maps. , l 

IV. Fourth Annual Eeport of the United States Geological Survey, 1882^83, by J. W. Powell.

1884. 8°. xii, 473 pp. 85 pi. and maps. ) 

The Fifth Annual Keport is in press. '.

MONOGRAPHS.

So far as already determined upon, the list of the Monographs is as follows: 

I. The Precious Metals, by Clarence King. In preparation.

n. Tertiary History of the Grand Canon District, with atlas, by Capt. C. E. Dutton. Published, 

m. Geology of the Comstock Lode and Washoe District, with atlas, by George F. Beoker. Published. 

TV. Comstock Mining and'Miners, by Eliot Lord. Published.

V. Copper-bearing Books of Lake Superior, by Prof. E. D. Irving. Published.

VI. Older Mesozoic Flora of Virginia, by Prof. William M. Fontaine. Published.

VII. Silver-lead Deposits of Eureka, Nevada, by Joseph S. Curtis. Published. 

VLtr. Paleontology of the Eureka District, Nevada, by Charles D. "Walcott. In press. 

IX. Brachiopoda and Lamellibranchiata of the Earitan Clays and Green sand Marls of New Jersey, 

by E. P. Whitfield. In press.
ADVERTISEMENT.

Geology and Mining Industry of Leadville, with atlas, by S. F. Bmmons. In preparation.

Geology of the Eureka Mining District, Nevada, with atlas, by Arnold Hague. In preparation.

Lake Bonneville, by G. K. Gilbert. In preparation.

Dinocerata: A Monograph on an Extinct Order of Ungulates, by Prof. 0. C. Marsh. In preparation.

Sauropoda, by Prof. 0. C. Marsh. In preparation.

Stegosauria, by Prof. 0. C. Marsh. In preparation.

Of these Monographs, Nos. II, III, IV, V, VI, and VII are now published, viz:

II. Tertiary History of the Grand Canon District, with atlas, by C. E. Dutton, Capt. IT. S. A. 1882. 

4°. 264 pp. 42 pi. and atlas of 26 double sheets folio. Price, $10.12.

HI. Geology of the Comstock Lode and Washoe District, with atlas, by G. F. Beoker. 1882. 4°. 

xv, 422 pp. 7 pi. and atlas of 21 sheets folio. Price, $11.

IV. Comstock Mining and Miners, by Eliot Lord. 1883. 4°. xiv, 451pp. 3 pi. Price, $1.50.

V. Copper-bearing Rocks of Lake Superior, by Prof. R. D. Irving. 1883. 4°. xvi, 464 pp. 29 pi. 

Price, $1.85.

VI. Contributions to the Knowledge of the Older Mesozoio Flora of Virginia, by William M. Fontaine. 

1883. 4°. xix, 128 pp. 54 11., 54 pi. Price, $1.05.

VLI. Silver-lead Deposits of Eureka, Nevada, by Joseph S. Curtis. 1884. 4°. xii, 200 pp. 15 pi. 

Price, $1.20.

Nos. VILT and IX are in press and will soon appear. The others, to which numbers are not assigned, 

are in preparation.

BULLETINS.

The Bulletins of the Survey will contain such papers relating to the general purpose of its work as 

do not properly come under the heads of ANNUAL REPORTS or MONOGRAPHS.

Each of these Bulletins will contain but one paper, and be complete in itself. They will, however, 

be numbered in a continuous series, and will in time be united into volumes of convenient size. To 

facilitate this each Bulletin will have two paginations, one proper to itself and another which belongs to it as part of the volume.

Of this series of Bulletins Nos. 1,2,3,4,5,6,7,8,9,10,11, and 12 are already published, viz:

1. Ou Hypersthene-Andesite and on Triclinic Pyroxene in Augitic Rocks, by Whitman Cross, with 

& Geological Sketch of Buffalo Peaks, Colorado, by S. F. Emmons. 1883. 8°. 42 pp. 2 pi. Price, 10 

cents.

2. Gold and Silver Conversion Tables, giving, the Coining Value of Troy Ounces of Fine Metal, &c.,by 

Albert Williams, jr. 1883. 8°. ii, 8 pp. Price, 5 cents.

3. On the Fossil Faunas of the Upper Devonian along the Meridian of 76° 30', from Tompkins County, 

New York, to Bradford County, Pennsylvania, by Henry S.Williams. 1884. 8°. 36pp. Price, 5 cents.

4. On Mesozoic Fossils, by Charles A. White. 1884. 8°. 36 pp. 9 pi. Price, 5 cents.

5. A Dictionary of Altitudes in the United States, compiled by Henry Gannett. 1884. 8°. 325pp. 

Price, 20 cents.

6. Elevations in the Dominion of Canada, by J. W. Spencer. 1884. 8°. 43 pp. Price, 5 cents.

7. Mapoteca Geologica Americana. A Catalogue of Geological Maps of America (North and South), 

17524881, by JulesMarcou and John BelknapMarcou. 1884. 8°. 184pp. Price, 10 cents.

8. On Secondary Enlargements of Mineral Fragments in Certain Rocks, by R. D. Irving and C. R. 

Vanhise. 1884. 8°. 56 pp. Price 10 cents.

9. A Report of the Work done in the Washington Laboratory during the fiscal year 1883-'84. F. W. 

Clarke, chief chemist; T. M. Chatard, assistant. 1884. 8°. 40pp. Price 5 cents.

10. On the Cambrian Faunas of North America. Preliminary studies by Charles Doolittle Walcott. 

1884. 8° 74pp. Price 5 cents.

11. On the Quaternary and Recent Mollusca of the Great Basin; with Descriptions of New Forms, by 

R. Ellsworth.Call; introduced by a sketch of the Quaternary Lakes of the Great Basin, by G. K. 

Gilbert. 1884. 8°. 66 pp. Price, 5 cents.

12. A Crystallographic Study of the Thinolite of Lake Lahontan, by Edward S. Dana. 1884. 8°. 

34 pp. Price, 5 cents.

STATISTICAL PAPERS.

A fourth series of publications, having special reference to the mineral resources of the United 

States, is contemplated. Of that series the first has been published, viz: Mineral Resources of the 

United States, by Albert Williams, jr. 1883. 8°. xvii, 813 pp. Price, 50 cents.

Correspondence relating to the publications of the Survey, and all remittances, which must be by 

postal note or money-order, should be addressed to the

DIRECTOR OP THE UNITED STATES GEOLOGICAL SURVEY,

Washington, D. 0. 

WASHINGTON, D. C., September 30,1884.
DEPARTMENT OP THE INTERIOB

BULLETIN

OF THE

UNITED STATES

GEOLOGICAL SURVEY

No. 13

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1884
U. S. GEOLOGICAL SURVEY BULLETIN NO. 12 PL. I

THINOLITE.
UNITED STATES GEOLOGICAL SURVEY

J. W. POWELL DIRECTOR

A.

CRYSTALLOGRAPHY STUDY

OF THE

THINOLITE OF LAKE LAHONTAN

BY

EDWARD S. DANA

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1884
LETTER OF TRANSMITTAL.

'UNITED STATES GEOLOGICAL SURVEY,

DIVISION OF THE GREAT BASIN,

Washington, Z>. (7., September 16, 1884.

SIR: I have the honor to transmit herewith, for publication, a paper 

on Thinolite, by Prof. Edward S. Dana, of New Haven.

The calcareous pseudomorph to which Mr, Clarence King gave the 

name "thinolite" has been referred by him and others to the mineral 

gaylussite, and the history of its conversion to calcite was believed to 

afford the key to the history of the oscillations of Lake Lahontan. Mr. 

Eussell's later and fuller investigations demonstrated the physical impossibility of the lake-history deduced by Eing, and the question of the' 

origin of the thinolite was thus reopened. Mr. Eussell determined its 

distribution and geologic relations in a thorough and satisfactory manner, but his acquaintance with mineralogy did not permit him to undertake the necessary crystallographic study with confidence.

Application was accordingly made to Profs. George J. Brush and E. 

S. Dana, and the study of the mineral was finally undertaken by the 

latter gentleman. His report, which is eminently judicial and conservative, does not contain a complete solution of the problem; but it clears 

the ground by dissipating all earlier hypotheses, and indicates the line 

of future investigation. It renders to the geologic study the important 

service of freeing it from the embarrassment occasioned by the gaylussite hypothesis. 

1 remain, with great respect, your obedient servant,

G. K. GILBERT,

Geologist in Charge. 

Hon. J. W. POWELL,

Director United States Geological Survey.

(425) 5

CONTENTS.

Letter of Transmittal.......................................................

Introductory statement .....................................................

Varieties of tufa......................................................

Succession of tufa deposits ............................................

Crystallographic study ......................................................

General aspect of the thinolite ... .....................................

Thinolite from Pyramid Lake.......................................... 15

Examination of sections of crystals .................................... 17

Thinolite from Mono Lake..........................'................... 19

Thinolite from Walker Lake and from Black Rock and Smoke Creek 

Deserts .............................. ................................ 20

Original crystalline form of the thinolite..................................... 20

Chemical nature of the original mineral...................................... 22

Eolation of the thinolite to the so-called Gaylussite pseudomorphs of Sangerhansen and other localities................................................. 25

ILLUSTRATIONS.

PLATE I. A characteristic specimen of thinolite ........................... 3

II. Illustrations of the structure of 'thinolite........................ 32

III. Illustrations of the structure of .thinolite ........................ 34

FIG. 1. Diagrammatic section, illustrating the relation of the tufas........... 11

(427) 7

A CRYSTALLOGRAPHIC STUDY OF THE THINOLITE 

OF LAKE LAHONTAN.

BY EDWARD S. DANA.

INTRODUCTORY STATEMENT.

Origin of the name Thinolite. The name Lake Lahontan was given 

by Mr. Clarence King to the great Quaternary lake of northwestern; 

Nevada, of which the present Walker, Carson, Humboldt, Winnenmcca, 

Pyramid and Honey lakes are the relics. The extent of Lake Lahoutan 

was first mapped out by Mr. King, and a description of it and of its history 

is given in his report.1 As shown by him, the characteristic feature of 

the Lahontan Basin is the great abundance in it of deposits of calcareous 

tufa. Of this he says :2

"As compared with Lake Bonneville, the chief characteristic difference 

in the phenomena of terraces and shore lines is the great abundance in 

the Lahontau Basin of calcareous tufas. Modern subaerial gravels have 

been in great measure washed down over the calcareous matter, but it 

frequently exists even in the broad bottom of the lake in thick accumu. 

lations covering areas of several miles with a tufaceous deposit from 

20 to 60'feet thick. As will be seen later, this tufa is of very great 

chemical interest, and its mineralogical nature affords a clew to the 

history of the lake. From its very great importance and its peculiar 

origin, 1 have taken the liberty of giving it a lithological name. Since 

it formed on the shores of the lake, I have called it, from the Greek ®{$ 

(shore), Thinolite." . . The occurrence and characters of this tufa are described in consider, 

able detail by Mr. King, and its general appearance is well shown in 

several plates in his report. Mr. King also discusses the condition of 

the formation of the calcareous tufa, and offers an explanation of its 

origin, to which reference will be made later.

'Clarence King: Report of the Geological Exploration of the Fortieth Parallel, VoL 

I, p. 488, et seq., 1878. 

*Loc. tit., p. 508.

(429) ' 9
10 THINOLITE OF LAKE LAHONTAN. luuLL.12.

VARIETIES OF TUFA.

The Lahontan Basin has recently been studied by Mr. I. 0. Eussell, 

and a preliminary sketch of its geological history was published in 

1883, embodying the results of a reconnaissance in the season of 1881.3 

A complete report, embracing the results of later observations, is now in 

preparation.

Mr. Eussell has mapped with great completeness the geographic 

extent of Lake Lahontan, and has traced out the topography of its shores 

at the different stages in its history. With respect to the calcareous 

deposits, he has been led to discriminate between three distinct varieties, 

superimposed upon each other, to which he gives the names litlioid, 

thinoUtic, and dendritic. The following points with regard-to them are 

taken nearly verbatim from his report.

The lithoid tufa was the first formed tufa deposit; it is found on the 

slopes of the basin from the level of the lithoid terrace, which is 30 feet 

below the highest water line of Lake Lahontan, downward as far as any 

sections are now exposed. This variety of tufa is usually gray in color 

and compact in structure; it occasionally shows concentric bands and 

open spaces, but is much more dense and stone-like than the varieties 

deposited later.

The thinolitic tufa forms the second layer, and was deposited at a 

lower stage of the water. Its upper limit on the sides of the basin is the 

thinolite terrace, which is 400 feet lower than the lithoid terrace just 

alluded to, and 1.00 feet above the present level (1881) of Pyramid Lake. 

A minoj.' deposit probably also occurred (as noted in a subsequent paragraph) after the formation of the dendritic tufa. This second variety 

of tufa, to which- the name thinolite is now restricted, is characterized 

by the fact that it consists of groups of distinct prismatic or pyramidal 

crystals, as will be described later. In the Lahontan Basin the thinolite 

is best developed about the base of the Marble Buttes, at the south end 

of Pyramid Lake; at the Needles, at the northern end; and at the 

Domes, and around the lower portions of Anaho and Pyramid islands, 

in the same lake. It occurs all along the borders of Winnemucca Lake, 

and less abundantly on Smoke Creek and Black Bock deserts. These 

deserts form a single basin, separated from the valley of Pyramid Lake 

by a low divide. It is found also along the borders of Carson Desert, 

-and at a single locality in Walker Lake Valley. Outside of the Lahontan Basin it occurs in the basin of Mono Lake, in California. The 

deposits of thinolite are of very considerable magnitude; where best 

exposed the layer of interlaced crystals has a thickness of from 6 to 8 

feet, and exhibits concentric zones of larger and smaller crystals.

3 1. C. Russell: Sketch of the Geological History of Lake Lahontan, a Quaternary 

lake of northwestern Nevada. Washington, 1883. (Department of the Interior, U. 8. 

'Geological Survey, J. W. Powell Director.)

(430)
DANA.) SUCCESSION OF TUFA DEPOSITS. 11

The dendritic tufa is the third variety of calcareous deposit in the 

Lahont'an Basin. Its upper limit is about 200 feet below the highest 

water line, and from this level it coats the sides of the basin wherever 

the conditions were favorable. It is by far the most abundant of the 

three kinds of tufa, and in places attains a great thickness. Its greatest 

depth is not less than 20 feet, and may be as much as 50 feet. This kind 

of tufa is characterized by its distinct dendritic structure. It occurs 

over large portions of the bottom of the old lake, forming mushroomshaped masses of all sizes up to 5 or 6 feet in diameter; in some places 

they make a pavement of blocks 2 feet in diameter, resting on the lake 

beds.

SUCCESSION OF TUFA DEPOSITS.

As has already been intimated, Mr. Eussell has found that the three

varieties of tufa succeeded each other in the order named above. Later 

observations have shown, as he has informed the writer, the probable existence of a second deposit of thinolite crystals, not exceeding 4 or 5 

inches in thickness, which followed the precipitation of the dendritic tufa. 

The succession of the three prominent deposits of tufa in their relation 

to each other and the sides of the basin is illustrated by Mr. Eussell by 

the accompanying figure. With his permission I insert this figure, and 

also quote two or three pages from his preliminary report descriptive 

of the succession of tufa deposits, their chemical composition, and general method of occurrence (pp. 215 to 218):

"The accompanying diagram, Fig. 48 [Fig. 1 of this publication], 

gives a generalized expression of the relation of the three successive

FIG. 1. Diagrammatic section illustrating the relations of the tufas.

tufas to each other and to the sides of the basin. The first formed deposit, the lithoid tufa, represented in the notation of the diagram by 

vertical lines, extends upward about 500 feet above the horizontal 

lake beds occupying the bottom of the basin. The second deposit, the 

thinolitic tufa, finds its upper limit 100 feet above the present level of 

Pyramid Lake. The third and last, the dendritic tufa, which is far

(431)
12 THINOLITE OF LAKE LAHONTAN. [BULL. 12.

more abundant than either of the others, extends upward to within 

about 200 feet of the highest shore line. The lower limits of these deposits cannot be determined with certainty, as they are concealed by 

lake beds.

" Chemical analyses were made by Prof. O. D. Alien of samples of each 

of these varieties of tufa, and the results, given below, show that their 

constituents are practically identical. The insoluble residue exhibited 

in each case may be due in part to foreign matter imprisoned in the tufa 

at the time of its formation, and is certainly due in a measure to foreign 

matter carried by atmospheric agencies into open cavities of the rock 

after the desiccation of the lake.

Constituents.

Water (HnO).. .......................................

Lithoid tufa.

1.70

50.48

2.68

.25

41.85

2.07

.30

TVflpA

99.53

Thinolitic tufa.

3.88

50.45

1.37

.71

40.90

1.50

98.81

Dendritic tufa.

5.0ft

49. 14)

1.99

1.29»

40.31

2.01

T^Tft/^A

np-portrt

99.80-

" Hot only do these tufa deposits still sheathe the slopes of the Lahontan Basin, but they appear also in isolated, castellated masses and rugged 

crags about the shores of Pyramid and Winnemucca Lakes and on theborders of the Carson Desert. These outstanding masses occur characteristically as upright cylinders, or groups of cylinders, with roundedr 

dome-shaped tops, and are of all sizes, from a few inches up to a hundred feet or more in height. The larger masses are composed of groupsof many tower-like, cylindric bodies of unequal height, and bear a striking resemblance to rugged mediaeval castles with rounded towers and 

castellated battlements. A fine example of such a water-built castle 

stands about the middle of the western shore of Pyramid Lake, and 

rises 100 feet above the waves that wash its base. The domes between 

the eastern shore of the lake and Pyramid Island are the tops of similar 

towers, the foundations of which are deeply submerged. Other masses 

of the same nature, but smaller in size and usually broken and weathered, occur in abundance. Frequently these outstanding cylinders and 

castles of tufa are broken across, or split from base to summit, so as to 

reveal every desired section of their interiors. An examination of a 

large number of these dissected masses brought to light the interesting fact that all the tufa crags below the broad terrace 100 feet above 

Pyramid Lake the thinolite terrace have a tripartite structure, and 

all above that horizon have a bipartite structure.

" Each of the tufa towers below the thinolite terrace has a core of compact gray tufa in all respects identical with the first-formed sheath of 

tufa on the rocky sides of the basin. This core of lithoid tafa is com-

(432)
DAKA.J SUCCESSION OF TUFA DEPOSITS. 13

monly from 2 to 6 feet in diameter, and sometimes shows a tubular 

structure. When the base is exposed it is occasionally seen to spring 

from a small nucleus of rock.

"Outside the core of gray tufa is a coating of thinolite crystals, from 

2 to 6 or 8 feet thick, that completely envelops its sides and top. These 

crystals are interlaced in every direction, but show a radial grouping, 

and also a concentric banded structure zones of elongated prisms 

alternating with narrow bands of smaller crystals. The largest crystals are from 6 to 10 inches in length and an inch or more in diameter. 

This layer of thinolite is best displayed in the masses of tufa that occur 

low down near the surface of Pyramid Lake. The deposit is there 

thickest and the crystals are largest.

"About the layer of thinolite, and in turn completely covering it, is a 

third tufa deposit, equal to or even exceeding in thickness either of the 

previous layers. It usually arches over the top of the column in a low 

dome. This third layer is of dendritic tufa, and always shows the characteristic branching structure, resembling a group of cedar boughs 

changed to stone.

"Frequently the dome-shaped summits of these tufa towers are 

weathered into holes, and sometimes the entire top is dissolved away 

down to the layer of thinolite crystals, or even deeper. In the hollows 

thus formed, which are frequently 10 or 12 feet in diameter, a person 

can stand as on the top of a wide tower, with a parapet of dendritic 

tufa 3 or 4 feet high all about him. On the west side of Winnemucca 

Lake, near the southern end, there stands a tufa tower, fully 40 feet 

high, that has been split from base to summit into three sections, the 

open fractures being wide enough for a person to pass through. In 

remembrance of Heidelberg, I have called this the 'Kent Tower.' The 

whole of this tower is composed of tufa, the nucleus from which it 

started being.some distance below the surface of the surrounding lake 

beds and gravels. It stands just above the level of the thinolite terrace, 

and is composed entirely of lithoid and dendritic tufa, the middle or 

thinolitic member being wanting. Near at hand, and a few feet below 

the horizon of the thiuolite terrace, are other dome-shaped masses, showing the intermediate thinolite also.

"While the isolated tufa towers having thinolite as a middle member 

are confined to the shores of Pyramid and Winnemucca Lakes and to 

the borders of the Carson Desert, the similar masses in which the thinolite is wanting occur over a much wider area, especially along the borders of the Black Rock Desert. Examples may also be seen along the 

line" of the Central Pacific Railroad southeast of Humboldt Lake.

"In some cases, where the lake beds and gravel have been washed 

away from the base of a tufa tower, we find the outer layer of dendritic 

tufa projecting as an irregular shoulder about the lower part of the column, thus showing how much of the column projected above the bottom 

of the lake at the time, the dendritic layer was added. In one instance,

(433)
14 THINOLITE OF LAKE LAHONTAN. IBULL. la.

where the entire mass has been uprooted, the layer of thinolitic crystals 

. extends about 2 feet lower down than the coating of dendritic tufa, and 

then terminates in the same abrupt manner. In this case the central 

core of lithoid tufa ends in a tapering, irregular base, the nucleus of 

which is a group of small pebbles.

"One of the physical conditions favorable, if not absolutely necessary, 

for the formation of tufa seems to be the presence of a solid nucleus 

about which the carbonate of lime can commence to crystallize. Thisnucleus may be a pebble resting at the bottom of the lake or it may be 

the solid cliff that forms the shore. It plays the same rdle here as it 

does in the crystallization of alum or rock candy in a laboratory experiment, or as may be seen in the structure of oolitic sand. The crystallization once started, the process was continued until hundreds and 

even thousands of tons had formed in a single isolated mass. Where 

the ( shores are too steep and solid for the ready formation of terraces 

and embankments of gravel, they favor the deposition of tufa. In such 

places the chemical deposit cannot be disturbed or carried away by the 

shore drift. The most favorable places of all for the accumulation of 

calcareous deposits are rocky islands. Tufa frequently cements the 

gravel and sand of which embankments are constructed, and sometimes 

forms a complete pavement on their surfaces. This happens when by 

a rise of the lake the surface of the embankment is so far submerged as 

to escape the action of the shore drift. Tufa has never been observed 

by the writer resting on beds of fine clay or silt unless there were pebbles for nuclei. In many'instances every pebble on a surface of fine 

lake beds has its upper surface coated with tufa, or perhaps supportsa mushroom-shaped growth some inches in height, while the surrounding plain of fine mud is entirely free from calcareous deposit."

CRYSTALLOGRAPHIC STUDY.

The introductory statements which have been made will have servedl 

to give a sufficiently clear idea of the general relations of the calcareoustufas of the Lahontan basin, as established by the labors of Mr. Eussell. 

The immediate object of the present writer is to state the results of a 

mineralogical study of the specimens of thinolite which have been placed 

in his hands, undertaken with the view to making out as fully as 

possible the crystalline form, so as to throw light upon the probable 

chemical nature of the original mineral, and thus further upon the history of the complex changes through which Lake Lahoutan has passed..

In order to avoid all misapprehension, it may be repeated here that 

the word thinolite is employed in the restricted sense used by Mr. 

Eussell, as designating that portion of the calcareous tufas which is 

distinctively crystalline, in distinction from the stony- (lithoid) and

(434J
DANA.] GENERAL ASPECT OF THE THINOLITE. 15

dendritic varieties. In a word, the thinolite is a crystalline deposit, 

now consisting chemically of almost pure calcium carbonate, but obviously pseudomorphous after some original mineral deposited on an 

immense scale during a certain period in the desiccation of Lake La: 

hontau.

GENERAL ASPECT OF THE THINOLITE.

In general it may be said that the thinolite collected from the different localities named, both in the basin of Lake Lahontan and of Mono 

Lake, while varying widely in external aspect, is yet remarkably uniform in all essential characters. It is thus established beyond question 

that the original mineral deposited was throughout the same, although, 

in consequence of the varied conditions to which it has been subjected, 

the forms resulting from its alteration are very diverse. Thus, in some

specimens there is only a delicate skeleton remaining, the whole consisting_of thin plates, held together in their parallel position by a slight 

central frame-work, while in others the whole is as firm and compact 

as a crystalline limestone, and between the two extremes many intermediate varieties occur. The most important condition upon which this 

difference depends is the varying extent to which a deposition of calcium carbonate has taken place subsequent to the first alteration of the 

original mineral. This will be more fully explained later.

THINOLITE FROM PYRAMID LAKE.

As has already been stated, the thinolite is most characteristically 

developed about Pyramid Lake. The writer has had in hand specimens 

from the Marble Buttes, from the Needles, from Anaho Island, and from 

the Domes, and, as they illustrate well the different varieties, it will be 

convenient to refer to them by localities, although no special significance 

is probably to be attached to the particular spot from which the individual specimens were collected.

The delicate, open, porous variety of thinolite is best shown in the 

specimens from the Marble Buttes, of which illustrations are given in 

Plate I (here inserted from Mr. Kussell's report) and in Fig. 1 (reduced 

one-half) of Plate II. The external form of the crystals is roughly 

that of a rectangular prism, with projecting edges and generally tapering toward the extremities. The color is gray to brown. These crystals are commonly from a quarter of an inch to an inch in diameter and 

up to .8 or 10 inches or more in length. They are generally grouped 

in a more or less closely parallel position, often compactly, with only 

very little interlacing. In other cases, especially when the forms are 

smaller,they have widely divergent positions, interpenetrating each other 

and giving a large mass an open, reticulated appearance. In addition 

to the elongated crystals, numerous smaller ones, half an inch or an inch

(435)
16 THINOLITE OF LAKE LAHONTAN. . [BULL. 12.

in length, make up parts of these masses, projecting from the sides of th'e 

larger crystals and forming divergent groups among themselves. The 

small crystals have generally the form of an acute pyramid, and are 

sometimes square in outline, sometimes rhombic; the sides are usually 

concave, and the edges project sharply. The exterior surface of the 

larger crystals is rough and open, often with a delicate mossy covering, 

and the whole crystal is porous throughout, as if eaten out so as to leave 

only a skeleton behind. Upon a superficial examination no regularity 

in the structure is evident, but on looking more closely it is seen that 

the. apparently rough and irregular surface is made up of portions of 

thin plates, each set parallel to the sides of the crystal and uniformly 

converging in one direction. Thus when one of the groups of nearly 

parallel crystals is viewed end on, from one extremity or the other, it is 

seen that the edges of the plates, irregular as they are in outline, are 

all presented to view at once, as if each crystal, though prismatic in 

general outline, were made up of a series of acute skeleton pyramids, 

hopper-like in form, placed one within another. Still further, when the 

section produced by the cross-fracture of one of these elongated crystals is examined, there is seen, more or less distinctly, a series of apparently rectangular ribs forming concentric squares or re9tangles, with 

diagonal ribs joining the opposite angles.

The specimens in hand from the Needles, Pyramid Lake, correspond 

closely with those which have been described, though hardly showing 

the structure so clearly. This is also true of some of those from Anaho 

Island. The majority from the latter locality, however, are much more 

firm and compact. Here, too, the crystals are usually elongated, and in 

a single specimen grouped in nearly parallel position. The edges of the 

plates are also commonly distinct on the sides, and show the same convergence toward one extremity. The masses, however, instead of being 

Open and porous, and consequently light in the hand, are close, compact, 

and heavy. Instead of the delicate, open skeleton, with fretted surface,. 

seen on'the cross-fracture, the section is nearly solid, and sparkles with 

the reflection from the cleavage surfaces of the calcite grains. ID other 

cases the outer surfaces are smooth and rounded, and the unaided eye 

sees little of the structure except on a cross-fracture; in these instances, 

as will be more fully explained immediately, a deposition of calcium 

carbonate has filled up the skeleton form and incrusted and smoothed 

over the surface.

The specimens from the Domes represent still another type of the 

thinolite. The crystals here have uniformly an acute pyramidal form, 

and are grouped in irregular, divergent positions. Their surfaces are 

brownish yellow in color and show little of the edges of the*parallel 

plates conspicuous in the variety from the Marble Buttes. They are, on 

the contrary, nearly smooth, except when covered with warty excrescences, which in some cases are thickly clustered about the edges and 

extremities. One of these crystals (natural size) is shown in Fig. 11 of

(436)
DANA.] STRUCTURE SHOWN IN SECTIONS OF CRYSTALS. 17

Plate II. On the fracture this variety is. found to be nearly as firm and 

compact as a fine-grained cystallme limestone; in fact, the unaided eye

 would regard the whole as crystalline throughout. The color on the 

fracture is slightly yellowish white.

EXAMINATION OF SECTIONS OF CRYSTALS.

Iii order to get at the true structure of the crystals which have been 

described it is necessary to resort to sections cut transversely and longitudinally; these reveal the form most clearly and satisfactorily. A

 cross-section of a crystal like those first described the open porous 

variety from the Marble Buttes is shown in. Fig. 2 (natural size). As 

seen in the figure it is made up of lines in positions parallel to the sides 

of a square prism, and in addition there are two sets of distinct diagonal lines intersecting at right angles to each other; between these ribs 

are open spaces. A closer examination of the specimen represented in 

Fig. 2 shows that the material consists of rhombohedral calcium carbon- 

,ate, or calcite, of a distinctly granular crystalline structure throughout. The whole presents an open tesellated appearance. The external 

form of the crystal which yielded Fig. 2 is shown, reduced one-half, in Fig. 

<6. The point at which it was divided is indicated by a black line. The 

form is roughly that of a square prism tapering slightly in both directions, but the ^external form does not conform, in this respect, to the internal structure except at the upper extremity. The irregular edges 

of the upwardly converging plates are clearly shown in this figure.

A longitudinal section of another crystal (one-half natural size) is 

shown in Fig. 5. It presents also an open skeleton appearance analogous to that of Fig. 2. As seen in the figure the plates converge up" 

wards on either side of the longitudinal axis, meeting at an angle of approximately 35°. Like the previous case, it consists entirely of purely 

granular crystallized calcite with only a little mossy covering on the 

surfaces of the plates. It is to be noticed here that the plates all converge upwards from one extremity of the crystal to the other, and this, 

as will be remarked later, is almost universally true even in the case 

of crystals, the external form of which tapers off at both ends.

Another transverse section (natural size) is shown in Fig. 3. It is 

like Fig. 2 in most respects, except that the square is elongated in one 

direction and the diagonals meet in a central rib. Moreover, while the 

skeleton frame-work consists as before of crystallized calcite (left white 

in the drawing), the intermediate spaces are partially filled up with a 

secondary deposit of calcium carbonate which is apparently amorphous, 

and has been deposited in granular form and, too, in lines parallel to 

the crystalline plates. This subsequent deposition, however, has not 

gone far, and the general appearance is nearly as open as the one first 

described. The outline of the crystal which yielded this section is 

shown in Fig. 7 (reduced one-half). As seen here it tapers gradually

(437) 

Bull. 12 2
18 THINOLITE OF LAKE LAHONTAN. [BULL. 12.

to the terminal edge, forming a,sharp extremity. The external form approximates to the true crystalline form of the original crystal, but is somewhat more acute, as shown by the edges of the plates exposed on the 

surfaces and by the angle at which the plates within converge.

In Fig. 13 another section is given (natural size). This shows much, 

the same tessellated appearance, the structure being essentially the 

same as in the others described, but the secondary deposition of 

amorphous calcium carbonate has gone still further, so that as a whole 

it is more compact. The skeleton ribs parallel to the sides and the diagonals are, however, still very distinct and entirely crystalline. The 

form of the crystal which gave this section is shown in Fig. 8 (one-half 

natural size). As seen here it is an acute square pyramid, approximately conforming in outward form to the internal structure. The surface is here no longer open and fretted, as in the others, but nearly 

smooth, except as it is covered with small wart-like prominences. The 

color is a dark brown. The line in which the section was cut is shown 

in the figure. s

Still another section is shown in Fig. 14 (natural size), and one which 

marks a further degree of deposition of secondary calcium carbonate. 

The crystal from which it was taken had a square form tapering slowly 

upward, and the surface was covered with small mammillary prominences. The skeleton of crystalline calcium carbonate is here nearly 

concealed by'the added amorphous material, and the outer portion consists of concentric layers of the same substance.

The exterior appearance of another crystal is shown in Fig. 4 (onehalf of natural size). As seen, it tapers slightly toward both extremities, and it was cut longitudinally, in the idea that it might be a 

doubly terminated crystal, but the structure lines all converged toward 

one end, showing that, like most of the others, the growth was only in 

one direction. As the surface indicates, the crystalline skeleton has 

been nearly filled up with amorphous calcium carbonate.

In addition to the sections given and others like them of large crystals, numerous thin sections were also cut transverse and longitudinal 

to smaller crystals. They revealed under the microscope the same 

points which the microscopic examination of the larger sections 

showed that is, the presence of the same skeleton of crystallized calcium carbonate with the concretionary depositions added to it. The 

calcite grains are large, each one having a distinct rounded or elliptical 

outline, and they are packed closely together, with a little brownish' 

amorphous matter between them. Many of them show the rhombohedral cleavage j others show a crystalline nucleus which has apparently 

grown by the addition of further crystalline matter. The secondary 

calcium carbonate has generally a concentric or banded structure resembling some kinds of opal.

These sections also show another point of interest, namely, the presence of groups of acicular crystals in parallel position filling more or
DANA.] THINOLITE FROM MONO LAKE. 19

less completely the cavities in the skeleton structure, and sometimes projecting into the cavities. These are seen in many cases, and are the general rule, though sometimes absent; they are indicated magnified eight 

times in Fig. 15. These acicular crystals show uniformly extinction parallel to their prismatic direction, and hence it seems clear that they must 

belong to an orthometric system. It seems probable that they are aragonite. A chemical examination of an uncovered slide gave results in 

accordance with this suggestion.

A section of one of the crystals from the Domes is shown in Fig. 12 

magnified eight times. To the eye the broken crystal appeared to be 

crystalline throughout; in the section, however, as examined under the 

microscope there is seen to be a crystalline frame-work made up of calcite grains, filled in with amorphous matter, and in addition outer 

layers of banded opal-like carbonate, so that it conforms in general to 

cases like those before represented. The diagonal lines are here clearly 

developed, and there are also rectangular lines more or less distinctly 

indicated. These are illustrated somewhat obscurely in the figures. 

Other sections illustrated essentially the same relations.

Structure in dissected crystals. As has been stated, the external 

form of the thinolite crystals seldom gives the true crystalline form. 

The process of dissection, however, which has laid bare the skeletonlike ribs which have been described, sometimes results in showing the 

true pyramidal form of the original mineral. In such cases we may 

have a series of skeleton crystals, each a hollow pyramid as a cap to 

the one preceding. This is sbown in Fig. 9, which will explain itself, 

and again in Fig. 10 (both natural size). In another case a mass of the 

calcareous tufa, stiowing little structure, has its surface partially covered with pyramidal crystals an inch in length. Each one was a skeleton 

crystal inclosing a pyramidal crystal, and sometimes several crystals, 

after the fashion of a nest of pill-boxes. The outer surface of the crystals was incrusted with a moss-like covering, often entirely hiding the 

form. Two of these are represented in Figs. 16 and 17 (natural size), 

and another in Fig. 29, Plate III.

THINOLITE FROM MONO LAKE.

The thinolite from the shores of Mono Lake conforms in all essential 

respects to ^hat which has been described from Pyramid Lake, although 

on a superficial examination it presents a somewhat different aspect. It 

belongs in general to the more compact variety, although the same 

skeleton character appears on the cross fracture, and occasional specimens are nearly as open and porous as those from the Marble Buttes. 

The common color is light gray to nearly white. Many of the specimens 

consist of groups of elongated crystals, in which each crystal is built up 

of an indefinite number of sub-individuals bundled together in parallel 

position, each of these having an acute pyramidal form more or less dis-

(439)
20 t THINOLITE OF LAKE LAHONTAN. [BULL, 12.

tinct. This is shown in Figs. 19 and 20, Plate III, and even more clearly 

in Fig. 21; Fig. 24 also shows something of it (all natural size). Groups 

of sharp, almost acicular crystals in widely divergent positions are also 

common, and their surfaces are generally studded with rounded warty 

elevations of subsequently deposited calcium carbonate (see Fig's. 23 and 

24). The substance of these crystals is frequently perfectly firm and 

compact, as much so as a very fine-grained white marble, and no evidence of the characteristic structure is seen until a cross-section is cut 

and polished. In other cases the groups of crystals are so thickly coated 

with the subsequent deposit that they appear like a mass of stalactites 

rather than crystalline forms. On the other hand, a cross-section of a 

composite group of minute parallel crystals, like that in Fig. 21, shows 

the same open system of rectangular and diagonal ribs represented in 

Plate II. Fig. 22 represents a section from the extremity of the specimen shown in Fig. 21, both ends of which were sawn across transversely.

THINOLITE FROM WALKER LAKE, AND FROM BLACK ROCK AND 

SMOKE CREEK DESERTS.

As has already been stated, Mr. Eussell has found evidence of a second 

deposit of thinolite in the Lahontan basin subsequent to the formation 

of the dendritic tufa. This deposit was apparently only of limited extent. The localities noted are on the shores of Walker Lake and in 

the Black Bock and Smoke Creek deserts. A few specimens have been 

placed in the hands of the writer. The specimen from Walker Lake is 

a little obscure and exhibits the characteristic forms with much less distinctness than the specimens from.Pyramid Lake. Many of the crystals 

have lost their original shape entirely, and others are only faintly suggestive of the square pyramidal form. There are enough, however, which 

do show this.to remove all doubt as to the correctness of identification.

The specimens from the Black Eock Desert are peculiar, in that the 

nucleus of thiuolite crystals passes into a dense stony tufa, which forms 

a 'cluster of rosettes about it somewhat like a head of cauliflower. This 

is shown in Fig. 18 (reduced one-half). The crystals offer no points of 

special interest, but exhibit the characteristic form distinctly enough.

ORIGINAL CRYSTALLINE FORM OF THE THINOLITE.

\

The description of the specimens of thinolite given has revealed 

clearly the crystalline form of the original mineral. Distinct crystals, 

showing the external form sharply, are, to be sure, rare, but there are 

many which suggest this form. What is wanting in them, however, is 

made good by the wonderful process of dissection which has gone on, 

revealing, as perfectly as could be desired, the true crystalline structure 

of the original mineral.

(440)
DANA.] CRYSTALLINE FORM OF THE THINOLITE. > 21

All of the forms observed conform to an acute tetragonal pyramid. 

The section in Pig. 2, showing the system of parallel plates* at right 

angles to each other, is alone evidence that the original crystals belonged 

to an orthometric system; and further, the diagonal lines, also crossing each other at right angles, fix this system as the tetragonal. The 

external form, wherever distinct, agrees with this (see Fig. 7; also Figs. 

9,10, 16, 17, 29) j so that the question may be considered as definitely 

settled beyond all reasonable doubt. A form approximating closely to 

the tetragonal, but belonging to a system of lower symmetry, would 

also answer the conditions} but everything seems to point to the fact 

that both the sets of diagonal ribs shown in the figures are similar 

crystallographic lines, and that the same is true of both sets of rectangular ribs, which can be the case only in the tetragonal system. The 

measurement of angles leads to the same conclusion, but only an

approximate degree of accuracy is attainable. If attention were directed alone to the external pyramidal form, many exceptions seemingly 

at variance with the tetragonal system might be observed. Many of the 

pyramidal forms are flattened in the direction of one of the diagonals. 

This is true both of the skeleton forms and of those which have been 

rounded out by subsequent deposition. In the former case the explanation is simply that in the direction of one of the diagonals more of 

the crystal has been dissolved away than in the other, and when this 

has first happened, and then calcium carbonate has been deposited upon 

the skeleton, the result has been to produce a form looking like an 

orthorhombic or mouoclinic pyramid, with a wide difference in the pyramidal angle.

The terminal angle of the ideal square pyramid, to which the thinolite 

is to be referred, can be measured only approximately. The measurement of the external forms of the crystals is extremely uncertain, because the alteration which has taken place, as noted above, has naturally 

had the result of changing the dimensions of the original form widely. 

The measurement of the angle given by the structure lines, as shown in 

Fig. 5, is more reliable, but is also uncertain because of their want of sharpness, and because of the doubt as to whether the longitudinal section 

has been cut exactly parallel to the vertical axis or somewhat inclined 

to it. The results given by such forms as those in Figs. 9 and 10 seem 

a little .more trustworthy, but those', too, do not admit of exact measurement. The angle obtained in a number of cases from such dissected 

crystals, measured over the summit, varied from 26° to 36°, and some 

forms were even more acute. The most probable result, perhaps, is 35° 

which, as nearly as can be measured, is the angle of the structure 

plates, as shown in Fig. 5. In any case the result can be considered as 

but a mere approximation.

. The ideal form, then, may be accepted as that of a tetragonal pyramid or octahedron, measuring over the summit 35°, and consequently 

having a terminal pyramidal angle of 95£° and a basal angle of 145°.
22 . TUINOLITE OF LAKE LAHONTAN. [BULL. 12.

The corresponding length of the vertical axis is c = 2.24. It is very 

probable that two or more acute pyramids, all referable to the same 

fundamental form, were present in the original crystals; the measurements seem to point to this, and the analogous pseudornorphs after 

. phosgenite, mentioned later, certainly show this variation.

It has already been stated that in all the larger elongated crystals 

the pyramidal structure is developed in one direction only, this being 

true even in cases like that of Fig. 4, where the external form would 

suggest that the crystal had a double termination. The small crystals, 

however, which have grown more freely, many of them attached in the 

middle, seem to be complete at both extremities, although the evidence 

gained of this is not absolutely conclusive.

CHEMICAL NATURE OF THE ORIGINAL MINERAL.

The description of the original crystalline form of the thinolite, so 

far as it can be made out, is sufficiently complete to give an emphatic 

negative answer to the question as to the nature of the original mineral. 

It was not gayiussite, nor gypsum, nor anhydrite, nor celestite, nor glauberite, nor, in fact, any one of the minerals which might suggest itself as 

a solution of the problem. The crystalline form is totally irreconcilable 

with any one of these. This is so clear, from what has gone before, that 

the question admits of no argument at all. But more can be said: the 

original mineral was one which does not appear thus far to have been 

observed in its natural condition, although, as will be shown later, it 

probably has occurred abundantly at numerous other localities. Furthermore, a review of all the artificial salts of calcium, sodium, and 

magnesium has failed to bring to light any one which would satisfy 

the conditions required.

It seems, therefore, that any explanation of the original condition of 

the thinolite beds of Lake Lahontan must, at present, rest on hypothetical 

grounds, and much as a definite solution of the problem is to be desired, 

it is not now attainable. A few suggestions may not be out of place here, 

although the full discussion of the subject belongs rather to the geologist 

who has the whole subject in charge. The open skeleton forms, consisting now of crystallized calcium carbonate, make it seem very probable 

that the original mineral was a double salt, and that a salt containing 

calcium carbonate as one of its members. Only on such a supposition 

is it easy to understand the removal of so large a part of the original 

material and the leaving behind of these plates of calcium carbonate, 

marking the original crystalline structure. Whether the original crystals were or were not solid throughout, at the time of their formation, it 

is not possible to say now with certainty ; very probably they varied 

much at different points in this respect. From the analogy of soluble

(442)
DANA.! CHEMICAL NATURE OF THE ORIGINAL MINERAL. 23

salts deposited rapidly from aqueous solutions, it seems likely that open, 

cavernous forms were common, perhaps the rule. But even supposing 

this to be true, no one can inspect such groups of skeleton crystals as 

those from the Marble Buttes without seeing that what now remains 

is only a part of what originally crystallized out of the saline waters of 

Lake Lahoutan. This fact, coupled with the other just mentioned, that 

the remaining skeleton consists of crystallized calc.ite in granular form, 

gives a very important hint as to the changes which these crystalline 

beds have undergone. The successive steps may have been as follows : 

(1) The deposition of crystals as the lake waters evaporated; (2) a 

change of conditions, e. g., an addition of fresh water to the lake (as 

supposed by King), leading to the solution of a part of the substance 

of the crystals and the simultaneous recrystallization of the remaining 

calcium carbonate; (3) the subsequent and independent deposition of the 

carbonate, solidifying and coating over the skeleton forms. The conclusion reached by Mr. King4 that the original mineral was gaylussite satisfies the requirements tolerably well, for it is then necessary only to 

explain the removal of the sodium carbonate, and the calcium carbonate 

remains behind. Unfortunately for this hypothesis, it is impossible to 

reconcile the forms which now remain, showing how the original mineral 

crystallized, with the monocliuic form of gaylussite.5 Furthermore, Mr. 

Eussell finds other grounds, independent of this crystallograpic proof, 

for the belief that the supposed enormous deposit of gaylussite could 

not have taken place. But if not gaylussite, what was the original 

mineral ?

It is hardly profitable to go beyond the above suggestion, that it may 

have been a double salt, containing OaCO3 , unless the hypothesis can be 

based upon some observed facts; but fortunately some facts can be 

pointed to which lead to a possible explanation of the enigma, and 

which are in any case very suggestive.

The only crystalline forms bearing any close resemblance to the acute 

tetragonal pyramids of the thinolite, of which the writer has any knowledge, are those of the pseudomorphs of lead carbonate after phosgenite,

4 Geological Exploration of the Fortieth Parallel, Vol. I, p. 517.

6At the time when Mr. King had this subject under investigation he submitted several 

specimens to the writer for inspection, and he then gave a qualified assent to the conclusion Mr. King had reached in regard to them. One of these specimens, as Mr. King 

had noted, showed some crystals which bore a remarkably close resemblance to the 

well known Sangerhausen pseudomorphs, then generally referred to gaylussite. This 

similarity suggested identity of origin a conclusion which (after a further study of 

the same specimen) the present investigation has confirmed, as noted below and 

thus gave apparent support to the gaylussite hypothesis. The other specimens then 

in hand were somewhat like Fig. 1, on Plate II, and upon the inspection given them 

no opportunity was had for careful study they gave negative results; a certain 

outward similarity to the elongated crystals of gaylussite from South America (called 

olavos, nails) was noted, but nothing more definite.

(443)
24 THINOLITE OF LAKE LAHONTAN. [BULL. 12.

first described by Krug von jSTidda,6 from the sine mines in Upper Silesia. This similarity in habit and angle is the more striking, as thethinolite form is^an unusual one. A number of these pseudomorphs are 

in the Blum collection, which became the property of the Yale Mineralogical Museum in 1872. They correspond to the description given by 

Krug von Nidda. They have the form of a square prism, sometimesterminated by a pyramid having an angle over the extremity of about 

36°, and occasionally show traces of an octagonal pyramid; other formsshow only a very acute square octahedron, with a summit angle of about 

13° in one case and 26° in another. One specimen shows these formsimbedded in a white clay. They are now completely altered to compact, 

fine-granular lead carbonate, except for the presence of an occasional 

minute nucleus of the original mineral.

The hypothesis to which this resemblance leads is this: that the original mineral may have been a chloro-carbonate of calcium isomorphous with 

phosgenite') that is, a mineral having the composition CaCO3 +Ca012 isomorphous with PbCO3 +PbC]2 , and now altered to CaCO3 as is the 

phosgenite to PbOO3 . The hypothesis, as far as the crystallographic 

relations are concerned, is a most natural one. The difficulty arises 

when we consider the peculiar nature of calcium chloride, and hence 

question whether an anhydrous molecular compound of calcium carbonate and calcium chloride could have been deposited from the waters 

of Lake Lahontan. Obviously this is a subject for synthetic experiment, and whatever the nature of the original mineral, it ought to be 

possible to approximate to the conditions under which it was made and 

so to reproduce it. It is to be hoped that the work now being carried 

forward by the chemists of the Geological Survey may lead to some decisive results in this direction.

In the mean time it is interesting to note the only case in which, sofar as the writer can ascertain, a chloro-carbonate of calcium has been 

formed. The experiments are described by Fritzsche in the Bulletin of 

the St. Petersburg Academy, iii, 285, Nov. 30,1860, and reprinted in the 

Journal fur praktische Chetuie.7 He states that on evaporating the 

solution of crystallized calcium chloride, prepared in large quantities 

for technical purposes, there remained a small amount of a sandy powder,, 

which kept a yellowish aspect so long as the calcium chloride solution 

was concentrated, but in a dilute solution became finally white. When, 

some of the crystals were placed on a glass slide under the microscope,, 

and then water poured upon them, it was observed that they for a moment were completely transparent and underwent no change; soon, however, the surface became clouded, and then a granular separation took 

place gradually. As the Ca012 was dissolved they entirely lost their

6 Krug von ,Nidda: Ueber das Vorkommen des Hornbleierzes und des Weissbleierzes 

in den Krystallformen des ersteren in Oberschlesien, Zeitsch. geol. Gesellsch. ii, 126, 

1850. See also Bliuh, Pseudornorphosen, Zweiter Nachtrag, 68.

7 J. Fritzsche: Ueber ein Doppelsalz aus kohlensaurem Kalk uud chlorcalciuni, 

Journ. prakt. Chem., Ixxxiii, 213, 1861.

(444)
DANA.J RELATION TO SANGERHAUSEN PSEUDOMORPHS. 25-

transparency, and finally there remained only a skeleton of calcium carbonate corresponding in form and size to the original crystal. These fell 

to pieces when touched, and there resulted minute spherical masses of 

probably amorphous carbonate. This salt was found to have the composition 2CaCO3+CaC]2 +6H2O. The crystals were shown by v. Kok> 

scharof to belong either to the orthorhombic or monoclinic system. It is 

not to be supposed that this salt of Fritzsche is in any way an explanation of the tbinolite enigma, and yet his observations are of great interest in this connection. In order to complete the subject the fact may be 

noled that Berthier 8 speaks of forming a compound of calcium carbonate and chloride by fusion.

Another hypothesis may be offered as to the composition of the orig 

inal mineral, viz, that it was a double salt of calcium and sodium, perhaps conforming to the formula CaC03+NaCl, or better CaC03 +2Na01,, 

'which, it is possible, might also be isomorphousx with phosgenite. 

This is so purely hypothetical that very little weight can be given to it;, 

still it may not be entirely useless to throw out the suggestion, although 

various serious objections at once come up to mind. In any case it 

must be borne in mind that carbonates and chlorides were the saltsmost likely to be precipitated from the lake water, and calcium and 

sodium were the prominent basic elements at hand.

RELATION OF THE THINOLITE TO THE SO-CALLED 

GAYLUSS1TE PSEUDOMORPHS OF SANGERHAUSEN 

AND OTHER LOCALITIES.

The interest connected with the thinolite is much increased by the 

fact of its relation to the well-known " barleycorn " pseudomorphs from 

Obersdorf, near Sangerhausen, in Thuringia, one of the most remarkable 

and enigmatical cases of pseudomorphs ever recorded. These crystals 

were first described by Freiesleben9 in 1827, and at that time referred 

by Breithaupt 10 to gaylussite. They were early called " natrocalcite" 

on the mistaken idea that they contained soda. This conclusion has been 

accepted by most authors since that time, although Des Cloizeaux,11 in 

1843, referred them to the variety of celestite called by Haiiy apotomer 

and Kenngott,12 in 1870, suggested that gypsum might be the original 

mineral, and Groth,13 in 1878, suggested anhydrite. The Sangerhausen

sBertbier: Ann. Chirn. Phys., II, xxxviii, 253, 1828.

9 Freiesleben: Isis, xx, 335 et seq., 1827. Mag. Orykt. Sacbson, No. 7, 118 et seq.r 

1836 (quoted by Blurn).

">Breitbaupt: Mag. Orykt. Sachsen, No. 7, 287, 1836 (quoted by Blum).

"Des Cloizeaux: Determinations des formes primitives et secondaires de la Gaylussite. Ann. Chirn. Pbys., Ill, vii, 489, 1843. Observations sur la calcite, ib., p.. 

494. See also Mine"ralogie, ii, 119, 1874.

)3Kenngott: Quoted by vom Ratb, PoggendoriFs Annalen, Erg.-Bd., v, 442, 1870*

13 Groth: Min. Samml. Strassburg, p. 142,1878.

(445)
26 THINOLITE OF LAKE LAHONTAN. [BULL. 12.

pseudomorphs are described in detail in Blurn's work on Pseudomorphs. 14 They occur imbedded in clay as complete crystals, either 

single or in complex groups formed by two or more crystals, interpenetrating each other; sometimes as many as twenty are united to form a 

star-shaped group. They average half an inch in length, but occasionally are 1, 2, or even 2£ inches long. The color is generally a pale 

yellow. They consist of a hard shell, with polished surface, smooth, 

except for a system of fine markings, and within contain a confused 

mass of loosely cohering calcite grains. They are represented in Figs., 

26, 31, and 32. Dr. E. Geinitz,15 who has made a special study of them, 

has observed within a series of zones of harder material parallel to the 

sides, rib-like, between which the loose calcite grains are inclosed. Similar pseudomorphs have been observed at a number of other localities. 

Haidinger 16 has described them as occurring in lake deposits in a limestone cave in the Tufna at Hermanecz, near Neusohl, Hungary. This' 

cave contained large quantities of bone remains, especially those of

 cave bears, and the crystals themselves came from the skull of an Ursus 

speloeus.

G. Eose17 announced.the occurrence of similar pseudomorphous crystals at the village Rating, in the neighborhood of Tonningen, in Silesia. 

They were found here in marl, 6 or 7 feet under the soil, and resembled 

those from Sangerhausen closely, except that they did not have the 

smooth, hard shell; one of these is represented in Fig. 38. Still other 

localities are the east coast of Australia, mentioned by Volger18 and 

Blum ; 19 in the clay at the Krummer Horn, on the Dollart, in North Friesland, as mentioned by Vom Eatb f° and from the Zechstein, between 

Amt-Gehren and Konigsee, at the base of the Thuringian forest, as 

noted by E. E. Schmid.21 To the above should probably be added 

(jlendon, in New South Wales, and Astoria, Oregon, mentioned by J. D. 

Dana.22 The first of these last-mentioned localities afforded in clay pseudomorphous crystals of granular crystallized calcite, dark in color, and 

having a rough surface, and up to 20 inches in length, but usually 3 or 

4 inches; often in star-shaped groups of two, four, or more crystals. At 

the second were obtained crystalline forms, also of compact granular

 calcite, and of an irregular quadratic or rhombic form, sometimes much

14 Blum: Pseudomorphoseu, p. 18, 1843.

16 E. Geinitz: Studien iiber Mineral-Pseudomorphosen. Inaug. Diss. Stuttgart, 

1876, p. 35. 

. 16 Haidinger: Ueber eine neue Localitat von Gay-Lussit-Pseudomorphosen. Pogg-

 endorffs Annalen, liii, 142,' 1841.

17 G. Rose: PoggendorfFs Annalen, liii, 144, 1841.

is Volger: Erde und Ewigkeit, die naturliche Geschichte der Erde, etc., p. 497,1857, 

Jahrb. Min., 1864, 339.

19 Blum: Pseudomorphoseii; dritter Nachtrag, p. 13,1863; vierterNachtrag, p. 8,1879.

80 G. vom Rath: Calcitkrystalle (Freiesleben) am Dollart in Oatfrieland, Poggen-

 dorff's Annalen, cxxxv, 588,1868.

81 E. E. Schmid: Sitz. med.-nat. Ges. Jena, July 9,1880. > 

88 J. D. Dana: Geology, U. S. Exploring Expedition, 1849, p. 481 and p. 656.

(446)
DANA.I IDENTITY WITH SANGERHAUSEN PSEUDOMORPHS. 27

flattened. Figs. 34,35 (Oregon), and 36,37 (New South Wales) are copied 

(reduced one-half) from those given in the report mentioned. Thin 

sections of both occurrences showed only a compact granular structure, 

nothing resembling Fig. 2 or 3. P. W. Jeremejew23 speaks of aragonite pseudomorphs (after celestite) from the sea bottom near Archangelsk, Eussia, which resemble the Sangerhausen crystals; they are 

brought up by the fishermen, and believed to have a remarkable healing 

power.

The suggestion of the probable identity of the Sangerhausen crystals 

with the Lake Lahontan thinolite may at first thought seem worthy of 

little attention. It is certainly true that the two occurrences are most 

diverse in many of N their forms. And yet, on the other hand, it is easy 

to find crystals of thinolite which bear a marvelously close resemblance 

to the Sangerhausen pseudomorphs. In the confused mass of small

interpenetrating crystals, which have been described as coming from 

the Marble Buttes, Pyramid Lake, many of the individuals have the 

same quadratic or rhombic section, the same curved and tapering form, 

and the same method of grouping. Among the crystals from Mono 

Lake, too, are many which have a like resemblance. One specimen in 

particular, collected by Mr. King from Pyramid Lake, exhibits the 

similarity most strikingly; it was this specimen which, as already mentioned, had most weight in leading Mr. King to his conclusion (1. c., p. 

518) that "the entire thinolite formation, with all its enormous development, its extent of hundreds of miles, its thickness of 20 to 150 feet, 

was nothing less than a .gigantic deposit of gaylussite crystals." This 

specimen shows a number of acute tapering pyramidal crystals closely 

resembling the Sangerhausen crystals. Two of these, which project into 

a little cavity, are represented in Figs. 27 and 28. The larger of these 

is nearly square in section, and the other is distinctly rhombic; both of 

them show on their surface markings similar to those which characterize the Thuringian pseudomorphs, as shown in Figs. 32 and 33. It 

should be added, too, that in the groups of crystals from Mono Lake 

are to be found some which have a hard, shell-like exterior, and which 

bear similar markings. These are, in the opinion of the writer, not striations characteristic of the original mineral (as suggested by Des Cloizeaux), but structure forms of the pseudomorphous calcite, analogous to 

the vicinal prominences of scalenohedral or rhombohedral form, which 

calcite crystals often show. Compare the figures given by Scharffu in 

his memoir on calcite; compare also Figs. 25 and 33 with 26; also 27, 

28, and 30 with 31 and 32.

Were a comparison, then, to be made only between these pseudomorphs 

and certain selected crystals of thinolite, exceptional in their perfection

!3 P. W. Jeremejew: Zeitsch. Kryst., vii, 204 (Verhandl. Russ. Min. Ges. St. Pet., II, 

xvii, 319,1882).

24 Scharff: Ueber den inneren Zusammenhang der verschiedenen Krystallgestalten. 

<des Kalkspaths. Abhandl. Senck. nat. Ges. x, 1876.

(447)
28 THINOLITE OF LAKE LAHONTAN. IBULL.I&,

of form, no one could hesitate to decide that there was every probability of their having had the same origin, especially when it is remembered that chemically they are identical. This conclusion is not 

invalidated by the fact that the thinolite crystals are developed in other 

forms in which this resemblance is not observable. It may be objected 

that it is difficult to believe that the original mineral, in the case of the 

Sangerhausen pseudomorphs, for example, belonged to the tetragonal 

system. It is true that many of these crystals are most decidedly rhombic 

in appearance. One in the writer's hands, for example, afforded approximate terminal pyramidal angles of 85° and 127°; but, on the other hand, 

of the crystals which the writer has had an opportunity to examine 

upwards of fifty in number three-fourths vary but little from the tetragonal type. Of course no trustworthy measurements are possible, because 

of the tapering, rounded form. The differences observed, then, are believed to be due to the pseudornorphous process through which they 

have passed, involving the solution and removal of part of the original 

substance and the deposition of more or less calcium carbonate subsequently. The variation from the tetragonal type in the acute pyramidal 

forms of the thinolite is as great as in the foreign crystals which they so 

closely resemble, and the true form of the former would be doubtful 

were it not for the dissected crystals in which the tetragonal structure 

is so clearly shown. Note here the observations of Dr. E. Geinitz on 

Sangerhausen crystals (p. 26) showing the presence of ribs within parallel to the sides; these appear to be analogous to the ribs as shown in 

Figs. 2 and 3, etc.

The writer is of the opinion, then, that the original mineral, deposited on an enormous scale in the Lahontan Basin, was, in all probability r 

the same as that which formed the isolated crystalsin the Sangerhausen 

clay, in the marl at Kating, and .in the skull of the cave bear at HerinaneCZJ and if this is the case, then whatever hypothetical conclusion 

is reached in regard to the origin of the thinolite must apply also to 

the other cases. It is on this account that, in view of the importance 

of the subject under discussion, it has seemed worth while to consider 

these foreign pseudomorphs at such length. Unfortunately this most 

interesting problem can be considered as only half solved.

In concluding this paper the writer would express his appreciation of 

the kindness with which Mr. Russell has assisted him at every point in 

his investigations.

(448)
INDEX.

Alien, Prof. 0. D., analyses of tufa by........................................ 12

Brush, Prof.G. J............................................................ 5

Dendritic tufa.............................................................. 10,11

Fritzscbe, J., experiments of ................................................

Oilbert,' G. K.; Letter of transmittal........................................

Gaylussite, So-called pseudoniorphs after.....................................

King, Clarence; description of tufa in Lahohtan basin,......................

; hypothesis of the origin of thinolite.........................

Krug von Nidda, description of pseudomorphs by ............................

Lithoidtufa ................................................................

Phosgenite, Pseutlomorphs after..............................................

Mono Lake, Thinolite from.................................................. 19

Pseudomorphs from New South Wales.............--......................... 26

Oregon........'............,....-........................ 26

Sangerhausen ........................................... 25,26

Russell, I. C., Succession of tufa deposits observed by........................ 11

Varieties of tufa described by.................................. 10

Sangerhausen, Pseudomorphs from .......................................... 25

Tufas, Analyses of........................................................... 12

of Lahontan basin described by King.................'................. 9

Succession of......................................................... 10

varieties .................>............................................ 10

Thinolite, Chemical nature of original mineral............................... 22

Crystallographic study of ............'............................. 14

Examinations of thin sections of................................... 17

from Black Rock Desert........................................... 20

MoaoLake................................................... 19

Pyramid Lake ............................................... 15

Smoke Creek Desert .......................................... 20

Walker Lake ................................................ 20.

General aspect of.................................................. 15

Origin of, as given by King........................................ 23

Original crystalline form of........................................ 20

Origin of the name of............................................... 9

not a pseudornorphafter gaylussite ................................ 23

Relation of, to Sangerhausen pseudomorphs ........................ 25

Second deposit of,in Lahontan basin............................... 20

Structure.of ....................s,-.................................. 19

Suggested hypothesis as to the origin of............................ 29

(440-450) - 29-30

PLATE II.

iFiG. 1. Group of tliinolite crystals from Marble Buttes, Pyramid Lake (reduced onehalf) ; open porous variety.

FlGS. 2 and 3. Transverse sections, natural size; Fig. 2, open skeleton form ; Fig. 3, partially filled up with amorphous CaCOa. These sections show the system of rectangular (square) and diagonal ribs, which consist of granular crystalline CaCOa.

.FiG. 4. External appearance (reduced one-half) of a single crystal, with part of a 

second, the internal structure of which shows that it, has but a single termination; the comparatively smooth surface is due'to the secondary deposition of 

CaCOa.

IFiG. 5. Longitudinal section of open variety (reduced one-half), showing the two systems of plates converging upward at an angle of about 35°.

.FiG. 6. Complete crystal (reduced one-half) which yielded the section in Fig. 2; the 

liuo in which the section was made is indicated.

.FiG. 7. Acnte pyramidal crystal (reduced one-half) which yielded at its base the section given in Figure 3. 

.FiG. 8. Square pyramidal crystal (reduced one-half) which gave, at the point indicated, the section in Figure 13; the surface-has been made smooth by subsequent 

deposition of CaCOs.

FIGS. 9 and 10. Skeleton crystals (natural size) showing cap-iu-cap structure, and thus 

revealing the true square pyramidal form of the original mineral.

.FiG. 11. Crystals (natural size) from the Domes, Pyramid Lake; the surface smoothed 

over by subsequent depositions of CaC03,with sproutings from the edges and extremities.

.FiG. 12. Section (magnified 8 times) of a crystal from the Domes, like that in Figure 

11, showing a diagonal and rectangular frame-work, partly crystalline, granular, 

partly amorphous, with layers of secondary carbonate opal-like in structure.

FIG. 13. Section (natural size) of the crystal shown in figure 8, cat transversely at 

point indicated; it shows the same frame-work of granular crystalline carbonate, 

partially filled in with secondary CaCOs.

,FiG. 14. Section (natural size) showing the usual frame-work, partially filled in with

secondary CaCOs, and with successive layers also around the outside. 

FIG. 15. Section of a crystal from the Marble Buttes, magnified 8 times, and showing 

the structure lines of crystallized carbonate, and also in the cavities the acicular 

crystals of aragonite. (?)

«FiGS. 16 and 17. Small pyramidal crystals (natural size), showing by dissection the 

cap-in-cap structure, and thus, like Figs. 9 and 10, revealing the true pyramidal 

form of the original mineral.

32 (452)
U. 8. (JKOLOGICAI. SUKVKY liCLLKTIN NO. 12 PL. II

TII1XOL1TK CRYSTALS
PLATE III.

FIG. 18. Thinolite from Black Eock Desert (reduced one-half), the individual crystals 

running off into a compact stony tufa, so that the mass from above has a cauliflower-like form.

FIGS. 19 and 20: Thinolite from Mono Lake, California (natural size), showing the 

grouping of the composite crystals. (

FIG. 21. Thinolite from Mono Lake (natural size), fragment of a large composite crystal, made up of small acicular crystals in parallel position. °

FIG. 22. Transverse section of the crystal represented in fig. 21, showing the same 

skeleton structure distinct in crystals from Pyramid Lake (Figs. 2,3, etc.).

FIGS. 23 and 24. Group of thinolite crystals from Mono Lake (natural size), showing 

the acicular form, and also the way in which the crystals are coated over with 

secondary carbonate.

FIG. 25. Group of small crystals (magnified 4 times) from Mono Lake, showing the 

same method of grouping common in the Sangerhausen pseudomorphs, as shown 

in Fig. 26.

FIG. 26. Group of Sangerhausen pseudomorphs (natural size); compare Fig. 25.

FIGS. 27 and 28. Isolated thinolite crystals (magnified twice), showing resemblance in 

form and surface marking to Sangerhausen crystals; compare Figs. 31 and 32.

FIG. 29. Thinolite crystal (natural size), showing cap-in-cap pyramidal structure, 

similar to Figs. 16 and 17, Plate II.

FIG. 30. Thinolite crystal (magnified 4 times), showing resemblance in form to the 

Sangerhausen pseudomorphs; compare with Figs. 31,32, and 38.

FIGS. 31 and 32. Single Sangerhausen crystals, showing form and external markings; 

fig. 31, natural size; Fig. 32, magnified twice..

FIG. 33. Group of small thinolite crystals (magnified 4 times); compare with Fig.26

FiGS. 34 and 35. Pseudomorphous crystals, consisting of granular calcite from Astoria,

Oregon, copied (reduced one-half) from figures by J. D. Dana in the Geology of

U'. S. Exploring Expedition, p. 656. 

FIGS. 36 and 37. Pseudomorphous crystals, consisting of granular calcite, from New

South Wales; copied (reduced one-half)from figures by J. D. Dana in the Geology

of the U. S. Exploring Expedition, p. 481. 

FIG. 38. Pseudomorphous crystal from Kating, Silesia (natural size).

34 (454)
LT . 8. GEOLOGICAL SUUVKY BULLETIN SO. 12 1'L. HI

THINOLITE CRYSTALS