SEARLESITE FROM THE GREEN RIVER
FORMATION OF WYOMING*
Josrrn J. Farruvt
Wrru X-Rev Norus nv Josnru M. Axrrnolx*
AssrRAcr
The third recorded occurrence of searlesite, hydrous sodium borosilicate, is in the Green
River formation of soutirwestern Wyoming.
It is found in flat anhedral crystals in the oil shale and in subhedral crystals as much as
7 inches long in the trona bed, 10 feet thick, at a depth of 1500 feet.
The optical properties of the searlesite from Wyoming are in close agreement with thosepreviously published. The indices of refraction, measuredwith sodium light, are: a: 1.516,(2V:55", neg., calculated). X-ray diffraction photographs and a
0:1.531, and":1.535
chemical analysis
confirm the identity of the Wyoming mineral as searlesite.

fNrnonucrroN
The Green River formation in southwestern Wyoming affords thethird recorded occurrence of searlesite, a hydrous sodium borosilicate.
This mineral was first described in 1914 by Larsen and Hicks,r from theold searlesdeep well at SearlesLake, san Bernardino county, california,
and named after Mr. John W. Searles, the pioneer rvho put down thewell. rt was found in clay at a depth of 540 feet as white spherulites
about a millimeter in diameter. Great difficulty was experienced in
preparing a sample for chemical analysis due to the intimate associationof tiny grains of calcite, quartz, feldspar, chlorite, and hornblende.
The analyzed sample contained about 40/6 of this extraneous material.
Larsen states that the optical properties were measured with difficulty
and that his results were only approximate.
The secondlocality of searlesiteis the Silver peak Range, Esmeralda
County, Nevada, described in 1934 by Foshag.2 The crystallographic
and optical constants of searlesitefrom this location were published byRogers3in 1924. These crystals are prismatic and seldom exceed3 mm.
in length. The sample analyzed by Foshag contained less than one percent of impurities and his analysis was very close to the theoreticalcomposition, NarO . BzOe. 4SiOz. 2HzO.
* Published by permissionof the Director, U. S. Geological Survey.
t U. S. Geological Survey, Washington, D. C.
1 Larsen, Esper S., andHicks, W. 8., Searlesite,a new mineral: Am. Jour. Sci., 3g,

437-40 (9r4\

2 Foshag, William F., Searlesitefrom Esmeralda County, Nevada: Am. Minera)., 19,268-274(res4).

a Rogers, Austin F., The crystallography

ofsearlesite: Am.Jour.Sci.,7r4gg-502(1924).

r0l4

SEARLESITE FROM GREENRIVER FORMATION

1015

OccunnbNcB RNI Assocrerrow
The third recorded occurrence of searlesite is at three places in theGreen River formation in Sweetwater County, Wyoming. These places
are the locations of the drill core of the John Hay, Jr., Well No. 1,
approximately 18 miles west of the town of Green River; the drill coreof the Union Pacific Well No. 4 that was put down 2f miles west of theJohn Hay, Jr., Well No. 1;and the shaft, and trona bed reachedby thisshaft of the Westvaco Chemical Corporation, formerly the Westvaco
Chlorine Products Company. This shaft is approximately 3] miles northof the John Hay, Jr., Well No. 1 and 4| miles northeast of the Union
Pacific WelI No. 4. The exact location of the shaft is 1650 feet south and1010 feet west of the north and east boundariesof Sec. 15, T.19 N., R.
110 W.,6 P.M. Wyoming. Drilling was started August 16, 1946, andcompleted to a total depth of 1552 feet on September22, 1947.
Searlesiteoccurs at depths of 1480 feet and 1706 feet respectively, in
the John Hay, Jr., WeIl No. 1 and the Union Pacific Well No. 4. This
indicates a dip of the shale to the west ol 216 feet in 2f; miles, the elevations at the surface of the wells being 6355 feet and 6365 feet in the ordernamed. In the shaft of the Westvaco Chemical Corporation searlesite
was found at a depth of 1300 feet. The elevation at the top of the shaft
is 6227 feet. These figures point to a dip of the strata to the north of 52
feet in the 3f miles between the John IJay, Jr., Well No. 1, and the shaft.
fn the two drill cores and in the shaft searlesiteis found in oil shalewith shortite and tiny crystals of pyrite. At the bottom of the shaft at
a depth of 1500 feet searlesite is found in association with trona.
The saline mineral assemblageof the Green River formation is unique.
Two species, shortite and bradleyite, heretofore reported in no otherlocation, are found associatedwith trona, pirssonite, gaylussite, and therare mineral northupite. Shortite is ubiquitous through a vertical distance of more than 600 feet. Trona and northupite, though restricted todefinite horizons, are found in great abundance.
Cnaurcer CoupostrtoN aNo PuysrcAl PRopERTTES
A crystal from the trona bed (depth 1500 ft.) of the Westvaco Mine
was carefully crushed so that a minimum of fines was formed, thensieved, and the portion passing 80 and retained on 100 mesh was allowed
to remain in distilled water, changed daily, for 1! months. This wasdone in order to remove the small percentageof sodium carbonate known
to be present. Searlesiteis not affected by such treatmentl a sample sotreated for 6 months showed no change of the indices of refraction.
The usual methods of chemical analysis were employed; BzOs was
titrated on a sample that had been decomposedby HCl, using mannitol

1016

JOSEPH J. FAHEY AND JOSEPH M, AXELROD

and methyl red and phenolphthalein indicators. NazO was determinedby the J. Lawrence Smith procedure, and the HzO determined as theloss in weight on heating the sample to 800o C. for one hour. No BzOr
is lost at this temperature. The results of the analysis are recorded inTable 1.
TAero 1. Cnnurc,qr- AN.Lr,vsrs ol Sr,qnr-rsrrn FRoM TrrE Gnnrx Rrvpn Fonlla.rtoN,
SwBnrwl.ren Co., WvorrrNc
J. J. Fennv, Anolyst
RatiosComposition
SiOz
B:Oa
NazO
KrO
HrO -110'C.
HrO +110'C.
AlzOa
FezOs
CaO
Mgo

s8.88%
1 69 5IJ.JI

3.992
0 .9 9 1
1.005

none
none
8.90

2.0r3

0.04
0.04
none

0.03

100.15
Total
G.:2.460
Formula: NarO B:Og 4SiO, 2HrO
When treated with (l+2) IICI, either cold or hot, searlesitebehaves
similarly to biotite mica under these circumstances. Silica remains
quantitatively as a skeleton that retains the shape of the original grain,
and can be filtered off without difficulty. The index of refraction of thissiliceousskeleton is between 1.455 and 1.460.
The speciflc gravity of searlesiteis 2.460 determined with an AdamsJohnston pycnometer of 5 cm. capacity, made of fused silica. This is ingood agreementwith the determination by Rogersa(2.45) obtained bysuspensionin a solution of methylene iodide and benzol.
Searlesitefuses readily to a glass that has an index of refraction of
1.515.
Cnvsrer-rocRAPHY
In both the core of the John Hay, Jr., Well No. 1 and that of theUnion Pacific Well No. 4, the searlesiteis found as segmentsabout 3
mm. thick of flat anhedral crystals that lie paraliel to the bedding of theoil shale. These crystals are so oriented that the perfect cleavageparallelaO p .c i . t . , p . 5 0 l .

SEARLESITE FROM GKEEN RIVER FORMATION

1017

to the front pinacoid is always parallel to the bedding of the oil shale.
Also this condition obtains in the shaft of the Westvaco Chemical
corporation at the 1300-foot level. However, in the stratum of trona
10 feet thick that is reached by the shaft at a depth of 1500 feet, subhedral crystals of searlesiteup to 7 inches long, 4 inches wide, and one
inch thick are not uncommon. The largest crystals heretofore reported(Esmeralda County, Nevada) are approximately 3 mm' Iong. Due tothe presenceof minute quantities of organic matter, they are light brownin color. These crystals are randomly oriented in the trona bed and commonly have the front pinacoid (100) and the prisms (110) and (110)developed.

_'

2V=55"",r7

Frc. 1. Orthopinacoidal section showing
traces of the (010) and (r02) cleavages andthe emergence of the optic axes.

Frc. 2. Clinopinacoidal section showing traces of the perfect cleavage (100)and the poor cleavage (102). The optic
axial plane is normal to the section.

Two cleavagesheretofore unreported are found as traces on the perfectcleavage (100), parallel to the front pinacoid shown in Fig. 1. These
are the (1OZ)cleavage and the clinopinacoidal cleavage (010). Both are

1018

JOSEPHJ. FAHEY AND JOSEPHM. AXELROD

imperfect but unmistakably present. A thin section cut parallel to theclinopinacoid (Fig. 2) shows the traces of the perfect cleavage parallelto the front pinacoid and the imperfect (102) cleavage,parallel to therear dome that Rogers and Foshag, not having tc-ray data, mistook
for the base. The inclination of the optic axial plane to the c axis is 32"
and B is equal to 93o 57', the latter figure determined by the r-ray study,
the form (001) not being present.
The indices of refraction measuredwith sodium light are: a:I.516,
9:1.53I, and 7:1.535. These values check well with those of Rogers5
and Foshag.6
Tenrn 2. X-nav PowornDrllucrrox Dnra lon Sllnr,nsrrnlnou Wvourxc(FelMnradiation,
I:1.9373A)
d(obs.)
8.01
5.32
4.31
4.06
3.98
3.70
3.54
3.48
3.24
3.21
2.99
2.92
2.76
2.66
2.49
2.45
2.41
2.39
2.28
2.16
2.12
2.06
2.02
1.992
1.978
1.945
t.916
1. 8 9 6

10
1
J

5
2
1
J

4
A

2
3
1
L

6 Op. eit., p. 501.
6 O?.cit.,p.272.

100
110
101
101
200
111
111

2r0
r20
201
201
2r1
2tl
r2l
310
002
301
r02
102
311
320

1.825
I.

/OJ

r.746
1.690
t.647
1.632
I.OIO

1. 6 0 5
t.592
1. 5 5 4
t.473
1.451
r.431
1.406
t.334
1.320
1 .304
t.292
1.282
t.260
I.239
IJI
1.224
230,202,0221 . 2 1 5
1. 2 0 0
1.182
1.161
1.153
1.140

I .131
1.110
1.o79

I

I

2

SEARLESITEFROM GREENRIVER FORMATION

1019

X-Rnv AN,q,rvsrs
The *-ray powder pattern of the searlesite from the shaft of theWestvaco Chemical Corporation is identical with that of the searlesitefrom Nevada described by Rogers and Foshag. Measurements of thestronger lines of the pattern and the Miller indices, obtained from Weissenberg studies, are given in Table 2.
For the single crystal investigation, a small crystal of the searlesitefrom Nevada was chosen. Weissenbergphotograph (with Cu/Ni radiation) taken about the b and c axes and a rotation photograph taken
about the a axis combined with positive results of piezoelectrictests
made by Dr. Paul Smith of the Naval Research Laboratory show thecrystal to be monoclinic with the space group P21(Cl). The unit cellhas the following dimensions:A,
ao:7.972+0.010
b o : 7 . 0 5 2 + 0 . 0A1 0A
co:4.900+0.010
9:93' 57'* l0'(The error figures are estimates)
Specific gravity:
2.46t
Calculated (r-ray)
Foshag
2.44
2.45
Rogers2.460
Fahey (this paper)

The axial ratio is atbic:1.130:1:0.695 and the cell content is2(NaBSizOo'HrO).
These axial ratios and the value for beta are different from those ofRogers and Foshag and are related to them through the following
transformations:
A: -Za-c
a: -l/2 A -l/6 C
B: -2bb: -1/2 B

Lower
case
tetters;;. ,:;" ,-,", o.r.lll"".
Figure 3 shows, on the clinopinacoid, the relationship of the unit cellto the dome faces and to the axial directions derived by Rogers.
The axial ratips found by Rogers and Foshag from goniometricmeasurements were recalculated to conform to the unit cell found byusing r-rays. Interfacial angles were then calculated from the r-ray data.
The values derived from the r-ray measurementsand from the morphological measurements are compared in Table 3. The dominance ofthe (201) face caused Rogers to select a different o axis from thatfound by r-ray measurements,but when the data are recalculatedto acommon basis, the agreement is very good.

t020

JOSEPH J, FAEEY AND JOSEPH M. AXELROD

Frc. 3. Projection on the clinopinacoid of the r-ray unit cell, the crystal axes
derived by Rogers, and the dome faces.
T,tslr

3. Coupanrsox ol CRysrAr, CoNsr.cNrs Dnrrnunml
AND lRoM X-nev Mn,q.suREMENTS
X-rayo : b :c

p
a

b
?n

r
.t

MAb
rAa
sAa

Rogers1.130:1:0.695
93"57'.
(100)
(010)
(110)
(201)
(101)
4r"35',
40"41'
55"35',

1.119:1:0.689
93059'*
(100)
(010)
(110)
(101)
(101)
41"50'
40"37|
55030',

lRoM MoRprrolocY

Foshag1.I2lil:O.691
93'56',*
(100)
(010)
(110)
(101)
(101)
41o49'(range:51')
40'35'(range:38')
55o32'(range:28')+ Recalculatedfrom Rogers'andFoshagtsdata to correspondto r-ray orientatlon.
AcrNowrBocMENTS
The authors wish to express their thanks to their colleagues, Marie
L. Lindberg, Michael Fleischer, George T. Faust, William T. Pecora,
and C. L. Christ for their helpful suggestions and critical reading of themanuscriDt,