RABBITTITE,

A NEW URANYLCARBONATE

FROM UTAH*

Many E. Tnonpsox, Alrcr D. Wnnrs, .tNu Ar-BxaNprn M. Sunnwoon,
U. S. GeologicalSuney, Washington 25, D. C.
ABsrRAcr
Rabbittite is a new hydrated calcium magnesium uranyl carbonate found in the Lucky
Stdke No. 2 mine, San Rafael district, Emery County, Utah, in July 1952. It is pale green,
finely acicular to fibrous, silky, and occurs as an eflorescence on the mine wall. It is optically biaxial, probably positive, with indices of refraction a:1.502+0.005, P:1.508*0.005 and z:1.525+0.003. The specific gravity is abont 2.6. The chemical analysis
shows CaO 10.6 per cent, MgO 9.2, UOt 37.4, COz 17.8, HrO 24.5, acid insoluble 0.5;
total 100 per cent, and indicates the formula CarMgr(UOz)z(COt6(OH)4. 18H2O.An r-ray
rotation photograph of a small bundle of fibers shows the unit cell length c6:p.45 +0.05 A.
From the indexing of iziO reflections os is thought to be 32 6 + 0.1 A and 6o23.8 + 0.1A, withz:8.
IxrnopucrroN AND AcrNowrnncMENTS
Rabbittite was collected from the Lucky Strike No. 2 mine, Emery
County, Utah, in July 1952by M. E. Thompson and A. D. Weeks when
they visited the mine with other U. S. Geological Survey geologists.The
mineral was determined as a new one becauseits r-ray diffraction powder
pattern and its physical and optical properties differ from those of otherknown uranium carbonates.
Of the uranyl carbonates in the literature, only swartzite might beconfused with rabbittite. Swartzite is, however, definitely distinct fromrabbittite, and to make the differences clear the optical properties,chemical analysis,and d-spacingsof the #-ray powder pattern of swartzite
are included for'comparison with those of rabbittite.
Rabbittite is named in honor of John C. Rabbitt, who was chief of theU. S. Geological Survey Trace Elements Section hom 1947 to 1953-in
recognition of the leadership and inspiration he gave to the members ofthe laboratory.
Thanks are gratefully extended to J. W. Gruner, University of Minnesota, for loan of an ore sample from the Lucky Strike No. 2 mine.
This work was part of a project on mineralogy of uranium in sandstonetype depositsthat is being conductedby the U. S. GeologicalSurvey onbehalf of the Division of Raw Materials of the U. S. Atomic Energy
Commission.
OccunnrNcn
Rabbittite occurs as an eflorescenceon a pillar of high-grade ore near
the portal of the Lucky Strike No. 2 mine, Emery County, Utah. The* Publication authorized by the Director, U. S. Geological Survey.

201

202

M. E. THOMPSON.A. D. WEEKS AND A, M, SHERWOOD

mine is in a uranium deposit in the Shinarump conglomerate (Triassic),
between the San Rafael River and the Muddy River on the west flankof the San Rafael Swell. Figure 1 is an index map showing the locationof the mine. The ore contains pitchblende and is only partly oxidized
becausethe deposit is protected by the overlying Chinle formation andWingate sandstone, which rise in a high cliff above the mine. The orenear the portal was high grade, containing pitchblende with a little

G R E E NR I V Ew
$I

EcChinlc lornolion

ond

Shinorump conglon!rolc

0SCALE!

l0 r{rl EsFro. 1. Index map of locality of rabbittite.

pyrite and galena, and many yellow and orange secondary uranium
minerals, including fourmarierite,l rabbittite, zippeite, another uranium
sulfate that is related to zippeite, and another new uranium mineral,
possibly magnesium uranyl sulfate, whose description is not yet completed. Gypsum and at least two pink cobalt effiorescences,bieberite andsphaerocobaltite, were collected from the same pillar on which the rabbittite occurred.
Pnvsrcar AND OPTTcALPnopBnrrBs
Rabbittite occurs as bundles of pale-green extremely small acicular
crystals with a silky luster. The bundles of fibers resemble talc, in thatsome of them are bent and twisted.
1 Specimen courtesy ofJ. W. Gruner.

RABBITTITE. A NEW LTRANYLCARBONATE

2O3

The hardness of rabbittite was determined approximately by rubbing

specific gravity was measured by suspending grains of the mineral in amixture of bromoform and acetone. The mineral floats just under thesurface of a Iiquid with specific gravity oI 2.57.
Rabbittite is considered to be monoclinic on the basis of its optical
The small acicular crystals are elongated parallel to the c-axis.
properties.
-utra".
the microscope the crystals show a cleavage across the fibers,
which is probably parallel to {001}, and two easy and perfect prismaticcleavages.
Even with the aid of an oil-immersion lens, individual crystals of rabbittite are too small to give an interference figure. The fibers in some of
the bundles seem to lie in parallel orientation, and measurementsof theoptical constants were made on several such bundles. Some of the bundles
seem to be flattened on {100} and give an optical figure thought to be
an obtuse bisectrix figure.
The optical properties of rabbittite are distinctly different from thoseof swartzite. as shown below:
Rabbi.nite
Orientation

xv:b
ZAc-15"1.50210.005
1.508t 0.005
1.525+ 0.003
Biaxial positive (?)

Swartzi.te
n

1.465
1.51
1.540
Biaxial negative

CnBurcer- CouposrrroN
With the aid of a binocular microscope,slightly Iessthan 0'1 g' of rabbittite was handpicked for analysis. The mineral was concentrated bypicking the Iargest aggregatesof rabbittite from the friable sandstone.
The aggregateswere crushed,examined under the binocular, and further
purifiJ. A semiqua.ttitative spectrographic analysis made by C' S'
Annell on a 10-mg. sample showed more than 10 per cent U, 1 to 10 per
cent Mg and Ca, 0.1 to 1 per cent Si, and 0.01 to 0.1 AI and Y' About
75 mg. was availablefor the chemicalanalysis (Table.1) made by A' M'
Sherwood.
In the chemical analvsis of rabbittite the sample was first dissolved in

201

M. E.
Tler,a'fuoMpsoN,

1. Cnrrrrclr,

A. D. WEEKSAND

A. W. SHERWOOD

ANar,vsrs elto Tnrolrrrc.tr,Coltpost'ow
nNo Crrnurcal ANer_ysrs or Swanrzrre

Rabbittite

Swartzite

Analysis of 75 mg.
b-v A. M. Sherwood

CaaMgr(UOz)z(COr)e(OH)l 18HrO

COz
HrO
Acid insoluble

1 0. 6
9.2
3 7. 4
1 7. 824.5
0.5

tl .328.09
38.54
1 7. 7 9
24.26

Total

100.0

100.00CaO

Mso
UO:or Raserttrtu

Analysis in Axelrod
et aI. (1951)by
F. S. Grimaldi
t -Jz

5.47
3 8. 8 5
1 7. 9 229.69
0. 75 (rem.)
100.00water, and carbon dioxide was determined by titration with standard
HCl. The silica was removed by volatilization with HF. The uranium
was then separatedwith NHTOH, reduced,and titrated with KrCrzOz.
Calcium was precipitated with (NH4)2CrO4
and ignited to CaO; and themagnesiumwas precipitated with (NH4)rHpoa and ignited to Mgzpzoz.
Total loss on ignition at 900" c. was determined,and the per cent co,
was subtracted from it to calculatethe total H2O.

bittite but in difierent proportions. The chemical analysis of swartzite
i n g i v e ni n T a b l e 1 .
X-Rev Dr'rrnacrroN Dare
The r-ray powder pattern of rabbittite distinguishesit from the otheruranyl carbonatesalthough, in common with the others, its powder pattern contains a number of lines with large d-spacings,indicating a largeunit cell. The pattern obtained with the r-ray spectrometershows thecloselyspacedinner lines (Table 2) with much better resolutionthan theA NEWRABBITTITE.
Tlril-n 2. X-nav Drrltactrolt

URANYL205

CAKBONATE

Powoen ParrnnNs on R.q.nstrtrtn

llro Swanrzrrr(d-spacings of rabbittite measured on r-ray spectrometer pattern'll4' per minute, Cu/Ni radiation)
Swartziter

J

15J

108JI

315, broad
53

19.4
1 8. 6

rt.28
8.63
8.24
7. 7 e
7.15
6.81
6.47
6.35

109.)
11018)
a

2

5 -6J

5.72
5.22
4.81
4 . 7|
4.51
4.37
4.28
4.05
4.03
3.84

7

1, broad

3.7r

5i

5

3.60
3.33

7I

8
13J

11I

7
18,,

I

882
2
32

8.76

7. 3 r
6.37
5.83
5 .5U

5.13
4.82
4.62
4.46
4.37
3.85
3.66
3. 5 3
3.39
J.JI

3.25
3.19
3.11
3.04
2.9r
2.82
2.6r
2.28
2.23
2.r9
2.70
2.06
1.8r7
1.707
r.375
1.268
t.2r7
0.9615

1 Axelrod et aI. (1951\.

fied version of Bjurstrom's chart (Bunn, 1946,p.280) and the hh} indices thus obtained are Iisted in Table 3. The o arrdb axes appear to be atright angles to one another, and according to the graphical solution
a o : 3 2 . 6 * 0 . 1 A a n d D o : 2 3 . 8* 0 . t A . t n e n u m b e ro f f o r m u l au n i t s i n t h eunit cell, is probably 8;by calculation from the approximate figures for206

M. E. THOMPSON, A. D, WEEKS AND A. M. SHERWOOD
Tanr,n 3.-TpNrLrrvn INorxrrc ol /2fr0Rnlr,ncrroNs or Ra.ssrrflrn(X-ray rotation photographaround c-axis;Cr/V radiation;
ao:32.62,bo:23.77)

J43, broadaJ

33
10J

J

1
J
J

ao:32.62

bo:23.77

il (meas.)il (catrc.)

hk0

1 9. 0L6.2
1 3. 5

19.2r
16.3
13.45
1 1. 8 8
lt.r7
9.89
9.60

1102Nt2.otI.24
9.89
9.60
8.96
8 .1 3

7. 7 r8 .1 58.02
7. 9 2
7. 7 1
1. 7 07. r s

7. r 3
5.95
5.82
5.70

5.72

5.21
4.80

5.21
4.80

4.70
4.40
4.34
4.10
4.03
3.84

4 . 7|
4.39
4.36
4.tl
4.01
3.85
3.84

5.94

5.06

1JA ,7<qJ51

5

2ro020
120
310
220
400
320
030
410
130
230
040
L40
520
430
340
440
050
150
540
350
450
640
260
550

as, bs, ctr,from the specific gravity, and with no allowance made for B
angle differing from 90o, the number of formula units is 7.8. The mineralis considered monoclinic because of its optical properties. The B angle
cannot be accurately determined on the present material, but it is probably close to 90o.
Rrlnnnncos
Axtr.noo,J. M., Gnnauor,F. S.,MtroN, C.,aNoMunerA,K. J. (1951),
Theuranium
mineralsfrom the Hillside mine, Yavapai County, Arizona: Am. Mineral.,36, l-22.
Bunt, C. W. (1946),ChemicalCrystallography,London,OxfordPress,422p.
Manuscri,ptrecehted
April I, 1954.