Tnn AUERTcAN M ll,uERALocIST
JOURNAL

Vol. 48

OF THE MINERALOGICALSOCIETY OF AMERICANOVEMBER.DECEMBER, 1963

Nos. 11and 12

THE OCCURRENCE AND PROPERTIES OF BARNESITE.
N a z V o O r o . 3 H z OA, N E W H Y D R A T E D S O D I U M
VANADATE MINERAL FROM UTAH1
Ar-rcBD. Weers, DapnNn R. Ross ano Rrcnano F. M,lnvrN,
Lr. S. GeologicalSurvey, Washington 25, D. C.
ABsrRAcr
Barnesite is a new hydrated sodium vanadate mineral found in the Cactus Rat groupof mines, 15 miles east southeast of Thompson, Grand County, Utah. It is found in small
cavities and fractures and as interstitial filling in sandstone in the oxidized zone of a vanadiferous uranium deposit. This deposit is in a conglomeratic bed in the basal part of theBrushy Basin Shale Member of the Morrison Formation (Late Jurassic).
Barnesite is dark red and consists of microscopic bladed to fibrous crystals either inloose aggregates or in radiating clusters. In continuous coatings, it is velvety with a botryoidal appearance. Barnesite has monoclinic symmetry with the b-axis parallel to the elongation. Optically the mineral is biaxial negative with parallel extinction on the fiber length(b-axis); a:1.797+.0O3, B above 2.0, and 7 above 2.0. The pleochroism is X yellow, Yorange-yellow, andZ red and the orientation isZ:b, parallel to the length of the blades
about 5'. The chemical analysis shows 82.40 per cent VzOs,
or fibers, Y:a, and Xlc
9.10 per cent Na2O, 7.73 per cent HzO and 0.40 per cent SiOz, total99.63 per cent and indicates the formula Na2V6O16.3H:O. The strongest lines of the x-ray difiraction powder
pattern are 7.90 A (intensity 100), 3.12 (70), 3.45 (35), 12.28(25),2.27 (25), and 1.800 (25)Unit cell data derived from least squares refinement of then-raypowder data, a:12.L7
A,U:S.AZ
L, c:7.78 A and B:95'2', com^parefavorably with the data of Barnes andQurashi (1952). The cell volume is 342.0 A3, cell contents NazVoOm.3HzO;calculated
density : 3.2 1 g/cm3, measured density : J. 1$ g7"-.:
Barnesite is named in honor of Dr. William H. Barnes, National Research Council of
Canada, who has made a major contribution to the knowledge of the crystal structure ofmany vanadium minerals.
h.rrnorucrroN

AND Acxxowr-BoGMENTS

Barnesite(NarVuOru.3HzO)was first studied in the spring of 1951in asample which had been collected by B. N. Webber and L. B. Riley(Union Mines Development Company) from the Cactus Rat group ofmines near Thompson, Grand County, Utah, during World War IL Thisofsample contained both barnesiteand metahewettite, CaV6Oro.3H2O,
similar appearance and caused confusion until spectrographic analyses
I Publication authorized by the Director

U. S. Geological Survey.

tt87

1188

A. D. WEEKS,D. R. ROSS.41TDR, F. MARVIN

on very small samplesaided in matching the r-ray diffraction powder patterns with the proper composition.
A reconnaissanceof the Cactus Rat open pits in the summer of 1951revealed only traces of carnotite but a more thorough search of the area in
1952 located a good occurrenceof barnesite in a small underground mine
(Weeks and Thompson, 1954). Study of the material confirmed it to be
the sodium analogueof metahewettite and led to the recognition that unit
cell data given by Barnesand Qurashi(1952,p.410-413) for Harvard No.
98019 sample from the "Cactus mine" Grand County, Utah, are forsodium vanadate rather than calcium vanadate.
In 1954A. D. Weeks and R. F. Marvin studied the area of the Cactus
Rat mines with regard to the origin of barnesite and the unusual assemblage of minerals in the Thompson district and collected better material
from the samemine where barnesitewas found in 1952.
We gratefully acknowledge the cooperation of W. H. Barnes and his
associates
M. M. Qurashiand H. G. Bachmannfor discussionand data on
the hewettite group minerals. Thanks also are gratefully extended to ourcolleagueson the U. S. GeologicalSurvey, H. T. Evans, Jr., E. A. Cisney,
and Malcolm Ross for discussionof.*-ray and electron difiraction data on
vanadium minerals and to C. L. Waring, A. M. Sherwood and G. B.
Magin, Jr., for spectrographicand chemical analyses.The mineral barnesite has been previously mentioned in papers by Ross (1959) and Weeks(1e61)
Occunnpxcr, aNo Ontcrx
AII samplesof barnesite for which the locality is known have come fromthe Cactus Rat group of mines, 15 miles east southeastof Thompson,
Grand County, Utah. These mines are chiefly in the NE. I of Section 33
and near the border of Section 34, T. 22 S., R. 22 E. Salt Lake meridan.
They are accessibleby two improved dirt roads leading south from U. S.
Highway 50,-one 5 miles east of Thompson and the other 7 miles westof Cisco. This group of mines consists chiefly of shallow open pits whichwere bulldozed and reworked in an everchanging pattern in the early
1950's.Severalsmall samplesof barnesitecame from theseopen pits but
the best material (used for chemical analysis) came from the only minein the group that had underground workings and a track along the haulageway. This mine is about 200 yards north of the improved road throughthe mining district, and near the Section 33-34 line.
The Cactus Rat mines are in the basal conglomeratic sandy beds of theBrushy Basin ShaleMember of the Morrison Formation (Late Jurassic),in contrast to the other mines in the Thompson district which are in theSalt Wash SandstoneMember of the Morrison and are stratigraphicallyBARNESITE

1189

next below the Brushy Basin. Although carnotite was known in this district as early as 1904,no significant production began until the expansionof vanadium mining in the ColoradoPlateau in the late 1930's.
In the vicinity of Cactus Rat, the Brushy Basin Member is about 450
feet thick (D. C. Alvord, written comm., 1952).Tt is predominantly red,
purple, and gray, variegated, bentonitic mudstone grading from pureclay to sandy mudstone.The conglomeraticsandy bedsat the baseof themember are discontinuous.At the Cactus Rat mines they contain fragments of vertebrate bones and coalified twigs and pieces of tree trunks.
The climate of the area is very hot and dry in the summer. This causestheaccumulation of a thick salt crust wherever moisture seeps from thebentonitic rocks.The salt crust consistschiefly of sodium sulfate (thenardite) and is found along the outcrop of certain layers of rock, along the
bed of dry gullies, and on mine walls. The abundance of sodium sulfate
locally in the Cactus Rat mine area led to the idea that its presencemay
have causedhewettite to changeto barnesiteby cation exchange.Credence is given this possible origin by the easewith which hewettite is converted to barnesite in the laboratory (see Chemical Analysis and Synthesis section and r-ray diffraction data in Table 3). Barnesite also may
have formed directly as an oxidation product of primary low-valent
vanadium minerals (which are still preserved in some of the deep, watersaturated ores two miles west of Cactus Rat and one and one half miles
east of it) if sodium was available at the time of oxidation.
Evans and Garrels (1958) and Evans (1959) have used all available
thermodynamic data to determine the stability fields of the various vanadium minerals in the oxidation sequenceon the Colorado Plateau. The
theoretical fields agreewith the assemblagesof minerals noted in the partially oxidized and oxidized deposits. The laboratory synthesis of barnesite and the hewettite minerals indicates also that they formed in slightly
acid environments.
Pnysrcer, AND OprrcAL PRopERTTES
Barnesite is brilliant, dark red with an adamantine luster when it isfresh, and it forms microscopic bladed to fibrous crystals. On exposure,the color becomesslightly brownish red, and the luster decreasessomewhat. This is due in part to handling becausethe grains are fragile, softand easily smeared. Barnesite forms small clusters of subparallel toradiating fibers as well as continuous coatings of bedding plane fractures
or small cavities where fragments of wood have weathered out. fn thesecoatings the grains stand vertically in a velvety mass that is nearly blackon the ends of the grains but the usual dark red on a broken surface.Somenearly spherical aggregatesof barnesite form on the irregular surface of

A. D. WEIiKS, '. R. ROSS,4ITDR. F. MARVIN

1190

the sandstoneand give a botryoidal growth of the coating. The thicknessof thesecoatingsis I to I mm; this representsthe maximum length of thebladedcrystals.Barnesiteis easilyfusiblein the Bunsenburner flame andprobably is about 2 on the fusibiiity scale.It is slowly soluble in dilute
HCI.
Barnesitehas monoclinicsymmetry with the b-axisparallel to the long
dimensionof the bladesor fibers. Optically it is biaxial negativeand has
parallel extinction on the b-axis;a: |.7 97 + 0.003,B and 7 are both above
2.0. The pleochroismis X yellow, Y orange-yellow,and Z ted, and theorientation is Z:b, parallel to the length of the blades,Y: a, and XAc
about5n.
CnBlrrcar- ANarvsrs AND SYNTHESTs
About 300 mg of barnesitewere purified from sample AW-202-54 collected by Weeks and Marvin from the underground mine in the Cactus
Rat group. This samplehas irregular coatingsabout one-half millimeter
Tasre

1 Cnnurcnl

vros

9 .1 0
82.40

HzO
SiOz

0.40

Total

99.63

NarO

ANar,vsrs or N.qrunaleNn SvNtnntrc

Blnxnsrrr

920
82 26
884

9.36
82.48
8.16

100.30100.001. Barnesite from Cactus Rat mine sample AW-202-54; analysis by A. M. Sherwood.
2. Synthetic barnesite, sample Na 1-1; analyst: G. B. Magin, Jr.
3. Synthetic barnesite, sample Na 4-1; analyst: G. B. Magin, Jr.
4. Theoretical composition for Na:O. 3VzOs' 3I{rO.

thick which were gently pried off in small piecesand separated from theattached sand grainsby handpicking. A semiquantitativespectrographic
analysisby K. E. Valentine showedover 10 per cent V, between5 and 10
per cent Na, and lessthan 0.5 per cent Si, Al, and Ca. A microchemical
analysis (Table 1) by A. M. Sherwoodshows 9.10 per cent Na2O' 82.40
per cent YzOs,7.73per cent HrO and 0.40 per cent SiOr, total 99.63andindicates the formula NazVeOro'3HrO.Analyses of synthetic barnesite
by G. B. Magin, Jr. (Table 1) are very similar to those of the natural material except for a slight difference in the water determination. This may
be due to excesswater held in the fine-grained, fibrous, crystalline mat of
the synthetic material. The apparent 5 per cent deficiency in water in the

BARNESITE

rr91

analysis of the natural sample may be due to analytical problems with asmall sample.
Barnesitehas been synthesizedboth by direct crystal growth and by
cation exchange (Marvin and Magin, 1959, pp. 109-110). At 55o C.,
NazVoOro.3HzOformed directly from a slowly evaporating solution of
NaOH (0.22}.{) and VzOs(0.11 M) adjusted with glacial acetic acid to a
pH rangebetween3.0 and 6.0. The precipitate was identifiedas barnesiteby r-ray diffraction powder pattern and chemical analyses' It would
probably form at lower temperaturesif the solution were evaporatedvery
slowly; rapid evaporation produces a metastable polyvanadate phase(pascoite)that is common on mine walls
analogousto CarVruOz4'16H2O
in the uravan district of colorado. Barnesitewas aiso formed by cationexchangeof hewettite in a sodium-bearingsolution with a pH between
3.0 and 6.0. Severalgramsof synthetic hewettite wereplacedin a solutionof NazSOq(concentrationvaried from 0.1 N to 0.7 N) for three weeksand
converted to barnesite. The r-ray pattern (Table 2) of this base-exchangedsample (I-Ca-18-23) is like that of natural and synthetic barnesite.
CnvsrerrocRApuy AND RELATToNTo OrHER VANADATESIn 1951, preliminary r-ray and electron diffraction study of barnesite
by E. A. Cisneyand A. D. Weeksindicated that it is monoclinic with theblades elongatedon the 6-axis,like the hewettite minerals' When it waslearnedthat W. H. Barnesand his associateM. M. Qurashi were engaged
in an r-ray investigation of vanadium minerals and had determined theunit cell of an unknown hewettite-like vanadate (now barnesite), nofurther r-ray work on this mineral was undertaken by us except to gather*-ray powder data on our analyzedsamples.The powder patterns of thesynthetic (Na-a-1) and cation-exchanged(1-Ca-18-23) barnesite arelisted in Table 2 with that of the analyzed, natural material from Cactus
Rat mine. AII three patterns have very similar d-spacingsand intensities.
Barnes and Qurashi in 1952 gave unit-cell data for what they thought
was a calcium hewettite (Harvard specimenNo. 98019from the Cactus
Rat mine). Later Barnes (1955) showed that this specimenwas in fact
a sodium hewettite identical with specimenAW-202-54 describedhere'
Qurashi (1961) has discussedthe relation between hewettite, CaVtOro'nHzO/ and its sodium analogue, barnesite. He examined in detail thesensitivity of hewettite to humidity changes and showed that barnesite
is insensitive to humidity.
Ross (1959) examined single crystals of specimen AW-202-54 by thetechnique of electron diffraction and obtained partial unit-cell data. His

1192

A. D. WEEKS, D. .R. ROSS ,4NT' R. F. MARVIN
Tnnr,B 2. X-Rav Drrrnacuor

Calculated dspacings, measured single
crystal intensities
hkl

Ir

Natural barnesite,
Cactus Rat Mine, Utah
AW-202-54 CrKa,),:2.2909 A, V filter

Synthetic barnesite
Na-4-1 CrlVd(meas )d(meas.)d(calc.)2

100 w 1 2 1 2001 s 7 . 7 5
T01
6. 8 1101
6.28
200 w 6 . 0 6
201 w 4 . 9 9201
4.58
300 w 4 . 0 4I

25
100

II

111s
2lo w
400 w
302 s
211 w
401 w
2tr
401 w
310 w
302
311 w
212 s

3.789
3-719
3.ffiz3 .601
3.461
3 .453
3.403
3.266
3.184
3.142)
Ii
3.12sJ
3.097
3.031
2.928
2.921
2.911
2.832
2.742
2.689
2.682
2.588
2.474

12.2"
7 .90*

3
2d

26
100

4 vvd
4 vvd

Synthetic barnesite(cation exchanged)l-Ca-18-23

K a , t r : 1 . 5 4 1 8A
Ni filterd(meas )

12.2
8.08

w
VS

L2.3
7.9

6.09
5.24

wF
wF

6.r
5.1

3.94

w2 w 3.87sJ
102
301 s
010
r02
301 w
110
202
011
111 w
202 s

Pomnn Dara lon B,q.nNrsrrr

3.70*

3.68

J.tz

J.)

3.45

3.M

3.45

70

3.12

18

2.92*

3.13

2.91

2.93
2.82

2.69*
2 vd
2 vd

2.65-2.583
2.49-2.423

I Intensities were estimatedby Qurashi (1961, Fig. 3) from singlecrystalphotographs.
'd-spacings are calculated
from the following unit-cell data: a:12.17 A, b:3.602,
c:7.78, and B:95o2'. This cell was obtained by Ieast squares refinement of the r-ray
powder data of natural barnesite indicated by an asterisk listed above. Calculated spacings
less than 2.681 A are listed only if indexed to an observed reflection.
3 Extremel]' difiuse bands.

tt93

BARNESITE
Tesrn 2-(continued)
Calculated dspacings, measured single
crystal intensities

hkl

Natural barnesite,
Cactus Rat Mine, Utah
AW-202-54CrKa,)\:2.2909 A, V fiIt".

I

11 d(calc.)'z

500 w
410 S
303 S

2.425
2.319
2.26e)

I

501 S 2.2s8J
4r2 s 2.052
502 S 1.979
304 w 1.810
020 s 1.801
021 s 1.754
214 S 1.677
222 S 1.563
800 s 1.s1sl
I

801 S
802 S
323 S

I

1.512J
1.455
1.411

Synthetic barnesite(cation exchanged)
Synthetic barnesite
l-Ca-18-23
Na-4-1 CrlV
CuKa, tr: 1.5418
A Ni filt"td(meas.)Id(meas.)

2.38
2.32*
25

2.27*4

3vd
3vd

2.06*
1.991x
1. 8 1 6
1 800*
1 . 755*
1.670*
r .558

z

25
3
2vd
3vd

2.26

wFd

WF
F
WFd

2vd
3vd
3vd

r.993

4

1.456
1.410

wFd
wFd

1.459
1.408

a This ambiguous line was erroneously included in the least squares calculation, but
the result is not significantly affected by it.
faint;
VF:very
F:faint;
W:weak;VS:very strong; S:strong; M:medium;
very, Iaint; d:difiuse; vd:very diffuse; vvd:very, vety, difiuse. Powder
WF:very,
patterns made with 114.6 mm diameter camera; error due to film expansion is less than
0.216 ol d.; cut-ofi for Cr radiation is 20 A and for Cu radiation, 15 A.

Table 1 (Ross,1959,p. 328) showsthe closesimilarity betweenbarnesite
and the hewettite minerals in the a-b plane.
In Table 3 are tabulated the crystallographic data of Barnes andQurashi (1952),Qurashi (1961),and Ross (1959)along with the unit-celldata obtained for the natural barnesitefrom the Cactus Rat mine, andthe synthetic barnesite(Na-a-1).Theseunit-cell data were obtainedfrom
least squaresrefinement of the *-ray powder data given in Table 2. The
refinementwas carriedout on the Burroughs220 computer by Howard T.
Evans, Jr. with a program written by H. T. Evans, J.., D. E. Appleman
and D. S. Handwerker. The measuredIines of the *-ray powder patterns
were indexed by comparing them to the calculated d-spacings based on
the unit cell of Barnes and Qurashi (1952) and to the intensities ob-

L194

A. D. WEEKS, D. R. ROSSAND R. F. MARVIN'felrn

3. Cnvsrer,r-ocnaprrrcDATAron Banxnsr:rrSingle crystal data

d (A)

, (A)
, (A)
p
a : b :cVolume (Aa)
Cell contents
Space Groupr
Density (meroured)Density (calculated)(Barnes and Qurashi)l
12 18
3.614
7.80
95"
3.370:1:2.158
342.O
NarV6Or6'3HrO
P2/m(Ros)r
12.17!O.O2
3.604i 0.005

3 .21 g/cmt

X-ray powder data (Table 2).
(Synthetic Na-4-1)
12 17+O.04
1 2 .1 8 t 0 . 0 9
3 . 6 0 21 0 . 0 1 03.59610.016
7.78t0 04
7.79 10 08
95"2'+24'
94"50',t 1'43'
3 . 3 7 9t 1 : 2 . 1 6 0 3 - 3 8 7 : l : 2 . 1 6 6
i39.7
340.0
NazZoOu 3HrO Na2Y6Or63H2O(Cactus Rat)

3.23 g/cma

3 -23 g/cmt

t Single crystal r-ray data from Barnes andQurashi (1952, p. 411), on material referred to as hewettite,
but later shown to be sodium vanadate (Barnes, 1955)r Single crystal electron diffraction data from Ross (1959, p. 328), on material lrom Cactus Rat mine.
' unit cell data obtained from least squaresrefinement o{
the r-ray powder data given in Table 2.
r Space group fromQurashi (1961, p, 660).

tained by Qurashi (1961, Fig.3) from single crystal weisenberg photographs.rn this figure Qurashi showsthe intensitiesof the hOl and h1l reflectionsas either missing,weak, or strong. Becauseof the nature of thecrystal structure (Bachmann and Barnes, 1962), the h2l pattern must be
similar to the hOl pattern. This information made it possibleto index allof the powder lines for barnesite without seriousdiscrepancy.The unit
cell given by Barnes and Qurashi (1952) was used as a starting point in
the refinement.All of Qurashi's"strong" reflectionsare observedon the
powder patterns, and most of his "weak" ones.The fact that all the unit
cell constants given in Table 3 are indistinguishabre within the experimental error strongly supports the conclusion that all the material representedis essentiallythe sameand characteristicof the mineral barnesite.
RrntnrNcEs
Bacnnexw, H. G. eNn w. H. BerNes (1962) The crystal structure of a sodium-calcium
variety of metahewettite. Canod. Mineral. Z, 2lg-235.
Brrurrs, W. H. (1955) "He$'ettite', and ,,metahewettite.,' Am. Mineral,.40. 6g9_691.
M. M. Qunesnt (1952) Unit cell and space group data for certain vanadiumminerals. A m. Mi.neroJ, 37, 407422.

MlnvrN, Rrcn^no F,, -LNo Mncrn, G. B.,
Jn. (1959) Synthesis of calcium vanadate minerals and related compounds, part 8, ia Go*nrr,s, R. M. ar.rn E. S. Lensooo, 3d,
Geochemistry and mineralogy of the cororado prateau uranium ores. u. s. GeoI.
Suney ProJ. Paper 320,103-111.

BARNESITE

1195

Qtrnasnr,M. M. (1961)The polymorphismand hydration characteristicsof hewettite andmetahewettite.Canail.M ineraJ.6, 647-662.
Ross, Merroru (1959) Mineralogital applicationsof electron diffraction. II Studies ofsomevanadium minerals of the ColoradoPlateau.Anr..MineraL.44,332-341.
Wonxs, A. D. (1961)Mineralogy and geochemistryof vanadiumin the ColoradoPlateau.
J our. Less-Common
M etatrs,
3, 414!450.
--AND M. B. TnoupsoN (1954) Identification and occurrenceor uranium andvanadiummineralsfrom the ColoradoPIateau.(J. S. Geol,.
Suney Bul,l,.1009-8.,7342,
Manuscriptruei.ad.,Ma1 3, 1963; accepted.for
publ,iration,Moy 29, 1963.