THE AMERICAN
MINERALOGIST'
VOL
.54, MAY'JUNE,
I969
CLIFFORDITE-A NEW TELLURITE MINERAL FROM
MOCTEZUMA, SONORA,MEXICO
BerylcoIndwstries,Inc',
Rrcnanp V. G,trNns,Kazerccki
19512.
P ennsYlaani'a
BoYertown,
ABsrRAcr
This new mineral occurs along joint surfaces in the oxidized zone of the san Miguel
mine, a telluriurn-gold-silver prospect near Moctezuma, sonora, associated with mackayite,
barite, quartz, and limonite. It has also been found in very small quantities at the Moctezuma mine in the same district, associated with native tellurium and paratellurite in small
vugs.
The small octahedrons are bright yellow with adamantine luster. The mineral is iso-
gave 31.3 percent U and 52.6 percent Te, which corresponds closely to the formula uTeroa.
Specific gravity, measured on synthetic material, was 6.57, and calculated specific gravity
ls o./o.
S i n g l e c r y s t a l p r e c e s s i o n p h o t o g r a p h s s h o w e d o : 1 1 . 3 7 1A a n d s p a c e g r o u p P a 3 , Z : 8 '
The principal powder lines with corresponding intensities are 3.273 (10): 2.844 (8): 2.007
( 8 ) : 2 . 7 5 5( 7 ) : a n d r . 7 1 2 ( 7 ) .
Cliffordite from the Moctezuma mine contains a little lead and is identical with the supposed lead oxy-fluoride from this mine described by Mandarino and Williams in 1961. The
lead oxy-fluoride is therefore not a valid species.
The name is for Clifiord Frondel, in recognition of his many contributions to the study
of the mineralogy of uranium.
INtnooucuow
In 1963 the writer noticed crusts of bright yellow microscopic crystals
on some mackayite specimensfrom the San Miguel Mine, Moctezuma,
Sonora,Mexico. Subsequentinvestigations establishedthat these crystals
consistedof uranium tellurite, a new mineral. Later on it was found that
this mineral is identical with a substance from the Moctezuma Mine
which had been first observed in 1961 and mistakenly identified as lead
oxy-fluoride. The name cliffordite is proposed for this mineral.
OccunnnNcB
The San Miguel Mine is about 10 km northwest of the Moctezuma
Mine in an environment of tertiary andesite porphyrys and altered tuffs.
Qtartz veins cutting these rocks sometimescontain substantial amounts
of barite and pyrite, and in local shoots may be mineralized with native
tellurium and other tellurides including gold and silver minerals. Oxidation of these veins has given rise to a number of oxidized tellurium min697
698
RICHARD v. GAINES
erals, especiallymackayite, besidesabundant jarosite and limonite and
other iron oxidescoating fractures.
Minerals recognized in very minor amounts include tetrahedrite,
rickardite, emmonsite,tellurite, schmitterite (a new uranyl tellurite, the
description of which is in preparation), cliffordite, and cerargyrite.
The cliffordite is rare and becauseof the small size of the crystals and
druses is not easy to find in spite of its bright color. Only about ten
specimensaltogether have been found so far. It occurstypically on oxidized joint surfacesin drusesand scatteredabout between larger mackayite crystals which are thickly disseminatedon t.he same surfaces.
Sometimesthe mackayite is vellowish,and sinceit has a crystal habit in
some respectssimilar to the cliffordite and both minerais tend to give
triangular adamantinereflections,this further tends to make recognition
of the clifforditedifficult at a quick glance.The crystalsare always small,
the largest observedbeing about 0.2 mm across,and the majoritl,- are
much smaller.
Puysrc,q.rAND OprrcAL PnoprnrrBs
Cliffordite is a bright sulphur-yellowcolor, with an adamantineluster.
Its hardnessis 4, and its density, measuredby pyknometer on synthetic
UTe3Os,is 6.57. Cliffordite is optically isotropic, and the index of refraction is greater than 2.11, the highest liquid available to the writer.
CnBlrrc,lr Tnsrs
cliffordite is solublein concentratedhydrochloric acid but insolublein
dilute acid. rt also dissolvesslowly in solutions of the alkali hydroxides.
By X-ray fluorescenceanalysisspecimensfrom the San Miguel Mine were
shown to contain onlv uranium and tellurium.
CouposrtroN
The first analysismade on cliffordite was done by Dr. Kurt Fredriksson of the Smithsonianrnstitution with the electron microprobe there.
Using as standardsgrains of moctezumite,tellurite, and other tellurium
minerals, the percentagesof U and Te were found to be 24]_ 1 and 54* 1
respectively.
since insufficient natural material was available for a wet chemical
analvsis,it was decided to try to svnthesizethe mineral. preliminary
effortsbasedon uranyl salts and tellurium dioxide were unsuccessfur,
but
when a quadrivalent uranium salt (UFa) was substituted for the uranyl
salts in the raw material, crystalswere producedwhich were identicarin
powder pattern, crystal habit, color and qualitative composition to
natural cliffordite, hence the crystals were assumed to be synthetic
CLIFFORDITE
699
cliffordite. Considerableexperimentationwas required before the optimum conditionsfor synthesiswere established;it was found for instance,
that a moderate oxidizing environment (using hydrogen peroxide) was
very helpful, probably in causingthe TeaOsa complex to form. An excess
of oxidizer resulted in the formation of uranyl tellurite plus tellurium
dioxide. Natural uranyl tellurite has also been found at both the San
Miguel and the Moctezuma Mines; its description is in preparation.
The synthesiswas carried out in pyrex and in vycor tubes in a stainless
steel bomb. The best results and largest crystals were obtained at about
360oCand 184 bars.
The synthetic product was analyzedby standard wet procedures.The
results of analysisare given in Table 1. The resulting formula, UTe3Os,
makes cliffordite the secondtellurium compound found in nature having
the TeaOsa radical, the first one being spiroffite,(Mn,Zn)2 TeaOs,which
was found at the Moctezuma Mine.
Tner,o1. Qu,lNuranvn Cnrnrc,lr,AN,rr.ysrs
ol Cr-rnlon-orro
UTe:Os
U
Te
31.79
TesOs
68.21
Total
Natural clifiordite microprobe analysis
Synthetic
cliffordite
3r.25
24tt
5 4 +1
( 7 2 +r . s )
70.25
100.00
r 0 1. 5 0
Monpuorocy
Crystals of cliffordite are isometrjc, and the only form observedin
natural material is the octahedron.Synthetic material, while dominantly
octahedral,also showed the cube.
X-nav Pownpn DrlrnlcrroN
Dnr.o.
Powder photographs of cliffordite gave a pattern in which the three
strongestlines are 3.273, 2.844 and 2.007. Table 2 gives a completelist of
d values with corresponding hkl indices. Since sharp lines were observed
even in the back reflection region, it was possible to use thesefor a refinement of the cell dimensions.
Cnvsrar, Srnucrunp
Buergerprecessionphotographswere made of the 100,hlo, h20planes,
and also of hh} and hhh planes.These establishedthe symmetry as cubic,
spacegroup Pa3.The value of o is 11.371A, and the cell volume is 1470.3
RICITARD V. GAINES
700
Teerr 2. Ivorxro X-Rev Powrnt PetrrnN ron Ctrrronortn
B a s i so: : 1 1 . 3 7 1A
Cu radiation,Ni frlter
I
|
4
1
6
6
3
2
10
3
6
4
2
7
4
|
3
5
1
2
6
2
2
2
|
l
hkl
d(obs ) d.(calc)
hkl
I
d(obs.)
6.52
566
5.07
463
4 02
3 80
3 423
3.273
3 159
3.037
2 844
2 755
2 683
2 537
2 479
2 322
2 270
2 226
2.t10
2.OO7
1.981
1.953
1 894
1 845
1 796
r.778
| 756
t.712
1 696
1.677
1.640
1.625
1. 6 0 8
1.575
I 518
1 505
| .457
1 446
| 421
1.408
111
200
210
211
220
221
311
222
320
321,
400
4tO,322
411,330
420
421
422
430
131
520,432
440
522,441
530,433
600,442
611,532
620
62t,540,443
541
622
630,542
631
444
632
7 1 0 ,s s o ,5 4 3
640
642
722,544
6 5 0 ,6 4 3
732,651
800
8 1 0 ,7 4 0 , 6 5 2
2
5
1
3
3
2
2
6
r
3
2
1
1.
2
1
6
1
3
3
2
2
1
1
2
3
1
5
3
4
3
1
4
5
2
2
2
t.40t
1 400 811,741,554
1 379 1 379 820,614
1.358 1.359 653
1.341 1 340 822,660
1 322 r.322 831,750,743
1 305 1.304 662
840
1 . 2 7 2 1 . 2 7|
1.241 | 241 842
1.225 1.226 92r,761,,655
1 212 1.212 664
1..204 1 20s 922,850,843,162
l 161 1.161 844
I r49 1.149 941,853,770
1.t38 1.137 10 0 0,860
1.131 1 131 10 1 0,942,861,764
1 1154 1.1150 10.2.0,862
1 0938 1.0942 10.2.2,666
1 0554 1 0558 10.4.0,864
1 0386 1.0380 10 4.2
9897 10.4 4,882
.9890
9751 10.6.0,866
.9741
9605 .9610 10.6.2
9116 .9476 12.O.O,884
9342 .9347 12 2.0
9221 .9223 12 2 2,10.6 4
8 9 6 0 . 8 9 6 2 1 2 4 l , l l . 6 . 2 , 1 0 6 . 5 ,9 8 4
8 8 7 9 1 2. 4 . 2 , 1 0 . 8 0 , 8 8 6
.8875
8773 10 8.2
.8771
.8476 .8175 12-60,10.84
8383 12.6.2
.8385
. 8 3 4 1 . 8 3 3 8 1 3 4 1 , 1 18 . 1 , 1 I . 7 4
8122 14 0 0,12 6.4
.8121
8 0 4 1 1 4 2 0 , 1 0 1 0 . 0 , 1 08 . 6
.8042
7961 14 2.2,10.1,0.2
.7961
7 9 4 2 1 4 . 3 . 0 , 1 36 . 0 , 1 2 6 s
.7941
7 9 2 2 . 7 9 2 3 1 4 3 . r , 1 3 6 1 , 1 1 . 92 ,
1 1 ? 6 , 1 09 . 5
.i862
.7865 14 3 2,13 6 2,12 8.1,
1 2 7 . 4 , 1 0 .1 0 3 , 9 8 8
.7809 .7810 11.1 0,12 8.2
7731 14.42,12 6.6,10 30.4
.7737
6.565
5686
5 085
4642
4.020
3.790
3.428
3 283
3 154
3 039
2 813
2 158
2 680
2.543
2 481
2 32r
2 274
2 230
2 112
2 010
1 979
l 950
1.895
1 845
1.798
r.776
1.755
I.714
1 695
|.677
1.641
1,.624
1. 6 0 8
1.577
1 520
1.506
1. 4 5 6
| 444
1.421
1.410
2
.1
3
d(calc.)
L3"Z:8, and the calculatedspecificgravity is 6.766,in reasonabieagreement with the measuredvalue of 6.57.
During the courseof this investigation,a samplewas borrowedfrom the
mineral collection of the American Museum of Natural History of a
mineral which had beenfound at the Moctezuma Mine in 1961and tentatively identified by Mandarino and Williams (1961) as lead oxy-fluoride,
a new mineral. This mineral occursas a bright yellow crystallinecoating
in cavities in native tellurium, associatedwith quartz and paratellurite.
CLIFFORDITT,
701
Becausethe color is identical with cliffordite,and someminute octahedral
crystals were visible, cliffordite was suspected.X-ray fluorescenceanalysis showed tellurium and uranium as major constituents,with a minor
quantity of lead alsopresent.The powder photograph of this substanceis
identical with that of cliffordite,with the exceptionthat o:11.47 A. This
slightly larger cell is probably due to the presenceol 2 to 3 percentlead in
substitution for some of the uranium. The three strongestlines of lead
oxy-fluorideare 3.33, 2.88 and 2.04.On the basisof thesedata, there can
be no doubt that the mineral found at the Moctezuma Mine is plumbian
cliffordite and the lead oxy-fluoride as a natural mineral has yet to be
found.
N.qlrn
The name cliffordite is proposedfor this mineral in honor of Professor
Clifford Frondel of Harvard University in recognition of his many contributions to the scienceof mineralogy and in particular in the fi.eldof the
mineralogyof uranium. Cliffordite has been approvedby the Committee
on New Minerals and New Mineral Names of the I.M.A.
Tvpo M-q.rBnr.q.r.
Specimensof "lead oxv-fluoride", now known to be plumbian cliffordite, are to be found in a number of museums.A specimenof cliffordite
from the San Miguel Mine has beendepositedin the mineral collectionof
the SmithsonianInstitution, U.S. National Museum, Washington, D.C.
AcxNorvlnocnlmNts
The writer wishes to express his appreciation to Ing. G. P. Salas, Director of the Instituto de Geologia of the National University of Mexico, under whose auspices this work
was undertaken; to Dr. Kurt Irredriksson of the Smithsonian Institution {or electron
microprobe analyses; to Quim Alberto Obregon, for chemical analyses, and to Vincent
Nlanson of the American Nluseum of Natural History for the loan of specimens.
RnnnnrNcns
GerNrs, R. V. (1965) Mineralizacion de telurio en la mina Moctezuma, cerca de Moctea)ma,Sonora. Unir. Nac Anton , Mex ,Inst. Geol.Bol.75, (pt. 1.)
(1967) Nuevos datos sobre mackayita. Unit. Nac Auton., Mex , Inst. GeoI. Bol.
82, (pt.2).
X{aNnenrwo,J. A., lxo S. J. Wrr.lraus (1961) F-ivenew minerals from Moctezuma, Sonora,
Mexico. Science, 133, 2017.
, S. J. Wrlrrelts e.xo R. S. Mrrcnrr.r, (1963) Spiroffite, a new tellurite mineral from
Mexico. Mi.neral, Soc. Amer. Spec. Pop. l.
kI anucripl
receired.,J anuary, 3 , 1969 ; acceptetlfor publ,icotion, February I 1, 1969.