Co±nite

U(SiO4 )1¡x (OH)4xc 2001 Mineral Data Publishing, version 1.2°

Crystal Data: Tetragonal; may be metamict. Point Group: 4=m 2=m 2=m: As crystals,
rarely > 20 ¹m, and in colloform to botryoidal incrustations, radially ¯brous. Commonly
pulverulent, in aggregates of extremely ¯ne crystallites, or massive.
Physical Properties: Fracture: Irregular to subconchoidal, earthy. Tenacity: Brittle orfriable. Hardness = 5{6 D(meas.) = · 5.1 D(calc.) = n.d. Radioactive.
Optical Properties: Opaque, transparent on very thin edges. Color: Black from included
organic matter; pale brown to dark brown in thin section. Luster: Dull to adamantine.
Optical Class: Isotropic due to ¯ne grain size; uniaxial (+) or ({). Pleochroism: Moderate; paleyellow-brown k length, medium brown ? length. n = 1.73{1.75
Cell Data:

Space Group: I41 =amd (synthetic USiO4 ):a = 6.979

c = 6.252

Z=4

X-ray Powder Pattern: Synthetic USiO4 ; natural material gives broad peaks or may bemetamict.
3.48 (100), 4.64 (95), 2.636 (95), 1.803 (70), 2.789 (45), 1.849 (35), 1.738 (35)Chemistry:
SiO2UO2Al2 O3
Fe2 O3As2 O5
V2 O5Pb
H2 O(1)
5.20
68.29
3.87
1.24
4.35
2.85
0.12
[8.49]

(2)
18.20
81.80

Total

[94.41]100.00

(3)
16.41
73.75

9.84
100.00(1) La Sal No. 2 mine, Colorado, USA; H2 O from loss on ignition, contains admixed clay
minerals, vanadates, organic matter, etc. (2) USiO4 : (3) USiO4 ² 2H2 O:
Occurrence: In Colorado Plateau-type black unoxidized U{V deposits, replacing organicmaterial in sandstone; in other sedimentary and hydrothermal vein uranium deposits.
Association:matter.

Uraninite, thorite, pyrite, marcasite, roscoelite, clay minerals, amorphous organic

Distribution: Numerous minor occurrences; those mentioned are for well-crystallized or
studied material. In the USA, in the La Sal No. 2 mine, Beaver Mesa, Gateway district, Mesa
Co., and in the Peanut mine, Montrose Co., Colorado; around the Jackpile and Crownpoint
mines, Valencia Co., New Mexico; in the Mi Vida, Homestake, and other mines, San Juan Co.,
Utah. From WÄolsendorf, Bavaria; at Niederramstadt, near Schneeberg, Johanngeorgenstadt,
and Niederpfannenstiel, Saxony, Germany. At HÄuttenberg, Carinthia, Austria. From J¶achymov(Joachimsthal) and P·ribram, Czech Republic. In the Geevor mine, St. Just, the South Terrasmine, St. Stephen-in-Brannel, and the Roskrow United mine, Ponsansooth, Cornwall, England.
Name: Honoring Reuben Clare Co±n (1886{1972), Tulsa, Oklahoma, USA, pioneer geologist in
the study of uranium deposits of the Colorado Plateau.
Type Material: The Natural History Museum, London, England, 1956,201; National Museumof Natural History, Washington, D.C., USA, 112646.
References: (1) Stie®, L.R., T.W. Stern, and A.M. Sherwood (1956) Co±nite, a uranoussilicate with hydroxyl substitution: a new mineral. Amer. Mineral., 41, 675{688. (2) Fuchs,
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permission of Mineral Data Publishing.

L.H. and E. Gebert (1958) X-ray studies of synthetic co±nite, thorite and uranothorites.
Amer. Mineral., 43, 243{248. (3) Dubinchuk, V.T., I.S. Naumova, I.Y. Kravtsova, and G.A.
Sidorenko (1981) Determination of the crystal structure of naturally occurring co±nite.
Mineral. Zhurnal, 3(4), 81{85 (in Russian with English abs.). (4) (1982) Mineral. Abs., 33, 222(abs. ref. 3). (5) Hansley, P.A. and J.L. Fitzpatrick (1989) Compositional and crystallographic
data on REE-bearing co±nite from the Grants uranium region, northwestern New Mexico.
Amer. Mineral., 74, 263{270.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted inany form or by any means, electronic, mechanical, photocopying, recording, or otherwise without the prior written
permission of Mineral Data Publishing.