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About ClarkeiteHide

Frank Wigglesworth Clarke
(Na,Ca,Pb)(UO2)O(OH) · 0-1H2O
Dark red-brown, dark brown
Resinous, Waxy, Greasy
4 - 4½
Specific Gravity:
Crystal System:
Named in 1931 by Clarence S. Ross, Edward P. Henderson, and Eugene Waldemar Posnjak in honor of Frank Wigglesworth Clarke [March 19, 1847 Boston, Massachusetts, USA - May 23, 1931 Washington, DC, USA], American mineral chemist, and former Chief Chemist of the U.S. Geological Survey. Clarke studied the composition of the Earth's crust and the unit of measure, the clarke, was named as a reference to the local enrichment of a chemical component relative to an average value for the chemistry of the crust.
Clarkeite is a waxy to resinous dark brown replacement of uraninite. It is very uncommon, but is frequently misidentified with brown gummite that is dominated by schoepite-group minerals. Frondel (1956) warned: "Clarkeite is best identified by its X-ray powder pattern. It is indistinguishable from the dark brown types of oxidized uraninite ... and from dense brown types of fourmarierite and vandendriesscheite."

Classification of ClarkeiteHide

Approved, 'Grandfathered' (first described prior to 1959)
First published:

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
G : Uranyl Hydroxides
C : With additional cations; with mainly UO2(O,OH)6 hexagonal polyhedra

4 : AX2O7·xH2O

7 : Oxides and Hydroxides
16 : Oxides of U

Physical Properties of ClarkeiteHide

Resinous, Waxy, Greasy
Dark red-brown, dark brown
4 - 4½ on Mohs scale
None Observed
Conchoidal, Sub-Conchoidal
6.39 g/cm3 (Measured)    

Optical Data of ClarkeiteHide

Biaxial (-)
RI values:
nα = 1.997 nβ = 2.098 nγ = 2.108
Measured: 30° to 50°, Calculated: 32°
Max Birefringence:
δ = 0.111
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Very High
relatively weak
Orange and slightly deeper orange

Chemical Properties of ClarkeiteHide

(Na,Ca,Pb)(UO2)O(OH) · 0-1H2O
IMA Formula:
Na(UO2)O(OH) · nH2O

Crystallography of ClarkeiteHide

Crystal System:
Cell Parameters:
a = 3.954 Å, c = 17.660 Å
a:c = 1 : 4.466
Unit Cell V:
239.11 ų (Calculated from Unit Cell)
Massive, dense.

Crystal StructureHide

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IDSpeciesReferenceLinkYearLocalityPressure (GPa)Temp (K)
0001902ClarkeiteFinch R J, Ewing R C (1997) Clarkeite: New chemical and structural data American Mineralogist 82 607-61919970293
CIF Raw Data - click here to close

X-Ray Powder DiffractionHide

Powder Diffraction Data:
5.903 Å(64)
3.365 Å(56)
3.195 Å(100)
2.945 Å(28)
2.707 Å(34)
1.977 Å(33)
1.8742 Å(19)
1.8554 Å(19)
1.6807 Å(14)
1.6410 Å(23)
AM 82, p. 615; JCPDS 8-315 has extraneous and differing d-values.

Type Occurrence of ClarkeiteHide

General Appearance of Type Material:
Massive, without cleavage
Geological Setting of Type Material:
Uranium bearing pegmatite
Associated Minerals at Type Locality:
Ross, C.S., Henderson, E.P., Posnjak, E. (1931) Clarkeite; a new uranium mineral. American Mineralogist: 16: 213-220.

Synonyms of ClarkeiteHide

Other Language Names for ClarkeiteHide

Simplified Chinese:水钠铀矿

Common AssociatesHide

Associated Minerals Based on Photo Data:
5 photos of Clarkeite associated with UraniniteUO2
4 photos of Clarkeite associated with Gummite
3 photos of Clarkeite associated with AutuniteCa(UO2)2(PO4)2 · 10-12H2O
3 photos of Clarkeite associated with CyrtoliteZr[(SiO4),(OH)4]
2 photos of Clarkeite associated with FourmarieritePb(UO2)4O3(OH)4 · 4H2O
2 photos of Clarkeite associated with KasolitePb(UO2)(SiO4) · H2O
1 photo of Clarkeite associated with UranophaneCa(UO2)2(SiO3OH)2 · 5H2O
1 photo of Clarkeite associated with MuscoviteKAl2(AlSi3O10)(OH)2

Related Minerals - Nickel-Strunz GroupingHide

4.GC.10Umohoite(UO2)MoO4 · 2H2OTric.
4.GC.15SpriggitePb3(UO2)6O8(OH)2 · 3H2OMon. 2/m

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

7.16.1UraniniteUO2Iso. m3m (4/m 3 2/m) : Fm3m
7.16.2Schoepite(UO2)8O2(OH)12 · 12H2OOrth. mmm (2/m 2/m 2/m) : Pbca
7.16.3ParaschoepiteUO3 · 2H2OOrth.
7.16.4Metaschoepite(UO2)8O2(OH)12 · 10H2OOrth. mmm (2/m 2/m 2/m) : Pbcn
7.16.5MetastudtiteUO4 · 2H2OOrth. mmm (2/m 2/m 2/m) : Pnma
7.16.6Studtite[(UO2)(O2)(H2O)2] · H2OMon.
7.16.7IanthiniteU4+(UO2)5O7 · 10H2OOrth. mm2 : Amm2
7.16.8CompreignaciteK2(UO2)6O4(OH)6 · 7H2OOrth.
7.16.9VandenbrandeiteCu(UO2)(OH)4Tric. 1 : P1
7.16.10RoubaultiteCu2(UO2)3(CO3)2O2(OH)2 · 4H2OTric. 1 : P1
7.16.11BecquereliteCa(UO2)6O4(OH)6 · 8H2OOrth. mm2 : Pna21
7.16.12RameauiteK2Ca(UO2)6O6(OH)4 · 6H2OMon. m : Bb
7.16.13AgrinieriteK2(Ca,Sr)[(UO2)3O3(OH)2]2 · 5H2OOrth.
7.16.14ProtasiteBa(UO2)3O3(OH)2 · 3H2OMon.
7.16.15BillietiteBa(UO2)6O4(OH)6 · 4-8H2OOrth. mm2
7.16.16BauranoiteBa(UO2)2(OH)6 · 1-2H2O
7.16.17Metacalciouranoite(Ca,Ba,Pb,K2)U2O7 · 2H2O
7.16.18Calciouranoite(Ca,Ba,Pb)U2O7 · 5H2O
7.16.22Davidite-(Ce)Ce(Y,U)Fe2(Ti,Fe,Cr,V)18(O,OH,F)38Trig. 3 : R3
7.16.23BranneriteUTi2O6Mon. 2/m : B2/m
7.16.24FourmarieritePb(UO2)4O3(OH)4 · 4H2OOrth.
7.16.25Richetite(Fe3+,Mg)Pb 8.6(UO2)36O36(OH)24 · 41H2O Tric.
7.16.26CuritePb3(H2O)2[(UO2)4O4(OH)3]2Orth. mmm (2/m 2/m 2/m) : Pnma
7.16.27MasuyitePb(UO2)3O3(OH)2 · 3H2OOrth.
7.16.28VandendriesscheitePbU7O22 · 12H2OOrth. mmm (2/m 2/m 2/m) : Pbca
7.16.29MetavandendriesscheitePbU7O22 · nH2O n < 12Orth.
7.16.30SayritePb2(UO2)5O6(OH)2 · 4H2OMon. 2/m
7.16.31WölsendorfitePb7(UO2)14O19(OH)4 · 12H2OOrth. mmm (2/m 2/m 2/m) : Cmcm
7.16.33UranosphaeriteBi(UO2)O2(OH)Mon. 2/m

Fluorescence of ClarkeiteHide

Other InformationHide

Readily dissolves in mineral acids and hydrochloric acid. Can be dissolved in very dilute acid (1 part acid to 4 parts water).
Health Risks:

References for ClarkeiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Ross, C.S., Henderson, E.P., Posnjak, E. (1931) Clarkeite; a new uranium mineral. American Mineralogist: 16: 213-220.
Palache, C., Berman, H., Frondel, C. (1944) The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged: 624-625.
Gruner, J.W. (1954) The chemical formula of clarkeite. American Mineralogist: 39: 836-838.
Frondel, C. (1956) Systematic Mineralogy of Uranium and Thorium. United States Geological Survey, Bulletin 1064: pp. 400.
Frondel, C., Meyrowitz, R. (1956) Studies of uranium minerals (XIX): rutherfordine, diderichite, and clarkeite. American Mineralogist: 41(1-2): 127–133.
Finch, R.J., Ewing, R.C. (1992) The Alteration of Uraninite to Clarkeite. MRS Online Proceedings Library: 294: 513–520.
Finch, R.J., Ewing, R.C. (1997) Clarkeite: New Chemical and Structural Data. American Mineralogist: 82: 607-619.
Kubatko, K.-A., Helean, K., Navrotsky, A., Burns, P.C. (2006) Thermodynamics of uranyl minerals: Enthalpies of formation of uranyl oxide hydrates: American Mineralogist: 91: 658-666.
Gorman-Lewis, D., Fein, J.B., Burns, P.C., Szymanowski, J.E.S., Converse, J. (2008) Solubility measurements of the uranyl oxide hydrate phases metaschoepite, compreignacite, Na–compreignacite, becquerelite, and clarkeite. The Journal of Chemical Thermodynamics: 40(6): 980-990.

Internet Links for ClarkeiteHide

Localities for ClarkeiteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
  • Nova Scotia
    • Cumberland Co.
Chatterjee, A.K. (1977) Uranium Mineralization at McLean Point, Cumberland County. Nova Scotia Department of Mines Report 77-1.
Czech Republic
  • Plzeň Region
    • Tachov District
      • Zadní Chodov (Hinterkotten)
Pauliš P., Kopecký S., Černý P. 2007: Uranové minerály České Republiky a jejich naleziště. 1. část. (Kutna Hora, issue 1)
  • Baranya County
    • Pécs District
Koch: Minerals of Hungary, 1985
  • Rajasthan
American Mineralogist: 41: 127-133
  • Agder
Neumann, H. (1985): Norges Mineraler. Norges geologiske Undersøkelse Skrifter 68, p 90
    • Lindesnes
      • Vigeland
Sverdrup, T. L. (1959): The pegmatite dyke at Rømteland. Norges Geologiske Undersøkelse 211 (Årbok 1959): 124-196
  • Viken
    • Krødsherad
Neumann, H. (1985): Norges Mineraler. Norges geologiske Undersøkelse Skrifter 68, pp. 89-90
  • Suceava
    • Suceava district
Hîrtopanu P., Udubaşa G., Scott P., Hârtopanu I. (2004) Uranium sulphide mineralisation in the Bistriţa Mts., East Carpathians, Romania. Romanian Journal of Mineral Deposits 81:108-111
  • Alaska
    • Yukon-Koyukuk Census Area
      • Sheenjek Mining District
U.S. Geological Survey, 2008, Alaska Resource Data File (ARDF): U.S. Geological Survey Open-File Report 2008-1225.
  • Maine
    • Oxford County
      • Newry
Not found according to King, V. T., 1994, Mineralogy of Maine, Descriptive Mineralogy, v. 1
      • Stoneham
Not found according to King & Foord, 1994. Mineralogy of Maine, V. 1.
  • New Hampshire
    • Grafton Co.
      • Grafton
Discredited by Clifford Frondel (1956) Mineral Composition of Gummite, American Mineralogist 41:539-568.; Rocks & Minerals (2005) 80:242-261 New Hampshire Mineral Locality Index
      • Groton
Not found at this locality: Frondel (1956); Foord et al. (1997), Korzeb et al (1997).
    • Rockingham Co.
      • Raymond
Rocks & Minerals (2005) 80:242-261 New Hampshire Mineral Locality Index
  • North Carolina
    • Mitchell Co.
Rocks and Minerals, Sep-Oct,2004
Roger Howell Collection
      • Penland
Ross, Henderson, and Posnjak (1931), American Mineralogist: 16: 213.; Arthur Roe and John S. White, Jr. (1976) A Catalog of the Type Specimens in the Mineral Collection, National Museum of Natural History
Rocks and Minerals,Sep-Oct,2004
      • Spruce Pine
Smithsonian Institution Mineral Reference Collection No.R13655-00
        • Greasy Creek Township
Rocks and Minerals,Sep-Oct,2004
    • Yancey Co.
      • Celo
        • Micaville
U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.; American Mineralogist, Volume 82, pages 607–619, 1997
      • Crabtree Creek
Rocks and Minerals,Sep-Oct,2004
Mineral and/or Locality  
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