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Clarkeite

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Formula:
(Na,Ca,Pb)(UO
 
2
)O(OH) · 0-1H
 
2
O
System:TrigonalColour:Dark red-brown, dark ...
Hardness:4 - 4½
Name:
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 Clarkeite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:4/H.05-10
Nickel-Strunz 10th (pending) edition ID:4.GC.05

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
Dana 8th edition ID:5.4.1.1

5 : OXIDES CONTAINING URANIUM OR THORIUM
4 : AX2O7·xH2O
Hey's CIM Ref.:7.16.32

7 : Oxides and Hydroxides
16 : Oxides of U
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Type Occurrence of Clarkeite

Type Locality:Deer Park No. 2 Mine, Penland, Spruce Pine District, Mitchell Co., North Carolina, USA
Year of Discovery:1931

Physical Properties of Clarkeite

Lustre:Resinous, Waxy, Greasy
Diaphaneity (Transparency):Translucent
Colour:Dark red-brown, dark brown
Streak:Yellow-brown
Hardness (Mohs):4 - 4½
Fracture:Conchoidal, Sub-Conchoidal
Density (measured):6.39 g/cm3

Crystallography of Clarkeite

Crystal System:Trigonal
Cell Parameters:a = 3.954Å, c = 17.660Å
Ratio:a:c = 1 : 4.466
Unit Cell Volume:V 239.11 ų (Calculated from Unit Cell)
Z:3
Morphology:Massive, dense.
X-Ray Powder Diffraction:
d-spacingIntensity
5.903 (64)
3.365 (56)
3.195 (100)
2.945 (28)
2.707 (34)
1.977 (33)
1.8742 (19)
1.8554 (19)
1.6807 (14)
1.6410 (23)
Comments:AM 82, p. 615; JCPDS 8-315 has extraneous and differing d-values.

Optical Data of Clarkeite

Type:Biaxial (-)
RI values: nα = 1.997 nβ = 2.098 nγ = 2.108
2V:Measured: 30° to 50°, Calculated: 32°
Birefringence:0.111
Maximum Birefringence:δ = 0.111

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Very High
Dispersion:relatively weak

Chemical Properties of Clarkeite

Formula:
(Na,Ca,Pb)(UO
 
2
)O(OH) · 0-1H
 
2
O
Simplified for copy/paste:(Na,Ca,Pb)(UO2)O(OH)·0-1H2O
Essential elements:H, Na, O, U
All elements listed in formula:Ca, H, Na, O, Pb, U

Relationship of Clarkeite to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
4.GC.10Umohoite
(UO
 
2
)MoO
 
4
· 2H
 
2
O
4.GC.15Spriggite
Pb
 
3
(UO
 
2
)
 
6
O
 
8
(OH)
 
2
· 3H
 
2
O
Related Minerals - Hey's Index Grouping:

- +
7.16.1Uraninite
UO
 
2
7.16.2Schoepite
(UO
 
2
)
 
8
O
 
2
(OH)
 
12
· 12H
 
2
O
7.16.3Paraschoepite
UO
 
3
· 2H
 
2
O
7.16.4Metaschoepite
UO
 
3
· 1-2H
 
2
O
7.16.5Metastudtite
UO
 
4
· 2H
 
2
O
7.16.6Studtite
[(UO
 
2
)(O
 
2
)(H
 
2
O)
 
2
] · H
 
2
O
7.16.7Ianthinite
U
4+
 
(UO
 
2
)
 
5
O
 
7
· 10H
 
2
O
7.16.8Compreignacite
K
 
2
(UO
 
2
)
 
6
O
 
4
(OH)
 
6
· 7H
 
2
O
7.16.9Vandenbrandeite
Cu(UO
 
2
)(OH)
 
4
7.16.10Roubaultite
Cu
 
2
(UO
 
2
)
 
3
(OH)
 
10
· 5H
 
2
O
7.16.11Becquerelite
Ca(UO
 
2
)
 
6
O
 
4
(OH)
 
6
· 8H
 
2
O
7.16.12Rameauite
K
 
2
Ca(UO
 
2
)
 
6
(OH)
 
16
· H
 
2
O
7.16.13Agrinierite
K
 
2
(Ca,Sr)(UO
 
2
)
 
3
O
 
3
(OH)
 
2
· 5H
 
2
O
7.16.14Protasite
Ba(UO
 
2
)
 
3
O
 
3
(OH)
 
2
· 3H
 
2
O
7.16.15Billietite
Ba(UO
 
2
)
 
6
O
 
4
(OH)
 
6
· 4-8H
 
2
O
7.16.16Bauranoite
Ba(UO
 
2
)
 
2
(OH)
 
6
· 1-2H
 
2
O
7.16.17Metacalciouranoite
(Ca,Ba,Pb,K
 
2
)U
 
2
O
 
7
· 2H
 
2
O
7.16.18Calciouranoite
(Ca,Ba,Pb)U
 
2
O
 
7
· 5H
 
2
O
7.16.19Orthobrannerite
U
4+
 
U
6+
 
Ti
 
4
O
 
12
(OH)
 
2
7.16.20Thorutite
(Th,U,Ca)Ti
 
2
(O,OH)
 
6
7.16.21Davidite-(La)
(La,Ce)(Y,U,Fe)(Ti,Fe)
 
20
(O,OH)
 
38
7.16.22Davidite-(Ce)
(Ce,La)(Y,U,Fe)(Ti,Fe)
 
20
(O,OH)
 
38
7.16.23Brannerite
(U
4+
 
,REE,Th,Ca)(Ti,Fe
3+
 
,Nb)
 
2
(O,OH)
 
6
7.16.24Fourmarierite
Pb(UO
 
2
)
 
4
O
 
3
(OH)
 
4
· 4H
 
2
O
7.16.25Richetite
Pb(UO
 
2
)
 
4
O
 
5
· 4H
 
2
O
7.16.26Curite
Pb
 
3
(UO
 
2
)
 
8
O
 
8
(OH)
 
6
· 3H
 
2
O
7.16.27Masuyite
Pb(UO
 
2
)
 
3
O
 
3
(OH)
 
2
· 3H
 
2
O
7.16.28Vandendriesscheite
PbU
 
7
O
 
22
· 12H
 
2
O
7.16.29Metavandendriesscheite
PbU
 
7
O
 
22
· nH
 
2
O n < 12
7.16.30Sayrite
Pb
 
2
(UO
 
2
)
 
5
O
 
6
(OH)
 
2
· 4H
 
2
O
7.16.31Wölsendorfite
(Pb,Ca)U
 
2
O
 
7
· 2H
 
2
O
7.16.33Uranosphaerite
Bi(UO
 
2
)O
 
2
(OH)

Other Names for Clarkeite

Synonyms:
Brown Gummite
Other Languages:
German:Clarkeit
Russian:Кларкеит
Simplified Chinese:水钠铀矿
Spanish:Clarkeita

Other Information

Fluorescence in UV light:none
Health Warning:radioactive

References for Clarkeite

Reference List:

- +
Ross, Henderson, and Posnjak (1931), American Mineralogist: 16: 213.

Palache, Charles, Harry Berman & Clifford Frondel (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.

Frondel, Clifford, 1956, Systematic Mineralogy of Uranium and Thorium, USGS Bulletin 1064, pp. 400.

Finch, Robert J. and Ewing, Rodney C., 1997, Clarkeite: New Chemical and Structural Data, American Mineralogist, 82: 607-619.

Finch, R.J. and R.C. Ewing (1997), Clarkeite: New chemical and structural data: American Mineralogist: 82: 607-619.

Kubatko, Karrie-Ann, Katheryn Helean, Alexandra Navrotsky, and Peter C. Burns (2006), Thermodynamics of uranyl minerals: Enthalpies of formation of uranyl oxide hydrates: American Mineralogist: 91: 658-666.

Internet Links for Clarkeite

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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Clarkeite details from Handbook of Mineralogy (PDF)
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  • Localities for Clarkeite

    The 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.
    (TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
    Canada
     
    • Nova Scotia
      • Cumberland Co.
    A.K. Chatterjee, "Uranium Mineralization at McLean Point, Cumberland County", Nova Scotia Dept. Mines Report 77-1, 1977.
    Czech Republic
     
    • Bohemia (Böhmen; Boehmen)
      • Plzeň Region
        • Planá u Mariánských Lázní (Plan)
    Pauliš P., Kopecký S., Černý P. 2007: Uranové minerály České Republiky a jejich naleziště. 1. část. (Kutna Hora, issue 1)
    Hungary
     
    • Baranya Co.
      • Mecsek Mtns
    Koch: Minerals of Hungary, 1985
    India
     
    • Rajasthan (Rajputana)
      • Ajmer Division
    American Mineralogist: 41: 127-133
    Norway
     
    • Aust-Agder
    Neumann, H. (1985): Norges Mineraler. Norges geologiske Undersøkelse Skrifter 68, p 90
    • Buskerud
      • Krødsherad
        • Krøderen Lake
    Neumann, H. (1985): Norges Mineraler. Norges geologiske Undersøkelse Skrifter 68, pp. 89-90
    • Vest-Agder
      • Lindesnes
        • Vigeland
    Sverdrup, T. L. (1959): The pegmatite dyke at Rømteland. Norges Geologiske Undersøkelse 211 (Årbok 1959): 124-196
    USA
     
    • Alaska
      • Yukon-Koyukuk Borough
        • Sheenjek District
    U.S. Geological Survey, 2008, Alaska Resource Data File (ARDF): U.S. Geological Survey Open-File Report 2008-1225.
    • Maine
      • Oxford Co.
        • 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
    Rocks and Minerals,Sep-Oct,2004
        • Spruce Pine District
          • 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
          • Spruce Pine
            • Greasy Creek Township
    Rocks and Minerals,Sep-Oct,2004
    www.excaliburmineral.com
    Rocks and Minerals,Sep-Oct,2004
      • Yancey Co.
        • Spruce Pine District
          • 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
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