Thorianite
Thorianite | |
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![]() Group of interpenetrating twinned thorianite crystals from Ambatofotsy, Madagascar (size: 1.6 x 1.4 x 1.3 cm) | |
General | |
Category | Oxide mineral |
Formula (repeating unit) | Thorium oxide, ThO2 |
Strunz classification | 4.DL.05 |
Crystal system | Isometric |
Crystal class | Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m) |
Space group | Fm3m |
Unit cell | a = 5.595 Å; Z = 4 |
Identification | |
Color | Dark gray, brown-black |
Crystal habit | Cubic crystals, usually rounded to some degree in detrital deposits |
Twinning | Penetration twins on {111} common |
Cleavage | Poor/Indistinct |
Fracture | Irregular to uneven, sub-conchoidal |
Mohs scale hardness | 6.5 – 7 |
Luster | Resinous, sub-metallic |
Streak | Grey, grey green to black |
Diaphaneity | Opaque, translucent on thin edges |
Specific gravity | 9.7 |
Optical properties | Isotropic |
Refractive index | n = 2.20 – 2.35 |
Other characteristics | ![]() |
References | [1][2][3] |
Thorianite is a rare thorium oxide mineral, ThO2.[4] It was originally described by Ananda Coomaraswamy in 1904 as uraninite,[5] but recognized as a new species by Wyndham R. Dunstan.[6] It was so named by Dunstan on account of its high percentage of thorium; it also contains the oxides of uranium, lanthanum, cerium, praseodymium and neodymium. Helium is present, and the mineral is slightly less radioactive than pitchblende,[7] but is harder to shield due to its high energy gamma rays. It is common in the alluvial gem-gravels of Sri Lanka, where it occurs mostly as water worn, small, heavy, black, cubic crystals. The largest crystals are usually near 1.5 cm. Larger crystals, up to 6 cm (2.4 in), have been reported from Madagascar.
Chemistry[]
Based on color, specific gravity and composition three types of thorianite are distinguished:[8]
- α-thorianite
- β-thorianite
- γ-thorianite
Thorianite and uraninite form a complete solid solution series in synthetic and natural material.[9] The division between the two species is at Th:U = 1:1 with U possibly making up to 46.50% and Th ranging up to 87.88%.[10] Rare earths, chiefly Ce, substitute for Th in amounts up to 8% by weight.[9][11] Ce is probably present as Ce4+. Complete series is known in synthetic material between CeO2 - PrO2 - ThO2 - UO2. Small amounts of Fe3+ and Zr also may be isomorphous with Th. Pb present is probably radiogenic.
Varieties[]
- Aldanite – a variety of thorianite containing 14.9% to 29.0% UO2 and 11.2% to 12.5% PbO.[12]
- Uranothorianite[13]
- Thorianite Cerian[14][15]
- Thorianite La bearing[14]
Occurrence[]
Usually found in alluvial deposits, beach sands, heavy mineral placers, and pegmatites.
- Sri Lanka – In stream gravels, Galle district, Southern Province; Balangoda district; near , Sabaragamuwa Province; and from a pegmatite in area.
- India – Reported from beach sands of Travancore (Kerala).[16]
- Madagascar – Found in alluvial deposits of Betroka and .[17] Also as very large crystals from Tôlanaro (Fort Dauphin); at and other localities.
- Russia – In black sands of a gold placer on , Transbaikalia, Siberia; in the by Kovdor, Kola Peninsula; in the Yenisei Range, Siberia.
- United States – reported from Easton, Pennsylvania; black sands in Missouri River, near Helena, Montana; Scott River, Siskiyou County, California;[18] black sands in and Wiseman districts, Alaska.[19][20]
- Canada – Reported with uraninite in a pegmatite on , east of Lake Athabasca;[21] Uranon variety reported from pegmatite and metesomatized zones in crystalline limestones from many locations in Quebec and Ontario.[22]
- South Africa – Occurs with baddeleyite as an accessory in carbonatite at Phalaborwa, Eastern Transvaal.[23]
- Democratic Republic of Congo - Kasaï region[24]
See also[]
- Uraninite
- Thorite
- Classification of minerals
- List of minerals
References[]
- ^ Handbook of Mineralogy
- ^ Mindat.org
- ^ Webmineral data
- ^ Frondel, C. (1958). Systematic Mineralogy of Uranium and Thorium. United States Government Printing Office.
- ^ Coomaraswamy, A.K. (1904). "Uraninite". Spolia Zeylanica. Pt. 6 (2): 57.
- ^ Dunstan, Wyndham R. (1904-03-31). "The occurrence of Thorium in Ceylon". Nature. 69 (1796): 510–511. Bibcode:1904Natur..69..510D. doi:10.1038/069510d0.
- ^ public domain: Chisholm, Hugh, ed. (1911). "Thorianite". Encyclopædia Britannica. 26 (11th ed.). Cambridge University Press. p. 878. One or more of the preceding sentences incorporates text from a publication now in the
- ^ Kobayashi, M. (1912). "On the composition of thorianite". Tohoku Imp. Univ. Sci. Repts. 1 (Ist Ser): 201–206.
- ^ a b Palache, C.; H. Berman; C. Frondel (1944). Dana's System of Mineralogy, Volume 1. John Wiley and Sons, New York. pp. 620–622.
- ^ Heinrich, E. W. (1958). Mineralogy and Geology of Radioactive Raw Materials. McGraw-Hill.
- ^ Graham, A. R. (1955). "CERIANITE CeO2: A NEW RARE-EARTH OXIDE MINERAL". Am. Mineral. 40.
- ^ Bespalov, M.M. (1941). "On discovery of a new mineral of the thorianite group [in Russian]". Sovietskaya Geologiya. II (6): 105–107.
- ^ "Uranothorianite mineral information and data". Retrieved 2007-06-28.
- ^ a b "Minerals with crystal structure determined". Archived from the original on 2007-09-27. Retrieved 2007-06-27.
- ^ "ICSD for WWW : Details (Thorianite Cerian)". Retrieved 2007-06-27.[permanent dead link]
- ^ Viswanathan, P. (1953). "Thorianite in Travancore". Mineral. Mag. 88: 282.
- ^ Lacroix, A. (1923). Minéralogie de Madagascar. Augustin Challamel, éditeur, Librairie maritime et coloniale.
- ^ George, D'Arcy (1949). "Mineralogy of Uranium and Thorium Bearing Minerals". USAEC Technical Information Service, Oak Ridge, Tennessee. RMO-563: 198.
- ^ White, M. G. (1952). Radioactivity of Selected Rocks and Placer Concentrates from Northeastern Alaska. GS-C-195, Geological Survey.
- ^ White, M. G.; J. M. Stevens (1953). "Reconnaissance For Radioactive Deposits In The Ruby-Poorman District, Ruby Quadrangle, Central Alaska,1949". TEI-192, Geological Survey. Cite journal requires
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(help) - ^ Lang, A. H.; J. W. Griffith; H. R. Steacy (1962). Canadian Deposits of Uranium and Thorium. Geological Survey of Canada.
- ^ Robinson, S. C.; A. P. Sabina (1955). "Uraninite And Thorianite From Ontario And Quebec". Am. Mineral. 40.
- ^ Hiemstra, S. A. (1955). "Baddeleyite from Phalaborwa, Eastern Transvaal". American Mineralogist. 40: 275–282.
- ^ Ledoux, A. "Les roches cristallines du Kasai". Soc. Geol. Belgique Annales. 40: C177.
External links[]
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Wikimedia Commons has media related to Thorianite. |
- Thorium minerals
- Oxide minerals
- Uranium minerals
- Lanthanide minerals
- Radioactive minerals
- Cubic minerals
- Minerals in space group 225