Thorianite

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title: "Thorianite" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["thorium-minerals", "oxide-minerals", "minerals-described-in-1904", "radioactive-minerals", "cubic-minerals", "minerals-in-space-group-225"] topic_path: "general/thorium-minerals" source: "https://en.wikipedia.org/wiki/Thorianite" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::data[format=table title="Infobox mineral"]

Field	Value
boxbgcolor	#6d625d
boxtextcolor	#fff
category	Oxide mineral
image	Thorianite-54888.jpg
caption	Group of interpenetrating twinned thorianite crystals from Ambatofotsy, Madagascar (size: 1.6 x 1.4 x 1.3 cm)
formula	Thorium oxide, ThO2
IMAsymbol	Tho
strunz	4.DL.05
system	Isometric
class	Hexoctahedral (mm)
H-M symbol: (4/m 2/m)
symmetry	Fm3m
unit cell	a = 5.595 Å; Z = 4
color	Dark gray, brown-black
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	6.5 – 7
luster	Resinous, sub-metallic
refractive	n = 2.20 – 2.35
opticalprop	Isotropic
streak	Grey, grey green to black
gravity	9.7
diaphaneity	Opaque, translucent on thin edges
other	[[Image:Radioactive.svg
references
::

|boxbgcolor=#6d625d| name = Thorianite | boxtextcolor = #fff | category = Oxide mineral | image = Thorianite-54888.jpg | caption = Group of interpenetrating twinned thorianite crystals from Ambatofotsy, Madagascar (size: 1.6 x 1.4 x 1.3 cm) | formula = Thorium oxide, ThO2 | IMAsymbol = Tho | molweight = | strunz = 4.DL.05 | system = Isometric | class = Hexoctahedral (mm) H-M symbol: (4/m 2/m) | symmetry = Fm3m | unit cell = a = 5.595 Å; Z = 4 | color = Dark gray, brown-black | 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 = 6.5 – 7 | luster = Resinous, sub-metallic | refractive = n = 2.20 – 2.35 | opticalprop = Isotropic | birefringence = | pleochroism = | streak = Grey, grey green to black | gravity = 9.7 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Opaque, translucent on thin edges | other = [[Image:Radioactive.svg|25px]] Radioactive | references =

Thorianite is a rare thorium oxide mineral, ThO2.{{Cite book | publisher = United States Government Printing Office | last = Frondel | first = C. | title = Systematic Mineralogy of Uranium and Thorium | year = 1958 | volume = Pt. 6 | issue = 2 | pages = 57 | last = Coomaraswamy | first = A.K. | title = Uraninite | journal = Spolia Zeylanica | year = 1904 | volume = 69 | pages = 510–511 | last = Dunstan | first = Wyndham R. | title = The occurrence of Thorium in Ceylon | journal = Nature | date = 1904-03-31 | doi = 10.1038/069510d0 | issue=1796 |bibcode = 1904Natur..69..510D | s2cid = 4032255 | url = https://zenodo.org/record/1429437

Chemistry

Based on color, specific gravity and composition three types of thorianite are distinguished:{{Cite journal | volume = 1 | issue = Ist Ser | pages = 201–206 | last = Kobayashi | first = M. | title = On the composition of thorianite | journal = Tohoku Imp. Univ. Sci. Repts. | year = 1912

• α-thorianite
• β-thorianite
• γ-thorianite Thorianite and uraninite form a complete solid solution series in synthetic and natural material.{{Cite book | pages = 620–622 | last = Palache | first = C. |author2=H. Berman |author3=C. Frondel | title = Dana's System of Mineralogy, Volume 1 | publisher = John Wiley and Sons, New York | year = 1944 | publisher = McGraw-Hill | last = Heinrich | first = E. W. | title = Mineralogy and Geology of Radioactive Raw Materials | year = 1958 | volume = 40 | last = Graham | first = A. R. | title = CERIANITE CeO2: A NEW RARE-EARTH OXIDE MINERAL | journal = Am. Mineral. | year = 1955

Varieties

• Aldanite – a variety of thorianite containing 14.9% to 29.0% UO2 and 11.2% to 12.5% PbO.{{Cite journal | volume = II | issue = 6 | pages = 105–107 | last = Bespalov | first = M.M. | title = On discovery of a new mineral of the thorianite group [in Russian] | journal = Sovietskaya Geologiya | year = 1941
• Uranothorianite{{Cite web | title = Uranothorianite mineral information and data | accessdate = 2007-06-28 | url = http://www.mindat.org/min-4114.html
• Thorianite Cerian{{Cite web |title = Minerals with crystal structure determined |accessdate = 2007-06-27 |url = http://sdpd.univ-lemans.fr/minknown.html#T |url-status = dead |archiveurl = https://web.archive.org/web/20070927022021/http://sdpd.univ-lemans.fr/minknown.html#T |archivedate = 2007-09-27 |title = ICSD for WWW : Details (Thorianite Cerian) |accessdate = 2007-06-27 |url = http://icsdweb.fiz-karlsruhe.de/details.php?id%5B%5D=24439&PHPSESSID=734118bb8
• Thorianite La bearing

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 Kodrugala, Sabaragamuwa Province; and from a pegmatite in Bambarabotuwa area.
• India – Reported from beach sands of Travancore (Kerala).{{Cite journal | volume = 88 | pages = 282 | last = Viswanathan | first = P. | title = Thorianite in Travancore | journal = Mineral. Mag. | year = 1953
• Madagascar – Found in alluvial deposits of Betroka and Andolobe.{{Cite book | publisher = Augustin Challamel, éditeur, Librairie maritime et coloniale | last = Lacroix | first = A. | title = Minéralogie de Madagascar | url = https://archive.org/details/MineralogieDeMadagascarTome3 | year = 1923
• Russia – In black sands of a gold placer on Boshogoch River, Transbaikalia, Siberia; in the Kovdor Massif 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;{{Cite journal | pages = 198 | last = George | first = D'Arcy | title = Mineralogy of Uranium and Thorium Bearing Minerals | journal = USAEC Technical Information Service, Oak Ridge, Tennessee | series = RMO-563 | year = 1949 | publisher = GS-C-195, Geological Survey | last = White | first = M. G. | title = Radioactivity of Selected Rocks and Placer Concentrates from Northeastern Alaska | year = 1952 | publisher = TEI-192, Geological Survey | last = White | first = M. G. |author2=J. M. Stevens | title = Reconnaissance For Radioactive Deposits In The Ruby-Poorman District, Ruby Quadrangle, Central Alaska,1949 | journal = USGS Report | year = 1953 | page = 62 | doi = 10.3133/tei192 | bibcode = 1953usgs.rept...62W | url = https://digital.library.unt.edu/ark:/67531/metadc1050378/m2/1/high_res_d/report.pdf
• Canada – Reported with uraninite in a pegmatite on Charlebois Lake, east of Lake Athabasca;{{Cite book | publisher = Geological Survey of Canada | last = Lang | first = A. H. |author2=J. W. Griffith |author3=H. R. Steacy | title = Canadian Deposits of Uranium and Thorium | year = 1962 | volume = 40 | last = Robinson | first = S. C. |author2=A. P. Sabina | title = Uraninite And Thorianite From Ontario And Quebec | journal = Am. Mineral. | year = 1955
• South Africa – Occurs with baddeleyite as an accessory in carbonatite at Phalaborwa, Eastern Transvaal.{{Cite journal | volume = 40 | pages = 275–282 | last = Hiemstra | first = S. A. | title = Baddeleyite from Phalaborwa, Eastern Transvaal | journal = American Mineralogist | year = 1955
• Democratic Republic of Congo - Kasaï region{{Cite journal | volume = 40 | pages = C177 | last = Ledoux | first = A. | title = Les roches cristallines du Kasai | journal = Soc. Geol. Belgique Annales

References

References

1. Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
2. "Handbook of Mineralogy".
3. [http://www.mindat.org/min-3944.html Mindat.org]
4. [http://www.webmineral.com/data/Thorianite.shtml Webmineral data]
5. {{EB1911

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