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A highly radioactive blackish, greenish, or yellow mineral, ThO2, isomorphous with uraninite.

[thoria + -an + -ite.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Minerals) a rare black mineral consisting of thorium and uranium oxides. Formula: ThO2.U3O8
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˈθɔr i əˌnaɪt, ˈθoʊr-)

a rare, black, radioactive mineral, mainly thoria, ThO2, usu. found mixed with uranium, dioxide, and rare-earth metals: a minor source of thorium.
[1900–05; thorian (thori (a) + -an2) + -ite1]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
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The main U minerals at the Olympic Dam are coffinite, brannerite, and uraninite-pitchblende, with minor to trace amounts of U hosted in hematite, thorite-uranothorite, thorianite, crandallite, xenotime-(Y), zircon, REE-group minerals, pyrite, chalcopyrite, bornite, and chalcocite [36].
Thorium is existed naturally in a tetravalent cation only adsorbed onto normal colloidal bulk matters or founding in natural residue either in detrital minerals like monazite, rutile and thorianite, but the most paramount provenance of thorium is the monazite (Syed, 1999).
Summary: Thorium, the radioactive metal, present in natural sediments produced in the form of detritus minerals such as monazite, rutile, granitic complexes, syenitic complexes, thorite, thorianite and progenitor of U, Th and Ac series.