thorite

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A vitreous brownish-yellow to black radioactive mineral, essentially ThSiO₄, an ore of thorium.

from The Century Dictionary.

• noun An explosive of the ammonium-nitrate class once experimented with as a bursting charge for shell.
• noun A silicate of thorium, generally compact with conchoidal fracture, and of a black color, or, as in the variety orangite, orange-yellow.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Min.) A mineral of a brown to black color, or, as in the variety orangite, orange-yellow. It is essentially a silicate of thorium.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun mineralogy A radioactive mineral, composed mostly of thorium silicate (ThSiO4), along with silicates of uranium and the rare earths.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a radioactive mineral consisting of thorium silicate; it is a source of thorium that is found in coarse granite