from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A highly radioactive blackish, greenish, or yellow mineral, ThO2, isomorphous with uraninite.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A radioactive mineral containing thorium dioxide (ThO2) plus oxides of uranium, lanthanum, cerium neodymium and praseodymium in smaller quantities.
from The Century Dictionary and Cyclopedia
- n. A mineral found in alluvial gravel near Kondurugala, in the province of Sabaragamuwa, and in the Galle district, Ceylon.
thoria + -an2 + -ite1.(American Heritage® Dictionary of the English Language, Fourth Edition)