yttrialite

from The Century Dictionary.

• noun A silicate of thorium and the yttrium earths, occurring in massive forms of a dark olive-green color. It is found with gadolinite and other rare species in Llano county, Texas.

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

• noun mineralogy A rare, highly radioactive yttrium thorium sorosilicate mineral with conchoidal fracture.