Dictionary.net

• A primitive earth with a metallic base, the oxide of thorium.

1914 - Nuttall's Standard dictionary of the English language
By Nuttall, P.Austin.

• One of the primitive earths obtained from the mineral thorite; oxide of thorium.

1874 - Etymological and pronouncing dictionary of the English language
By Stormonth, James, Phelp, P. H.