1910–1911
Britannica 11th
Encyclopaedia Britannica · 11th edition
THORITE, a rare mineral consisting of thorium silicate, crystallizing in the tetragonal system and isomorphous with zircon. The theoretical formula, ThSiCu, requires 81-5 % of thoria, but analyses show only 50-70%, there being also some uranium, cerium, &c. The mineral is almost always altered by hydration and is then optically isotropic and amorphous. Owing to differences in composition and to alteration, the specific gravity varies from 4-4 to 5-4. The colour is usually light brown, but in the variety known as " …
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- Vol. 26, pp. 878-878