The Rare Earths: Their Occurrence, Chemistry, and Technology

by Stanley Isaac Levy

Monoclinic.

G = 4·23. H = 6¹⁄₂. Bright red and yellow,

Österby, Sweden.

Thorianite.

Mixed ThO₂ + UO₂, with E, Pb, Zr, Si, Fe, etc. ThO₂ = 72-79; Cer = 1-8%.

Rhombohedral; pseudocubic.

G = 8·0-9·7. H = 7. Jet black; bright resinous lustre.

Gem-gravels of Ceylon.

Thorite.

ThSiO₄, with H₂O, U, Fe, E, Ca, Al, etc. ThO₂ = 41·4-57·9; E₂O₃ = 0-6%.