The Rare Earths: Their Occurrence, Chemistry, and Technology

by Stanley Isaac Levy

Amorphous.

G = 5-6·5. H = 3-4. Black; resinous lustre.

Bohemia; Cornwall; Carolina; Norway, etc.

Plumboniobite.

A variety of [Samarskite] (q.v.) containing Pb; R´´₂Cb₂O₇, R´´´₄(Cb₂O₇)₃, where R´´ = Fe, Pb, Ca, UO, R´´´ = E, Al. Yttr = 14·3%.

Massive, isotropic.

G = 4·80-4·81. H = 5-5¹⁄₂. Dark brown to black.

Morogoro, Uluguru Mountains, German E. Africa.

Polycrase.

A titano-columbate of E and U; Yttr = 19·5-32·5; TiO₂ = 25-33%. Cer and ThO₂ traces. Isomorphous with Euxenite.