Читать книгу The Rare Earths: Their Occurrence, Chemistry, and Technology - Stanley Isaac Levy - Страница 122

R´´₃R´´´₂(Cb,Ta)₆O₂₁, where R´´ = Fe, Ca, UO₂; R´´´ = E. Cer = 1·2-6·4; Yttr = 4·72-21·2; ThO₂ + ZrO₂ → 7%.

Orthorhombic; usually massive.

G = 5·6-5·8. H = 5-6. Deep velvet black; opaque.

Miask; Urals; Mitchell Co., N. Carolina.