The Rare Earths: Their Occurrence, Chemistry, and Technology

by Stanley Isaac Levy

Cubic (cf. Garnet).

Dark reddish brown (cf. Garnet).

Stockö, Norway; Schreiberhau, Germany.

Yttrogummite.

UO₃, 3ThO₂, 3SiO₂, 6H₂O? E₂O₃ = 6·7; ThO₂ = 41·4%.

Tetragonal; angles near Zircon. Usually massive.

G = 4·43-4·54. H = 4-4¹⁄₂. Yellowish brown.

Llano Co., Texas.

Yttrotantalite.

R´´R´´´₂(Cb,Ta)₄O₁₄ + 4H₂O; R´´ = Fe´´, Ca; R´´´ = E; Cer = 0-2·4; Yttr = 17·2-38·3%.