The Rare Earths: Their Occurrence, Chemistry, and Technology

by Stanley Isaac Levy

Orthorhombic.

G = 3·25-3·27. H = 6¹⁄₂-7. Deep red to yellow; pleochroic.

Pfunders, Tyrol; Zermatt, Switzerland.

Tritomite.

A fluo-borosilicate of E, Th, Ca, with Zr, Na, H₂O, etc. Cer = 44·2-59·2; Yttr = 0·4-4·6; ThO₂ + ZrO₂ = 0-10·6%.

Rhombohedral; in crystals resembling regular tetrahedra.

G = 4·15-4·25. H = 5¹⁄₂. Dark brown; transparent to opaque.

Langesund Fiord, Norway.

Tscheffkinite.

Titano-silicate of E, Th, Fe, Ca, etc. Cer = 23-47; Yttr = 0-3·4; ThO₂ + ZrO₂ = 0-20; TiO₂ = 16-21%.