The Rare Earths: Their Occurrence, Chemistry, and Technology

by Stanley Isaac Levy

Hjelmite (Hielmite).

A stanno-tantalate of Ca, Mn, Fe, E, related to [Yttrotantalite] (q.v.). E₂O₃ = 1-6%.

Orthorhombic.

G = 5·82. H = 5. Black; lustre metallic.

Fahlun, Sweden.

Homilite.

(Ca,Fe)₃(BO)₂(SiO₄)₂. Sometimes with ceria earths, 0-2·6%.

Monoclinic—isomorphous with Gadolinite (? Brögger).

G = 3·34-3·38. H = 4¹⁄₂-5. Black; pleochroic.

Islands of Lanegsund Fiord, Norway.