The Rare Earths: Their Occurrence, Chemistry, and Technology

by Stanley Isaac Levy

Hellandite.

3H₂0, 2R´´O, 3R´´´₂O₃, 4SiO₂, where R´´ = Ca, Mg, Th 2; R´´´ = E, Al, Fe, Mn. E₂O₃ = 40%.

Monoclinic; habit prismatic.

G = 3·70. H = 5¹⁄₂. Reddish-brown when fresh.

Lindvikskollan and Kragerö, Norway.

Hiortdahlite.

3CaSiO3,Ca(F,OH)NaZrO₃. ZrO₂ = 21·5; TiO₂ = 1·5%.

Anorthic; habit tabular.

G = 3·27; H = 5-5¹⁄₂. Yellow, with weak pleochroism.

Island of Läven, Langesund Fiord, Norway.