The Rare Earths: Their Occurrence, Chemistry, and Technology

by Stanley Isaac Levy

Elpidite, Erdmannite and Cainosite, more complex silicates.

Rowlandite, a comparatively simple silicate of the yttrium metals.

Yttrogarnet, a variety of garnet containing yttrium metals.

(b) Silicates of Thorium and Zirconium

Thorite.

—Thorite and its variety Orangite are somewhat altered forms of a pure silicate of thorium, ThSiO₄, containing also small quantities of water, usually uranium, and often rare earths, with iron, lead, calcium, and aluminium. Orangite differs from thorite in its beautiful orange colour and greater specific gravity. Both varieties are radio-active.

When unaltered, the crystals are tetragonal and uniaxial, the pure mineral ThSiO₄ being isomorphous with [zircon], ZrSiO₄ (q.v.). By alteration they become isotropic.

Crystals are tetragonal, holosymmetric; c = 0·6402; p ∧ p´ = 56° 40´.

Common forms are the prism m {110} with the pyramids p {111} and z {311}.

Hardness 4¹⁄₂-5; sp. gr. 4·4 to 4·8 for thorite, 5·2 to 5·4 for orangite.