(b) The Carbonates
Lanthanite, Hydrocerite.
—This mineral is a carbonate of ceria earths, chiefly lanthana, of the formula La₂(CO₃)₃,9H₂O.
Orthorhombic; a : b : c = 0·9528 : 1 : 0·9023. Common forms—the pinakoids a {100} and c {001}, with m {110} and o {111}.
Angles—(100) ∧ (110) = 43° 37´; (001) ∧ (101) = 43° 261⁄2´; (001) ∧ (011) = 42° 31⁄2´.
Habit tabular, parallel to c; cleavage perfect, ∥ c.
Double refraction negative; optic axis plane a (100).
Usually amorphous, being probably an alteration product of a mineral rich in lanthanum. Hardness 2; sp. gr. 2·6-2·7.
Colour white to yellowish-white, usually opaque; infusible before the blowpipe (being converted to the oxide), readily soluble in acids.
Lanthanite occurs with cerite at Bastnäs, and at Bethlehem, Pennsylvania.