Bastnäsite

Formula:  (Ce,La)(CO₃)F

Origin of name:  After locality; Bastnäs, Västmanland, Sweden

Crystal system:  Hexagonal

Crystal class:  -6m2

Twinning:

Unit cell: a = 7.129 Ǻ, c = 9.774 Ǻ

Colour:  Wax-yellow to reddish-brown

Luster:  Vitreous to greasy

Habit:  Tabular or rarely short prismatic; anhedral masses, granular

Hardness:  4 to 4.5

Specific gravity:  4.78 to 5.2

Cleavage:  2; {1000} parting, distinct to perfect, {10-10} imperfect

Tenacity:  Brittle

Streak:

Synonyms/varieties:

Comments:  Three distinct species with the extensions -(Ce), -(La) and -(Y) indicating the predominant rare earth cation in the formula; series with hydroxylbastnäsite