Chevkinite-(Ce)

Formula:  (Ca,Ce,Th)₄(Fe,Mg)₂(Ti,Fe)₃Si₄O₂₂

Origin of name:  For K. Tschevkin, Russian

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:  Uncommon on {001}

Unit cell: a = 13.5 Ǻ, b = 5.7 Ǻ, c = 11.2 Ǻ, β = 100.6°

Colour:  Dark reddish brown to velvety black

Diaphaneity:  Nearly opaque

Luster:  Resinous

Habit:  Short stubby or pencil-shaped prisms; irregular masses

Hardness:  5 to 6

Specific gravity:  4.3 to 4.6

Cleavage:  None

Tenacity:

Streak:

Synonyms/varieties:  Tscheffkinite

Comments:  Dimorphous with perrierite