Johannsenite

Formula:  CaMnSi₂O₆

Origin of name:  For A. Johannsen, American geologist

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:  Common on {100}, simple or lamellar

Unit cell: a = 9.88 Ǻ, b = 9.04 Ǻ, c = 5.27 Ǻ, β = 105.5°

Colour:  Gray, greenish, brown, black

Diaphaneity: 

Luster: 

Habit:  Crystals short prismatic; massive, columnar; fibers and prisms in radiating and spherulitic aggregates

Hardness:  6

Specific gravity:  3.44 to 3.55

Cleavage:  4; {110} good, {001}, {010}, and {100} parting

Tenacity:  Brittle

Streak: 

Synonyms/varieties:

Comments:  Series with diopside and with hedenbergite