Grossular

Formula:  Ca₃Al₂(SiO₄)₃

Origin of name:   From Latin for gooseberry

Crystal system:  Cubic

Crystal class:  4/m -3 2/m

Twinning:

Unit cell: a = 11.85 Ǻ

Colour:   Colourless, white, gray, yellow to green, brown, pink, red, black

Diaphaneity:

Luster:  Vitreous to resinous

Habit:  Crystals dodecahedrons or trapezohedrons; massive, compact; granular; embedded grains

Hardness:  6.5 to 7

Specific gravity:  3.4 to 3.6

Cleavage:  1; {110} parting

Tenacity:  Conchoidal to uneven; brittle

Streak:  White

Synonyms/varieties:  Grossularite, hessonite/essonite (orange to red var.), tsavorite/tsavolite (gree, Cr/V-rich var.)

Comments:  Forms three series: with andradite, with hibschite and katoite, and with uvarovite