Epidote

Formula:   Ca2(Fe,Al)3(Si2O7)(SiO4)(O,OH)2

Origin of name:   From Greek for increase

 

Crystal system:   Monoclinic

Crystal class:   2/m

Twinning:   Common on {100}, contact or lamellar

Unit cell: a = 8.90 Ǻ, b = 5.63 Ǻ, c = 10.20 Ǻ, β = 115.4°

 

Colour:  Yellowish green to brownish to dark green, gray, grayish

Diaphaneity:

Luster:   Vitreous to pearly

Habit:   Crystals short to long prismatic, may be deeply striated; thick tabular; acicular; massive, coarse to fine granular; fibrous

Hardness:   6 to 7

Specific gravity:   3.35 to 3.5

Cleavage:   1; {001} perfect

Tenacity:   Uneven; brittle

Streak:   Colourless to grayish

 

Synonyms/varieties:

 

Comments:   Series with clinozoisite

 

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