Formula: Ca2Al2Si3O10(OH)2
Origin of name: for H. von Prehn, Dutch soldier and discoverer of mineral
Crystal system: orthorhombic
Crystal class: mm2
Twinning: common fin lamellar
Unit cell: a = 4.642 Å, b = 5.487 Å, c = 18.49 Å
Colour: pale to dark green, yellow, gray, white, colourless
Diaphaneity:
Luster: vitreous to somewhat pearly
Habit: crystals tabular, prismatic or steep pyramidal, in tabular groups or barrel-shaped aggregates, massive, botryoidal
Hardness: 6 to 6.5
Specific gravity: 2.90 to 2.95
Cleavage: 2; {001} distinct, {110} indistinct
Tenacity: uneven, brittle
Streak: colourless
Synonyms/varieties: chrysolite
Comments:
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