Formula: (Mg, Fe)3Si2O5(OH)4
Origin of name: Locality; Val Antigorio, Italy
Crystal system: Monoclinic
Crystal class: m
Twinning: may exhibit 2- or 3-fold twins rotated 60° about an axis perpendicular to [001]
Unit cell: a = 43.53 Å, b = 9.259 Å, c = 7.263 Å, b = 91.633°
Colour: White, yellowish, green, bluish white, yellowish to brownish green, brownish red
Diaphaneity: Translucent
Luster: Resinous, greasy, pearly, waxy, earthy
Habit: Minute crystals flaky or lath-like; usually massive, very fine-grained; lamellar, columnar, commonly fibrous
Hardness: 2.5 to 3.5
Specific gravity: about 2.65
Cleavage: 3; {001} perfect, {010} and {100} distinct
Streak: White
Synonyms/varieties: Bowenite, Jenkinsite, Picrolite, Picrosmine, Williamsite
Comments: Polymorphous with clinochrysotile, lizardite, orthochrysotile and parachrysotile. Member of the kaolinite-serpentine group. Commonly replaces ultramafic rocks, pervasively or in crosscutting veinlets. As a replacement of siliceous dolostone along contacts with diabase sills.
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