Stilbite

Formula: NaCa₂Al₅Si₁₃O₃₆.14H₂O

Origin of name: from Greek for to shine

Crystal system: monoclinic, also orthorhombic

Crystal class: 2/m

Twinning: universal on {001} penetration, cruciform

Unit cell: a = 13.68 Å, b = 18.13 Å, c = 11.30 Å, b = 129.1°

Colour: white, gray, yellowish pink, reddish, orange, light to dark brown

Diaphaneity: 

Luster: vitreous, pearly on cleavage

Habit: sing crystals are rare, bladed aggregates or twinned crystals widening at terminations forming hourglass or sheaf-like

Hardness: 3.5 to 4

Specific gravity: 2.09 to 2.20

Cleavage: 2; {010} perfect, {100} distinct

Tenacity: uneven, brittle

Streak: colourless

Synonyms/varieties: desmine, epidesmine

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