Vertumnite

Formula: Ca₄Al₄Si₄O₆(OH)₂₄.3H₂O

Origin of name: for Vertumnus, the god worshipped by the ancient Etruscan people who inhabited the region where the mineral was found.

Crystal system: Monoclinic, pseudohexagonal

Crystal class: 2/m

Twinning: Cyclic, contact plane || {001} common

Unit cell: a = 5.744, b = 5.766, c = 25.12, β = 119.72°

Colour: Colourless

Diaphaneity: Transparent

Luster: Vitreous

Habit: Crystals prismatic, pseudohexagonal, flattened, to several mm thick

Hardness: 5

Specific gravity: 2.15

Cleavage: None

Tenacity: Very brittle, conchoidal fracture

Streak: White

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