Tobermorite

Formula: Ca₉Si₁₂O₃₀(OH)₆.4H₂O

Origin of name: after locality Tobermory, Island of Mull, Scotland

Crystal system: Orthorhombic or monoclinic, pseudo-orthorhombic

Crystal class: 2

Twinning:

Unit cell: a = 11.17, b = 7.38, c = 27.94, β = 90.0°

Colour: White, pale pinkish white, reddish white, brown

Diaphaneity: Transparent to translucent

Luster: Vitreous, silky in fibrous aggregates

Habit: Massive, platy, granular or finely fibrous, radial

Hardness: 2.5

Specific gravity: 2.42 to 2.44

Cleavage: 2; {001} and {100} distinct

Tenacity: 

Streak: White

Synonyms/varieties: Crestmoreite-mixture with wilkeite

Comments:  A hydrothermal alteration product of calcium carbonate rocks, due to contact metamorphism and metasomatism. Filling vesicles and cavities in basaltic rocks. Fluorescent