Gmelinite

Formula:  (Na₂,Ca)Al₂Si₄O₁₂ .6H₂O

Origin of name:  For Christian Gmelin, German chemist

Crystal system:  Hexagonal

Crystal class:  6/m 2/m 2/m

Twinning: Common on {10-11}, penetration

Unit cell: a = 13.72  Ǻ, c = 9.95 Ǻ

Colour:  Colourless, white, yellowish, greenish white, reddish white

Diaphaneity:

Luster:  vitreous

Habit:  Crystals pyramidal, tabular, or rhombohedral, striated vertically

Hardness:  4.5

Specific gravity:  2.04 to 2.17

Cleavage:  2; {10-10} distinct, {0001} parting

Tenacity:  Uneven; brittle

Streak:

Synonyms/varieties:

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