Gismondine

Formula:  Ca₂Al₄Si₄O₁₆ ^.9H₂O

Origin of name:  For C. Gismondi, Italian mineralogist

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:  On {100}

Unit cell: a = 10.24 Ǻ, b = 10.61 Ǻ, c = 9.84 Ǻ, β = 92.8°

Colour:  Colourless, white, bluish white, grayish, reddish

Diaphaneity:

Luster:  Vireous

Habit:  Crystals pseudotetragonal bipyramids

Hardness:  4.5

Specific gravity:  2.27

Cleavage:  1; {001} distinct

Tenacity:

Streak:

Synonyms/varieties:

Comments: