Harmotome

Formula:  (Ba,K)_1-2(Si, Al)₈O₁₆ ^. 6H₂O

Origin of name:   From Greek for joint and to cut

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:  On {001}, {021}, or {110} repeated

Unit cell: a = 9.87 Ǻ, b = 14.14 Ǻ, c = 8.71 Ǻ, β = 124.8°

Colour:  Colourless, white, gray, pink, yellow, orange, brown

Diaphaneity:

Luster:  Vitreous

Habit:  Crystals complex penetration twins, may be tetragonal or orthorhombic in aspect; groups or radiating aggregates

Hardness:  4.5

Specific gravity:  2.41 to 2.50

Cleavage:  2; {010} distinct, {001} indistinct

Tenacity:  Subconchoidal to uneven; brittle

Streak:  White

Synonyms/varieties:

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