Fluorapophyllite

Formula:  KCa₄Si₈O₂₀(F,OH) ^. 8H₂O

Origin of name:  The fluorine member of the apophyllite group

Crystal system:  Tetragonal

Crystal class:  4/m 2/m 2/m

Twinning:

Unit cell: a = 8.96 Ǻ, c = 15.71 Ǻ

Colour:  White, colourless, pink, green

Diaphaneity:

Luster:  Vitreous, pearly on {001}

Habit:  Crystals pseudocubic, tabular, pyramidal or long square prismatic; massive, lamellar or granular

Hardness:  4.5 to 5

Specific gravity:  2.37

Cleavage:  2; {001} perfect, {110} imperfect

Tenacity:

Streak:

Synonyms/varieties:

Comments:  Series with hydroxyapophyllite; orthorhombic dimorph has been found at Christmas, Arizona