scapolite series

Formula: (Na,Ca)₄Al₃Si₉O₂₄Cl

Origin of name: from Greek skapos = shaft and lithos = stone

Crystal system: Tetragonal

Crystal class: 4/m

Twinning:

Unit cell: a = 12.05, c = 7.58

Colour: Colourless, white, gray, bluish, greenish, yellowish, pink, violet, brownish

Diaphaneity: Transparent

Luster: Vitreous to pearly or resinous

Habit: Crystals prismatic, massive, granular or columnar

Hardness: 5.5 to 6

Specific gravity: 2.50 to 2.78

Cleavage: 2; {100} and {110} distinct

Tenacity: Splintery fracture

Streak: Colourless, white

Synonyms/varieties: Wernerite

Comments: see also the end-members of the scapolite series: marialite and meionite, fluorescent