Meionite

Formula:  Ca₄Al₆Si₆O₂₄(CO₃,SO₄)

Origin of name:  From Greek for less

Crystal system:  Tetragonal

Crystal class:  4/m

Twinning: 

Unit cell: a = 12.26 Å, c = 7.61 Å

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

Diaphaneity: 

Luster:  Vitreous to somewhat pearly

Habit:  Crystals prismatic; massive, granular, sometimes colomnar

Hardness:  5.5

Specific gravity:  2.72 to 2.78

Cleavage:  2; {100} and {110} distinct

Tenacity:  Conchoidal to uneven; brittle

Streak:  Colourless

Synonyms/varieties:  Mizzonite (Na-rich var.)

Comments:  Series with marialite; end member of scapolite series