Formula: NaAl3(SO4)2(OH)6
Origin of name: from natrium = sodium and alunite
Crystal system: hexagonal
Crystal class: -3 2/m
Twinning:
Unit cell:
Colour: white, discoloured grayish, yellowish, reddish, brownish
Diaphaneity: transparent to nearly opaque
Luster: vitreous, pearly on base
Habit: crystals rhombohedral, often pseudocubic, tabular or lenticular, druses and aggregates, massive, granular to dense compact
Hardness: 3.5 to 4
Specific gravity: 2.6 to 2.9
Cleavage: 2; {1110} distinct, {01-12} traces
Tenacity:
Streak: white
Synonyms/varieties:
Comments:
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