Formula: (NH4)2Mg2(SO4)3
Origin of name: For Ivan A. Yefremov, Russian geologist
Crystal system: Cubic
Crystal class: 23
Twinning:
Unit cell:
Colour: Gray, white
Diaphaneity:
Luster: Vitreous
Habit: Equant grains 0.01-0.05 mm in dull aggregates
Hardness: 2
Specific gravity:
Cleavage: None
Tenacity:
Streak:
Synonyms/varieties:
Comments: Soluble in water; in air at room temperature hydrates to boussingualtite in several days
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