Zincovoltaite

Formula: K₂Zn₅Fe₃Al(SO₄)₁₂ ^.18H₂O

Origin of name: from zinc and Voltaite

Crystal system: Cubic/Isometric

Crystal class: 4/m 3 2/m

Twinning:

Unit cell: a = 27.18

Colour: Green-black to green, black

Diaphaneity: Transparent to translucent

Luster: Vitreous to resinous

Habit: Single grains 1-2 mm and granular aggregates, octahedra, cubes and combinations

Hardness: 3

Specific gravity: 2.756

Cleavage: None

Tenacity:

Streak: Gray green

Synonyms/varieties:

Comments: Zn analogue of voltaite; slowly soluble in water, readily soluble in HCl, decomposes slowly in air