Alvanite

Formula:  (Zn, Ni)Al₄(VO₃)₂(OH)₁₂ ^. 2H₂O

Origin of name:  From composition with aluminium and vanadium

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning: Polysynthetic parallel to {010}

Unit cell: a = 17.808 Å, b = 5.123 Å, c = 8.881 Å, b = 92.11°

Colour:  Light bluish green to bluish black

Diaphaneity: Semi-transparent

Luster:  Vitreous, pearly on cleavage

Habit:  Mica-like platelets with hexagonal form

Hardness:  3 to 3.5

Specific gravity:  2.41 to 2.50

Cleavage:  1; {010} perfect

Tenacity:

Streak:  White

Synonyms/varieties:

Comments: Found in the oxidation zone of a vanadiferous clay-anthraxolite horizon.