Hemimorphite

Mineral formula: Zn₄Si₂O₇(OH)₂ · H₂O

Crystal system: orthorhombic

Crystal habit: Thin tabular crystals, sheaf-like or fan-like aggregates, stalactitic, mammillary, botryoidal.

Cleavage: perfect on {110}, poor on {101}, {001} rare

Fracture: irregular/unevent, sub-conchoidal

Color: colorless, white, pale blue, pale green, grey or brown

Luster: sub-adamantine, vitreous, sub-vitreous, greasy, silky, pearly

Diaphaneity: transparent, translucent

Moh’s scale hardness: 4 ½ - 5

Streak: white

Specific gravity: 3.475

Named: in 1853 by Adolph Kenngott in allusion to the hemimorphic morphology of the crystals. Many names were previously assigned to this species, including calamine. Hemimorphite was chosen by the International Mineralogical Association, over calamine, in 1962.

Type locality: Băiţa mining district (Băiţa Bihor), Nucet, Bihor, Romania

Geological occurrence: Secondary mineral in the weathered portions of zinc deposits.