Chemistry:Hydrozincite

Hydrozincite
General
Category	Carbonate mineral
Formula (repeating unit)	Zn5(CO3)2(OH)6
Strunz classification	5.BA.15
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/m
Unit cell	a = 13.58 Å, b = 6.28 Å, c = 5.41 Å; β = 95.51°, Z = 2
Identification
Color	White to grey, stained pale pink, or pale yellow or brown; colourless in transmitted light.
Crystal habit	Lathlike or bladed crystals uncommon, in fibrous, stalactitic, reniform, pisolitic aggregates; also earthy, chalky, massive
Twinning	Contact twinning on {100}
Cleavage	Perfect on {100}
Fracture	Irregular/uneven
Tenacity	Very brittle
Mohs scale hardness	2–​2 1⁄2
|re|er}}	Silky, pearly, dull, earthy
Streak	White
Diaphaneity	Transparent, translucent
Specific gravity	3.5–4
Optical properties	Biaxial (−)
Refractive index	nα = 1.630 nβ = 1.642 nγ = 1.750
Birefringence	δ = 0.120
2V angle	Measured: 40°, calculated: 40°
Dispersion	relatively strong
Ultraviolet fluorescence	Fluoresces pale blue to lilac under UV
Solubility	Readily soluble in acids.
References

Hydrozincite, also known as zinc bloom or marionite, is a white carbonate mineral consisting of Zn₅(CO₃)₂(OH)₆. It is usually found in massive rather than crystalline form.

It occurs as an oxidation product of zinc ores and as post mine incrustations. It occurs associated with smithsonite, hemimorphite, willemite, cerussite, aurichalcite, calcite and limonite.

It was first described in 1853 for an occurrence in Bad Bleiberg, Carinthia, Austria and named for its chemical content.

References

• Mineral galleries data