Hydrozincite

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.

Hydrozincite
General
CategoryCarbonate mineral
Formula
(repeating unit)
Zn5(CO3)2(OH)6
Strunz classification5.BA.15
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Unit cella = 13.58 Å, b = 6.28 Å,
c = 5.41 Å; β = 95.51°, Z = 2
Identification
ColorWhite to grey, stained pale pink, or pale yellow or brown; colourless in transmitted light.
Crystal habitLathlike or bladed crystals uncommon, in fibrous, stalactitic, reniform, pisolitic aggregates; also earthy, chalky, massive
TwinningContact twinning on {100}
CleavagePerfect on {100}
FractureIrregular/uneven
TenacityVery brittle
Mohs scale hardness2 - 2 12
LusterSilky, pearly, dull, earthy
StreakWhite
DiaphaneityTransparent, translucent
Specific gravity3.5 - 4
Optical propertiesBiaxial (-)
Refractive indexnα = 1.630 nβ = 1.642 nγ = 1.750
Birefringenceδ = 0.120
2V angleMeasured: 40° , calculated: 40°
Dispersionrelatively strong
Ultraviolet fluorescenceFluoresces pale blue to lilac under UV
SolubilityReadily soluble in acids.
References[1][2][3]

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.[1]

It was first described in 1853 for an occurrence in Bad Bleiberg, Carinthia, Austria and named for its chemical content.[2]

References

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