Rosasite

Rosasite is a carbonate mineral with minor potential for use as a zinc and copper ore. Chemically, it is a copper zinc carbonate hydroxide with a copper to zinc ratio of 3:2, occurring in the secondary oxidation zone of copper-zinc deposits. It was originally discovered in 1908 in the Rosas mine in Sardinia, Italy, and is named after the location. Fibrous blue-green rosasite crystals are usually found in globular aggregates, often associated with red limonite and other colorful minerals. It is very similar to aurichalcite, but can be distinguished by its superior hardness.

Rosasite
Rosasite-291101.jpg
Blue velvety mass lining a cavity
General
CategoryCarbonate mineral
Formula
(repeating unit)
(Cu,Zn)2(CO3)(OH)2
Strunz classification5.BA.10
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/a
Unit cella = 12.873(3) Å, b = 9.354(3) Å
c = 3.156(2) Å; β = 110.36(3)°; Z = 4
Identification
ColorBlue, bluish green, green
Crystal habitAcicular crystals as radiating fibrous clusters; botryoidal; mammillary; encrustations
TwinningOn {100}
CleavagePerfect on {100} and {010}
FractureSplintery, fibrous
TenacityBrittle
Mohs scale hardness4
LusterSilky, vitreous to dull
StreakLight blue or green
Specific gravity4-4.2
Optical propertiesBiaxial (-)
Refractive indexnα = 1.672 - 1.688 nβ = 1.796 - 1.830 nγ = 1.811 - 1.831
Birefringenceδ = 0.139 - 0.143
PleochroismStrong: X = pale emerald green or colourless; Y = dark emerald green or pale blue; Z = dark emerald green or pale blue
2V angleMeasured: 33°
SolubilityEffervesces in cold, dilute hydrochloric acid
References[1][2][3]
Major varieties
Nickeloan rosasiteDark green

ReferencesEdit