Rosasite

(repeating unit)(Cu,Zn)₂(CO₃)(OH)₂IMA symbolRss^[1]Strunz classification5.BA.10Crystal systemMonoclinicCrystal classPrismatic (2/m)
(same H-M symbol)Space groupP2₁/aUnit cella = 12.873(3) Å, b = 9.354(3) Å
c = 3.156(2) Å; β = 110.36(3)°; Z = 4IdentificationColorBlue, bluish green, greenCrystal habitAcicular crystals as radiating fibrous clusters; botryoidal; mammillary; encrustationsTwinningOn {100}CleavagePerfect on {100} and {010}FractureSplintery, fibrousTenacityBrittleMohs scale hardness4LusterSilky, vitreous to dullStreakLight blue or greenSpecific gravity4–4.2Optical propertiesBiaxial (−)Refractive indexn_α = 1.672 – 1.688 n_β = 1.796 – 1.830 n_γ = 1.811 – 1.831Birefringenceδ = 0.139 – 0.143PleochroismStrong: X = pale emerald green or colourless; Y = dark emerald green or pale blue; Z = dark emerald green or pale blue2V angleMeasured: 33°SolubilityEffervesces in cold, dilute hydrochloric acidReferences^[2][3][4]Major varietiesNickeloan rosasiteDark green

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.

References

• Mineral galleries