Rosasite

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Rosasite
Rosasite.jpg
Blue velvety mass lining a cavity
General
Category Carbonate mineral
Formula
(repeating unit)
(Cu,Zn)2(CO3)(OH)2
Strunz classification 05.BA.10
Crystal symmetry Monoclinic prismatic H–M Symbol 2/m Space group P21/a
Unit cell a = 12.873(3) Å, b = 9.354(3) Å, c = 3.156(2) Å; β = 110.36(3)°; Z = 4
Identification
Color Blue, bluish green, green
Crystal habit Acicular crystals as radiating fibrous clusters; botryoidal; mammillary; encrustations
Crystal system Monoclinic
Twinning On {100}
Cleavage Perfect on {100} and {010}
Fracture Splintery, fibrous
Tenacity Brittle
Mohs scale hardness 4
Luster Silky, vitreous to dull
Streak Light blue or green
Specific gravity 4-4.2
Optical properties Biaxial (-)
Refractive index nα = 1.672 - 1.688 nβ = 1.796 - 1.830 nγ = 1.811 - 1.831
Birefringence δ = 0.139 - 0.143
Pleochroism Strong: X = pale emerald green or colourless; Y = dark emerald green or pale blue; Z = dark emerald green or pale blue
2V angle Measured: 33°
Solubility Effervesces in cold, dilute hydrochloric acid
References [1][2][3]
Major varieties
Nickeloan rosasite Dark 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 colourful minerals. It is very similar to aurichalcite, but can be distinguished by its superior hardness.

References[edit]