"Rock of the Month # 87, posted September 2008" ---
Azurite is a colourful secondary salt formed by the alteration of pre-existing copper-rich minerals, often sulphides. The mineral most often occurs as thin films on older minerals, often accompanied by other colourful weathering products, such as the related green carbonate malachite, and orangey iron oxide, goethite. In the figured sample, these three minerals occur in an oxidized sulphide-rich carbonate vein. Associated minerals are the primary copper sulphide, chalcopyrite, plus chalcocite and pyrite. Photomicrograph in plane-polarized transmitted light, 100X magnification, long-axis field-of-view 0.9 mm. The sample is from a property in southern Spain, currently being explored by AuEx Ventures and its successor company, Renaissance Gold. The area has been identified as a focus of IOCG (iron oxide- copper- gold) mineralization. Azurite, the associated oxidized minerals and chalcocite are all secondary species, formed from the older chalcopyrite. The azurite is pleochroic in thin section, and displays both radiating and stacked tabular habits.
Azurite, formula Cu3(CO3)2(OH)2 is a monoclinic carbonate, first described by Beudant in 1824. The name is derived from the Persian word for blue. It was previously known as chessylite.
Melchiorre,EB, Criss,RE and Rose,TP (2000) Oxygen and carbon isotope study of natural and synthetic azurite. Economic Geology 95, 621-628.
North,RM (1991) Azurite and malachite from the Morenci and Metcalf mines, Greenlee County, Arizona. Mineralogical Record 22, 66-67.
Vink,BW (1986) Stability relations of malachite and azurite. Mineralogical Magazine 50, 41-47.
Wenrich,KJ (1991) Azurite and other copper carbonates in northern Arizona solution- collapse breccia pipes. Mineralogical Record 22, 67-68.
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