Tham khảo tài liệu 'materials handbook 15th ed - g. brady_ h. clauser_ j. vaccari (mcgraw-hill_ 2011) ww part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 280 COPPER OXIDE ore of copper occurring in the oxidized parts of copper veins of Arizona and New Mexico. It is a hydrous copper silicate of composition CuSiO3 2H2O. It occurs in compact masses with a specific gravity of 2 to and a hardness of 2 to 4. The color is green to bluish. It was used as a green pigment by the ancient Greeks. Large reserves of this ore occur in Gambia and other copper regions of Africa and it is treated by high-temperature methods to obtain the copper. Atacamite is an ore found in Bolivia Arizona and Australia. It is a copper chloride with copper hydroxide CuCl2 3Cu OH 2 generally found in confused crystalline aggregates fibrous or granular. The hardness is 3 to specific gravity and the color may be various shades of green. The unique copper ores of Japan called kuromono are complex sulfide-sulfate replacement minerals. Much native copper metal occurs in the Lake Superior region particularly in Michigan but it occurs irregularly and not in continuous veins. The Ontonagon boulder of native copper in the National Museum weighing 3 tons metric tons came from Michigan. Amass of native copper found in 1847 was 10 ft 3 m long and weighed 6 tons metric tons . The largest ever found weighed 18 tons metric tons . COPPER OXIDE. There are several oxides of copper but usually the term refers to red copper oxide or cuprous oxide Cu2O a reddish crystalline powder formed by the oxidation of copper at high temperatures. It also occurs naturally in cuprite ore. The specific gravity is and the melting point 2255 F 1235 C . It is insoluble in water but soluble in acids and alkalies. It is used in coloring glass and ceramics red in electroplating and in alternating-current rectifiers. Rextox of Westinghouse Electric Corp. is copper upon which a layer of copper oxide has been formed. Electric current will flow easily from the oxide to the copper but only with difficulty from the copper to the oxide. It may be used for transforming
