. . 320 CholcopyriteCerussite coaling GaleniteGaleiiitp Size. AnglesiteNative Copper * v. CHAPTER IV ORES^ MARBLES^ ETC. COPPER AND LEAD ORES Native Copper scarcely needs a description. Its occur-rence in its free state provides an interesting subject ofconjecture. Briefly stated, the question of origin is whetherthe copper was set free by the decomposition of siHcates orwas in the form of a sulphide in the rock. The chief regionof occurrence of native copper is the Lake Superior district. The ore chalcocite, sometimes call
. . 320 CholcopyriteCerussite coaling GaleniteGaleiiitp Size. AnglesiteNative Copper * v. CHAPTER IV ORES^ MARBLES^ ETC. COPPER AND LEAD ORES Native Copper scarcely needs a description. Its occur-rence in its free state provides an interesting subject ofconjecture. Briefly stated, the question of origin is whetherthe copper was set free by the decomposition of siHcates orwas in the form of a sulphide in the rock. The chief regionof occurrence of native copper is the Lake Superior district. The ore chalcocite, sometimes called copper glance, hasa metallic luster, often tarnished green or blue. It is com-monly lead-gray and rather soft. Its streak is a blackishlead-gray. Chalcopyrite is a sulphide of copper and ironcombined. When copper is much in predominance the colorof the ore is golden yellow. The streak is dark green. Themineral is harder than chalcocite, but less hard than pyrite,being easily scratched with a knife. Both chalcocite andchalcopjTite frequently occur in silver-
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