copper 259 



rectangular four-sided prism. The crystals are generally aggregated 

 in groups, and variously modified by truncation and bevclment. 

 Thus fig. a, represents a cube truncated on the angles ; fig. /-, an 

 octahedron truncated on the lateral edges, forming the passage of 

 that solid into the rhomboidal dodecahedron, fig. c. It occurs 

 also capillary, dendritic, botryoidal, in thin plates, disseminated, 

 and in amorphous masses. It is softer than native silver, sectile, 

 perfectly malleable, and flexible, but not elastic. It is very tough 

 and its fracture is hackly. Its specific gravity varies from 7*7 to 

 8*5. Before the blow-pipe, it melts into a bead of apparently pure 

 copper. It may be distinguished from copper nickel by its mal- 

 leability and inferior hardness ; from native gold by its inferior 

 specific gravity and its solubility in nitric acid. Native copper 

 occurs in veins, and imbedded in various primitive, transition, and 

 secondary rocks. It is occasionally accompanied by several of the 

 ores of copper, and sometimes those of other metals. It also occurs 

 in large blocks in alluvial soil, in various parts of the globe. One 

 of the largest masses hitherto noticed was discovered by School- 

 craft, the North American traveller, about thirty miles from Lake 

 Superior, on the western bank of the river Ontonagon. It weighs 

 by estimation 2200 pounds. Native copper is frequently found in 

 connexion with the secondary green-stone, and red sand-stone 

 formation in the United States. It is likewise found in several 

 different mining districts in Germany and in Norway ; but its 

 greatest known depositaries in England are the mines of Cornwall. 

 Sp. 2. Black Sulphuret of Copper, Vitreous Copper, or 

 Copper Glance. Pl. XXXIV, fig. 3. — Kupferglanz, Werner ■ 

 Cuivre sulfure, Hauy. ; Cuivre vitricux, Brongniart. — Its colour 

 is blackish lead-grey. It occurs massive, disseminated, and crys- 

 talized in six-sided prisms, (iig. b,) and six-sided pyramids. 

 According to Hauy, the primitive form is a six-sided prism. One 

 of the varieties of this figure, a flattish dodecahedron is represented 

 at fig. e ; fig./, a six-sided prism truncated on the terminal edges; 

 fig. a, an acute dodecahedron with triangular planes. The struc- 

 ture in some varieties is distinct laminar. The fracture is imper- 

 fectly conchoidal, with a glistening or vitreous metallic lustre. 

 This ore varies considerably in density, hardness, and colour. It 



