2f30 COPPER. 



sometimes yields easily to the knife ; and its specific gravity varies 

 from 4*8 to 5 '4. Before the blow-pipe it melts into a grey glo- 

 bule containing iron, and is frequently magnetic. A specimen 

 analysed by Chenevix, contained copper 81, sulphur 12, iron 4. 

 This ore is found abundantly in Cornwall ; also at Middleton, in 

 Yorkshire, and other mining districts. 



Sp. 3. Yellow Sulphuret of Copper, or Copper Pyrites. 

 Pl. XXXIV. fig. 4.— Kupferkies, Werner ; Octaedrischer Kup- 

 ferkies, Mohs. Cuivre pyriteux, Brong. — Its colour is brass- 

 yellow, but is often externally tarnished. It occurs massive, 

 disseminated, in various particular forms, and crystalized, in tetra- 

 hedrons, which are frequently truncated on the angles or edges, 

 more rarely in cubes, octahedrons, and rhomboidal dodecahedrons. 

 Internally it is shining, with a metallic lustre. The fracture is 

 commonly uneven, sometimes conehoidal. The structure of the 

 crystals is laminar, of the mamillated and botryoidal varieties, fig. 

 a 4, granular. The specific gravity varies from 4*1 to 4*2. It is 

 harder than calcareous spar, brittle, and yields to the knife. Before 

 the blow-pipe it decrepitates, emits a green-coloured sulphureous 

 vapour, and melts into a black globule. Its composition varies 

 considerably ; a specimen analysed by Chenevix yielded, copper 30, 

 iron 53, sulphur 121. Copper pyrites is one of the most abun- 

 dant metalliferous minerals ; and, according to professor Jameson, 

 occurs in almost every kind of repository, in all the great classes 

 of rocks. " It may be distinguished," says this celebrated mine- 

 ralogist, " from native gold by its fracture and also by its tenacity, 

 it being brittle, whereas gold is malleable. It is distinguished from 

 iron pyrites by its hardness, it being rather soft, whereas iron 

 pyrites give sparks with steel ; also by its colour, and the form of 

 its crystals." 



Sp. 4. Purple Copper. Pl. XXXV. fig. 1. — Buntkupfererz, 

 Werner ; Cuivre pyriteux hepatique, Hauy ; Variegated Copper 

 Ore, Jameson. — This ore is merely a variety of copper pyrites. 

 Its colour is intermediate between copper-red and pinchbeck 

 brown, with an iridescent tarnish of violet-blue or yellow. It 

 occurs massive, and crystalized in cubes, fig. a, frequently trun- 

 cated on the angles, fig. b, and also in tables. Its constituents are 



