COPPER ORES. 47 



Structure brittle. 



Colour between steel grey and iron black, sometimes 



brownish. 

 Streak between steel grey and iron black, sometimes 



brownish. 



H. 3 to 4; S.G. 4-75 to 5-1. 

 Composition per cent. copper, 38 - 6 ; sulphur, 26*3 ; 



antimony and arsenic, zinc, iron, silver, &c. 



It sometimes contains 30 per cent, of silver in place 

 of part of the copper. After roasting, yields a globule of 

 copper before the B.F. When powdered and dissolved in 

 nitric acid, the solution is brownish green. The ore can be 

 distinguished from any silver ore by the blowpipe and 

 chemical tests. The darker the colour the less arsenic in it. 



Red Copper Ore (ruby copper). 



Found massive, earthy, granular, &c. 



Crystallization octahedral, and dodecahedral. 



Structure brittle . 



Lustre adamantine, or submetallic. Is subtransparent 



or nearly opaque. Detached crystals look rather 



like spinel rubies. 

 Colour deep red, ruby colour, though it is often iron 



grey on the surface. 

 Streak always brownish red. 

 H. 3-5 to 4 ; S.G. 6. 

 Composition per cent. copper, 88*78 ; the remainder 



oxygen. 



Heated in a tube closed at one end, it darkens. Yields 

 globule of copper before the blowpipe. Dissolves in nitric 

 acid. Soluble in ammonia : solution eventually azure blue. 



Black Oxide of Copper. 



Usually found on the surface, due to the decomposition of 

 a sulphide or other copper ore. Black copper at the top of 

 a lode may indicate some other copper compound deeper 

 clown. If the dusty powder be rubbed between the fingers 

 and dropped on a flame, the latter will be coloured green. 

 Soluble in ammonia : solution azure blue. 



