116 



The specimens look red most by candle-light. They are 

 found in Wheal Unity, near Redruth, in Cornwall, and 

 in other parts of that county, as well as in different parts 

 of Europe. Foreign specimens, as far as I have seen de- 

 scribed, seem not to be superior in the size or perfection of 

 their crystals to the Cornish ones. The matrix of our upper 

 figure is shattery quartz, supporting native copper, from 

 which the oxide seems to proceed. It is worthy of remark, 

 that this kind of oxygenizement should form so regular a 

 crystallization, for it appears to be only a decomposition of 

 the native copper from which it commences. 



The lower Jigures are in different matrices, — one in a red 

 powdery oxide of copper and iron ; the other in an ochra- 

 ceous matrix, chiefly oxide of iron. 



It agrees with the following parts of Mr. Kirwan's de- 

 scription ^ (i It is often cochineal red, or intermediate be- 

 tween blueish-gray and carmine red. Found massive, in- 

 vesting, disseminating :" he does not mention its being found 

 crystallized. " Fracture even, approaching to the minute 

 conchoidal, sometimes earthy. Hardness 4 to 5, brittle. 

 Effervesces with nitrous acid, to which it gives a green 

 tinge, and a blue to caustic volalkali." 



Thus much till Mr. Chenevix had shown that there was 

 only one proper oxide of copper of a black colour, and that 

 the present species is rather a suboxide of copper, con- 

 taining 



Copper 88-5 



Oxygen 11-5 



whereas the black oxide contains 20 per cent, of oxygen. 



