Mr. J. Napier on Copper Smelting. 51 



are not selected specimens, but are taken from and after the mass 

 is crushed and ready for the furnace; and they are mostly all 

 poorer in copper than those from the same mines that are im- 

 ported into this country. 



The two grand divisions of ores in the smelting-house are those 

 with and without sulphur, constituting oxides, carbonates and 

 sulphurets, a few of which we will briefly describe. There are 

 two oxides of coppei", the black and the red. The former, as its 

 name denotes, is a black crystalliue mineral inclining to brown 

 and blue ; it often occui's as a friable mass, and forms a sort of 

 coating over the surface of other ores, such as the sulphm-ets 

 when they have been subjected to exposure to air and water. 

 Black oxide is not found in great quantities in a pui-e state, but 

 in combination with iron it is abundant in some of the Australian 

 mines. ^Vhen pure, the composition is — 



Copper . . . 79-83 



Oxygen . . . 20'18 



100-00 

 It is abundant in the Burra Burra mines. The average of a 

 good many analyses of selected specimens may be stated to be — 

 Copper . . . 72'6 

 Oxygen . . . 18-1 

 Protoxide of iron . 4-3 

 Silica .... 4-5 



99-5 

 Red oxide of copper differs from the black oxide by containing 

 less oxygen ; it is more abundant as an ore than the black, has 

 a reddish-brown colom-, often approaching to rich red, espe- 

 cially when crushed. When native copper occurs, it is generally 

 surrounded by red oxide ; it is associated in the Australian mines 

 both with the black oxide and carbonate. When pure its com- 

 position is — 



Copper . . . 88-8 

 Oxygen . . . 11-2 



1000 

 This oxide has occasionally been termed tile ore, said to be 

 from its colour ; but we think this a corruption. There are 

 many poor ores which have the same coloiu-, in mass, from the 

 matrix being a rich red clay, red jluccan : the copper made 

 from some of these ores being inferior, is termed tile copper, 

 hence probably the error. We have spccmiens of red oxide 

 from Cornwall fr)nniug small veins through other qualities of 

 ore, which contain upwards of 82 per cent, of copper, with a little 

 silica and ii-on as impurity. A massive specimen from Burra 



E2 



