Copper . 3 
and Chili. Grey copper ore, usually containing antimo- 
ny, lead, iron and silver : poor in copper. Brown earthy 
coloured copper ores containing much iron. 
The sulphurets and arsenicated ores, are those which are 
usually smelted for the purposes of manufacture, almost 
all of which contain iron also in various proportions. The 
copper ore at Mr. Coleman ? s Cornwall Furnace, contains 
so much iron, as to be of little value, either as copper or 
iron ore. 
Of the assay , and analy sis of copper ores. By an assay 
of an ore, is meant the process used to ascertain the quan- 
tity of metal contained in it : by the analysis of an ore, is 
meant the process used to ascertain all its component parts. 
The assay of copper ores, (though by no means so ac- 
curate a method of ascertaining their metallic contents as 
a regular analysis) being the method by which the market 
price of the ore is always determined, requires the first 
notice. The best method, upon the whole, of conduct- 
ing it, is as follows. 
First, expose a small piece of the ore, under examina- 
tion to the action of the blow-pipe, and by the appear- 
ance and odour of the vapour given out, it is easy to dis- 
cover whether it contains any arsenic or sulphur. It may 
very probably contain both, in which case take 300 grains 
of thebre coarsely pulverized, mix it with half its weight 
of saw- dust, and keep it at a moderate red heat in an 
earthen crucible, till the disengagement of arsenical va- 
pour entirely ceases. Then pour the contents of the cru- 
cible into an iron mortar, and reduce them carefully to a 
fme powder. Transfer this powder to a test, a tile or piece 
of earthen ware that will stand the fire and expose it to a 
good red heat, with occasional stirring, till both the char- 
coal and the sulphur are burnt off. The residue is then 
to be accurately mixed with one twelfth of its weight of 
lamp-black, half its weight of clear white sand, one fourth 
of its weight of dry pearl ash, and its weight of pidverized 
