This Ore seems to have been overlooked by lute authors; its peculiar aspect, however, appears to me to deserve to be identified as much as many other species; and it is pretty well known by the name of Fitch Copper among the Cornish miners.
The specimen here figured is in some parts of a blackish brown colour, with a pitchy lustre, and is much mixed with Copper Pyrites; in other parts it is less mixed, has a browner cast and fractures like Pitclistone, with sharp angular, and sometimes large or small conchoidal fragments, still retaining that lustre which has been considered as a distinction in Pitehstone: perhaps it is even a little more greasy in the aspect, therefore still more resembling Pitch.
It is the gangue for Green Carbonate of Copper and Arseruate of Copper.
It wants analysing. At present we can only say that we suppose it to be an Oxide of Copper mixed with Oxide of Iron and Silex. Some specimens seem to hold very little Silex, and to result from the decomposition of Copper Pyrites; others hold very little Copper, and Kirwan speaks of some that hold Bitumen: both these may possibly be produced by mixtures of Iron and Copper Pyrites, the latter of which is sometimes accompanied by Bitumen.