Blistered Sulphuret of Copper

This often very superb variety of Copper Pyrites occurred chiefly in Cook’s Kitchen mine, and in other places in Cornwall. It may be said to occur of ah colours, viz., yellow, red, and blue, in binary varieties, such as orange violet and green; also the ternaries, or all varieties of brown; but this variety of colour is only superficial. Sulphate of Copper is often found in solution in water, as I have elsewhere observed , and that it was said to be discovered by its precipitating on an Iron instrument or spade used in digging, as the solvent had a greater affinity for Iron than for Copper: thus there will be but little difficulty (as it may have been in a soluble state) in presuming these formations, at first sight so aptly resembling the bubbling of boiling metal by great heat, to have been formed or subsided from watery solutions: indeed the formations could not, when duly considered, have been otherwise: yet, prepossessed with common appearances, we should not think so; and the notice of it in this manner is therefore the more necessary, and may perhaps be useful to attend to in forming conclusions regarding different substances. The whole may be as variable inside and in its component parts as it is in colour outwardly; but commonly consists of Copper in the greatest proportion, Sulphur next, and Iron least. Sometimes Gray Sulphuret of Copper in hexaëdral crystals or spiculæ surmounts the bubbles, or is found among them. The somewhat brassy appearance on being rubbed is in this figure represented by aurum musivum, a preparation of Tin with Sulphur. Mr. John Davey has made the best I have seen, and expects to improve on the certainty of producing it in perfection, which is rather difficult.