Crystallized Red Oxide of Copper, Crystal Octaëdral

Some of the crystalized red oxides of copper deserve from their lustre the appellation of Ruby Coppers more than others, which will be shown hereafter. The present fine specimen has more of the steel-like lustre, as mostof the octaëdrons have: however, the beautiful red sparkles internally with much brilliancy. It is not difficult to scrape it with a knife, and the least scratch produces a rich red powder of the colour of the gum called Dragon’s Blood^*. 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 described, seem not to be suprior in the size or perfection of their crystals to the Cornish ones. The matrix of our upper figure is shattery quartz, supporing 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 figures are in different matricies,—one in a red powdery oxide of copper and iron; the other in an ochraceous matrix, chiefly oxide of iron.

It agrees with the following parts of Mr. Kirwan’s description: “It is often cochineal red, or intermediate between blueish-gray and carmine red. Found massive, investing, 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, containing

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