Subsulphuret of Copper, or vitreous Copper ore
Cornwall often a affords us remarkable subjects, and this Copper is certainly one;—not from the variety of the form of the crystal, but from the strange manner in which the crystals are attached to each other and to the mass; at first sight like a number of forged nails with broad clouted heads, such as are beat into shape by a certain number of strokes of the hammer: the oddity of driving such a number of nails half way, or a little further, into any thing, would make a novice suspect it to be something else, and even an adept is at first in doubt. The number on a fine specimen that was in the possession of Mr. Ma we, part of which I have figured, puts us in mind of some fungusses that grow in heaps. The whole specimen, 9 or 10 inches long by 8 wide, had at least 120 principal crystals supported upon other smaller and more obscure ones forming a kind of stems; as in the lower fig. taken from a small specimen in the possession of—Lowndes, Esq.
I have figured the six-sided prism (tab. 501) and the acute pyramid (tab. 360), but had in my collection only a poor specimen (tab. 359) that shewed this obtuse pyramid obscurely; the crystals upon the one now figured are so conspicuous and remarkable, that I am pleased to have it before I close the work:—it is still very rare; I have however obtained a similar, although inferior, specimen to shew my friends.
The crystals are most of them truncated; and according to the proportion of their sides the faces are from 3 to 6 angled: sometimes the pyramids are united by short six-sided prisms: they are often rendered a little irregular by transverse striæ: they have but little metallic lustre, somewhat resembling Plumbago; the iridescent, or blued steel colour of their surfaces often adds to their beauty.
The mine from which it was risen, in 1813, is called Wheal Abraham.