Variegated Copper Ore, Buntkupfererz

This ore is found in many places, besides Tincroft mine in Cornwall, whence our specimens. It was in Mr. Day’s collection, and I have received it from my late friend P. Rashleigh, esq. It is found in masses, plates, and also crystallized, its crystals are described to be octaëdrons. This expression of the form of the crystal may have arisen from the peculiar and remarkable appearance of certain groups of cubes which are often confused. My specimens, however, show the cubes in some instances very clearly, in others the aggregation of cubes is perhaps such as has hitherto escaped notice, viz. two cubes placed so as to form the resemblance of two pyramids united base to base, each composed of six concave sides with re-entering angles; the edges of the cubes form those of the pyramids; the faces of the cubes intersecting each other form the re- entering angles; supposing the axis of each cube to run through two opposite solid angles; the axes of the two cubes coincide with the axes of the double pyramid. The two cubes thus mixed, with their bounding and bisecting lines, are represented in the upper outline, with dots. &c. to make it as distinct as such an outline can well be. The right hand outline has the pyramids nearly in profile, and in the left hand figure the apex is brought near to the front.

The groups in the lower specimen are chiefly these figures placed like the upper outline; in the middle one the larger cubes are rather rounding aggregates of many small cubes, hence they are roughish and crowded; their surfaces are partially covered with a greenish patina, showing a forward state of decomposition. The cubes in the upper specimen are smooth, variously tarnished or coloured, generally blackish, or steel gray and iridescent in many parts. They also show an inclination to vary inside when broken, as the flaws are often tarnished and iridescent: the darkness of the tints, however, helps to distinguish it from other Copper ores. They are rather easily scraped with a knife, and may always be known from the other Kulphurets of Copper by the purplish red colour of the fresh fractured surfaces.

I have a beautiful specimen accompanied by green and bronzed mammillated Copper from Cook’s Kitchen, in which the faces of the crystals are yellow bronzed in one view, and green bronzed in another; thus the two cubes in the groups are distinguished from each other by their colour, I am obliged to the Count de Bournon. for the loan of the two lower specimens.