Gray Sulphuret of Copper

My kind friend, the well-known and scientific Mr. Stackhouse, of Pendarvis, favoured me with the best specimens I had seen of this substance from Cornwall, some six or eight years since, I did not then know that 1 should not sec better. I now believe there are not much better specimens, nor larger Crystals known. It is more common in small steel-grained-looking Crystals, whence this Ore has commonly been called Steel-grained Copper Ore. Its surface resembles line polished steel, with rather a whiter lustre; and my friends must conceive a little from the description, as our methods of imitation will not so nearly resemble this steel-like lustre as could be wished. The figure at the bottom of the plate shows the forms of the crystals magnified: the right hand figure shows the truncations on the triëdral angles, which are sometimes only one or two, and correspond with the planes of the tetraëdron or octaëdron; and are so irregular in size, as to confound young crystallographers, by disguising the other faces; especially among such shining groups in holes and corners.