The late Mr. Philip Rashleigh in 1802 figured a specimen of tins appearance as a Gray Copper, which it was then understood to be, and of which there are some specimens that much resemble this, being hexaëdral tables; but the grayness of the surface, generally, and the want of redness inside, constantly, distinguish them.
The present specimen was probably some time before the above period presented by Mr. Rashleigh to Mr. Day, from whom it came into my possession; and it is really so nearly similar to Mr. R’s figure, that it might seem to be the same specimen. I have some tolerable specimens without the prismatic colours on the surface; but the coppery redness of the interior is, however, conspicuous.
Some of the plates are three- four- or five-sided, arising from the enlargement of some of the sides at the expense of others; the angles necessarily remaining 60° or 120°, in conformity with the regular hexaëdral prism. The middle figure represents the common appearance of this substance in a moderate specimen. The bottom figure is from an amorphous fragment, I presume all are from Tincroft Mine in Cornwall. The primitive Crystal, &c. has been described at tab. 496.