Oxygenized Tin

Octaëdral crystals of oxygenized tin, destitute of any truncations, bevellings, or other modifications, I understand have never been yet found; those here represented are among the nearest known to that simple figure. My friend Mr. Richard Phillips, who possesses one of the finest and earliest collections of tins, &c. from Cornwall, lent me one of his best specimens for this figure, and I am possessed of a similar specimen. They seem in every thing so very like each other, as readily to imply that they came from the same place. They are very black, with much lustre, lying in every direction; some are macled or transposed with various truncations, bevellings, &c. The middle figure at the bottom shows the most perfect octaëdron I have yet seen. The edges of the pyramids are truncated more or less; the prism is perhaps shorter than here represented. The left-hand outline shows what it should be as a perfect octaëdron. The angles of the base of the two pyramids are 90°. Those of the face at the summit are 70° 31′ 44″, and at the base 54° 44′ 8″.

There have been two opinions concerning the primitive form of oxide of tin: the one, that it is an octaëdron; and the other, that it is a cube. We have obtained very neat fractures parallel to four faces of the latter, and signs of the faces inclined upon them, so as to form a rhomboidal dodecaëdron.