Crystals of this are included in the denser rock in great abundance; they are very small, seldom over a few lines in diameter, of an iron black color, of a regular octahedral form; sometimes large crystals may be found in place or in the disintegrated loose rock. I have seen them a half inch in diameter, and a half dozen in a small mass, thus forming an excellent cabinet specimen. By finding out by observation where they are the thickest in the rock, and cutting in at this point, more or less fine crystals may be obtained. This is readily found where they are so very abundant, near the equidistant points of the walk, that no difficulty should be encountered in so doing. These characteristics are interesting, and if large specimens cannot be obtained, any quantity of the small crystals may be split out, and, as a group, used for a representative at least. Before the blowpipe it is infusible, but if powdered, it slowly dissolves in the molten borax bead and yields a beautiful green globule. The specific gravity, which is generally unattainable, is about 4.5, and hardness 5 to 6.

License information: nan
MPAA: G
Go to source: http://www.gutenberg.org/files/8452/8452-h/8452-h.htm