This section is from "Scientific American Supplement Volumes 275, 286, 288, 299, 303, 312, 315, 324, 344 and 358". Also available from Amazon: Scientific American Reference Book.
This beautiful mineral has been found in fair abundance at times in Shafts No. 1 and 2 in pockets, and seldom in place, most of it being taken from the loose stone at the mouth of the shaft, and it may generally be found on the dump. It is readily mistaken for calcite by the miners and those unskilled in mineralogy, but a drop of acid will quickly show the difference. The sizes of the crystals are very various, from an eighth of an inch long or thick, to, in one case, an inch and a half. The colors have been varied from white to nearly all tints, including pink, purple, blue, and green; the white variety is, however, the most abundant, and makes a handsome cabinet specimen. The crystals are generally packed together in a mass, but are frequently set apart as heavy druses of crystals having the form shown in Fig. 7. Sometimes, as in the former grouping, the crystals are without the pyramidal terminations, and are then right square prisms. The fracture being at perfect right angles, distinguishes it from calcite. Its hardness is generally fully 5, the specific gravity between 2.4 and 2.5; it is difficult to fuse before the blowpipe, but is finally fused into an opaque globule. Upon heating with nitric acid it partly dissolves, and the remainder becomes flaky and gelatinous. Apopholite, although quite rare, now may be bought from the men, or at least one of the engineers of Shaft No. 2's elevator, and generally at low terms.