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 mineral is quite abundant in Shafts No. 1 and 2, in very small masses, incrustations, and even in small crystals. It occurs embedded in or incrusting the trap, and also with calcite and apopholite. The only sure place to find it is at the southwest side of an opening through the pile of drift rock under the trestle work of the tramway, between shaft No. 1 and the dump, and within a few feet of a number of wooden vats sunk into the ground seen just before descending the hills and near the edge. Here on a number of blocks of trap it may be found, a greenish white incrustation about as thick as a knife blade; it also may be found on the main dump, and is sometimes found in plates one-eighth of an inch thick, of a darker green color, upon calcite. Its easiest distinguishment from the other minerals of this locality, with which it might be confounded, is its great hardness of from 6 to 7. It is very fragile and brittle, however, and is never perfectly transparent, but quite opaque; its specific gravity is 2.9, and it is readily fused before the blowpipe after intumescing. It partly dissolves in acid without gelatinizing, leaving a flaky residue; it is a beautiful mineral when in masses or crystals of a dark green color, but the best place in the vicinity to secure specimens of this kind is, as I will detail hereafter, at Paterson, N. J.