Sulphuret of Zinc
Black Jack, as this substance is commonly called by the miners, is exemplified in this specimen with the usual appearance, and is indeed black to a proverb, for I know of no substance that has a blacker aspect. Coal is perhaps even blacker when powdered, in which state Jet is brown; but this, which in full as dense and brilliant in the mass, scrapes nearly to white dust, viz. light yellowish brown, not much unlike rosin, which gives a whitish dust. The splendent black crystals are generally grouped as well as confusedly crystallized, showing their brilliant polished facets one at a time occasionally very distinctly, but in the group are merely jumbled masses. As they often form among white Quartz, they are the more richly relieved; and the present specimen is additionally so, by the peculiarity of some of the Quartz, which is found to be, when examined, beautifully crystallized in relieved six-sided crystals, terminated at each end by six-sided pyramids, but they are again covered by an opaque, very white, almost mealy coat; or perhaps, having been acted upon externally, have become opaque by a division of the particles, which on that account are so separable as to be scraped with a steel blade of a knife. Specimens with a thin coat of Chalcedony next to the Blende, and transparent Quartz above it, are less rare.