Sulphuret of Zinc Enlarge
Feb 1. 1811 published by Jas Sowerby London.
British Mineralogy
CCCXCVII
Zincum sulphureum

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.

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