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Ostracias, Marcasite

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248
NATURAL HISTORY OF GEMS.
OSTRACIAS, or OSTEACITIS : Crude Vitriol? Pyrites ?
Thus briefly noticed by Pliny (65):—"Like a potsherd (testacea), of a harder quality than the Cerarnitis, re­sembling the Agate, except that the Agate becomes smooth and fatty by polishing. The harder kind possesses such force that gems may be engraved with its fragments. The Ostracitis derives its name from its similarity to a shell (or oyster)." Two distinct substances are here described as the same, the confusion arising from the circumstance that üóôñáêïí means both a potsherd and an oyster-shell All to be learnt is that the Ostracias was some mineral capable of being used in gem-engraving, resembling burnt clay in colour, rough, and incapable of polish ; the Ostracitis merely a fossil shell.* What the Ostracias really was may, however, be conjectured from the other notices of it. " The Cadmitis is the same as what is called Ostracitis, except that the last is sometimes surrounded by azure bubbles (bulla;)." The Cadmea, possibly so named after the mythic Phœnician father of mining in Greece, was either cupper or tin ore, being "ipse lapis ex quo fit ses" (xxxiv. 22). But it also signified certain chemical products of its fusion adhering to the sides of the furnace, and therefore of a vitriolic and arsenical nature, much used in the ancient
* Pliny seems to have included these minerals in lus list of Gem, merely in virtue of their employment in engraving.
Opalus, Opal Page of 384 Ostracias, Marcasite
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