It
is indubitable that the Greeks derived all their processes of the
glyptic art from Persia, whence by the way of the Ionian cities the use
of intagli had been introduced amongst them ; and whence, from Sardis
in particular, the gems were exported.
But
the use of Pyrites amongst the Romans in this art is not a mere matter
of conjecture. Heraclius, in his unintelligible doggrel, ' De Artibus
Romanorum,' written in the 7th century, actually speaks of engraving
upon glass with " the hard stone known by the name of Pyrites."
Nevertheless a suspicion that actual copper-slag may be meant by Ostracias is
favoured by a passage in the same obscure author, where he describes
the polishing of Rock-Crystal by means of " fomacis fragmine, micas,"
ground to powder, and spread upon a leaden plate,—
" Nam pliimbo solo tribuetur cura secandi."
" Haec etenim plumbum conjunctio reddit acutum, Et suum rursus habent lateris fragmenta vigorem."
Yet
it seems hardly possible that any merely vitrified matter should be
sufficiently hard to be thus employed as a substitute for emery, even
if he means the Ostracitis of the copper-furnace.
Again,
if we suppose the name Ostracitis to be derived from the resemblance to
a shell, it is a singular coincidence that fossil shells, especially
echini and small ammonites, are very plentiful, composed entirely of
Iron Pyrites, forming beautiful golden objects which must have often
excited the admiration of the ancient mineralogist.3
From
its use to the lapidary the Marcasite was an important article to the
Persians. Ben Mansur devotes a separate chapter to it, dividing the
kinds, according to their colour, into gold, silver, iron, and copper,
Marcasites. Marcasites, when facetted, have a true adamantine lustre
(though perfectly opaque), which they preserve without tarnishing. In
the last century they were much used in jewelry as a cheap substitute
for Diamonds.
