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60 NATURAL HISTORY OF GEMS.
Sapphirine Calcedony (jaspis). On
the other hand, there are many points of analogy to induce a belief
that our ; Turquois was the Hermean or Persian Smaragdus of
De-mocritus, " protuberant, not transparent, of an agreeable
and '. even colour, like the eye of a leopard or cat ; losing their
beauty in the sunshine, but lustrous in the shade, and con-spicuous
from a greater distance than any other precious stone :" one grand
distinction of the Turquois being that its colour is improved by
artificial light, in which, even though greenish, it becomes a perfect
celestial blue. A strong confirmation of this view is to be found in
the war so hotly waged between the mediaeval doctors as to whether that
great oracle of the science, the Arabian Mesues, meant the Emerald or
the Turquois by his "Firuzegi,"* that essential ingredient in his
highly-esteemed electuary.
The "Fossil Ivory "of Theophrastus (37) "dark blue ; mottled
with white," can hardly be other than the Occidental Turquois, or
petrified bone, tinged by copper oxide, in which the osseous structure
is plainly discernible under the microscope, and which, besides, is
much softer than the true Persian Turquois ("de la vieille roche" in
jewellers' parlance), which is sufficiently hard to strike fire with
steel. According to Hill, the blue that mottles the surface of the
former species can, by the judicious application ot heat, be evenly
diffused throughout its mass, thus greatly improving its appearance,
and often enabling it to pass muster for the actual and precious stone. Its
Greek appellation, so much more correct than the modern, may be set
down amongst the proofs that continually strike us of the sagacity of
the primitive naturalists in discovering by observation and induction
alone the true origin of many substances. Barbot found by experiment
that the teeth of
* " The Victor," an epithet attesting its reputation amongst the Persians.
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