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ASTERIA.
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ASTERIA : the Girasol Sapphire.
Pliny thus
describes this stone :—" The Asteria, holding the first rank by a
natural claim, because it contains a kind of lustre within its
substance like the pupil of the eye, and pours it from side to side,
when held at an angle, as though it moved about in the inside,
presenting itself now from one point, now from another. Also, when held
against the sun, it reflects rays of a brilliant white, whence it
derives its name (Star-stone). The Indian sort is hard to engrave upon.
That found in Carmania is preferred to the others." No description can
better suit our Girasol Sapphire, which in its native state is usually
somewhat globose, being composed of concentric layers like an onion, to
which arrangement its opalescence is due. In this state the light
appears as a small orb shifting to and fro within the stone,
according as it is turned; but when cut to a plane and polished, this
orb becomes a most delicate star of numerous silky rays diverging from
one centre. This variety is pale and milky : hence the propriety of
the term " candicaules," applied by Pliny to its radiance. The
character of extreme hardness restricts his description to this kind of
Sapphire; for the Adularian Felspar, or Moonstone, answering to it in
some respects, is extremely soft. This latter would indeed seem to be
the next stone in his list, the Astrion, also colourless, approaching
to Rock-crystal in appearance, produced in India on the coast of
Patallene : " within from the centre shines a star with the light of
the full moon." Indeed this exactly applies to the Moonstone, the
Indian sort of which is incomparably superior to the European, and
which presents upon its silver-grey surface that softly lustrous and
full orb comparable to nothing except the luminary whence comes its
name.
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