diamond—
such a stone would pass very well as a diamond, and many so cut are
sold by unscrupulous people as the more valuable stone, which fraud an
expert would, of course, detect.
Sapphires
are mentioned by Pliny, and figure largely in the ancient history of
China, Egypt, Rome, etc. The Greeks dedicated the sapphire specially to
Jupiter, and many of the stones were cut to represent the god ; it also
figured as one of the chief stones worn by the Jewish High Priest on
the breast-plate. Some stones have curious rays of variegated colour,
due to their crystalline formation, taking the shape of a star ; these
are called " asteriated," or " cat's eye" sapphires. Others have
curious flashes of light, technically called a ''play-' of
light (as described in Chapter VI. on " Colour "), together with a
curious blue opalescence ; these are the " girasol." Another
interesting variety of this blue sapphire is one known as '" chatoyant"
; this has a rapidly changing lustre, which seems to undulate between a
green-yellow and a luminous blue, with a phosphorescent glow, or fire,
something like that seen in the eyes of a cat in the dark, or the
steady, burning glow observed when the cat is fascinating a bird—hence
its name. This is not the same variety as the " asteriated, " or "
cat's eye " or " lynx eye " mentioned above.
