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Tigers Eyes, Hawks Eye
stones display what is known as chatoyancy.
The result is a series of minor gemstones differing only in
their ground color and that of the mobile reflection. The
variety crocidolite is quartz pseudomorphous after riebeckite.
Appearance When the ground color is greenish
gray or green, the gem is known as cat's-eye quartz; if the
ground is blue-gray or bluish, the variety is called hawk's-eye;
a golden yellow reflection on a brown ground is called a tiger's-eye;
and a stone with a mahogany-colored ground is called bull's-eye
or ox-eye. It is normally cut en cabochon, to bring out the
chatoyancy, which is, after all, its main characteristic;
but it can be cut into more or less round, polished pieces,
for necklaces and pendants. The tiger's eye variety, in particular,
is also used for carvings. boxes, ashtrays, and other ornamental
items, although in these, the fibers are seen as stripes of
color, not chatoyancy as such.
Distinctive features The colors and clearly
fibrous appearance are normally distinctive, although other
stones, as, for instance, some nephrites or chatoyant feldspars,
may look quite similar. Cymophane chrysoberyl, on the other
hand, is usually much more translucent and greenish yellow,
with much greater hardness and density.
Occurrence Cat's-eye quartz comes mainly
from Sri Lanka and West Germany (Bavaria), but also from Burma.
Hawk's-eye, bull's-eye, and the much more plentiful tiger's-eye,
in particular, come principally from South Africa.
Value Despite its attractiveness, this material
is not very valuable. The less common hawk's-eye variety is
worth somewhat more.
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