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Cat's-eye or Cymophane
This is the name given to the yellow, yellow-green
or gray green variety of chrysoberyl, which displays the phenomenon
of chatoyancy because of the inclusion of numerous fine, parallel
crystal needles.
Appearance The color is greenish
yellow or yellowish, sometimes with a rather cold, almost
grayish tone. Some fine stones are a honey brown. In the proper
light, the near side will appear yellowish white while the
brown of the far side will be intensified, creating a milk-and-honey
effect. Cat's-eye is always cut en cabochon, round or oval,
to emphasize the cat's eye effect, and can be fairly transparent.
Due to its hardness, it takes and maintains good luster, and
the more pronounced and pleasing the cat's-eye effect, the
greater is its value.
Distinctive features The most
common cat's-eye stones are the quartzes, which, however,
usually have a rather different color from chrysoberyl and
are less transparent with brighter, but more superficial,
chatoyancy. If there is any doubt, they can immediately be
distinguished by their different density, because refractive
indices are always hard to establish for curved stones.
Occurrence Cymophanes are mainly
found in Sri Lanka and Brazil, although they are not common.
Value Cat's-eye is highly prized
by collectors and connoisseurs. Its value is accordingly quite
high. Very fine examples are less valuable than the principal
gemstones. including alexandrite, but more so, for example,
than a fine topaz or spinel. Due to its value and hardness,
it is also known as "noble cat's-eye."
Simulants and synthetics Various
natural stones have been used as substitutes, including fluorite,
which, however, is much softer, and kornerupine, a gem still
rarer than cymophane, with lower hardness and density. Quartz
has also been used, although its color rarely resembles that
o` cymophane and its density is also much lower. To our knowledge,
no attempts have been made to produce this gem synthetically.
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