Cymophane has its derivation also from the Greek words meaning 'wave' and 'appearance',
in reference to the chatoyancy sometimes exhibited. In this variety, microscopic tube like
cavities or needlelike inclusions of rutile occur in an orientation parallel to the
c-axis producing a chatoyant effect visible as a single ray of light passing across the
crystal. This effect is best seen in gemstones cut in cabochon form perpendicular to the
c-axis. The color in yellow chrysoberyl is due to Fe3+ impurities.
Although other minerals such as tourmaline, scapolite, corundum, spinel and quartz can
form "cat's eye" stones similar in appearance to cymophane, the jewelry
industry designates these stones as "quartz cat's eyes", or "ruby cat's eyes"
and only chrysoberyl can be referred to as "cat's eye" with no other designation.
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