Editing Chrysoberyl (section)

==Cymophane==
[[Image:Cymophane.jpg|thumb|Fine-color cymophane with a sharp and centered eye|alt=Fine-color cymophane with a sharp and centered eye]]
Translucent yellowish [[chatoyancy|chatoyant]] chrysoberyl is called '''cymophane''' or '''cat's eye'''. Cymophane has its derivation also from the Greek words meaning 'wave' and 'appearance', in reference to the haziness that visually distorts what would normally be viewed as a well defined surface of a cabochon. This effect may be combined with a cat eye effect. In this variety, microscopic tubelike cavities or needle-like inclusions<ref>"Mitchell, T. E. and Marder, J. M., "Precipitation in Cat's-Eye Chrysoberyl," Electron  Microscopy Soc. Proceedings, 1982.</ref> 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 forms perpendicular to the c-axis. The color in yellow chrysoberyl is due to Fe<sup>3+</sup> impurities.{{Citation needed|date=May 2024}}

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.{{Citation needed|date=May 2024}}

Gems lacking the silky inclusions required to produce the cat's eye effect are usually faceted. An alexandrite cat's eye is a chrysoberyl cat's eye that changes color. "Milk and honey" is a term commonly used to describe the color of the best cat's eyes. The effect refers to the sharp milky ray of white light normally crossing the cabochon as a center line along its length and overlying the honey-colored background. The honey color is considered to be top-grade by many gemologists but the lemon yellow colors are also popular and attractive. Cat's eye material is found as a small percentage of the overall chrysoberyl production wherever chrysoberyl is found.{{Citation needed|date=May 2024}}

Cat's eye became significantly more popular by the end of the 19th century when the [[Prince Arthur, Duke of Connaught and Strathearn|Duke of Connaught]] gave a ring with a cat's eye as an engagement token; this was sufficient to make the stone more popular and increase its value greatly. Until that time, cat's eye had predominantly been present in gem and mineral collections. The increased demand in turn created an intensified search for it in Sri Lanka.<ref>{{cite web | url = http://www.farlang.com/gemstones/us-geol-survey-1887/page_031 | title = U.S. Geological Survey, 1887, George Frederick Kunz, Cymophane, Cat's Eye as gemstone | year = 1887 | access-date = 2007-07-09 | url-status = live | archive-url = https://web.archive.org/web/20070711150335/http://www.farlang.com/gemstones/us-geol-survey-1887/page_031 | archive-date = 2007-07-11 }}</ref>