Photo of Chatoyant Quartz in Processed & Rough Form
Chatoyant Quartz is a mineral with a hardness of 7 out of 10 on the Mohs scale of mineral hardness [?]. These Trigonally structured gems are made of silicon dioxide, their full chemical compound being SiO2.
When quartz contains similarly-oriented fibrous inclusions, and is then appropriately-cut, in cabochon, curved stones display what is known as chatoyancy, meaning 'like a cat's eye.' The result is a series of minor gemstones differing only in their ground color and the mobile reflection.
Comes in colors white, gray, green, yellow, brown. When the ground color is greenish-gray or green, the gem is known as cat's-eye quartz (Sri Lanka, Bavaria, Burma). 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 tiger's-eye; and a stone with a mahogany-colored ground is called bull's-eye or ox-eye (all principally from South Africa).
Chatoyant quartz can also be cut into more or less round, polished pieces, for necklaces and pendants. It is sensitive to some acids.
What causes the cat's eye effect in Quartz?
The chatoyancy occurs from parallel inclusions of rutile or asbestos fibers within the quartz crystal. When cut as a cabochon with these fibers running parallel to the base, it creates the distinctive single line of light resembling a cat's eye.
Why are some Cat's Eye lines sharper than others?
Eye sharpness depends on inclusion density and alignment. The finest specimens show a thin, sharp line that moves smoothly across the dome. Too many or scattered inclusions create fuzzy or weak eyes.
Does color affect Chatoyant Quartz value?
While most chatoyant quartz is grey or brown, rare golden and green specimens command premium prices. The base color matters less than the strength and sharpness of the cat's eye effect.
How is it different from Tiger's Eye?
While both show chatoyancy, tiger's eye forms when crocidolite fibers are replaced by quartz, creating a more banded appearance. Regular chatoyant quartz contains intact rutile or asbestos needles.
Can the eye effect be enhanced?
While the phenomenon is natural, proper cutting is crucial. The cabochon must be oriented correctly to display the eye. Some stones are treated to enhance transparency, but the chatoyancy itself cannot be artificially created.
Why do some pieces show multiple lines?
Multiple chatoyant bands can occur when inclusion layers exist at different depths or angles. While unusual, these specimens are often valued by collectors, especially if the lines are distinct and symmetrical.
Are Sri Lankan specimens better?
Sri Lankan chatoyant quartz is often considered superior due to stronger eye effects and better transparency. However, quality specimens also come from Brazil, India, and other locations.
The specific gravity [?] for Chatoyant Quartz is 2.65, its refractive index [?] is 1.54-1.55, and its double refraction [?] is 0.009.
History
It can be confused with chrysoberyl cat's-eye. The name "cat's-eye' without the word "quartz" is taken to mean only chrysoberyl cat's-eye. The tiger's-eye appearance was believed to improve eyesight and prevent eye diseases.
Industrial Usages
Chatoyant quartz has sometimes been imitated by glass, but is not produced synthetically. Dark stones have had their colors improved and been artificially lightened using nitric acid treatments.
The tiger's eye variety, in particular, is also used for carvings, boxes, ashtrays, wherein the fibers are seen as stripes of color instead of chatoyancy.
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