Chatoyant quartz occurs in three different varieties. All of them have a wavy and fibrous structure, with inclusions of crocidolite (blue asbestos) that cause a cat’s-eye effect known as chatoyancy. This effect is best seen when the stone is cut en cabochon. Each stone displays different colors according to the nature of the inclusions. It is common for the rough of the crystal to display no chatoyancy.
The greyish yellow, semi-translucent appearance of quartz cat’s-eye is due to inclusions of crocidolite (asbestos) and, less commonly, hornblende. It has a silky luster.
Tiger’s-eye is black, with iron oxide staining that gives yellow and golden brown stripes. The markings on its surface resemble tiger stripes. The yellow-brown stripes exist due to iron oxide.
Hawk’s-eye forms when crocidolite changes to quartz. But the blue-green and blue-grey color of the original remains.
Chatoyant quartz is always called quartz cat’s eye to avoid confusion with other chatoyant gems, particularly chrysoberyl.
Occurrence
Quartz cat’s-eye occurs in Brazil, India, and Sri Lanka. The most important source of tiger’s-eye is in South Africa. There, it is found in thick slabs, together with the less common hawk’s eye. Chatoyant quartz is also found in the USA and Australia.
Chatoyant Quartz Properties
- Specific Gravity: 2.65
- Refractive Index: 1.54-1.55
- Birefringence (DR): 0.009
- Luster: Vitreous
- Crystal Structure: Trigonal
- Composition: Silicon dioxide
- Hardness: 7
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