Tigers Eye stone mounted on pin

Tigers Eye stone mounted on pin

I got this pin from Ron Eberhardt, formerly of TxDot.

The polished bit of rock forming this pin has no designated location. It is the gemstone, Tiger’s Eye, probably from Arizona.

Tiger’s eye (also called Tigers eye or Tiger eye) is a chatoyant[1] gemstone that is usually a metamorphic rock that is a golden to red-brown color, with a silky luster. A member of the quartz group, it is a classic example of pseudomorphous [a mineral having the characteristic outward form of another species] replacement by silica of fibrous crocidolite (blue asbestos). An incompletely silicified blue variant is called Hawk’s eye.

The gems are usually cut en cabochon[2] in order to best display their chatoyancy. Red stones are brought about through gentle heat treatment. Dark stones have had their colors improved and been artificially lightened using nitric acid treatments.

Honey-colored stones have been used to imitate the much higher valued cat’s eye chrysoberyl (cymophane), but the overall effect is unconvincing. Artificial fiberoptic glass is a common imitation of tiger’s eye, and is produced in a wide range of colors. Tiger’s Eye mostly comes from South Africa and East Asia.

Arizona and California have serpentine deposits in which are occasionally found chatoyant bands of chrysotile fibers. These have been cut and sold as “Arizona tiger-eye” and “California tiger’s eye” gemstones. Dark blue-gray fibrous varieties of tiger’s eye and hawk’s eye is sold under the trade name of Pietersite

Notable sources of tiger’s eye include Australia, Burma, India, Namibia, South Africa, United States, Brazil, Canada, China, Korea, and Spain.

Location: 17-F3

[1] In gemology, chatoyancy, or chatoyance or cat’s eye effect, is an optical reflectance effect seen in certain gemstones. Coined from the French “œil de chat,” meaning “cat’s eye,” chatoyancy arises either from the fibrous structure of a material, as in tiger’s eye quartz, or from fibrous inclusions or cavities within the stone, as in cat’s eye chrysoberyl. The precipitates that cause chatoyance in chrysoberyl are the mineral rutile, composed mostly of titanium dioxide. There was no evidence of tubes or fibers in the samples examined. The rutile precipitates were all aligned perpendicularly with respect to cat’s eye effect. It is reasoned that the lattice parameter of the rutile matches only one of the three orthorhombic crystal axes of the chrysoberyl, resulting in preferred alignment along that direction.

[2] Method of cutting gemstones with a convex, rounded surface that is polished but unfaceted. Opaque, asteriated, iridescent, opalescent, or chatoyant stones are usually cut en cabochon.

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