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Chatoyancy: Unique optical characteristics which are caused by the reflection of light along parallel fibers. It is the play of light across a surface caused by the fiberous materials which are compacted together in tight bundles. When cut from a 90 degree angle, the results are a "cat's eye" effect. Hence, the word derives from the French word for cat, "chat." Just as interesting, as the viewer changes direction, the "pupil" or center point of the "eye" follows. Chaytoyancy is a term unknown to many, even to some mineral enthusiasts. But everyone knows the beauty of Tiger Eye, Nature's perfect demonstration of chatoyancy. For the purpose of this month's column, we will also note spheres with other special optical characteristics, including "asterism", starring effect; and "opalescence." Cat's Eye: Tiger Eye, that lovely honey-and-golden-brown mineral that has such a beautiful luster, as well as a highly defined "cat's eye," mostly comes from Africa today. Its structure is a replacement of crocidolite (blue asbestos) or gold asbestos fibers. But Tiger Eye has a close cousin in "Tiger Iron" a mineral, largely from Australia, that features wavy bands of alternating Tiger Eye, red jasper and hematite. The cat's eye and color of "Tiger Eye" creates a beautiful symphony with the other two minerals. Ulexite is an American favorite. Little known except by collectors, this milky white mineral comes from Death Valley, closely related to borax. It features a stunning "cat's eye," but one thing to know about ulexite--it loses its sharpness if displayed in a region that is slightly humid because it absorbs water from the air. How to bring back the effect? Rub it gently with Minwax Paste Finishing Wax, a product available in most hardware stores. In recent years Selenite, gorgeous vivid orange-colored mineral from Russia, has been gaining in popularity. A crystallized gypsum, selenite features a fabulous contrast with it's lovely white "cat's eye." Chrysoberyl or "Cat's Eye Opal" a beautiful mint green sphere, also features ribbons of "cat's eye." Asterism Asterism is a result of fibers running in many different opposite directions. Everyone has seen stunning star rubies and sapphires, but now one can have a starred sphere. Emerging from Madagascar and Brazil today are remarkable high quality Star Rose Quartz. These lovely and delicate looking minerals bring starlight into one's life. The Brazilian variety tends to have a great lucid quality, almost "see-through." Madagascar star rose quartz is slightly more opaque, but offers a brilliant, bright pink and demonstrates very distinctive "showy" stars. Opalescence Melody, in Love is in the Earth describes Labradorite as "a type of feldspar which crystallizes in the form of masses, grains and tabular crystals. Often, a display of spectral colours, due to the interference of light rays from the plate-like composition, causes labradorite to flame with broad patches of peacock blue, coppery red or dusky gold labradorescence." Frequently called "spectralite," this mineral comes from many parts of the world--Labrador, Canada, from which it received it name, Madagascar and the northern reaches of Europe (Russia, Finland, etc.) Many other minerals offer these unique qualities, but a limited number can be sphered. It is hoped that as time unfolds, deposits can be found that provide sufficient hardness and quantity of solid rough a provide a growing class of optically interesting spheres. |
Article from : SPHERESTOYOU