![]() Photographed by David Weinberg for and published here under a GNU Free Document License. A photo of cat's-eye chrysoberyl showing the milk-and-honey effect is shown on this page.Īlexandrite: A faceted specimen of color-change alexandrite of 26.75 carats from Tanzania, showing a blue-green color in daylight and a purple-red color under incandescent light. This phenomenon is known as the "milk-and-honey" effect. It gives the illusion that the stone is made of two different materials, a light material on one side of the line and a dark material on the other. Some specimens of cat's-eye will appear to have a different color on each side of the cat's-eye line when illuminated from the proper direction with respect to the observer's eye. ![]() ![]() The line of light is very similar to how a spool of silk thread will produce a line of reflection across the top of the spool as it is moved back and forth under a source of light. The "cat's-eye" is a line of light that reflects from the dome of the cabochon at right angles to the parallel inclusions. The phenomenon of cat's-eye occurs in cabochon-cut stones that contain a high density of parallel fibrous inclusions. Cat's-eye chrysoberyl has also been called "cymophane." If a person uses the name "cat's-eye" without the name of another gemstone (for example, "cat's-eye tourmaline"), then they are most likely referring to chatoyant chrysoberyl. 2) Cat's-EyeĬhrysoberyl is the gemstone that produces the most distinct " cat's-eye," or chatoyance. This green cat's-eye chrysoberyl was produced in Sri Lanka and is about 5.6 x 4 millimeters in size. This specimen exhibits the "milk-and-honey" effect - when properly oriented, the stone has two apparently different colors on each side of the cat's-eye line. Chrysoberyl is the gem that exhibits the finest cat's-eyes, and when the term "cat's-eye" is used without a mineral name as a modifier, the speaker is most likely referring to chrysoberyl. See our section below about synthetic and imitation chrysoberyl.Ĭat's-Eye Chrysoberyl: Chrysoberyl that contains large numbers of fibrous inclusions can produce a "cat's-eye," a line of light across the surface of the stone that orients perpendicular to the included fibers. If you are paying major money for a piece or you only want to purchase natural gems, be careful in your transactions. These should be priced significantly less than similar jewelry made with natural chrysoberyl. Much of the chrysoberyl jewelry being sold online is made with synthetic chrysoberyl or imitation chrysoberyl. If you are interested in chrysoberyl jewelry, you might find it at a store owned by a jewelry designer who specializes in rare and seldom-seen gems.īe cautious when buying chrysoberyl. Natural nonphenomenal chrysoberyl is rare, moderately expensive, seldom seen in jewelry stores, and most jewelry shoppers have never heard of it. Gemologists simply call them "chrysoberyl". Most chrysoberyl crystals are nonphenomenal (that is, they do not exhibit chatoyance or color-change). Rare blue chrysoberyl crystals have also been found. They are often yellow, yellowish green, green, brown or yellowish brown, and weigh less than five carats. Translucent to transparent crystals of chrysoberyl are usually found in pegmatites, dolomitic marbles, and stream sediments. These stones were produced in Sri Lanka and are about 4.3 millimeters in diameter and weigh about 0.52 carats each - a very high weight for stones of this size, caused by chrysoberyl's high specific gravity. Natural gem-quality chrysoberyls that exhibit the highest levels of these phenomena can sell for higher prices per carat than all but the highest quality diamonds.Ĭhrysoberyl: Three faceted chrysoberyls showing a range of yellow and yellow-green color. However, some rare specimens of chrysoberyl exhibit the phenomena of chatoyance and/or color-change. Most gem-grade chrysoberyl is translucent to transparent and is cut into faceted gems or en cabochon. It is only found in small occurrences that cannot be mined at a profit. Well-formed crystals are valuable and highly desirable - especially those that exhibit twinning.Īlthough chrysoberyl contains beryllium, it is not mined as a source of beryllium. The only gem minerals with a higher hardness are diamond and corundum (the mineral of ruby and sapphire).Ī minor use of chrysoberyl is as a collector's mineral. It excels in that use because of its high hardness - 8 1/2 on the Mohs hardness scale. The main commercial use of chrysoberyl is as a gemstone. It is sometimes confused with the silicate mineral known as beryl, which has a composition of Be 3Al 2Si 6O 18. Chrysoberyl is a rare beryllium aluminum oxide mineral with a chemical composition of BeAl 2O 4.
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