Alexandrite
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− | '''Alexandrite''' | + | '''Alexandrite''' |
==Phenomenon== | ==Phenomenon== | ||
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===Color Change=== | ===Color Change=== | ||
− | Only chrysoberyl that contain | + | Only chrysoberyl that contain distinctly change colors can officially be called an alexandrite in the jewelry industry. When viewed in in natural daylight or fluorescent light these gemstones appear green. When viewed in incandescent light or a candle flame they appear red. So striking is the transformation by the Alexandrite above other color changing gemstones, that this phenomenon is referred to as the 'alexandrite effect' in the world of [[Gemology|gemology]]. Alexandrites are pleochroic gemstones but their color change properties are totally independent of this, instead resulting from their unusual light-absorbing properties that cause a strong absorption of light in the blue and yellow portions of the color spectrum. Color change in Alexandrites are caused by minor traces of chromium ions that replace aluminum in the crystal structure. Occasionally vanadium also takes part in the process. Some alexandrite owner enjoy flicking the gem's colors back and forth by rotating it between fluorescent and incandescent light sources. |
===Pleochroism=== | ===Pleochroism=== | ||
− | Aside from its unique color changing abilities, Alexandrites are a strongly pleochroic gem, displaying different colors when viewed from different directions. Depending on the angle viewed, alexandrites can display various shades of orange, red, yellow and green. Its pleochroic properties are completely independent from the 'alexandrite effect'. Typically | + | Aside from its unique color changing abilities, Alexandrites are a strongly pleochroic gem, displaying different colors when viewed from different directions. Depending on the angle viewed, alexandrites can display various shades of orange, red, yellow and green. Its pleochroic properties are completely independent from the 'alexandrite effect'. Typically the three pleochroic colors seen in an Alexandrite are are orange, green and purple-red. |
===Cat's Eye=== | ===Cat's Eye=== | ||
− | Extremely rare specimens of Alexandrite contain long, thin inclusions that are aligned parallel to each other, causing it to exhibit chatoyancy (cat's eye effect) when the stone is cut into a cabochon. Cat’s-eye alexandrite generally originates in Brazil and is more valuable then | + | Extremely rare specimens of Alexandrite contain long, thin inclusions that are aligned parallel to each other, causing it to exhibit chatoyancy (cat's eye effect) when the stone is cut into a cabochon. Cat’s-eye alexandrite generally originates in Brazil and is more valuable then its standard form. |
==Details== | ==Details== | ||
===Color=== | ===Color=== | ||
− | Shades and hues of | + | Shades and hues of the Alexandrite vary widely and are often influenced by their mining origin. Alexandrites most treasured colors are green by daylight and red by incandescent light, with pure hues that display a strong color change, as was prevalent in many of the gemstones originating from the initial Russian find. Brazilian alexandrite is known to be highly saturated and display a bluish green to purplish red color change. Alexandrite originating in Zimbabwe often have very little color change and are typically darker in color with tints of purple. Sir Lanka alexandrites have a muddy appearance and exhibit a khaki to brown color change. Specimens from Tanzanian tend to have lighter tones and possess decent color change. Other varieties of alexandrite can appear yellowish or pink in daylight and turn raspberry red by incandescent light. As a general rule; Alexandrites that are too light lack the intensity found in high quality gems. Stones that are too dark lack brightness and can appear almost black. |
===Sizes=== | ===Sizes=== | ||
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===Clarity and Luster=== | ===Clarity and Luster=== | ||
− | Alexandrite rough ranges from transparent to opaque. It is type II gemstone, and can be expected to show some inclusions to the unaided eye that | + | Alexandrite rough ranges from transparent to opaque. It is type II gemstone, and can be expected to show some inclusions to the unaided eye that don't detract much from its beauty, although many cut stones are clean. Once cut and polished, alexandrites exhibit a vitreous luster. |
===Varieties=== | ===Varieties=== | ||
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===Usage in Jewelry=== | ===Usage in Jewelry=== | ||
− | Alexandrites are hard and durable making them ideal for any jewelry design | + | Alexandrites are hard and durable making them ideal for any jewelry design such as earrings, rings, brooches, pendants, pins and pendants. They are often found as accent stones since they are small and expensive. Original alexandrites from Russia's Ural Mountains are typically center stones and are often found in estate jewelry. It is difficult to find matching alexandrites for earrings, three stone rings and necklaces that share the same shape, color, size and color change. |
===Synthetics=== | ===Synthetics=== | ||
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==Alexandrite Identification== | ==Alexandrite Identification== | ||
− | An Alexandrite can easily be separated from most stones through its color change properties. A simple flicker between fluorescent and incandescent light sources does the job. This leaves only color change garnets, synthetic color change sapphire, and synthetic color change spinel. After a stone has been identified as an Alexandrite it still has to be determined if it is a synthetic or natural | + | An Alexandrite can easily be separated from most stones through its color change properties. A simple flicker between fluorescent and incandescent light sources does the job. This leaves only color change garnets, synthetic color change sapphire, and synthetic color change spinel. After a stone has been identified as an Alexandrite it still has to be determined if it is a synthetic or natural. |
==History== | ==History== | ||
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==Sources== | ==Sources== | ||
− | Current sources of Alexandrite include Russia, Brazil, Sri Lanka, Myanmar, Tanzania, Zimbabwe, Madagascar and India | + | Current sources of Alexandrite include Russia, Brazil, Sri Lanka, Myanmar, Tanzania, Zimbabwe, Madagascar and India |
===Russia=== | ===Russia=== | ||
− | + | Original source of the Alexandrite. Gemstones are very high quality with distinct color changes and saturated colors. These mines produced many of the larger Alexandrites on the market weighing 5 carats or more. Mines have since dried out but still continue producing alexandrite in low volume. | |
===Brazil=== | ===Brazil=== | ||
− | + | Also produced large specimens of 5 carats and up. Hematita is still one of the most important deposits of alexandrite, although production has decreased in resent years. Its stones show a nice color change from bluish green to raspberry red. Occasionally stones with chatoyancy are discovered in Brazil, mainly around the Americana and Santana valleys, and are cut as cabochon cat's eyes. | |
===Sri Lanka=== | ===Sri Lanka=== | ||
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==Buyers Guide== | ==Buyers Guide== | ||
− | Distinct color change is the | + | Distinct color change is the important factor when purchasing an alexandrite. Top quality alexandrites show a strong color change from purplish red in incandescent light to bluish green in daylight, without any trace of brown or gray and have moderately strong to strong color saturation. Such stones command heavy prices so any inexpensive gems with these colors is likely a synthetic or simulant. For a significant purchase, a certification of gem identity and natural vs. synthetic is recommended. |
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===Certification=== | ===Certification=== | ||
− | GIA offers identification reports for loose or mounted | + | GIA offers identification reports for loose or mounted Alexandrite but no grading as is their policy with all other gemstones. Their cert also states whether the alexandrite is natural or synthetic, and lists any detectable treatments as well as providing the weight, measurements, shape, cutting style and color of the stone. |
===Alternatives=== | ===Alternatives=== |