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. | + | Alexandrite rough ranges from transparent to opaque. Most cut stones are typically 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. |
===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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Stones from the Ural Mountains were of very fine quality, displaying vivid hues and strong color changes. When the Russia mines dried up after a few decades of production, the alexandrite almost lost mention in the jewelry industry. Things changed dramatically in 1987, when alexandrites were uncovered in the Hematita region of Minas Gerais, Brazil, once again giving the gemstone a boost. Although they did not compete with the quality of the Russian material, Brazilian alexandrites did show a distinct color change along with good clarity and color. Later deposits were found in Sri Lanka, Myanmar, Tanzania, Zimbabwe, Madagascar and India. Some of the new stones were high quality but many had less defined color changes and muddier hues. | Stones from the Ural Mountains were of very fine quality, displaying vivid hues and strong color changes. When the Russia mines dried up after a few decades of production, the alexandrite almost lost mention in the jewelry industry. Things changed dramatically in 1987, when alexandrites were uncovered in the Hematita region of Minas Gerais, Brazil, once again giving the gemstone a boost. Although they did not compete with the quality of the Russian material, Brazilian alexandrites did show a distinct color change along with good clarity and color. Later deposits were found in Sri Lanka, Myanmar, Tanzania, Zimbabwe, Madagascar and India. Some of the new stones were high quality but many had less defined color changes and muddier hues. | ||
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[[Category:Gemology]] | [[Category:Gemology]] |