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www.mineralgallery.co.za Minerals A-E |
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Alexandrite |
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Name
Alexandrite
Chemistry
BeAl2O4
Uses
As a gemstone or mineral specimen
Color
This is one of the color changing gems. It appears red in indoor lighted places and green in normal daylight
Hardness
8.5
Specific gravity
3.7
Streak
White
Crystals
(Rhombic) thick tabular, short columnar, often striped; usually intergrowth; frequent twinning, intergrowth triplings or sixlings.
Accompanied by:
Beryl, garnet, tourmaline, spinel, phenakite
Similar to:
Brazilianite, beryl, corundum, olivine and spinel
Alexandrite is the birthstone for June together with pearl and moonstone.
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It forms orthorhombic crystals. This stone was first discovered in the Ural mountains in Russia on the day of birth of the Tsar of Russia, Alexander. So they named the stone after him. This is a rare stone. It is almost always cut up as gemstones. Because of it's rarity it is one of the most expensive of the faceted stones. See our selection in the facet stone section.
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The color is caused by chrome. In Alexandrite the color is so balanced that it is seen as green in normal daylight. The wavelength of a normal indoor bulb differs, it is incandescent light. Under this light the stone appears as red.
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Synthetic corundums treated to react like Alexandrite can also have a color changing ability. Only buy from a reputable dealer.
Look out for Alexandrite which is too clean, or at a price which seems too low, it's probably synthetic. Natural Alexandrite rarely exceeds 2 carats. It can be confused with synthetic Alexandrite, or synthetic color change corundum.
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Alexandrite is related to the more common mineral chrysoberyl but differs somewhat. Its colour is much more brilliant than the chrysoberl, which is found in granite, whilst alexandrite is found in metamorphic rocks.
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Alexandrite crystals are round while chrysoberyls chrystals are flat.
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Alexandrite has the uniqueness to change color in daylight and artificial lights which chrysoberyl does not have. The color changes are caused by the presence of iron and chrome in the alexandrite crystal.
Man made alexandrite is produced on a small scale and used in lazers and salelites as protection against harmfull cosmic rays. Normal glass or plastic windows in space craft do not offer enough protection, whereas alexandrite is ideally suited because of its ability to filter out dangerous rays
