Alexandrite Gemstone Information
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ALEXANDRITE
It is one of the scarcest and cherished of coloured stone among the Collectors due to its peculiar nature of exhibiting green in natural light and a reddish-purple under incandescent lighting. It is believed that it is been first to have found near River of Tokovaya in the emerald mines in Ural Mountains.
Similar to other precious stones. Alexandrite also emerges millions of years ago. Unlike many other stones this requires specific geological condition. The main composition of beryllium and the colouring agent Chromium are found in different types rocks the combination is very hard to come by making them the scarce stones.
Sri Lanka is one of the finest producers of this remarkable stone along with Russia, Madagascar, Tanzania, Brazil, India, Burma, Zimbabwe, Zambia. Naleem Alexndrite largest alexandrite in the world weight at 112 ct Sold by famous gem Business Merchant Naleem from China fort, Beruwala Sri Lanka valued over staggering price of $100 Million.
Alexandrite is a variety of the mineral chrysoberyl (a cyclosilicate) which is an aluminate of beryllium (BeAl2O4).Colour-change Alexandrite is the rarest and most valuable among the member of the Chrysoberyl family.
Spectroscopic analysis typically discriminate the alexandrite from usual Chrysoberyl. The presence of chromium as a main compound is the critical factor that is differentiating the alexandrite from the normal Chrysoberyl. The Chrysoberyl normally owns greenish yellow colour due to manifestation of Iron.
The remarkable colour change is fundamentally due to the how chromium iron absorb and reflect the lights in three different direction. Alexandrite has a colour absorption band of 580 Nano meters which falls between 550 nanometer for Rubies and 600 Nanometers for Emeralds. Daylight is typically balanced to experience different colours. Human eyes are sensitive to green as a result most alexandrite will favor the colour of green. Under incident light where source of light is reddish the stone adjusts its colour to red colour trying to emulating the property of Rubies.
Existence of florescence in the stone Alexandrite is another critical property that differentiate Chrysoberyl as normal Chrysoberyl does not shows florescence which red fluorescence can be observed in Alexandrite under cross filter method.
Attributes
Origin - Sri Lanka, Madagascar, Russia, Tanzania, Rhodesia, Brazil, India, Burma, Zimbabwe, Zambia.
Refractive Index - 1.741 to 1.760
Chemical Composition - BeAl2O4
Harness - 8.5
Colour - Colour Change- Green in normal light to Red in incident light
Refractive Index - 1.741 to 1.760
Density - 3.73
Crystal Structure - Orthorhombic
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