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Ruby--the name given to red, gem-quality corundum--is one of the best gemstones for jewellry settings. Rubies may be any shade of red, from pinkish to purplish or brownish red, depending on the chromium and iron content of the stone. Frequent twinning of the crystals makes the material liable to fracture, yet ruby is a tough mineral, second only to diamond in hardness. Cristal prisms are hexagonal with tapering or flat ends. Ruby Sapphire is the birth stone of July.
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Worldwide in igneous and metamorphic rocks, or as waterworn pebbles in alluvial deposits. The finest stones come from Burmar; those from Thailand, the main source, are brownish red; Afghanistan, Pakistan, and Vietnam produce bright red stones; those from India, North Carolina(USA), Russia, Australia, and Norway are dark, sometimes even opaque.
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