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...ch sapphire cannot be is red – as red colored corundum is called ruby, Commonly,Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moiss...
... owing to its high melting point.It occurs naturally in its crystalline polymorphic phase α-Al₂O₃ as the mineral corundum, varieties of which form the precious gemstones ruby and sapphire. 2. Feature Advanta...