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Star Sapphire: A Stellar Corundum
Species Corundum var. Star Sapphire Chemical Formula Al2O3 w/ TiO4, Fe2O3, and/or FeTiO3 Mohs Hardness 9 Cleavage None Luster Vitreous to Subadamantine, w/ Silky an...
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The Splendour of Spinel, part 1: A Cousin to Corundum
Species Spinel Chemical Formula MgAl2O4 Mohs Hardness 7.5 - 8 Cleavage None Luster Vitreous to Subadamantine Refractive Index 1.719 - 1.920 Birefringence N...
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