CHEMISTRY Al2O3 CRYSTALLOGRAPHY Hexagonal REFRACTIVE INDEX 1.757 - 1.779 HARDNESS 9 SPECIFIC GRAVITY 3.99 - 4.0 CLEAVAGE None HEAT SENSITIVE No WEARABILITY* Excellent SPECIAL CARE INSTRUCTIONS None ENHANCEMENTS Heat treated. Common. Diffusion treatment, (places a thin blue coating on colorless sapphire.) Occasional. Irridation, (turns colorless gems yellow, orange or light blue.) Rare. *Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It! For more details see the article on "Hardness and Wearability."
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