Species ........................................................................ Natural Corundum Variety .............................................................................................. Sapphire Shape & Cutting Style ............................................... Oval, Mixed Cut Measurements ................................................. 6.66 x 5.90 x 4.04 mm Carat Weight ............................................................................. 1.51 Carat Color .................................................................... Intense Blue (Greenish) Transparency ......................................................................... Transparent Indications of heating present. Chemical Composition ................................................................. Al2O3 Crystal System .......................................................................... Trigonal Mohs Hardness ................................................................................... 9.0 Specific Gravity ..................................................... 3.97 - 4.10 g/cm3 Optical Character .................................................................... Uniaxial Refractive Index ............................................................ 1.757 - 1.779 Birefringence ................................................................... 0.008 - 0.009