Mohs Hardness: 9 out of 10
Color: Blue. Ranges from blue to violetish blue to greenish blue. (Sapphires occur in all colors, including colorless. Any other color outside of the blue color range is considered a fancy sapphire.)
RI: 1.762 to 1.770 (+0.009 / -0.005)
Birefringence: 0.008 to 0.010
Clarity Type: Type II
Optic Character: Uniaxial negative
Pleochroism: Violetish blue & greenish blue
Spectrum: Strong bands at 450nm, 460nm, and 471nm with the 450 band being the strongest. Heat treated material may only show the 450nm band or no bands at all.
Fluorescence: Generally inert. Might fluoresce red to orange under LW. Weak chalky blue or yellowish green under SW may indicate heat treatment.
SG: 4.00 (+0.10 / -0.05)