Mohs Hardness: 9 out of 10
Color: Red. (Can be light pink to orangy red to strongly purplish red, but red must be the dominant color.)
RI: 1.762 to 1.770 (+0.009 / -0.005)
Birefringence: 0.008 to 0.010
Optic Character: Uniaxial negative
Pleochroism: Orangy red & slightly purplish red
Spectrum: Fine lines at 659nm, 668nm, 693nm. Broad absorption at 500nm to 610nm.
Fluorescence: Weak to strong red under LW & SW, with best reaction under SW. Slightly weaker than synthetic ruby. Heat treated rubies may show chalky fluorescence.
SG: 4.00 (+0.10 / -0.05)