Mohs Hardness: 6.5 to 7 out of 10
Color: Yellowish green to greenish yellow to brownish green.
RI: 1.654 to 1.690 (+/-0.020)
Birefringence: 0.035 to 0.038 (usually 0.036)
Clarity Type: Type II
Optic Character: Biaxial positive or negative (common point is usually halfway between the 2 extremes)
Pleochroism: Weak yellow-green and green, only noticeable in dark stones.
Spectrum: Strong, narrow bands at 453, 477 & 497nm.
SG: 3.34 (+0.04 / -0.07)