Hambergite: Gemstone Information
Hambergite is Be2BO3(OH,F) and occurs as transparent colourless orthorhombic prismatic crystals which are usually well crystallized, sometimes twinned. There is one direction of perfect cleavage and the hardness is 7.5. The SG is 2.35–2.37 and the RI for the alpha, beta and gamma rays is 1.54–1.560, 1.587–1.591, 1.628–1.631, biaxial positive with a high birefringence of 0.072. Hambergite occurs in granite pegmatites, ornamental-quality material coming usually from Anjanabanoana, Madagascar.