Bronzite: Gemstone Information

Bronzite is not used as a mineral name today, having been dropped from the latest revision of the composition of the pyroxene group of minerals (1988). The name was used to denote a member of a solid solution series with end-members enstatite, Mg2Si2O6 and ferrosilite(Fe2,Mg)2Si2O6. The iron content is between 5 and 13% (this applies to the ‘bronzite’ of old).Crystals are orthorhombic, the hardness is 5–6 and there is a distinct cleavage. Yellowish brown bronzite has been reported to come from SriLanka with SG 3.25 and RI  1.663,  1.669 and  1.677 with a birefringence of 0.014, the optic sign positive.Brown six-rayed star bronzite has been found in Sri Lanka. The SG is 3.41 and the RIs are  1.680,  1.689 and  1.693 with a birefringence of 0.013. The star effect is caused by scattering of light at oriented hollow tubes.