Strain-Induced Birefringence in Natural Diamond: A Review
D. Howell, European Journal of Mineralogy, Vol. 24, No. 4, 2012, pp. 575–585
Diamond belongs to the cubic crystal system and should therefore exhibit isotropic optical properties. However, it has long been documented that diamonds often show weak birefringence. This study has focused on the causes of strain-induced birefringence in natural diamonds. Dislocations, lattice parameter variations, inclusions, fractures and plastic deformation are the causes of strain-induced birefringence in diamonds.
Strain patterns shed light on the internal stresses within the stone, which in turn give indications as to the growth and transport history of the diamond. The imaging of diamonds between crossed polarizers still remains a simple and rapid technique for obtaining visual information on strain patterns in diamonds.