The chemical composition of crystal is pure silica with a specific gravity of 2.66, which is very stable. Khác với những loại đá quý khác, which contain many other elements or contained substances, the specific gravity will be in a range. Its refractive index is 1.544～1.553. , The birefringence difference is 0.009, tốc độ phân tán là 0.013, Và [...]
