Benitoite has an appearance that is very similar to sapphire. Its blue color and pleochroism are very much like sapphire’s. Benitoite and sapphire have overlapping refractive indices, but benitoite has a much higher birefringence, which often shows birefringence blink. Sapphire has a Mohs hardness of 9, while benitoite is much softer at 6 to 6.5. Benitoite has a…

Benitoite is an extremely rare mineral that is best known for being the official state gemstone of California. It is a barium titanium silicate mineral, usually blue in color, that is found in rocks that have been altered by hydrothermal metamorphism. Its chemical composition is BaTi(Si3O9). Benitoite’s identification and original description was based upon specimens found in the headwaters of…