16.26: Charoite Last updated Save as PDF Page ID4362 Contributed by gemologyGemology Project Charoite Chemical composition Complex potassium silicate Crystal system Monoclinic Hardness 7 - 7.5 Optic nature Biaxial - Refractive index 1.545 - 1.560 Specific gravity 2.66 - 2.68 Figure \(\PageIndex{1}\): Charoite