Sillimanite and Grandidierite Optic Character
Sillimanite and Grandidierite optical properties play a significant role while distinguishing these gemstones from each other. These properties are influenced by the Sillimanite Vs Grandidierite like crystallographic symmetry, pleochroism,etc. in the crystal. Some of the optical properties are refractive index, luster, optic character, pleochroism etc. Prominent among these is Sillimanite and Grandidierite optic character. You might have noticed your gemologist rotating the gemstone while testing it. Rotating a gemstone along its optic axis helps in determining its optic character.