Umbalite and Sillimanite Optic Character
Umbalite and Sillimanite optical properties play a significant role while distinguishing these gemstones from each other. These properties are influenced by the Umbalite Vs Sillimanite 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 Umbalite and Sillimanite 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.