Biotite and Axinite optical properties play a significant role while distinguishing these gemstones from each other. These properties are influenced by the Biotite and Axinite Physical Properties 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 Biotite and Axinite 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. Axinite has Biaxial/+ character.
Similar to their colors, Biotite and Axinite transparency can also be used as criteria for their primary identification. Although transparency cannot be the only criteria for gemstone identification, it can efficiently used in gemstone grading. Talking about their transparency, Biotite is Not Available while Biotite is Not Available in appearance.