Proustite and Fayalite optical properties play a significant role while distinguishing these gemstones from each other. These properties are influenced by the Proustite and Fayalite 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 Proustite and Fayalite 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.
Similar to their colors, Proustite and Fayalite 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, Proustite is Gemmological Tables (2004) Rarely transparentMore from other references and OpaqueUlrich Henn and Claudio C. Milisenda while Proustite is Gemmological Tables (2004) Rarely transparentMore from other references and OpaqueUlrich Henn and Claudio C. Milisenda in appearance.