Hornblend and Optical Glasses

This is a hornblend crystal and two different optical glasses in a mounting medium of 1.664 refractive refractive index index medium. The 1.64 refractive index glass is in moderate relief along the left edge of the image. The hornblend and the 1.67 refractive index optical glass are in low relief. Particle visibility is not a measure of relief. The hornblend is visible due to absorption, the imaginary part of the refractive index, not differences in the real part of the refractive index.