Abbe numbers and refractive indices of tektites and volcanic glasses

Knowledge of the optical properties is highly important for technical glasses. However, the optics of natural glasses are insufficiently described. Thus, Abbe numbers and refractive indices of several obsidians and tektites as well as pitchstone and synthetic obsidians with different water content are presented. Results are compared to calculated values. Refractive index measurements were in very good agreement with theoretical calculations depending on the glass chemistry. The Abbe number was found to be comparably low in the case of obsidians, but it increased after heat treatment. This is due to the high water content and magnetite particles.