Internal conical refraction of elastic waves in orthorhombic crystals

The elastic wave propagation in orthorhombic crystals has been studied and a condition has been derived for the existence of internal conical refraction for crystals belonging to this class. It is shown that the direction in which ICR occurs is given by the roots of a quadratic equation. Expressions have been derived for the angle of the cone and other parameters relating to the cone for the three principal planes, and these have been numerically evaluated for Barytes, Celestites, and lodic acid.