Almandine Garnet

Red garnets, like this almandine, may also resemble rubies. However, unlike rubies, garnets have no birefringence. Gemologist can used a dichroscope to test for birefringence. But, some almandines may show anomalous birefringence or anomalous double refraction (ADR). A polariscope examination can help spot ADR. Photo by Didier Descouens. Licensed under CC By-SA 3.0.