Tourmaline is notable for exhibiting strong pleochroism. They may exhibit pleochroism or double refraction. It shows a distinct pleochroism in browns and greens. Has published important work on pleochroism in crystals and its relation to photo-dissociation. Alexandrite displays a colour change dependent upon light, along with strong pleochroism. Brookite exhibits very weak pleochroism, yellowish, reddish and orange to brown. In plane polarized light, uvite is colorless to pale yellow and shows weak pleochroism. This property, known as "pleochroism" is of great value in the determination of mineral composition. Hiddenite has a strong vitreous luster and displays strong colors due to pleochroism. Crystals show pleochroism from red to blue to violet. In plane polarized light, suessite is a reddish-brown color that shows no pleochroism. Marthozite shows pleochroism from yellowish brown to greenish yellow. When looking at a thin section, metzeunerite is anisotropic, meaning that it has pleochroism. Experienced geologists using pleochroism can successfully detect gemstones from other artificial stones using this instrument. It displays strong pleochroism, the pleochroic colors being usually green, yellow and brown.