The third and perhaps most interesting is Alexandrite . This rare and valuable gemstone has the unique property of changing color depending on the type of light that hits it. In sunlight, it appears almost emerald green, while in artificial incandescent light it appears a violet-red. Color is yellow, green and brown. Luster is vitreous.
Crystals are transparent to translucent.
Crystals tend to be blocky and are often distorted by twinning effects that sometimes produce a psuedo-hexagonal cyclic twin. Cleavage is fair in one direction and poor in another. Fracture is conchoidal. Streak is white. Associated Minerals include garnet , mica and feldspars .