First and foremost, we need to look at the quality and strength of the color change. A strong change where the colors are bright and attractive under any kind of light is most desirable. Many stones are either a beautiful green in daylight or a nice pinki
Several other well known gemstones, including diaspore, sapphire, garnet and spinel may also change color as a function of the light source but the color change of top alexandrites is distinctive and attractive under any light conditions.
Chrysoberyl is the species name and Alexandrite is the variety name. Alexandrite is that variety of chrysoberyl that changes color as a function of the light source; green in daylight and red under incandescent light.