Alexandrite is known as the color-changing gem. In the case of the Alexandrite from Nova Era Brazil the change is most often the change from the color of an Indicolite tourmaline to the color of an amethyst. In both cases the colors are attractive. Other mining locations produce color changes that are different than Nova Era. For instance years ago when traveling to Sri Lanka we saw a few pieces of very expensive Alexandrite that went from muddy brown (with a little rusty orange) to muddy green (emphasis on muddy). The change was not startling but the colors were unattractive. About 16 years ago (or so) there was a discovery of Alexandrite in India. The colors in that case are nice to look at and resemble (to a certain degree) the colors of Morganite which are: kind of peachy to kind of pink (both phases are accompanied by a little, very little tan). The Indian stones are attractive and the color change is noticeable.
One interesting thing about the color change of Alexandrite is that most films and most cameras are partially color blind to the color-change. We ran across this issue when we wrote our first book. That was back before digital cameras and we had a devil of a time getting the color at all right. We went from Kodachrome to Ektachrome to Fuji and it was all a bust. Even now the digital cameras will tend to only see the blue or green phase and not see the other. Interesting to know how much more sensitive our eyes are in comparison to cameras and films.
Alexandrite is a color variety of the mineral Chrysoberyl. Chrysoberyl is the third hardest of the commonly known gems. Chrysoberyl is a crystalline form of Beryllium-Aluminate. As you may recall Sapphire and Ruby are collectively known as corundum. Corundum is the second hardest of the commonly known gems. Corundum is pure aluminum oxide. The second and third hardest gems both have aluminum as a major ingredient. Interesting!!!