Chrysoberyl contains the varieties of ordinary chrysoberyl and the rare and much more famous alexandrites. Chrysoberyl is one of the hardest gemstones on the Mohs hardness scale and is rarely treated. It is not the same mineral as beryl although beryl is contained in its name (this refers to the presence of beryllium as an element).
Chrysoberyls are generally yellow-green-brown transparent gemstones. They are greatly appreciated for the cat's-eye effect (or cymophane) that can be found in some chrysoberyls ("Cat's-eye chrysoberyl"). The yellowish color is due to substitution of trivalent iron. The prized green vanadium chrysoberyl variety is colored by vanadium. Main sources of chrysoberyl, cat's eye chrysoberyl and vanadium chrysoberyl include Brazil, Burma (Myanmar), India, Madagascar, Sri Lanka, Tanzania and Zimbabwe.
Alexandrite is a rare and prized variety of chrysoberyl that was first discovered in the 19th century in Russia. It is greatly appreciated for its colour change effect, in ideal cases green in daylight and raspberry red in incandescent light. The cause of this colour change effects are small traces of chromium. The most famous sources of alexandrites include Brazil, Russia and Sri Lanka. Other more recent sources include India, Madagascar, Tanzania and Zimbabwe.