Today however, the most popular varieties of chrysoberyl are cat’s eye and alexandrite
. Alexandrite, which is a very durable and rare stone, displays a beautiful color change. In the daylight, it is green, but under incandescent light, it changes to a red, mauve, or brown color. It has been said that alexandrite was named after czar Alexander II, as it was discovered on the czar’s birthday in 1830, in the Ural Mountains. Cat’s eye, which is also known as cymophane
, contains many parallel, featherlike fluid inclusions or needle like inclusions of rutile. These inclusions, when cut as cabochons, display a white line across the yellowish gray stone. Chrysoberyl is a beryllium aluminum oxide. It is a very hard, durable stone, rating an 8.5 on the hardness scale
. In fact, chrysoberyl is exceeded in hardness only by diamonds and corundum
. Chrysoberyl has a vitreous
luster and occurs in a wide range of colors, from green, to greenish yellow, yellow and brown. When cut well, gems are quite brilliant, but lack fire.