Alexandrite is a variety of Chrysoberyl, a beryllium aluminum oxide with a hardness of 8.5. It is one of the hardest gemstones, second only to diamond and corundum. It crystal pattern is orthorhombic, and it sometimes forms in hexagonal-looking twinned crystals. It was discovered in the Ural Mountains of Russia in 1830, on the birthday of Czar Alexander II, and was named after him. The magic of Alexandrite is in its property of color change— it is light red or red-purple in incandescent artificial light and green or blue-green in daylight. (Appropriate to its name, the red and green colors of Alexandrite were the same as those of the Russian Imperial Guard.)
Since its discovery, Alexandrite was believed in Russia to be a stone of good fortune. As belief in the magical properties of stones faded with the rise of science and rationalism, Alexandrite was the only gemstone still believed to be a beneficial talisman as late as the nineteenth century. In current metaphysical thought, Alexandrite is said to carry a very joyful vibration and to be a powerful agent of inner transformation and spiritual evolvement. It embodies both the heart energy (green) and the higher mind energy (purple). Its property of changing color in different lights symbolizes the ideal of inner adaptability in which one is able to respond from the mind, the heart, or both together, in whatever way is most appropriate. Using Alexandrite in meditation, in stone layouts, or in jewelry can stimulate a harmonic opening of the heart chakra, third eye and crown chakras, in which the three operate as an integrated whole.
Simmons, Robert; Ahsian, Naisha. The Book of Stones, Revised Edition: Who They Are and What They Teach (several pages). North Atlantic Books. Kindle Edition.