A hard, important gem mineral, of which alexandrite and cymophane are two varieties. Occasionally a greenish chatoyancy can be seen which was formerly known as cymophane, but is now called chrysoberyl cat's eye, or oriental cat's eye, when cut en cabochon. Frequently star chrysoberyls are found. Some crystals are twined as trillings, called flowers or cyclic twins, which appear in a pseudohexagonal symmetrical form. Alexandrite is an emerald green variety in daylight, which alters in color to red under artificial light. Chrysoberyl or alexandrite is a trichroic crystal. Synthetic chrysoberyl has been mabe by different techniques, such as floating-zone and flux, Czochralski or the pulling method. Imitation alexandrite is a misleading term for synthetic spinel or corundum or sapphire, with the property of changing color, which, like alexandrite is reddish-green in daylight and reddish under artificial light. Such stones were at first mislabeled as scientific alexandrite. Imitations are also made, from glass such as the cathay cat's eye or cathay stone and the Victoria cat's eye, which is two types of glass chrysoberyl imitations.