A rare variety of natural sapphire, known as color-change sapphire, exhibits different colors in different light. Color change sapphires are blue in outdoor light and purple under incandescent indoor light. Color change sapphires come from a variety of locations are mostly Thailand, Sri Lanka and Tanzania. The color-change effect is caused by the interaction of the sapphire, which absorbs specific wavelengths of light, and the light-source, whose spectral output varies depending upon the illuminant. Transition-metal impurities in the sapphire, such as chromium and vanadium, are responsible for the color change.
Sapphire is a precious gemstone, a variety of the mineral corundum, an aluminium oxide.
Color: Blue, Green, Purple, Black, Yellow, Pink, White, Grey, Brown, Orange
Luster: Vitreous, Adamantine
Birthstone zodiac sign: Virgo
Associated month: September
Crystal system: Hexagonal crystal system
Chemical formula: Al₂O₃
Hardness (Mohs hardness scale): 9