Alexandrite is the color-change variety of the mineral chrysoberyl. A change of color occurs when the light source is changed; the more distinct the change of color, the more valuable the stone. A fine alexandrite is green in daylight and red in incandescent light (light bulb).

Finely faceted alexandrites above one carat are some of the most expensive gems in the world. They are extremely rare, rarer than fine ruby, sapphire or emerald.

The picture above is a set of alexandrite and diamond jewelry. A set comprised a ring set with a circular-cut alexandrite weighing 4.25 carats and pavé-set diamond surround; and a pair of ear pendants en suite, each set with a circular-cut alexandrite weighing 4.42 and 4.41 carats,mounted in 18k white gold.

Three alexandrites were certified by Gübelin Gemmological Laboratory for color change phenomenon. A set was auctioned for $141,796 at Christie's, Hong Kong.