opal

The green play of color in this fire opal from Shewa, Ethiopia is certainly eye-catching. Photo by Géry Parent. Licensed under CC By-SA 3.0.

Although these cabbed opals all came from the same piece of rough, they exhibit different characteristics. © All That Glitters. Used with permission.…

Hyalite opal, UV light. Photo © Rob Lavinsky, www.iRocks.com. Used with permission.

Hyalite opal, normal light. Photo © Rob Lavinsky, www.iRocks.com. Used with permission.

This gray opal shows a wide range of hues in its play of color. Precious opal (Bulldog Shale, Lower Cretaceous; Coober Pedy Opal Field, South Australia),…

Over a white background, the play of color in an opal is usually less intense. Photo by Ra’ike. Licensed under CC By 3.0.

Lapidaries often cut common opals into beads for their color and translucence. Hematite and opal armband, photo by Mathilda Samuelsson. Licensed…

With a black body color, the bright blue play of color seems more intense. Lightning Ridge black opal ring with diamond and sapphire, photo…

Precisely how opals form is still a mystery to science. “Opale (Ethiopie) 5,” photo by Géry Parent. Licensed under CC By-SA 3.0.