opal

While asterism in other gemstones, like this sapphire, is caused by inclusions, the star effect in opals is caused by the diffraction of light from…

Opal. Photo by Yagan Kiely. Licensed under CC By-SA 2.0.

A faceted Mexican fire opal in a 22k gold and sterling silver heart setting. Opal by La Rocka Gems and Minerals, jewelry and photo by Jessa and Mark…

Mosaic opal. Photo by Mauro Cateb. Licensed under CC By 2.0.

Crystal opal set in 22k gold, with 24k granule accents and pierced sterling silver base with overlay. Jewelry and photo by Jessa and Mark Anderson.…

Matrix opal. Photo by John Hritz. Licensed under CC By 2.0.

Opal triplet, made of Australian rough, a ceramic base, and a quartz top (30 x 23 mm).

“Harlequin Prince” black opal, 215.85 cts, Lightning Ridge, American Museum of Natural History. Photo by greyloch. Licensed under…

This black opal shows a wide range of colors. Stayish Mine, Wollo Province, Ethiopia. Photo by James St. John. Licensed under CC By 2.0.