Rock & Mineral Encyclopedia

Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.

Precious Opal

The classic gem opal that flashes shifting spectral colors, defined by the diffraction effect known as play-of-color.

A cheerful yellow opal ranging from translucent common opal to golden fire opal, colored by trace iron in the silica.

Precious opal with a warm chocolate-brown body tone that makes its rainbow play-of-color glow, mainly from Ethiopia and Mexico.

A rare opal whose play-of-color appears only when light passes through it, glowing best when backlit or held to the light.

Nevada's famous precious opal, including vivid black opal and opalized wood, renowned for brilliance but a notable tendency to craze.