Rock & Mineral Encyclopedia

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

Matrix Opal

Opal in which precious play-of-color is intimately dispersed through the pores of its host rock rather than forming a solid seam.

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

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.