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.

The rarest and most valuable opal, with a dark body tone that makes its flashing rainbow play-of-color blaze brilliantly.

The most common precious opal, with a pale milky body that shows softer pastel flashes of play-of-color throughout.

Opal from Australia, the world's leading source of precious opal, ranging from white and crystal to prized black and boulder types.

An intermediate plutonic rock with nearly equal alkali and plagioclase feldspar and very little quartz, sitting between diorite and syenite.