Rock & Mineral Encyclopedia

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

Opalite

A man-made opalescent glass that glows milky blue in reflected light and warm orange when backlit, often sold as a crystal.

A hydrated silica gemstone famous for its shimmering play-of-color, ranging from white and black opal to fiery orange fire opal.

Opal without play-of-color, valued for solid body hues; also called potch, it occurs in a wide range of colors worldwide.

A chemical deposit precipitated around hot springs and geysers, either siliceous (geyserite) or calcareous, forming delicate terraces and crusts.

Fossil bone in which opal has replaced the original tissue, sometimes showing play-of-color, a rare collector fossil.

Porous opaline silica deposited around geysers and hot springs, often preserving delicate microbial textures.

Fossil material whose original substance has been replaced by opal, preserving ancient shapes in common or play-of-color opal.

Fossilized wood in which the original organic structure has been replaced by opal, sometimes showing precious play-of-color.

Fossil shells whose original material has been replaced by opal, preserving ancient marine forms in common or precious opal.

Fossil wood replaced by opaline silica that preserves wood grain, occasionally showing the play-of-color of precious opal.

A translucent to transparent opal in warm yellow, orange, and red tones, prized for body color rather than play-of-color.

An Australian silicified radiolarite jasper in warm mustard, red, burgundy, and cream earth tones, found only in Western Australia.

A soft, lightweight, chalky sedimentary rock made of the silica shells of microscopic diatoms, prized for its absorbency and filtering ability.