Rock & Mineral Encyclopedia

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

Opalized Wood

Fossilized wood in which the original organic structure has been replaced by opal, sometimes showing precious play-of-color.

Rhyolite that has been metamorphosed, recrystallizing its silica-rich volcanic material into a tougher felsic metamorphic rock.

Fossil shells whose original material has been replaced by opal, preserving ancient marine forms in common or precious opal.

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

Fossil material whose original substance has been replaced by opal, preserving ancient shapes in common or play-of-color opal.