Rock & Mineral Encyclopedia

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

Tactite

A contact-metasomatic calc-silicate rock, essentially a skarn, formed where intrusions react with carbonate rocks and often host ore.

A fossiliferous jasper packed with spiral snail shells, technically a silicified gastropod limestone from Wyoming.

A calcium-magnesium tourmaline that forms in metamorphosed limestones, typically dark green to brown and often in well-formed crystals.

A tough, dark, medium-grained igneous rock with the composition of basalt, common in dikes and sills.

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

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

A pure, translucent white marble from the Greek island of Paros, the preferred stone of ancient sculptors for its waxy glow.

A rock formed from hot pyroclastic flows, often welded, sometimes containing flattened glass lenses called fiamme.

A bright yellow native element mineral that forms around volcanic vents and hot springs and burns with a blue flame.

A rare, ancient ultramafic volcanic rock formed from extremely hot magma, famous for its spinifex texture.

A high-grade metamorphic rock formed in the deep, hot crust, marked by anhydrous minerals like pyroxene and garnet.