Rock & Mineral Encyclopedia

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

Eltyubyuite

A rare chlorine-bearing iron garnet-supergroup mineral, the ferric analogue of wadalite, formed in high-temperature combustion-metamorphic rocks.

Sandstone altered by metamorphism, with partly recrystallized quartz grains, transitional between true sandstone and quartzite.

A dark, glassy rock formed when frictional heat from fault movement or impact melts rock along narrow veins.

A white, porous borate mineral webbed with gray-black veins, widely dyed to imitate turquoise and other stones.

Precious opal that forms in thin veins within brown ironstone boulders, cut with the host rock left as a natural dark backing.