Rock & Mineral Encyclopedia

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

Tufa

A porous, spongy freshwater limestone that precipitates around springs, streams and lakes, often encrusting plants and moss.

A common opal containing moss- or fern-like mineral inclusions that resemble plants suspended in a pale silica body.

A pale jasper threaded with black, fern-like mineral dendrites that mimic plants, trees, and frost despite being inorganic.

A soft, lightweight siliceous sedimentary rock made of fossil diatom remains, prized as a fine natural abrasive and polishing powder.

Extremely fine-grained, even-textured limestone famous for lithographic printing and for preserving exquisite fossils like Archaeopteryx.

A soft carbonate sedimentary rock made mostly of calcite, often packed with marine fossils and prone to forming caves.

A limestone packed with visible shells and shell fragments, recording the accumulation of marine invertebrate remains on ancient sea floors.

A dark green-and-black stromatolite jasper patterned with swirling orbs, formed from fossilized ancient microbial colonies.