Rock & Mineral Encyclopedia

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

Argillite

Hardened, fine-grained mudrock intermediate between shale and slate, dense and non-fissile, often carved into ornaments.

An opaque, porcelain-white common opal prized for its milky, pearl-like appearance and high porosity, often carved or beaded.

A calcium carbonate mineral and polymorph of calcite, aragonite forms distinctive needle clusters, sea shells, and pearls.

Translucent banded calcium-carbonate stone deposited in caves and springs, prized for ornamental carvings despite its softness.

An accumulated deposit of bird or bat droppings rich in nitrogen and phosphate, historically a prized natural fertilizer.

A sedimentary rock built from pea-sized concentric spheres called pisoids, often carbonate but sometimes iron or aluminum-rich.

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

A famous white to blue-grey Italian marble from Carrara, prized for centuries by sculptors and architects for its purity and fine grain.

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