Rock & Mineral Encyclopedia

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

Aragonite

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

A soft, porous limestone made of loosely cemented shell and coral fragments, used as a coastal building stone.

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

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

Sand-grained limestone composed of carbonate particles such as shell fragments and ooids cemented into a calcite rock.

A banded, porous limestone deposited by mineral springs, prized as a warm-toned natural building and tile stone.

A rounded sedimentary nodule cracked internally and filled with veins of yellow calcite, prized for its striking dragon-skin patterning.

Calcium-carbonate sedimentary rock packed with visible fossils, recording ancient marine life within an easily scratched, fizzing matrix.

A soft, lightweight, chalky sedimentary rock made of the silica shells of microscopic diatoms, prized for its absorbency and filtering ability.

An organic gem formed inside mollusks from layered nacre, prized for its iridescent luster and classic elegance.