Rock & Mineral Encyclopedia

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

Calcarenite

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

A clastic sedimentary rock made of cemented sand grains, often quartz, recording ancient beaches, deserts, and rivers.

Natural obsidian with a frosted, matte surface produced by weathering, abrasion, or etching rather than a separate variety of glass.