Rock & Mineral Encyclopedia

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

Chert

A hard, fine-grained sedimentary silica rock that breaks with sharp conchoidal edges, prized by ancient toolmakers.

An iron-rich sedimentary rock, often heavy and rusty-weathering, historically mined as a major source of iron ore.

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

A tough, quartz-rich sandstone cemented by silica, transitional toward true quartzite but still sedimentary in origin.

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