Rock & Mineral Encyclopedia

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

Flint

A hard, dark variety of chert that knaps into razor-sharp edges and sparks against steel, central to Stone Age technology.

A landscape-patterned Chinese jasper prized for warm cherry-red, cream, and green bands resembling painted scenery.

Ancient chemically deposited rock of alternating iron-oxide and silica bands recording Earth's early oxygenation and a major iron ore source.

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

A coarse sedimentary rock of rounded pebbles and gravel cemented in a finer matrix, recording ancient rivers and beaches.

Iron-stained sandstone whose red color comes from hematite coatings, formed in oxidizing desert, river, and coastal environments.