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

A black volcanic glass speckled with gray-white cristobalite snowflakes, formed as obsidian begins to crystallize.

A hard, fine-grained siliceous rock with a dull porcelain-like texture, intermediate between soft diatomite and dense chert.