Rock & Mineral Encyclopedia

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

Crocodile Jasper

A deep green-and-black stromatolitic jasper, essentially Kambaba Jasper, with circular eye patterns resembling crocodile skin.

A fine-grained, feldspar-rich dike rock with a trachytic texture, essentially a hypabyssal equivalent of trachyte or syenite.

A fine-grained, low-grade metamorphic rock that splits into flat sheets along slaty cleavage, long used for roofing and flooring.

A dark, mineral-rich dike rock with abundant mica or amphibole phenocrysts set in a fine groundmass, often associated with gold and diamonds.

A fine-grained sedimentary rock rich in solid organic matter (kerogen) that yields oil and gas when heated.

Chromite is the only commercial ore of chromium, a black iron-chromium oxide of the spinel group found in mafic igneous rocks.

A fine-grained, sodium-rich contact-metasomatic rock formed where shale is albitized next to intruding diabase or spilite.

A fine-grained, silica-rich volcanic rock that is the extrusive equivalent of granite, often pale, banded, or flow-textured.

Ilmenite is the world's leading source of titanium, a heavy iron-black oxide common in mafic rocks and black sands.

A soft, fine-grained, translucent form of gypsum (or banded calcite) long prized as a carving and ornamental stone.

Hardened, fine-grained mudrock intermediate between shale and slate, dense and non-fissile, often carved into ornaments.

A general term for light-colored, fine-grained volcanic rocks rich in quartz and feldspar, like rhyolite.

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