Rock & Mineral Encyclopedia

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

Graphite Schist

A dark, foliated schist rich in graphite that leaves a grey-black mark and forms from metamorphosed carbon-rich sediments.

A banded variety of chalcedony quartz, famed for its colorful concentric layers and enormous range of patterns and colors.

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

A deep red banded agate colored by iron oxides, valued as a vivid red lapidary and jewelry stone.

A chalcedony agate with red, orange, and yellow plume or banding patterns that rise like dancing flames within the stone.

A pink, manganese-rich variety of zoisite used as an ornamental gemstone, often mottled with white quartz and grey matrix.

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

A high-grade metamorphic gneiss of garnet, sillimanite, quartz, and graphite, derived from ancient aluminous sediments.