Rock & Mineral Encyclopedia

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

Banded Iron Formation

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

An altered granite mottled pink and green from feldspar and epidote, popular as a tough, colorful ornamental rock.

A banded, metamorphosed iron formation in which bright red jasper alternates with silvery hematite or magnetite layers.

A trade name for golden-yellow gem feldspars, including golden orthoclase, golden sunstone, and golden labradorite.

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

The classic agate defined by concentric or parallel bands of chalcedony in varied colors, the archetype of all agate varieties.

An umbrella term for green members of the garnet group, including prized tsavorite, demantoid, and rare chrome-rich uvarovite.

A group of silicate gemstones best known for deep red but spanning nearly every color, including green tsavorite and orange spessartine.