Rock & Mineral Encyclopedia

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

Hematite

The principal iron ore, a heavy iron oxide ranging from metallic silver-gray to earthy red, always leaving a tell-tale red-brown streak.

Limonite is an amorphous brown iron oxide ore, the rust-colored material behind ochre pigments and bog iron.

Clear quartz coated with orange-red hematite, giving points a vivid tangerine color, mainly from Brazil.

A field term for hard black massive manganese oxides, often botryoidal, mined as an important manganese ore.

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

An iron-rich sedimentary rock, often heavy and rusty-weathering, historically mined as a major source of iron ore.

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

A metamorphosed banded iron formation of alternating quartz and iron-oxide layers, mined as a major iron ore.

A coarse-grained mafic plutonic rock similar to gabbro but with orthopyroxene as the dominant pyroxene instead of clinopyroxene.

A feldspar gemstone that sparkles with metallic glints (aventurescence) caused by tiny reflective copper or hematite platelets.

A vivid yellow-and-black banded stone from Indonesian volcanic vents, colored by sulfur, arsenic minerals and iron oxides, not true jasper.

Agate that forms in flat cracks or veins of host rock rather than rounded nodules, producing straight, parallel banding.

Clear quartz mined in the Himalayan region, often double-terminated and containing dark hematite or carbon inclusions.