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.

A waxy, translucent microcrystalline form of quartz that serves as the parent group for agate, jasper, carnelian, and onyx.

An agate whose layered, segmented banding resembles the jointed stalks and leaves of bamboo.

A banded chalcedony with straight, ribbon-like parallel layers, often cut across the bands for striking striped cabochons.

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

A prized plume agate from near Carey, Idaho, showing red, pink and black feathery plumes floating in translucent chalcedony.

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

A brown fossiliferous chalcedony packed with spiral freshwater snail shells, technically agatized fossil rock from Wyoming.

A soft sky-blue chalcedony from the Owyhee region of Oregon and Idaho, prized for its calming, opaque powder-blue color.

A richly colored red banded agate prized by lapidaries for its deep crimson-to-brown tones reminiscent of pigeon's blood.

A banded combination rock of golden tiger's eye, red jasper, and metallic hematite, formed in ancient iron deposits.

A translucent chalcedony from Montana filled with black and red dendritic inclusions that look like moss, ferns, or scenic landscapes.

An earthy olive to yellowish-green tourmaline, a muted green-brown gem variety colored by iron with subtle warm undertones.