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.

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

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

A soft, glowing orange variety of calcite colored by iron oxides, popular as tumbled stones and known for fizzing in acid.

A brecciated, chatoyant quartz with swirling blue, gold, and brown fibers that shimmer like a stormy sky.

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

Iron-stained sandstone whose red color comes from hematite coatings, formed in oxidizing desert, river, and coastal environments.

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

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

A pale translucent chalcedony threaded with brown-black manganese and iron dendrites that mimic tiny ferns, mosses or landscapes.