Rock & Mineral Encyclopedia

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

Onyx

A banded variety of chalcedony quartz, classically black or black-and-white, long favored for cameos and beads.

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

A glacier-transported banded agate from the Lake Superior region, colored by iron into rich reds and oranges, and Minnesota's state gemstone.

A soft, fine-grained, translucent form of gypsum (or banded calcite) long prized as a carving and ornamental stone.

A chalcedony agate marked by round, concentric ring patterns that resemble eyes when cut and polished.

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

Obsidian colored brown by iron oxide inclusions, frequently banded or swirled with black as in mahogany obsidian.

A banded agate whose internal structures resemble cathedral spires, arches, or a city skyline of towers and pinnacles.

A banded agate that displays a moving shadow or flash across its surface when tilted under light, caused by closely spaced parallel bands.