Rock & Mineral Encyclopedia

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

Bamboo Agate

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

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

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

Glacially transported banded agates found along Lake Huron's shores, typically small, frosted pebbles with red-orange iron banding.

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

A deep red banded agate colored by iron oxides, valued as a vivid red lapidary and jewelry stone.

A red-toned banded chalcedony colored by iron oxides, ranging from natural carnelian-like reds to heat-treated stones.

A bronze-colored iron sulfide notable for being the most magnetic of the common sulfide minerals and an important nickel host.

A black spinel-group zinc iron oxide, essentially unique to Franklin, New Jersey, where it was a key zinc and manganese ore.