Rock & Mineral Encyclopedia

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

Feather Jasper

A jasper marked with soft feather- or plume-like mineral inclusions that drift through a pale silica body.

An opaque patterned jasper named for its scaly, snakeskin-like surface markings of interlocking tan and brown cells.

A fiery jasper whose red, orange, and yellow plumes lick across the stone like flames against an earthy background.

A nodular rhyolite geode-like ball whose plain exterior hides a star-shaped agate or chalcedony core when cut.

Abundant banded chalcedony from southern Brazil, the world's main source of agate slices and dyed agate products.

A purple-toned banded chalcedony, sometimes naturally amethystine but frequently produced by dyeing gray agate.

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

A glacially transported agate found in Midwestern gravels, named for the Coldwater area, showing banded chalcedony patterns.

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

A vivid blue-green hydrated copper silicate, soft on its own but prized as a gem when hardened by intergrown quartz or chalcedony.