Rock & Mineral Encyclopedia

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

Mustard Jasper

A warm mustard-to-ochre yellow jasper colored by iron, valued by lapidaries for its rich, earthy golden tone.

A dense, opaque black variety of microcrystalline quartz historically used as a touchstone for testing precious metals.

A rare Australian jasper from the Pilbara with bold red, yellow, and black abstract patterns, prized by collectors.

An opaque brown chalcedony whose iron-stained banding mimics deserts, dunes, and distant mountain skylines.

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

A microcrystalline quartz jasper marked by small concentric ring or eye patterns that resemble the eyes of birds.

Clusters of tiny botryoidal chalcedony spheres resembling bunches of grapes, famously purple, found in Indonesia.

A high-grade metamorphic gneiss of garnet, sillimanite, quartz, and graphite, derived from ancient aluminous sediments.