Rock & Mineral Encyclopedia

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

Geode

A hollow rock nodule whose interior cavity is lined with inward-pointing crystals such as quartz, amethyst, or calcite.

Exceptionally clear, naturally double-terminated quartz crystals from Herkimer County, New York, prized for their diamond-like brilliance.

A prized Namibian quartz combining amethyst, smoky, and clear quartz in single crystals, often with phantoms and enhydros.

A natural bicolor quartz that combines purple amethyst and golden citrine in a single crystal.

A natural bicolor quartz blending amethyst purple with prasiolite green in a single crystal, prized as a metaphysical heart-crown stone.

A hard, dark, poorly sorted sandstone with a muddy matrix, typically deposited by underwater turbidity currents.

Fine acicular (needle-like) tourmaline crystals, often black schorl, frequently seen as slender inclusions within clear quartz.

A mica schist containing bladed blue kyanite crystals, a marker of medium- to high-grade metamorphism of aluminous rocks.

Agate that was shattered and naturally re-cemented by silica, creating a mosaic of angular fragments in a quartz matrix.

A jasper made of angular fragments naturally cemented back together, typically showing red and brown pieces in a quartz matrix.

A shiny, foliated schist studded with red garnet crystals that grew during medium-grade regional metamorphism.

A dark, foliated schist rich in graphite that leaves a grey-black mark and forms from metamorphosed carbon-rich sediments.

A pale chalcedony agate with cloudy, frost-like white patterning suggesting frost on a window or icy crystalline textures.