Rock & Mineral Encyclopedia

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

Polyhedroid Agate

A rare agate that forms naturally with flat polygonal faces and angular geometric shapes rather than the usual rounded nodule.

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

A translucent chalcedony agate containing delicate, feather- or plume-shaped mineral inclusions that branch like soft feathers.

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

A chalcedony agate with soft, billowing cloud-like masses of gray and white suspended in a translucent body.

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

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

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