Rock & Mineral Encyclopedia

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

Diamond

The hardest known natural material, a crystalline form of pure carbon prized as the ultimate gemstone for its brilliance and fire.

A colorless, transparent variety of topaz valued as an affordable, hard, brilliant alternative to diamond in jewelry.

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

The blue gem variety of corundum, prized for its rich color, extreme hardness, and brilliance second only to diamond.

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