Rock & Mineral Encyclopedia

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

Sapphire

The gem variety of corundum in every color except red, most prized in velvety blue and exceptionally hard and durable.

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

The red, chromium-colored variety of corundum, prized as one of the most valuable colored gemstones and second only to diamond in hardness.