Rock & Mineral Encyclopedia

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

Thulite

A pink, manganese-rich variety of zoisite used as an ornamental gemstone, often mottled with white quartz and grey matrix.

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

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

A boron-rich silicate gemstone group famous for occurring in every color of the rainbow, sometimes several within a single crystal.

A deep cranberry-red to purplish-pink variety of lithium-rich elbaite tourmaline, prized as a rich, saturated rubellite gemstone.

A lightweight black organic gemstone formed from fossilized wood under pressure, a type of lignite long used in mourning jewelry.

A group of silicate gemstones best known for deep red but spanning nearly every color, including green tsavorite and orange spessartine.

A glacier-transported banded agate from the Lake Superior region, colored by iron into rich reds and oranges, and Minnesota's state gemstone.