Rock & Mineral Encyclopedia

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

Malachite

A vivid green copper carbonate mineral famous for swirling concentric bands, used as an ore of copper and an ornamental gemstone.

The pure colorless variety of beryl, valued as crystal specimens and as a brilliant alternative to clearer gemstones.

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

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

A hard, brilliant fluorosilicate gemstone occurring in many colors, from precious golden imperial topaz to popular blue topaz.

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

A hydrated silica gemstone famous for its shimmering play-of-color, ranging from white and black opal to fiery orange fire opal.

An exceptionally coarse-grained igneous rock, often granitic, famous for hosting large crystals and many gemstones.

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

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

The green chromium- and vanadium-colored variety of beryl, one of the four classic precious gemstones renowned for its rich green color.

A dull, resinous volcanic glass similar to obsidian but with higher water content and a waxy pitch-like luster.

The titanium-rich black variety of andradite garnet, with a brilliant resinous luster prized for mourning and statement jewelry.

A porous limestone built from the calcium carbonate skeletons of corals and reef organisms, the lithified remains of ancient or modern reefs.