Rock & Mineral Encyclopedia

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

Emerald Crystal

The natural crystalline form of emerald, the prized green chromium-and-vanadium variety of beryl and the May birthstone.

A rare mushroom-shaped tourmaline growth habit, typically magnesium-rich dravite/uvite, prized by collectors for its fungus-like cap-and-stem form.

A fine-grained foliated metamorphic rock between slate and schist, recognized by its silky silvery sheen and wavy, crinkled surfaces.

Rhyolite that has been metamorphosed, recrystallizing its silica-rich volcanic material into a tougher felsic metamorphic rock.

A soft, talc-rich metamorphic rock with a soapy feel, easily carved and highly heat-resistant for cookware and sculpture.

A metamorphosed banded iron formation of alternating quartz and iron-oxide layers, mined as a major iron ore.

A green, gold-associated metamorphic rock made of chrome-rich mica and quartz, named for Mariposa County in California's gold country.

The smoky brown to gray variety of quartz, colored by natural irradiation, valued as both a gemstone and crystal specimen.

An unusually pure, transparent-to-translucent obsidian with few inclusions; truly water-clear specimens are rare in nature.

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

A naturally magnetic black iron oxide and a major iron ore; strongly magnetic specimens are known as lodestone.

A striking lead chromate mineral prized for its brilliant orange-red prismatic crystals, with the finest specimens from Tasmania.

The calcium-aluminum garnet species spanning green tsavorite, cinnamon hessonite, and colorless leuco garnet — one of the most varied garnets.

The calcium-iron garnet species, ranging from brilliant green demantoid to golden topazolite and jet-black melanite.