Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Prehnite
A translucent yellow-green silicate famous for its botryoidal 'grape' clusters, often hosting needle-like sprays of black epidote.
mineral
Diamond
The hardest known natural material, a crystalline form of pure carbon prized as the ultimate gemstone for its brilliance and fire.
gemstone
Emerald
The green chromium- and vanadium-colored variety of beryl, one of the four classic precious gemstones renowned for its rich green color.
gemstone
Demantoid Garnet
A rare green andradite garnet famed for fire exceeding diamond and distinctive horsetail inclusions in Russian stones.
gemstone
Herkimer Diamond
Exceptionally clear, naturally double-terminated quartz crystals from Herkimer County, New York, prized for their diamond-like brilliance.
crystalRed Emerald
A marketing name for red beryl, the rare manganese-colored beryl from Utah, evoking emerald to convey its prestige and rarity.
gemstone
Pink Emerald
A trade name sometimes used for pink beryl (morganite), the manganese-colored rose-to-peach variety of the emerald mineral.
gemstone
Golden Emerald
A trade name occasionally used for golden-yellow beryl (golden beryl or heliodor), the iron-colored yellow variety of the emerald mineral.
gemstone
Emerald Crystal
The natural crystalline form of emerald, the prized green chromium-and-vanadium variety of beryl and the May birthstone.
crystal
Emerald in Matrix
Natural emerald crystals still embedded in their host rock, prized as mineral specimens that show how the gem grew in place.
gemstone
Trapiche Emerald
A rare emerald showing a six-spoked star pattern of dark inclusions, named after the spokes of a sugar-mill wheel.
gemstoneEmerald Green Obsidian
A bright emerald-green glass sold as obsidian; saturated transparent green is manufactured, while rare natural green obsidian is only faintly tinted.
igneous
Emerald Green Tourmaline
A richly saturated green variety of elbaite tourmaline whose color rivals emerald, colored by trace iron, chromium, or vanadium.
gemstone
Lamprophyre
A dark, mineral-rich dike rock with abundant mica or amphibole phenocrysts set in a fine groundmass, often associated with gold and diamonds.
igneous
Andesine
An intermediate plagioclase feldspar between albite and anorthite, marketed as a red to champagne gemstone, sometimes color-treated.
gemstone
Andesite
A fine-grained, intermediate volcanic rock common at subduction-zone volcanoes, between basalt and rhyolite in composition.
igneous
Andalusite
A pleochroic aluminum silicate that flashes green and reddish-brown from different angles, with a cross-marked variety called chiastolite.
mineral
Andamooka Opal
Precious opal from the Andamooka field of South Australia, famous for solid crystal opal and its distinctive treatable matrix opal.
gemstone
Andradite Garnet
The calcium-iron garnet species, ranging from brilliant green demantoid to golden topazolite and jet-black melanite.
gemstone
Andesine-Labradorite
An intermediate plagioclase feldspar spanning andesine and labradorite, marketed as a red-to-green gem, much of which is copper-diffusion treated.
gemstone
Eye Agate
A chalcedony agate marked by round, concentric ring patterns that resemble eyes when cut and polished.
gemstone
Zircon
A natural zirconium silicate gem with high brilliance and fire, often confused with the synthetic imitation cubic zirconia.
gemstone
Yttrium Aluminum Garnet
A synthetic garnet-structured oxide (YAG) used as a diamond simulant and laser crystal, with no natural counterpart.
gemstone
Kimberlite
A rare ultramafic volcanic rock that erupts from deep in the mantle and is the primary natural source of diamonds.
igneous