Rock & Mineral Encyclopedia

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

Pegmatite

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

A pegmatitic granite in which quartz and feldspar intergrow to resemble ancient runic or Hebrew script.

A pegmatite rock of feldspar intergrown with wedge-shaped quartz that resembles ancient runic or Hebrew writing.

A dark, foliated schist rich in graphite that leaves a grey-black mark and forms from metamorphosed carbon-rich sediments.

An extremely rare rubidium-dominant alkali feldspar, the rubidium analogue of microcline, found in rare-element granitic pegmatites.

A striking platy, blade-like variety of albite feldspar that grows in fanned aggregates of thin white crystals within granite pegmatites.

A rare lithium-aluminum tourmaline with a vacant X site, typically pale pink to colorless and found in lithium pegmatites.

A high-grade metamorphic gneiss of garnet, sillimanite, quartz, and graphite, derived from ancient aluminous sediments.

A granite-like rock containing orthopyroxene, formed at high temperatures and pressures and often classed with the granulites.

A hard zinc-rich member of the spinel group, usually dark blue-green to black, forming octahedral crystals in metamorphic and pegmatitic rocks.

Molybdenite is the primary ore of molybdenum, a soft, greasy, silver-gray sulfide that closely resembles graphite.

A silver-white gold-silver telluride and important gold-silver ore, noted for crystals arranged in writing-like graphic patterns.

A common coarse-grained intrusive rock like granite but richer in plagioclase than potassium feldspar.

A rare granitic rock containing concentric, onion-like spheres called orbicules, prized as a striking ornamental stone.

A hydrated volcanic glass with pearly, onion-like concentric cracks that pops into lightweight white granules when heated.