Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Gneiss
A high-grade metamorphic rock defined by alternating light and dark mineral bands, formed under intense heat and pressure.
metamorphic
Granite
A coarse-grained, speckled intrusive rock built from quartz, feldspar, and mica, forming the bedrock of the continents.
igneous
Orbicular Granite
A rare granitic rock containing concentric, onion-like spheres called orbicules, prized as a striking ornamental stone.
igneous
Calc-Silicate Rock
A metamorphic rock of calcium-rich silicate minerals formed from impure limestone or dolomite altered by heat and fluids.
metamorphic
Felsite
A general term for light-colored, fine-grained volcanic rocks rich in quartz and feldspar, like rhyolite.
igneous
Pegmatite
An exceptionally coarse-grained igneous rock, often granitic, famous for hosting large crystals and many gemstones.
igneous
Granulite
A high-grade metamorphic rock formed in the deep, hot crust, marked by anhydrous minerals like pyroxene and garnet.
metamorphic
Gabbro
A coarse-grained, dark mafic intrusive rock that is the plutonic equivalent of basalt, rich in plagioclase and pyroxene.
igneous
Diorite
A coarse-grained intrusive rock with a distinctive salt-and-pepper look, the plutonic equivalent of andesite.
igneous
Granodiorite
A common coarse-grained intrusive rock like granite but richer in plagioclase than potassium feldspar.
igneous
Khondalite
A high-grade metamorphic gneiss of garnet, sillimanite, quartz, and graphite, derived from ancient aluminous sediments.
metamorphic
Mylonite
A fine-grained, strongly foliated rock formed deep in fault zones where rocks flowed and ground down rather than fracturing.
metamorphic
Migmatite
A 'mixed rock' showing swirling light and dark bands, formed where high-grade metamorphism causes rock to begin partially melting.
metamorphic
Albitite
A pale rock made almost entirely of the sodium feldspar albite, formed by sodic magmatism or sodium metasomatism.
igneous
Rhyolite
A fine-grained, silica-rich volcanic rock that is the extrusive equivalent of granite, often pale, banded, or flow-textured.
igneous
Unakite
An altered granite mottled pink and green from feldspar and epidote, popular as a tough, colorful ornamental rock.
metamorphicUnakite Jasper
An altered granite of pink feldspar, green epidote and quartz, mottled pink-and-green and popular as a tumbled and carving stone.
metamorphic
Fenite
A metasomatic rock formed when alkali-rich fluids from carbonatite or alkaline intrusions transform surrounding country rock.
metamorphic
Norite
A coarse-grained mafic plutonic rock similar to gabbro but with orthopyroxene as the dominant pyroxene instead of clinopyroxene.
igneous
Charnockite
A granite-like rock containing orthopyroxene, formed at high temperatures and pressures and often classed with the granulites.
igneous
Arkose
A coarse, feldspar-rich sandstone, often pink, that records rapid erosion of granitic source rock under arid conditions.
sedimentary
Larvikite
A Norwegian intrusive rock whose feldspar crystals flash silvery-blue, widely used as blue pearl granite countertops.
igneous
Amphibolite
A dark, dense metamorphic rock dominated by hornblende and plagioclase, formed by medium- to high-grade metamorphism of basalt.
metamorphic
Metarhyolite
Rhyolite that has been metamorphosed, recrystallizing its silica-rich volcanic material into a tougher felsic metamorphic rock.
metamorphic