Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Pseudotachylite
A dark, glassy rock formed when frictional heat from fault movement or impact melts rock along narrow veins.
metamorphic
Serpentinite
A green, often mottled metamorphic rock formed by the hydration of mantle rocks, soft and waxy with a smooth, slippery feel.
metamorphic
Black Shale
Dark, organic-rich fine-grained sedimentary rock formed in oxygen-poor waters, often a source rock for oil and gas.
sedimentaryMintabie Opal
Precious opal from the Mintabie field in South Australia, known for hard, bright crystal opal and some dark-bodied stones.
gemstone
Pyroxenite
A dense, dark ultramafic plutonic rock composed almost entirely of pyroxene minerals, often associated with peridotite and layered intrusions.
igneous
Tibetan Quartz
Clear quartz mined in the Himalayan region, often double-terminated and containing dark hematite or carbon inclusions.
crystal
Lapis Lazuli
An intensely blue metamorphic rock of lazurite flecked with golden pyrite, prized for millennia as a gemstone and ultramarine pigment.
metamorphicWhiteschist
A rare high-pressure metamorphic schist defined by the diagnostic assemblage of talc plus kyanite, often pale and silvery.
metamorphic
Diabase
A tough, dark, medium-grained igneous rock with the composition of basalt, common in dikes and sills.
igneous
Khondalite
A high-grade metamorphic gneiss of garnet, sillimanite, quartz, and graphite, derived from ancient aluminous sediments.
metamorphic
Gabbro
A coarse-grained, dark mafic intrusive rock that is the plutonic equivalent of basalt, rich in plagioclase and pyroxene.
igneous
Pegmatite
An exceptionally coarse-grained igneous rock, often granitic, famous for hosting large crystals and many gemstones.
igneousAppinite
A group of coarse, water-rich plutonic rocks dominated by large hornblende crystals set in feldspar, intermediate between lamprophyre and diorite.
igneous
Limburgite
A dark, glass-rich volcanic rock of olivine and augite phenocrysts set in a feldspar-free glassy groundmass, named from the Kaiserstuhl region.
igneous
Dalmatian Jasper
A cream-colored spotted stone resembling a Dalmatian dog, made of feldspar and quartz dotted with dark mineral grains.
igneous
Dalmatian Stone
A cream-colored feldspar-and-quartz rock peppered with dark spots, named for its resemblance to a Dalmatian dog.
igneous
Talc Schist
An extremely soft, soapy-feeling foliated rock made largely of talc, formed by metamorphism of magnesium-rich rocks.
metamorphic
Kambaba Jasper
A dark green-and-black stromatolite jasper patterned with swirling orbs, formed from fossilized ancient microbial colonies.
sedimentary
Desert Rose
A rosette-shaped cluster of bladed gypsum or barite crystals that traps sand, forming flower-like formations in arid deserts.
mineral
Greywacke
A hard, dark, poorly sorted sandstone with a muddy matrix, typically deposited by underwater turbidity currents.
sedimentary
Larvikite
A Norwegian intrusive rock whose feldspar crystals flash silvery-blue, widely used as blue pearl granite countertops.
igneous
Chrome-Dravite
A chromium-dominant tourmaline related to dravite, producing intensely deep green to blackish-green crystals from chromium-rich metamorphic rocks.
mineral
Foitite
A rare alkali-deficient tourmaline whose X crystal site is largely vacant, giving slender dark blue to bluish-black crystals.
mineral
Acanthite
A silver sulfide that is one of the most important silver ore minerals, forming dark metallic crystals and wires.
mineral