Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Lithic Sandstone
A sandstone in which the dominant grains are fragments of pre-existing rocks rather than single minerals, signaling rapid erosion nearby.
sedimentary
Rock Gypsum
A soft sedimentary evaporite made of massive gypsum, deposited when sulfate-rich seawater or lake water evaporates and concentrates.
sedimentary
Coral Rock
A porous limestone built from the calcium carbonate skeletons of corals and reef organisms, the lithified remains of ancient or modern reefs.
sedimentary
Rock Salt
An evaporite rock of the mineral halite (sodium chloride), the source of common salt, with a distinctive salty taste.
sedimentaryAsphalt Rock
A porous sedimentary rock naturally saturated with bitumen, dark, tarry-smelling, and historically mined for paving.
sedimentary
Honey Calcite
A warm golden-to-amber variety of calcite, a soft calcium carbonate mineral valued for its honeyed glow and easy carving.
mineral
Calc-Silicate Rock
A metamorphic rock of calcium-rich silicate minerals formed from impure limestone or dolomite altered by heat and fluids.
metamorphic
Talc-carbonate Rock
A soft metamorphic rock made of talc and magnesite or dolomite, formed by hydrothermal alteration of ultramafic rocks.
metamorphic
Mariposite
A green, gold-associated metamorphic rock made of chrome-rich mica and quartz, named for Mariposa County in California's gold country.
metamorphicBronze Sheen Obsidian
Black volcanic glass with a warm bronze or coppery sheen produced by light reflecting off aligned microscopic inclusions.
igneous
Goldstone
A man-made glittering glass packed with tiny copper crystals, traditionally reddish-brown but also made in blue and green.
crystal
Limonite
Limonite is an amorphous brown iron oxide ore, the rust-colored material behind ochre pigments and bog iron.
mineral
Coquina
A soft, porous limestone made of loosely cemented shell and coral fragments, used as a coastal building stone.
sedimentary
Gold
A dense, soft, intensely yellow native metal valued for millennia in coinage, jewelry, and electronics.
mineral
Picture Jasper
An opaque brown chalcedony whose iron-stained banding mimics deserts, dunes, and distant mountain skylines.
mineral
Breccia
A coarse rock of angular, sharp-edged fragments cemented in a matrix, marking nearby rockfall, faulting, or impact.
sedimentary
Lignite
The lowest rank of coal, a soft brown carbon-rich rock formed from compacted peat, used mainly for electricity generation.
sedimentary
Cataclasite
A cohesive fault rock formed by brittle crushing and grinding of rock along a fault zone, with angular fragments in a fine matrix.
metamorphic
Goldmanite
A green, vanadium-dominant garnet that forms in vanadium-rich metamorphic and sedimentary rocks, notably in uranium-vanadium districts.
mineralOutlaw Jasper
A boldly patterned western jasper in browns, reds, and golds, prized by lapidaries for its dramatic scenic and brecciated figures.
gemstone
Fossiliferous Limestone
Calcium-carbonate sedimentary rock packed with visible fossils, recording ancient marine life within an easily scratched, fizzing matrix.
sedimentaryStone Canyon Jasper
A warm-toned brecciated jasper from central California known for swirling browns, golds, and creams broken by darker seams.
gemstone
Golden Beryl
The pure golden-yellow gem variety of beryl, colored by iron and valued for its clarity, brilliance, and durability.
gemstone
Greywacke
A hard, dark, poorly sorted sandstone with a muddy matrix, typically deposited by underwater turbidity currents.
sedimentary