Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Red Sandstone
Iron-stained sandstone whose red color comes from hematite coatings, formed in oxidizing desert, river, and coastal environments.
sedimentary
Slate
A fine-grained, low-grade metamorphic rock that splits into flat sheets along slaty cleavage, long used for roofing and flooring.
metamorphic
Sandstone
A clastic sedimentary rock made of cemented sand grains, often quartz, recording ancient beaches, deserts, and rivers.
sedimentary
Lithic Sandstone
A sandstone in which the dominant grains are fragments of pre-existing rocks rather than single minerals, signaling rapid erosion nearby.
sedimentary
Asphalt Rock
A porous sedimentary rock naturally saturated with bitumen, dark, tarry-smelling, and historically mined for paving.
sedimentary
Phyllite
A fine-grained foliated metamorphic rock between slate and schist, recognized by its silky silvery sheen and wavy, crinkled surfaces.
metamorphic
Arkose
A coarse, feldspar-rich sandstone, often pink, that records rapid erosion of granitic source rock under arid conditions.
sedimentary
Argillite
Hardened, fine-grained mudrock intermediate between shale and slate, dense and non-fissile, often carved into ornaments.
sedimentary
Quartzite
An extremely hard metamorphic rock formed from sandstone, made of fused quartz grains that break across rather than between the grains.
metamorphic
Calcarenite
Sand-grained limestone composed of carbonate particles such as shell fragments and ooids cemented into a calcite rock.
sedimentary
Greywacke
A hard, dark, poorly sorted sandstone with a muddy matrix, typically deposited by underwater turbidity currents.
sedimentary
Turbidite
A graded sedimentary deposit laid down by underwater turbidity currents, recording avalanches of sediment cascading down submarine slopes.
sedimentary
Scoria
A dark, highly vesicular volcanic rock full of gas bubbles, denser than pumice, common as red or black lava rock.
igneous
Picture Jasper
An opaque brown chalcedony whose iron-stained banding mimics deserts, dunes, and distant mountain skylines.
mineral
Metaquartzite
A hard, tough metamorphic rock of fused quartz grains, formed by recrystallizing quartz sandstone under heat and pressure.
metamorphic
Woodbine Jasper
An earthy-toned jasper with vine-like or scenic patterning, valued by lapidaries for warm browns, reds, and creams that polish to a smooth finish.
gemstone
Feldspathic Sandstone
A feldspar-rich sandstone, often pink, that points to granitic source rocks eroded quickly in dry or cold climates.
sedimentary
Dragon Blood Jasper
A green-and-red ornamental stone of epidote and red piemontite or iron oxide, named for its dragon-skin coloring; not a true jasper.
metamorphic
Eclogite
A dense, high-pressure metamorphic rock famous for its red garnets set in bright green pyroxene, formed deep within subduction zones.
metamorphic
Red Opal
An opal with a deep red body color, often a variety of Mexican fire opal, prized for its warm, glowing intensity.
gemstone
Cherry Creek Jasper
A landscape-patterned Chinese jasper prized for warm cherry-red, cream, and green bands resembling painted scenery.
mineral
Siltstone
A fine-grained clastic rock of silt-sized grains, intermediate between sandstone and mudstone, with a gritty feel.
sedimentary
Red Jasper
An opaque, iron-rich variety of microcrystalline quartz known for its deep brick-red color and ancient history as a stone of strength and grounding.
gemstone
Bruneau Jasper
A prized Idaho picture jasper from Bruneau Canyon known for brown and cream orbicular egg-rock patterns and scenic landscapes.
mineral