Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Quartz Arenite
A clean, mature sandstone made almost entirely of quartz grains, representing extreme weathering, sorting, and recycling of sediment.
sedimentary
Turbidite
A graded sedimentary deposit laid down by underwater turbidity currents, recording avalanches of sediment cascading down submarine slopes.
sedimentarySandstone
A clastic sedimentary rock made of cemented sand grains, often quartz, recording ancient beaches, deserts, and rivers.
sedimentary
Quartzite Sandstone
A tough, quartz-rich sandstone cemented by silica, transitional toward true quartzite but still sedimentary in origin.
sedimentary
Feldspathic Sandstone
A feldspar-rich sandstone, often pink, that points to granitic source rocks eroded quickly in dry or cold climates.
sedimentary
Ferricrete
Hard surface crust formed when iron oxides cement soil and sediment into a rusty, durable duricrust in tropical and weathered terrains.
sedimentaryMatte Obsidian
Obsidian with a dull, non-reflective surface from natural weathering or deliberate sandblasting/etching, rather than a distinct type of volcanic glass.
igneousFrosted Obsidian
Natural obsidian with a frosted, matte surface produced by weathering, abrasion, or etching rather than a separate variety of glass.
igneousAsphalt Rock
A porous sedimentary rock naturally saturated with bitumen, dark, tarry-smelling, and historically mined for paving.
sedimentary
Quartzite
An extremely hard metamorphic rock formed from sandstone, made of fused quartz grains that break across rather than between the grains.
metamorphic
Sapropel
A soft, dark, organic-rich mud deposited in stagnant, oxygen-poor water, a key precursor to oil and gas source rocks.
sedimentary
Phosphorite
Phosphate-rich sedimentary rock, the world's main source of phosphorus for fertilizers, formed in nutrient-rich marine settings.
sedimentary
Ironstone
An iron-rich sedimentary rock, often heavy and rusty-weathering, historically mined as a major source of iron ore.
sedimentary
Breccia
A coarse rock of angular, sharp-edged fragments cemented in a matrix, marking nearby rockfall, faulting, or impact.
sedimentary
Pelitic Schist
A schist derived from clay-rich sediments, rich in mica and often bearing index minerals like garnet, staurolite, or kyanite.
metamorphic
Garnierite
A vivid green hydrous nickel-magnesium silicate that is a major ore of nickel, mined from weathered ultramafic rocks.
mineral
Bituminous Shale
A dark, organic-rich shale loaded with kerogen and bitumen that can yield oil and gas, often finely laminated and combustible.
sedimentary
Siltstone
A fine-grained clastic rock of silt-sized grains, intermediate between sandstone and mudstone, with a gritty feel.
sedimentary
Siderite
Siderite is an iron carbonate ore, a brown rhombohedral mineral of the calcite group found in sediments and veins.
mineral
Kambaba Jasper
A dark green-and-black stromatolite jasper patterned with swirling orbs, formed from fossilized ancient microbial colonies.
sedimentary
Black Shale
Dark, organic-rich fine-grained sedimentary rock formed in oxygen-poor waters, often a source rock for oil and gas.
sedimentary
Oil Shale
A fine-grained sedimentary rock rich in solid organic matter (kerogen) that yields oil and gas when heated.
sedimentary
Pisolite
A sedimentary rock built from pea-sized concentric spheres called pisoids, often carbonate but sometimes iron or aluminum-rich.
sedimentary
Mookaite
A vivid Australian jasper-like silica stone in earthy reds, yellows, and purples, formed from silicified radiolarian sediment.
mineral