Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Ferricrete
Hard surface crust formed when iron oxides cement soil and sediment into a rusty, durable duricrust in tropical and weathered terrains.
sedimentary
Owyhee Blue Jasper
A soft blue-gray jasper from the Owyhee region of Oregon and Idaho, prized for its rare, calming blue tones among earthy jaspers.
gemstone
Shadow Agate
A banded agate that displays a moving shadow or flash across its surface when tilted under light, caused by closely spaced parallel bands.
gemstone
Phyllite
A fine-grained foliated metamorphic rock between slate and schist, recognized by its silky silvery sheen and wavy, crinkled surfaces.
metamorphic
Royal Blue Obsidian
A deep royal-blue glass sold as obsidian; the rich blue body color is manufactured, unlike natural blue-sheen obsidian whose blue is only a surface effect.
igneous
Tripolite
A soft, lightweight siliceous sedimentary rock made of fossil diatom remains, prized as a fine natural abrasive and polishing powder.
sedimentary
Bastnasite
A rare-earth fluorocarbonate that is one of the world's most important ores of cerium, lanthanum, and other rare earth elements.
mineral
Selenite
A clear, soft crystalline variety of gypsum that forms glassy or fibrous wands, so soft it can be scratched with a fingernail.
crystal
Monazite
A reddish-brown rare-earth phosphate that is a primary ore of cerium, thorium and other rare-earth elements, often found in placer sands.
mineral
Anglesite
A heavy lead sulfate secondary mineral, often colorless to white with adamantine luster, formed by the oxidation of galena.
mineral
Anhydrite
A water-free calcium sulfate mineral closely related to gypsum, forming in evaporite deposits and swelling into gypsum when it absorbs water.
mineral
Gypsum
A very soft sulfate mineral defining Mohs 2, occurring as selenite, satin spar, alabaster, and desert rose, used to make plaster.
mineral
Diatomite
A soft, lightweight, chalky sedimentary rock made of the silica shells of microscopic diatoms, prized for its absorbency and filtering ability.
sedimentary
Celestite
A soft, sky-blue strontium sulfate mineral famous for the glittering pale-blue crystal geodes from Madagascar.
mineral
Glauconite
A soft, green iron-potassium mica that forms in marine sediments and gives greensand its characteristic olive color.
mineral
Euxenite
A black rare-earth niobium-tantalum oxide, often radioactive and metamict, mined for yttrium, niobium, and associated rare elements.
mineral
Loess
A loose, wind-blown silt deposit, typically buff-colored and very fertile, that forms thick blankets and stands in steep cliffs.
sedimentary
Radiolarite
A hard, fine-grained siliceous rock built from the microscopic silica skeletons of radiolarians, often forming colorful ribbon-banded cherts.
sedimentary
Brown Jasper
An opaque earth-toned jasper colored brown by iron oxides, ranging from pale tan to deep chocolate.
mineral
Angelite
A soft pale-blue calcium sulfate, the anhydrous form of gypsum, prized as a gentle, calming tumbled stone.
mineral
Rock Gypsum
A soft sedimentary evaporite made of massive gypsum, deposited when sulfate-rich seawater or lake water evaporates and concentrates.
sedimentary
Desert Rose
A rosette-shaped cluster of bladed gypsum or barite crystals that traps sand, forming flower-like formations in arid deserts.
mineral
Polychrome Jasper
A warm earth-toned jasper from Madagascar in flowing reds, oranges and golds, also called desert jasper, discovered in the early 2000s.
gemstone
Autumn Jasper
A warm-toned jasper named for its autumn-leaf palette of browns, rust, gold, and cream, popular as soothing earth-tone beads.
mineral