Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Coal
A combustible black sedimentary rock formed from ancient plant matter and burned for centuries as a primary fossil fuel.
sedimentary
Belomorite
A regional Russian name for a moonstone-like plagioclase from the White Sea coast, prized for its bluish, slightly iridescent schiller.
gemstone
Aquamarine Crystal
The blue iron-bearing variety of beryl, forming clear hexagonal crystals prized both as specimens and as a March birthstone gem.
crystal
Frosted Obsidian
Natural obsidian with a frosted, matte surface produced by weathering, abrasion, or etching rather than a separate variety of glass.
igneous
Pearl
An organic gem formed inside mollusks from layered nacre, prized for its iridescent luster and classic elegance.
gemstone
Opalite
A man-made opalescent glass that glows milky blue in reflected light and warm orange when backlit, often sold as a crystal.
crystal
Crystal Opal
Precious opal with a transparent or translucent body, letting play-of-color glow with exceptional depth and clarity.
gemstone
Aquamarine Matrix
Aquamarine crystals still attached to their natural host rock, prized as mineral specimens showing beryl in its original pocket setting.
mineral
Phosphorite
Phosphate-rich sedimentary rock, the world's main source of phosphorus for fertilizers, formed in nutrient-rich marine settings.
sedimentary
Micrite
A very fine-grained limestone made of microcrystalline calcite mud, dense and smooth, deposited in calm carbonate settings.
sedimentary
Povondraite
A rare ferric-iron-dominant tourmaline that forms in oxidized evaporite settings, appearing as black to red-brown prismatic crystals.
mineral
Oolite
A limestone made of tiny spherical ooids, resembling fish roe, formed in warm, agitated shallow seas.
sedimentary
Aragonite
A calcium carbonate mineral and polymorph of calcite, aragonite forms distinctive needle clusters, sea shells, and pearls.
mineral
Shelly Limestone
A limestone packed with visible shells and shell fragments, recording the accumulation of marine invertebrate remains on ancient sea floors.
sedimentary
Blue Beryl
The blue color variety of beryl, ranging from pale sky tones to rich sea-blue, best known in its finest grades as aquamarine.
gemstone
Oolitic Limestone
Limestone built from tiny rounded ooid grains resembling fish roe, formed in warm, agitated shallow seas.
sedimentary
Blue-Green Tourmaline
Elbaite tourmaline spanning the blue-to-green range, from sea-green to deep peacock hues, popular for its versatile color.
gemstone
Larimar
A rare sky-blue variety of pectolite found only in the Dominican Republic, prized for its sea-like color and white volcanic patterning.
gemstone