Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Zebra Jasper
A black-and-white striped chalcedony-quartz rock whose bold zebra-like banding makes it a popular ornamental and lapidary stone.
sedimentary
Picasso Jasper
A marbled, abstractly patterned stone resembling modern art, technically a metamorphosed limestone rather than a true silica jasper.
metamorphic
Chalcedony
A waxy, translucent microcrystalline form of quartz that serves as the parent group for agate, jasper, carnelian, and onyx.
mineral
Migmatite
A 'mixed rock' showing swirling light and dark bands, formed where high-grade metamorphism causes rock to begin partially melting.
metamorphic
Crinoidal Limestone
A fossiliferous limestone built largely from the disc-shaped skeletal plates of crinoids, marine animals known as sea lilies.
sedimentary
Serpentinite
A green, often mottled metamorphic rock formed by the hydration of mantle rocks, soft and waxy with a smooth, slippery feel.
metamorphic
Calc-schist
A foliated metamorphic rock of calcite mixed with mica, quartz, and calc-silicate minerals, derived from marly sediments.
metamorphic
Snow Quartz
An opaque, snow-white variety of quartz whose milky color comes from countless tiny gas and fluid inclusions.
crystal
Leuco Garnet
The rare colorless variety of grossular garnet, a near-flawless transparent gem free of the iron and chromium that color most garnets.
gemstone
Milk Opal
An opaque to translucent milky-white common opal valued for its soft porcelain-like color rather than play-of-color.
gemstone
Whiteschist
A rare high-pressure metamorphic schist defined by the diagnostic assemblage of talc plus kyanite, often pale and silvery.
metamorphic
Marl
A soft, earthy sedimentary rock made of a mixture of calcium carbonate and clay, intermediate between limestone and mudstone.
sedimentary
Coober Pedy Opal
Australia's classic light-bodied precious opal from Coober Pedy, famed for milky white stones flashing pastel rainbow play-of-color.
gemstone
Skutterudite
A metallic cobalt-nickel arsenide, an important cobalt ore, named for the Skutterud mines of Norway.
mineral
Magnesite
A magnesium carbonate mineral, usually chalky white with grey veining, widely dyed to imitate turquoise and other stones.
mineral
Chalk
A soft, white, fine-grained limestone made almost entirely of microscopic marine plankton skeletons.
sedimentary
Goshenite
The colorless variety of beryl, named after Goshen, Massachusetts, prized for its purity, clarity, and durability.
gemstone
Howlite
A white, porous borate mineral webbed with gray-black veins, widely dyed to imitate turquoise and other stones.
mineral
Sylvanite
A silver-white gold-silver telluride and important gold-silver ore, noted for crystals arranged in writing-like graphic patterns.
mineral
Clear Beryl
Transparent, colorless beryl (goshenite), the pure form of the species valued for its clarity, hardness, and well-formed crystals.
gemstone
Topaz
A hard, brilliant fluorosilicate gemstone occurring in many colors, from precious golden imperial topaz to popular blue topaz.
gemstone
Milky Quartz
The most common variety of quartz, milky white from microscopic fluid and gas inclusions, forming massive veins worldwide.
crystal
Alabaster
A soft, fine-grained, translucent form of gypsum (or banded calcite) long prized as a carving and ornamental stone.
mineral
Danburite
A glassy calcium borosilicate forming wedge-tipped prismatic crystals, usually colorless to pale yellow or pink, sometimes faceted as a gem.
crystal