Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Limestone
A soft carbonate sedimentary rock made mostly of calcite, often packed with marine fossils and prone to forming caves.
sedimentary
Jasper
An opaque, often colorfully patterned variety of chalcedony quartz, popular for tumbling, carving, and jewelry.
mineral
Tufa
A porous, spongy freshwater limestone that precipitates around springs, streams and lakes, often encrusting plants and moss.
sedimentary
Jelly Opal
A translucent, gelatinous-looking opal whose transparency gives floating, glowing play-of-color a watery, jelly-like appearance.
gemstoneCarrara Marble
A famous white to blue-grey Italian marble from Carrara, prized for centuries by sculptors and architects for its purity and fine grain.
metamorphic
Green Obsidian
Green-tinted volcanic glass; some is naturally colored by trace iron, but vivid emerald-green pieces are usually manufactured glass.
crystal
Zincite
A rare zinc oxide best known for its deep red to orange color, classically from Franklin, New Jersey, and as colorful man-made crystals.
mineralMint Garnet
A delicate pastel-green grossular garnet, lighter than tsavorite, most famously from the Merelani Hills of Tanzania.
gemstone
Smoky Quartz
The smoky brown to gray variety of quartz, colored by natural irradiation, valued as both a gemstone and crystal specimen.
crystalReptile Jasper
A green-and-black mottled jasper whose scale-like patterning resembles reptile skin, often linked to Kambaba and crocodile jaspers.
mineral
Peacock Ore
A copper-iron sulfide ore famous for its iridescent peacock-like purple and blue tarnish; often sold as treated chalcopyrite.
mineral
Poppy Jasper
An orbicular jasper with red and orange flower-like spots resembling poppies, famously from Morgan Hill, California.
mineral
Bituminous Shale
A dark, organic-rich shale loaded with kerogen and bitumen that can yield oil and gas, often finely laminated and combustible.
sedimentaryLavender Obsidian
A soft lavender-purple glass sold as obsidian; uniform lavender material is essentially always manufactured glass, not natural volcanic obsidian.
igneous
Owyhee Jasper
A picture jasper from the Owyhee region of Oregon and Idaho, prized for scenic tan, cream, and blue-grey landscape patterns.
mineral
Sideromelane
A transparent, pale brown basaltic volcanic glass formed when basalt lava is quenched extremely fast, often underwater.
igneous
Lemon Quartz
A vivid greenish-yellow quartz, usually heat-treated or irradiated, prized for its clean clarity and bright lemon color.
crystalButterstone Jasper
A soft-toned cream-to-butterscotch jasper colored by iron oxides, prized by lapidaries for its smooth, even, opaque finish.
gemstone
Charnockite
A granite-like rock containing orthopyroxene, formed at high temperatures and pressures and often classed with the granulites.
igneousImperial Jasper
A prized Mexican jasper known for pastel green, lavender, and cream orbicular patterns that take an exceptional polish.
mineralStone Canyon Jasper
A warm-toned brecciated jasper from central California known for swirling browns, golds, and creams broken by darker seams.
gemstone
Greywacke
A hard, dark, poorly sorted sandstone with a muddy matrix, typically deposited by underwater turbidity currents.
sedimentarySpiderweb Jasper
A jasper crossed by fine dark veins forming a spiderweb-like network, often a brecciated stone cemented by darker matrix.
mineral
Orange Garnet
A trade term for orange garnets, mainly manganese-rich spessartine and the brownish hessonite variety of grossular.
gemstone