Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Maxixe Aquamarine
A deep blue beryl whose intense color comes from radiation-induced color centers and tends to fade in light, named after the Maxixe mine in Brazil.
gemstone
Melteigite
A dark, pyroxene-dominated plutonic rock at the mafic end of the ijolite series, made mainly of aegirine-augite with subordinate nepheline.
igneous
Biotite Schist
A foliated metamorphic rock dominated by glittering dark biotite mica, formed from mudstones under medium-grade regional metamorphism.
metamorphicBurgundy Tourmaline
A deep wine-red to maroon tourmaline colored by manganese, a rich darker-toned member of the red-pink rubellite family.
gemstoneMaxixe
A deep blue beryl with a color caused by radiation that fades in light, named after the Maxixe mine in Brazil.
gemstoneSmoky Obsidian
Translucent smoky-gray obsidian that transmits a hazy light, intermediate between clear and fully black volcanic glass.
igneous
Smoky Quartz
The smoky brown to gray variety of quartz, colored by natural irradiation, valued as both a gemstone and crystal specimen.
crystal
Morion Quartz
The darkest, near-opaque black variety of smoky quartz, colored by natural radiation acting on trace aluminum.
crystal
Black Shale
Dark, organic-rich fine-grained sedimentary rock formed in oxygen-poor waters, often a source rock for oil and gas.
sedimentarySemiblack Opal
Opal with a dark grey body tone sitting between black and light opal, giving play-of-color rich contrast at an accessible price.
gemstone
Cranberry Tourmaline
A deep cranberry-red to purplish-pink variety of lithium-rich elbaite tourmaline, prized as a rich, saturated rubellite gemstone.
gemstone
Forest Green Tourmaline
A deep, rich forest-green elbaite tourmaline (verdelite) colored mainly by iron, with strong pleochroism and excellent durability.
gemstone
Black Moonstone
A dark gray-to-black feldspar variety of moonstone that shows blue and white adularescent flash against a smoky body.
gemstone
Black Opal
The rarest and most valuable opal, with a dark body tone that makes its flashing rainbow play-of-color blaze brilliantly.
gemstoneDallasite Jasper
A green-and-white volcanic breccia from Vancouver Island, cemented by jasper and rich in epidote, popular as a regional lapidary stone.
gemstone
Amphibolite
A dark, dense metamorphic rock dominated by hornblende and plagioclase, formed by medium- to high-grade metamorphism of basalt.
metamorphicSesame Jasper
A finely speckled pale jasper trade stone named for its sesame-seed-like flecks, closely related to Kiwi Jasper.
mineral
Sapropel
A soft, dark, organic-rich mud deposited in stagnant, oxygen-poor water, a key precursor to oil and gas source rocks.
sedimentary
Septarian Concretion
A rounded sedimentary nodule cracked internally and filled with veins of yellow calcite, prized for its striking dragon-skin patterning.
sedimentary
Seam Agate
Agate that forms in flat cracks or veins of host rock rather than rounded nodules, producing straight, parallel banding.
gemstoneLeopard Obsidian
Black volcanic glass marked with rounded spots and patches that resemble a leopard's coat, caused by spherulitic crystallization.
igneous
Andesite
A fine-grained, intermediate volcanic rock common at subduction-zone volcanoes, between basalt and rhyolite in composition.
igneous
Tillite
A lithified glacial till, a poorly sorted rock of mixed boulders, pebbles and fine matrix that records ancient glaciations.
sedimentary
Eye Agate
A chalcedony agate marked by round, concentric ring patterns that resemble eyes when cut and polished.
gemstone