Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Blue Line Jasper
A pale jasper crossed by distinctive blue-gray veins or lines, valued by lapidaries for its calm color contrast.
gemstone
Larvikite
A Norwegian intrusive rock whose feldspar crystals flash silvery-blue, widely used as blue pearl granite countertops.
igneous
Alnöite
A rare dark ultramafic lamprophyre rich in melilite, biotite and olivine, named for Alnö Island in Sweden.
igneous
Bixbite
An old trade name for red beryl, the extremely rare manganese-colored beryl from Utah, now largely replaced by the term red beryl.
gemstone
Granulite
A high-grade metamorphic rock formed in the deep, hot crust, marked by anhydrous minerals like pyroxene and garnet.
metamorphic
Mica Schist
A glittery, strongly foliated rock made mostly of aligned mica flakes that split into thin, shiny sheets.
metamorphic
Albitite
A pale rock made almost entirely of the sodium feldspar albite, formed by sodic magmatism or sodium metasomatism.
igneous
Diorite
A coarse-grained intrusive rock with a distinctive salt-and-pepper look, the plutonic equivalent of andesite.
igneous
Kersantite
A dark mica lamprophyre with biotite and augite phenocrysts in a plagioclase-dominated groundmass, the feldspar counterpart of minette.
igneous
Graphite Schist
A dark, foliated schist rich in graphite that leaves a grey-black mark and forms from metamorphosed carbon-rich sediments.
metamorphic
Mica
A family of sheet silicate minerals that split into thin, flexible, shiny sheets, giving rocks a sparkling, layered appearance.
mineral
Hornfels
A tough, fine-grained, non-foliated rock formed by the intense heat of nearby magma baking surrounding rock at contact zones.
metamorphic
Arkose
A coarse, feldspar-rich sandstone, often pink, that records rapid erosion of granitic source rock under arid conditions.
sedimentary
Norite
A coarse-grained mafic plutonic rock similar to gabbro but with orthopyroxene as the dominant pyroxene instead of clinopyroxene.
igneousGrandite Garnet
Grandite is an intermediate garnet between grossular and andradite, common in skarns and prized for vivid green to golden crystals.
mineral
Amphibolite
A dark, dense metamorphic rock dominated by hornblende and plagioclase, formed by medium- to high-grade metamorphism of basalt.
metamorphic
Gneiss
A high-grade metamorphic rock defined by alternating light and dark mineral bands, formed under intense heat and pressure.
metamorphic
Gabbro
A coarse-grained, dark mafic intrusive rock that is the plutonic equivalent of basalt, rich in plagioclase and pyroxene.
igneousPrase
An old name for a dull leek-green variety of quartz or chalcedony colored by green mineral inclusions, historically called mother of emerald.
crystal
Chalcedony
A waxy, translucent microcrystalline form of quartz that serves as the parent group for agate, jasper, carnelian, and onyx.
mineral
Ametrine
A natural bicolor quartz that combines purple amethyst and golden citrine in a single crystal.
crystal
Citrine
The golden-yellow variety of quartz, ranging from pale lemon to deep madeira amber, often produced by heating amethyst.
gemstone
Herkimer Diamond
Exceptionally clear, naturally double-terminated quartz crystals from Herkimer County, New York, prized for their diamond-like brilliance.
crystal
Amethyst
The purple variety of quartz, colored by iron and natural irradiation, prized as the classic violet birthstone of February.
crystal