Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Goldstone
A man-made glittering glass packed with tiny copper crystals, traditionally reddish-brown but also made in blue and green.
crystal
Pumice
A frothy, lightweight volcanic glass so full of gas bubbles that it can float on water.
igneous
Pegmatite
An exceptionally coarse-grained igneous rock, often granitic, famous for hosting large crystals and many gemstones.
igneous
Jacupirangite
A rare dark ultramafic alkaline igneous rock built mostly of titanaugite and magnetite, named for Jacupiranga in Brazil.
igneous
Dalmatian Jasper
A cream-colored spotted stone resembling a Dalmatian dog, made of feldspar and quartz dotted with dark mineral grains.
igneous
Monzonite
An intermediate plutonic rock with nearly equal alkali and plagioclase feldspar and very little quartz, sitting between diorite and syenite.
igneous
Lamproite
A rare ultrapotassic, magnesium-rich volcanic rock from deep in the mantle, famous as the diamond host at Argyle in Australia.
igneous
Cataclasite
A cohesive fault rock formed by brittle crushing and grinding of rock along a fault zone, with angular fragments in a fine matrix.
metamorphic
Peridotite
A dense, coarse-grained ultramafic rock rich in olivine that makes up most of the Earth's upper mantle.
igneous
Phosphorite
Phosphate-rich sedimentary rock, the world's main source of phosphorus for fertilizers, formed in nutrient-rich marine settings.
sedimentaryGondite
A metamorphic rock made chiefly of manganese-rich spessartine garnet and quartz, formed from ancient manganese-bearing sediments.
metamorphic
Snowflake Obsidian
A black volcanic glass speckled with gray-white cristobalite snowflakes, formed as obsidian begins to crystallize.
igneous
Dunite
An ultramafic intrusive rock made almost entirely of olivine, representing mantle material.
igneous
Limestone
A soft carbonate sedimentary rock made mostly of calcite, often packed with marine fossils and prone to forming caves.
sedimentaryUrtite
A pale, nepheline-dominated plutonic rock at the leucocratic end of the ijolite series, sometimes associated with major apatite ore deposits.
igneous
Water Opal
A transparent, colorless opal that looks like water or jelly, sometimes flashing subtle play-of-color from within.
gemstone
Epidosite
A hard, pistachio-green rock composed mainly of epidote and quartz, formed by hydrothermal alteration of mafic rocks.
metamorphic
Albitite
A pale rock made almost entirely of the sodium feldspar albite, formed by sodic magmatism or sodium metasomatism.
igneous
Phonolite
A silica-poor volcanic rock of alkali feldspar and feldspathoids that rings when struck, hence 'clinkstone.'
igneousEulysite
A rare, dense iron-rich metamorphic rock composed of fayalite, iron pyroxene, and almandine garnet.
metamorphic
Breccia
A coarse rock of angular, sharp-edged fragments cemented in a matrix, marking nearby rockfall, faulting, or impact.
sedimentaryMadupite
A rare ultrapotassic lamproite rich in phlogopite mica and diopside, classically from the Leucite Hills of Wyoming.
igneous
Coquina
A soft, porous limestone made of loosely cemented shell and coral fragments, used as a coastal building stone.
sedimentary
Komatiite
A rare, ancient ultramafic volcanic rock formed from extremely hot magma, famous for its spinifex texture.
igneous