Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Peridotite
A dense, coarse-grained ultramafic rock rich in olivine that makes up most of the Earth's upper mantle.
igneous
Granite
A coarse-grained, speckled intrusive rock built from quartz, feldspar, and mica, forming the bedrock of the continents.
igneous
Metagabbro
Coarse-grained gabbro that has been metamorphosed, partly recrystallizing into amphibole, plagioclase, and other metamorphic minerals.
metamorphic
Platinum
A dense, durable, silvery-white precious metal that resists corrosion, used in fine jewelry and catalytic converters.
mineralSpiderweb Obsidian
Black volcanic glass crossed by a fine network of grey or brown veins that resemble a spider's web.
igneous
Ijolite
A coarse-grained, feldspar-free plutonic rock composed mainly of nepheline and sodic pyroxene, the intrusive equivalent of nephelinite.
igneous
Cat's Eye Green Tourmaline
Green tourmaline cut as a cabochon to show a sharp moving band of light (chatoyancy) caused by fine parallel inclusions.
gemstonePentelic Marble
The fine white marble of Mount Pentelikon used to build the Parthenon, famous for the golden patina it develops with age.
metamorphicPulaskite
A coarse-grained alkali syenite of perthitic feldspar with sodic pyroxene or amphibole and minor nepheline, from Pulaski County, Arkansas.
igneous
Red Obsidian
Volcanic glass tinted red by fine iron-oxide inclusions, often blended with black to form mahogany-patterned obsidian.
crystalTripolite
A soft, lightweight siliceous sedimentary rock made of fossil diatom remains, prized as a fine natural abrasive and polishing powder.
sedimentary
Cataclasite
A cohesive fault rock formed by brittle crushing and grinding of rock along a fault zone, with angular fragments in a fine matrix.
metamorphicLace Obsidian
Black volcanic glass laced with delicate web-like veins of contrasting color, formed by flow banding and fine crystallization.
igneous
Conglomerate
A coarse sedimentary rock of rounded pebbles and gravel cemented in a finer matrix, recording ancient rivers and beaches.
sedimentarySyrian Garnet
Syrian Garnet is an old trade name for fine deep-red almandine, historically tied to the Syriam region and prized as 'precious garnet.'
gemstone
Blue Chalcedony
A translucent, soft blue variety of microcrystalline quartz whose color comes from light scattering through its fine structure.
mineral
Needle Tourmaline
Fine acicular (needle-like) tourmaline crystals, often black schorl, frequently seen as slender inclusions within clear quartz.
mineral
Lamprophyre
A dark, mineral-rich dike rock with abundant mica or amphibole phenocrysts set in a fine groundmass, often associated with gold and diamonds.
igneous
Ceylon Garnet
Ceylon Garnet is a historic trade name for fine red almandine (and hessonite) garnet from the gem gravels of Sri Lanka.
gemstoneSpiderweb Jasper
A jasper crossed by fine dark veins forming a spiderweb-like network, often a brecciated stone cemented by darker matrix.
mineral
Peristerite
A sodium-rich plagioclase moonstone whose fine intergrowth lamellae scatter light into a delicate blue, pigeon-neck sheen.
gemstone
Wood Opal
Fossil wood replaced by opaline silica that preserves wood grain, occasionally showing the play-of-color of precious opal.
gemstone
Dalmatian Jasper
A cream-colored spotted stone resembling a Dalmatian dog, made of feldspar and quartz dotted with dark mineral grains.
igneous
Perthite
An intimate intergrowth of potassium feldspar and sodium feldspar formed when a single alkali feldspar unmixes on cooling, producing fine wavy lamellae.
mineral