Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Lherzolite
The most common type of mantle peridotite, made of olivine with both orthopyroxene and clinopyroxene, representing fertile upper-mantle rock.
igneous
Harzburgite
A depleted mantle peridotite of olivine and orthopyroxene, the refractory residue left after basaltic melt is extracted from the mantle.
igneous
Crinoidal Limestone
A fossiliferous limestone built largely from the disc-shaped skeletal plates of crinoids, marine animals known as sea lilies.
sedimentary
Clear Quartz
The pure, colorless form of crystalline quartz, valued for its clarity, abundance, and piezoelectric properties used in electronics.
crystal
Cloudy Obsidian
Obsidian with a hazy, cloud-like translucency caused by uneven distribution of tiny bubbles or incipient crystallites in the glass.
igneous
Brecciated Jasper
A jasper made of angular fragments naturally cemented back together, typically showing red and brown pieces in a quartz matrix.
sedimentary
Gold Sheen Obsidian
A black obsidian displaying a golden metallic sheen caused by light reflecting off aligned microscopic gas bubbles or mineral inclusions.
igneous
Jadeite
The rarer and more valuable of the two jade minerals, prized for its translucent emerald-green 'imperial' color and extreme toughness.
gemstone
Tri-Color Tourmaline
Tourmaline displaying three distinct color zones in a single crystal, a striking natural result of changing growth chemistry.
gemstone
Pink Lady Obsidian
Obsidian showing a pink-to-rose sheen or hue; natural examples get color from interference effects, while uniform pink material is often manufactured glass.
igneous
Latite
The fine-grained volcanic equivalent of monzonite, an intermediate lava with nearly equal feldspars and little free quartz.
igneous
Cat's Eye Pink Tourmaline
Pink tourmaline cut en cabochon to reveal a moving band of light, a phenomenal gem colored by manganese with parallel inclusions.
gemstone
Knorringite
A chromium-rich magnesium garnet of the pyrope series that crystallizes in the deep mantle and is a valuable diamond indicator mineral.
mineral
Turbidite
A graded sedimentary deposit laid down by underwater turbidity currents, recording avalanches of sediment cascading down submarine slopes.
sedimentary
Tactite
A contact-metasomatic calc-silicate rock, essentially a skarn, formed where intrusions react with carbonate rocks and often host ore.
metamorphic
Mexican Fire Opal
A transparent to translucent opal prized for its glowing orange-to-red body color, mined chiefly in the volcanic highlands of Mexico.
gemstone
Metaconglomerate
A conglomerate altered by heat and pressure, often with its rounded pebbles stretched and flattened into elongated lenses.
metamorphic
Gary Green Jasper
An Oregon jasper, also called larsonite, of silicified fossil wood showing olive-green fields laced with black dendritic patterns.
mineral
Coral Rock
A porous limestone built from the calcium carbonate skeletons of corals and reef organisms, the lithified remains of ancient or modern reefs.
sedimentary
Columbite
A black iron-manganese niobate that is a primary ore of niobium, forming a continuous series with tantalite (together called coltan).
mineral
Skarn
A calc-silicate rock formed by chemical exchange between magma and carbonate rock, often rich in garnet and economically important ore minerals.
metamorphic
Shelly Limestone
A limestone packed with visible shells and shell fragments, recording the accumulation of marine invertebrate remains on ancient sea floors.
sedimentary
Fire Obsidian
A rare obsidian showing brilliant fiery iridescence caused by thin nanolayers of magnetite crystals diffracting light within the glass.
crystal
Chalky Limestone
A soft, fine-grained, porous white limestone made largely of microscopic calcareous plankton skeletons, the rock that forms classic white cliffs.
sedimentary