Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Banded Iron Formation
Ancient chemically deposited rock of alternating iron-oxide and silica bands recording Earth's early oxygenation and a major iron ore source.
sedimentary
Metasandstone
Sandstone altered by metamorphism, with partly recrystallized quartz grains, transitional between true sandstone and quartzite.
metamorphic
Mariposite
A green, gold-associated metamorphic rock made of chrome-rich mica and quartz, named for Mariposa County in California's gold country.
metamorphic
Granite
A coarse-grained, speckled intrusive rock built from quartz, feldspar, and mica, forming the bedrock of the continents.
igneous
Millerite
A nickel sulfide famous for delicate brass-yellow hairlike crystals that form radiating sprays inside cavities and geodes.
mineral
Unakite
An altered granite mottled pink and green from feldspar and epidote, popular as a tough, colorful ornamental rock.
metamorphicDragon Blood Jasper
A green-and-red ornamental stone of epidote and red piemontite or iron oxide, named for its dragon-skin coloring; not a true jasper.
metamorphic
Porcelanite
A hard, fine-grained siliceous rock with a dull porcelain-like texture, intermediate between soft diatomite and dense chert.
sedimentary
Brazilian Agate
Abundant banded chalcedony from southern Brazil, the world's main source of agate slices and dyed agate products.
gemstoneCoyamito Agate
A prized banded agate from Rancho Coyamito in Chihuahua, Mexico, known for eyes, pom-poms and vivid fortification.
gemstone
Mookaite
A vivid Australian jasper-like silica stone in earthy reds, yellows, and purples, formed from silicified radiolarian sediment.
mineral
Ocean Jasper
A multicolored orbicular chalcedony from Madagascar famous for its circular eye-like orbs in greens, pinks, whites, and yellows.
sedimentary
Eye Agate
A chalcedony agate marked by round, concentric ring patterns that resemble eyes when cut and polished.
gemstone
Condor Agate
A vividly banded fortification agate from Argentina prized for its bold red, gold and white concentric patterns.
gemstone
Loess
A loose, wind-blown silt deposit, typically buff-colored and very fertile, that forms thick blankets and stands in steep cliffs.
sedimentary
Flint
A hard, dark variety of chert that knaps into razor-sharp edges and sparks against steel, central to Stone Age technology.
sedimentaryStone Canyon Jasper
A warm-toned brecciated jasper from central California known for swirling browns, golds, and creams broken by darker seams.
gemstoneOutlaw Jasper
A boldly patterned western jasper in browns, reds, and golds, prized by lapidaries for its dramatic scenic and brecciated figures.
gemstone
Lotus Jasper
A softly patterned jasper in cream, gray, and tan whose markings can suggest lotus petals, popular for calm, neutral-toned jewelry.
gemstoneWoodbine Jasper
An earthy-toned jasper with vine-like or scenic patterning, valued by lapidaries for warm browns, reds, and creams that polish to a smooth finish.
gemstone
Madagascar Jasper
A broad family of vividly patterned jaspers from Madagascar, including orbicular and scenic varieties prized for colorful, eye-catching designs.
gemstonePolychrome Jasper
A warm earth-toned jasper from Madagascar in flowing reds, oranges and golds, also called desert jasper, discovered in the early 2000s.
gemstoneSesame Jasper
A finely speckled pale jasper trade stone named for its sesame-seed-like flecks, closely related to Kiwi Jasper.
mineral
Calc-schist
A foliated metamorphic rock of calcite mixed with mica, quartz, and calc-silicate minerals, derived from marly sediments.
metamorphic