Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Pele's Hair
Fine, golden, hair-like strands of basaltic volcanic glass spun from fluid lava droplets during eruptions, named for the Hawaiian volcano goddess.
igneous
Diabase
A tough, dark, medium-grained igneous rock with the composition of basalt, common in dikes and sills.
igneous
Metabasalt
Basalt that has been metamorphosed, developing new minerals like chlorite, actinolite, and epidote that give it a greenish color.
metamorphic
Limburgite
A dark, glass-rich volcanic rock of olivine and augite phenocrysts set in a feldspar-free glassy groundmass, named from the Kaiserstuhl region.
igneousTintenbar Opal
Rare precious opal from Tintenbar in northern New South Wales, Australia, occurring in volcanic basalt rather than sedimentary rock.
gemstone
Palagonite
A yellow-brown alteration material formed when basaltic volcanic glass reacts with water, common in hydrovolcanic tuffs and pillow lavas.
igneous
Gabbro
A coarse-grained, dark mafic intrusive rock that is the plutonic equivalent of basalt, rich in plagioclase and pyroxene.
igneousRiband Agate
A banded chalcedony with straight, ribbon-like parallel layers, often cut across the bands for striking striped cabochons.
gemstone
Morion Quartz
The darkest, near-opaque black variety of smoky quartz, colored by natural radiation acting on trace aluminum.
crystalSardonyx
A banded chalcedony combining reddish-brown sard with white or black onyx layers, prized since antiquity for carved cameos.
gemstone
Black Agate
A deep black variety of banded chalcedony, often closely related to or treated like onyx, used for jewelry and carvings.
gemstone
Greenstone
A general field term for green, low-grade metamorphosed basaltic rocks colored by chlorite, epidote, and actinolite.
metamorphic
Green Marble
A green ornamental stone, often serpentine-rich marble or verde antique, valued for its rich green color and white veining.
metamorphic
Cipollino Marble
A green-and-white banded metamorphic marble whose wavy mica layers resemble the rings of a sliced onion.
metamorphic
Banded Agate
The classic agate defined by concentric or parallel bands of chalcedony in varied colors, the archetype of all agate varieties.
gemstone
Travertine
A banded, porous limestone deposited by mineral springs, prized as a warm-toned natural building and tile stone.
sedimentary
Jelly Opal
A translucent, gelatinous-looking opal whose transparency gives floating, glowing play-of-color a watery, jelly-like appearance.
gemstoneMintabie Opal
Precious opal from the Mintabie field in South Australia, known for hard, bright crystal opal and some dark-bodied stones.
gemstoneIce Opal
A clear, glassy, near-colorless opal resembling ice, sometimes with subtle internal flashes of play-of-color.
gemstone
Rose Quartz
The soft pink, usually cloudy variety of quartz colored by trace titanium or microscopic inclusions, popular for carvings and beads.
crystal
Clear Quartz
The pure, colorless form of crystalline quartz, valued for its clarity, abundance, and piezoelectric properties used in electronics.
crystal
Scepter Quartz
Quartz with a wider crystal 'cap' that grew over a narrower stem, forming a natural scepter or mushroom shape.
crystalLemurian Seed Quartz
Clear quartz crystals marked by distinctive horizontal ladder-like striations, popularized from Brazil as a metaphysical stone.
crystal
Zincite
A rare zinc oxide best known for its deep red to orange color, classically from Franklin, New Jersey, and as colorful man-made crystals.
mineral