Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Plum Tourmaline
A purplish, plum-toned elbaite tourmaline colored by manganese, blending the red of rubellite with violet-blue undertones.
gemstone
Opalite
A man-made opalescent glass that glows milky blue in reflected light and warm orange when backlit, often sold as a crystal.
crystal
Tachylite
An opaque, iron-rich basaltic volcanic glass formed by the rapid chilling of basalt lava, darker and denser than rhyolitic obsidian.
igneous
Cave Creek Jasper
An opaque jasper from the Cave Creek area of Arizona, prized for earthy mottled and banded patterns in warm desert tones.
mineralTri-Color Tourmaline
Tourmaline displaying three distinct color zones in a single crystal, a striking natural result of changing growth chemistry.
gemstoneQuartz Arenite
A clean, mature sandstone made almost entirely of quartz grains, representing extreme weathering, sorting, and recycling of sediment.
sedimentary
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
Coral Rock
A porous limestone built from the calcium carbonate skeletons of corals and reef organisms, the lithified remains of ancient or modern reefs.
sedimentaryGreen Sheen Obsidian
Black volcanic glass that flashes a green sheen at certain angles due to light interference off aligned microscopic inclusions.
igneous
Columbite
A black iron-manganese niobate that is a primary ore of niobium, forming a continuous series with tantalite (together called coltan).
mineral
Coober Pedy Opal
Australia's classic light-bodied precious opal from Coober Pedy, famed for milky white stones flashing pastel rainbow play-of-color.
gemstone
Turbidite
A graded sedimentary deposit laid down by underwater turbidity currents, recording avalanches of sediment cascading down submarine slopes.
sedimentary
Latite
The fine-grained volcanic equivalent of monzonite, an intermediate lava with nearly equal feldspars and little free quartz.
igneous
Metaconglomerate
A conglomerate altered by heat and pressure, often with its rounded pebbles stretched and flattened into elongated lenses.
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
Schorlomite
A lustrous black titanium-rich garnet of the andradite series, found in alkaline igneous rocks like nepheline syenite and ijolite.
mineralGary Green Jasper
An Oregon jasper, also called larsonite, of silicified fossil wood showing olive-green fields laced with black dendritic patterns.
mineral
Limburgite
A dark, glass-rich volcanic rock of olivine and augite phenocrysts set in a feldspar-free glassy groundmass, named from the Kaiserstuhl region.
igneousPurple Sheen Obsidian
Black volcanic glass that reveals a soft purple-to-violet sheen at certain angles, caused by light interference off aligned inclusions.
igneous
Tactite
A contact-metasomatic calc-silicate rock, essentially a skarn, formed where intrusions react with carbonate rocks and often host ore.
metamorphic
Oregon Sunstone
A copper-bearing labradorite feldspar from Oregon, famous for its range of natural colors and glittery aventurescent copper schiller.
gemstone
Spectrolite
A premium dark Finnish labradorite displaying the full color spectrum of iridescent flashes, prized as one of the most vivid feldspar gems.
gemstone
Rock Gypsum
A soft sedimentary evaporite made of massive gypsum, deposited when sulfate-rich seawater or lake water evaporates and concentrates.
sedimentary
Goethite
Goethite is a common brown iron oxyhydroxide, the main crystalline component of limonite and rust, with shimmering botryoidal forms.
mineral