Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Petrified Wood
Ancient wood whose organic tissue has been replaced by silica, preserving the grain, rings, and structure of the original tree in stone.
sedimentary
Graphic Feldspar
A pegmatite rock of feldspar intergrown with wedge-shaped quartz that resembles ancient runic or Hebrew writing.
igneous
White Moonstone
The classic moonstone: a milky-white feldspar showing the prized floating blue-to-silver adularescent glow that gives the gem its name.
gemstoneStar Moonstone
A rare moonstone that shows a four-rayed star of light (asterism) across its domed surface along with adularescence.
gemstone
Garden Quartz
Clear quartz filled with mineral inclusions that look like underwater gardens, mossy landscapes, or floating scenery.
crystal
Opalite
A man-made opalescent glass that glows milky blue in reflected light and warm orange when backlit, often sold as a crystal.
crystal
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
Peacock Ore
A copper-iron sulfide ore famous for its iridescent peacock-like purple and blue tarnish; often sold as treated chalcopyrite.
mineral
Graphic Granite
A pegmatitic granite in which quartz and feldspar intergrow to resemble ancient runic or Hebrew script.
igneousWonderstone
A banded rhyolitic volcanic rock with swirling tan, red, and yellow iron-oxide layers prized as a decorative picture stone.
igneousGrey Moonstone
A smoky gray feldspar moonstone, often called new moon stone, showing a silvery-blue adularescent sheen over a translucent gray body.
gemstone
Star Garnet
A rare almandine garnet that displays a four- or six-rayed star (asterism) from oriented rutile inclusions; the state gem of Idaho.
gemstone
Ceylon Garnet
Ceylon Garnet is a historic trade name for fine red almandine (and hessonite) garnet from the gem gravels of Sri Lanka.
gemstone
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
Snowflake Obsidian
A black volcanic glass speckled with gray-white cristobalite snowflakes, formed as obsidian begins to crystallize.
igneous
Mariposite
A green, gold-associated metamorphic rock made of chrome-rich mica and quartz, named for Mariposa County in California's gold country.
metamorphic
Staurolite Schist
A mica schist studded with brown staurolite porphyroblasts, sometimes forming the cross-shaped twins known as fairy stones.
metamorphic
Rutilated Quartz
Clear or smoky quartz threaded with golden to reddish needles of rutile, also poetically called Venus hair stone.
crystal
Chocolate Garnet
A rich brown variety of andradite (or grossular-andradite) garnet, marketed for its warm chocolate color and notable brilliance.
gemstoneRoyal Blue Obsidian
A deep royal-blue glass sold as obsidian; the rich blue body color is manufactured, unlike natural blue-sheen obsidian whose blue is only a surface effect.
igneousEmerald Green Obsidian
A bright emerald-green glass sold as obsidian; saturated transparent green is manufactured, while rare natural green obsidian is only faintly tinted.
igneousTurquoise Obsidian
A vivid turquoise-blue glass sold as obsidian; this bright color is virtually always manufactured rather than natural volcanic glass.
igneousTeal Obsidian
A deep teal glass sold as obsidian; the saturated blue-green color is manufactured and not found in natural volcanic glass.
igneousStrawberry Obsidian
A pink-red glass sold as obsidian, sometimes with metallic flecks; the strawberry color is manufactured rather than a natural volcanic glass tone.
igneous