Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Coldwater Agate
A glacially transported agate found in Midwestern gravels, named for the Coldwater area, showing banded chalcedony patterns.
gemstone
Feather Agate
A translucent chalcedony agate containing delicate, feather- or plume-shaped mineral inclusions that branch like soft feathers.
gemstone
Pelitic Schist
A schist derived from clay-rich sediments, rich in mica and often bearing index minerals like garnet, staurolite, or kyanite.
metamorphic
Blue Jasper
An opaque blue variety of chalcedony jasper, less common than red or green forms, colored by mineral inclusions.
mineral
Diorite
A coarse-grained intrusive rock with a distinctive salt-and-pepper look, the plutonic equivalent of andesite.
igneous
Serpentine
A group of green magnesium silicate minerals with a smooth, waxy feel, often carved and sometimes sold as imitation jade.
mineral
Blue Goldstone
A man-made glittering glass colored deep blue with cobalt and studded with tiny copper crystals that mimic a starry night sky.
gemstone
Serpentinite
A green, often mottled metamorphic rock formed by the hydration of mantle rocks, soft and waxy with a smooth, slippery feel.
metamorphic
Moss Agate
A translucent chalcedony filled with green or brown dendritic mineral inclusions that resemble moss, foliage, or landscapes.
gemstone
Idaho Star Garnet
Idaho's official state gem: a dark almandine garnet showing a four- or rare six-rayed star from oriented rutile inclusions.
gemstone
Golden Rainbow Obsidian
Black obsidian that displays a golden-to-rainbow iridescent sheen caused by aligned microscopic inclusions reflecting light.
igneous
Green Jasper
An opaque green variety of chalcedony quartz colored by iron and chlorite-group inclusions, prized as a durable carving and cabochon stone.
mineralOutback Jasper
An earthy Australian-style jasper in red, ochre, and yellow tones evoking the colors of the Outback desert.
mineralSlate
A fine-grained, low-grade metamorphic rock that splits into flat sheets along slaty cleavage, long used for roofing and flooring.
metamorphic
Graphite Schist
A dark, foliated schist rich in graphite that leaves a grey-black mark and forms from metamorphosed carbon-rich sediments.
metamorphic
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
Larvikite
A Norwegian intrusive rock whose feldspar crystals flash silvery-blue, widely used as blue pearl granite countertops.
igneous
Bloodstone
A dark green chalcedony speckled with blood-red spots of iron oxide, traditionally known as heliotrope.
gemstone
Goldstone
A man-made glittering glass packed with tiny copper crystals, traditionally reddish-brown but also made in blue and green.
crystal
Pietersite
A brecciated, chatoyant quartz with swirling blue, gold, and brown fibers that shimmer like a stormy sky.
gemstoneTurritella Jasper
A fossiliferous jasper packed with spiral snail shells, technically a silicified gastropod limestone from Wyoming.
sedimentary
Black Shale
Dark, organic-rich fine-grained sedimentary rock formed in oxygen-poor waters, often a source rock for oil and gas.
sedimentary
Sagenite Agate
A chalcedony agate filled with radiating needle-like mineral inclusions, prized for its starburst and spray patterns.
gemstoneRed Sandstone
Iron-stained sandstone whose red color comes from hematite coatings, formed in oxidizing desert, river, and coastal environments.
sedimentary