Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Mahogany Obsidian
A natural volcanic glass with rich brown and black mahogany-like swirls created by iron oxide inclusions.
igneous
Blue Lace Agate
A soft sky-blue banded chalcedony prized for its delicate, lace-like white and blue swirling patterns.
gemstone
Black Agate
A deep black variety of banded chalcedony, often closely related to or treated like onyx, used for jewelry and carvings.
gemstoneLace Obsidian
Black volcanic glass laced with delicate web-like veins of contrasting color, formed by flow banding and fine crystallization.
igneousMidnight Lace Obsidian
A black volcanic glass threaded with delicate grey, swirling lace-like bands of flow lines that show beautifully when polished.
igneous
Lake Superior Agate
A glacier-transported banded agate from the Lake Superior region, colored by iron into rich reds and oranges, and Minnesota's state gemstone.
gemstone
Chalcedony
A waxy, translucent microcrystalline form of quartz that serves as the parent group for agate, jasper, carnelian, and onyx.
mineralBamboo Agate
An agate whose layered, segmented banding resembles the jointed stalks and leaves of bamboo.
gemstone
Rhyolite
A fine-grained, silica-rich volcanic rock that is the extrusive equivalent of granite, often pale, banded, or flow-textured.
igneous
Chert
A hard, fine-grained sedimentary silica rock that breaks with sharp conchoidal edges, prized by ancient toolmakers.
sedimentaryLake Huron Agate
Glacially transported banded agates found along Lake Huron's shores, typically small, frosted pebbles with red-orange iron banding.
gemstone
Lake Michigan Agate
Glacially deposited banded agates found along Lake Michigan beaches, small waterworn pebbles with concentric red and grey banding.
gemstone
Unakite
An altered granite mottled pink and green from feldspar and epidote, popular as a tough, colorful ornamental rock.
metamorphicCarey Plume Agate
A prized plume agate from near Carey, Idaho, showing red, pink and black feathery plumes floating in translucent chalcedony.
gemstone
Turritella Agate
A brown fossiliferous chalcedony packed with spiral freshwater snail shells, technically agatized fossil rock from Wyoming.
sedimentarySwazi Lace Agate
A swirling, intricately banded lace agate from Eswatini (Swaziland) in soft greys, blues and lavenders with delicate folded patterns.
gemstone
Mexican Lace Agate
A vividly swirling banded agate from northern Mexico with intricate looping patterns in warm reds, golds and creams.
gemstoneAlabaster
A soft, fine-grained, translucent form of gypsum (or banded calcite) long prized as a carving and ornamental stone.
mineralOwyhee Blue Agate
A soft sky-blue chalcedony from the Owyhee region of Oregon and Idaho, prized for its calming, opaque powder-blue color.
gemstonePigeon Blood Agate
A richly colored red banded agate prized by lapidaries for its deep crimson-to-brown tones reminiscent of pigeon's blood.
gemstone
Ruin Agate
A fractured and re-cemented agate whose angular broken bands resemble crumbling walls and ruined cityscapes when polished.
gemstone
Rainbow Obsidian
A black volcanic glass that reveals concentric rainbow bands of color when cut and polished against the light.
igneous
Green Agate
A green-hued banded chalcedony, ranging from natural soft greens to brightly dyed commercial stones.
gemstone
Fairburn Agate
The state gemstone of South Dakota, a rare fortification agate known for tight, holly-leaf concentric banding.
gemstone