Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Stripe Obsidian
Obsidian crossed by parallel flow bands of differing color, formed as layers of lava with slightly different compositions froze into glass.
igneousFlame Obsidian
Black volcanic glass that flashes flame-like bands of iridescent color when light strikes aligned nanoscale inclusions.
igneousSmoky Obsidian
Translucent smoky-gray obsidian that transmits a hazy light, intermediate between clear and fully black volcanic glass.
igneous
Metarhyolite
Rhyolite that has been metamorphosed, recrystallizing its silica-rich volcanic material into a tougher felsic metamorphic rock.
metamorphic
Gabbro
A coarse-grained, dark mafic intrusive rock that is the plutonic equivalent of basalt, rich in plagioclase and pyroxene.
igneous
Landscape Agate
A translucent chalcedony agate whose mineral inclusions form miniature scenes resembling mountains, trees, deserts, and skies.
gemstone
Gray Obsidian
Obsidian in gray tones, often semi-translucent, colored by light scattering and minor inclusions within the volcanic glass.
igneousBronze Sheen Obsidian
Black volcanic glass with a warm bronze or coppery sheen produced by light reflecting off aligned microscopic inclusions.
igneous
Clear Obsidian
An unusually pure, transparent-to-translucent obsidian with few inclusions; truly water-clear specimens are rare in nature.
igneous
Granulite
A high-grade metamorphic rock formed in the deep, hot crust, marked by anhydrous minerals like pyroxene and garnet.
metamorphicGreen Sheen Obsidian
Black volcanic glass that flashes a green sheen at certain angles due to light interference off aligned microscopic inclusions.
igneousOrange Obsidian
Obsidian colored orange by iron oxide inclusions; vivid uniform orange material is frequently manufactured glass rather than volcanic.
igneousPurple Sheen Obsidian
Black volcanic glass that reveals a soft purple-to-violet sheen at certain angles, caused by light interference off aligned inclusions.
igneousPink Lady Obsidian
Obsidian showing a pink-to-rose sheen or hue; natural examples get color from interference effects, while uniform pink material is often manufactured glass.
igneous
Lamproite
A rare ultrapotassic, magnesium-rich volcanic rock from deep in the mantle, famous as the diamond host at Argyle in Australia.
igneous
Red Obsidian
Volcanic glass tinted red by fine iron-oxide inclusions, often blended with black to form mahogany-patterned obsidian.
crystalPolychrome Jasper
A warm earth-toned jasper from Madagascar in flowing reds, oranges and golds, also called desert jasper, discovered in the early 2000s.
gemstone
Mookaite
A vivid Australian jasper-like silica stone in earthy reds, yellows, and purples, formed from silicified radiolarian sediment.
mineral
Buergerite
A rare iron-rich (ferric) species of the tourmaline group, dark brown to bronze-black, named after crystallographer Martin Buerger.
mineralCloud Agate
A chalcedony agate with soft, billowing cloud-like masses of gray and white suspended in a translucent body.
gemstone
Sapropel
A soft, dark, organic-rich mud deposited in stagnant, oxygen-poor water, a key precursor to oil and gas source rocks.
sedimentary
Cathedral Agate
A banded agate whose internal structures resemble cathedral spires, arches, or a city skyline of towers and pinnacles.
gemstone
Shale
The most common sedimentary rock, a fissile mudrock of compacted clay and silt that splits into thin layers.
sedimentary
Guano
An accumulated deposit of bird or bat droppings rich in nitrogen and phosphate, historically a prized natural fertilizer.
sedimentary