Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Onyx Marble
Translucent banded calcium-carbonate stone deposited in caves and springs, prized for ornamental carvings despite its softness.
sedimentary
Multicolor Tourmaline
Tourmaline crystals displaying two or more distinct colors at once, including the famous pink-and-green watermelon variety.
gemstone
Metaconglomerate
A conglomerate altered by heat and pressure, often with its rounded pebbles stretched and flattened into elongated lenses.
metamorphic
Metabasalt
Basalt that has been metamorphosed, developing new minerals like chlorite, actinolite, and epidote that give it a greenish color.
metamorphic
Majorite
An ultra-high-pressure garnet with silicon in the octahedral site, formed in the deep mantle transition zone and in shocked meteorites.
mineral
Lithographic Limestone
Extremely fine-grained, even-textured limestone famous for lithographic printing and for preserving exquisite fossils like Archaeopteryx.
sedimentary
Latite
The fine-grained volcanic equivalent of monzonite, an intermediate lava with nearly equal feldspars and little free quartz.
igneous
Limburgite
A dark, glass-rich volcanic rock of olivine and augite phenocrysts set in a feldspar-free glassy groundmass, named from the Kaiserstuhl region.
igneous
Laguna Agate
A highly prized Mexican fortification agate from Chihuahua, famed for vivid red and orange banding with tight, intricate patterns.
gemstone
Lake Michigan Agate
Glacially deposited banded agates found along Lake Michigan beaches, small waterworn pebbles with concentric red and grey banding.
gemstone
Landscape Agate
A translucent chalcedony agate whose mineral inclusions form miniature scenes resembling mountains, trees, deserts, and skies.
gemstone
Kerimasite
A zirconium-rich garnet related to kimzeyite, formed in carbonatites and skarns, named after the Kerimasi volcano in Tanzania.
mineral
Jadeite
The rarer and more valuable of the two jade minerals, prized for its translucent emerald-green 'imperial' color and extreme toughness.
gemstone
Jade
A tough, prized ornamental gem that is actually two distinct minerals, jadeite and nephrite, revered for millennia in many cultures.
gemstone
Iceland Spar
A transparent, optical-grade variety of calcite famous for strong double refraction, splitting images and light into two rays.
mineral
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
Cosmic Obsidian
A trade name for sheen obsidian whose swirling, patchy iridescence resembles galaxies and nebulae against deep black glass.
igneous
Buddingtonite
A rare ammonium feldspar formed by hydrothermal alteration, in which ammonium ions replace potassium, and a useful exploration indicator.
mineral
Albite
The sodium end-member of the plagioclase feldspar series, a common white rock-forming mineral and parent of peristerite moonstone.
mineral
Bixbyite
A black metallic manganese iron oxide famous for sharp cubic crystals, classically found with red beryl and topaz in Utah rhyolite.
mineral
Tinguaite
A fine-grained green phonolitic dike rock rich in nepheline and aegirine, the hypabyssal equivalent of phonolite.
igneous
Snake Skin Agate
A chalcedony with a distinctive scaly, reptile-skin surface texture, typically in pale tan, pink, and gray tones.
gemstone
Leopard Opal
A patterned common opal with mottled, leopard-like spots and blotches, prized as an ornamental and cabochon stone.
gemstone
Calcilutite
A very fine-grained, mud-sized limestone formed from carbonate mud, smooth and dense with conchoidal fracture.
sedimentary