Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Lamprophyre
A dark, mineral-rich dike rock with abundant mica or amphibole phenocrysts set in a fine groundmass, often associated with gold and diamonds.
igneous
Kentucky Agate
The official state rock of Kentucky, a banded agate famous for striking deep-red and black fortification patterns.
gemstone
Cherry Creek Jasper
A landscape-patterned Chinese jasper prized for warm cherry-red, cream, and green bands resembling painted scenery.
mineral
Montana Moss Agate
A translucent chalcedony from Montana filled with black and red dendritic inclusions that look like moss, ferns, or scenic landscapes.
gemstone
Sölvsbergite
A fine-grained, sodic alkali-feldspar dike rock with trachytic texture, the silica-saturated counterpart to tinguaite.
igneous
Shonkinite
A dark, mafic potassic alkaline rock rich in augite with alkali feldspar and often nepheline, classically forming the base of layered sills.
igneous
Bostonite
A fine-grained, feldspar-rich dike rock with a trachytic texture, essentially a hypabyssal equivalent of trachyte or syenite.
igneous
Riband Agate
A banded chalcedony with straight, ribbon-like parallel layers, often cut across the bands for striking striped cabochons.
gemstone
Wonderstone
A banded rhyolitic volcanic rock with swirling tan, red, and yellow iron-oxide layers prized as a decorative picture stone.
igneous
Stripe Obsidian
Obsidian crossed by parallel flow bands of differing color, formed as layers of lava with slightly different compositions froze into glass.
igneous
Ribbon Jasper
A banded jasper showing parallel ribbon-like stripes of contrasting color formed by layered silica and mineral deposition.
mineral
Sardonyx
A banded chalcedony combining reddish-brown sard with white or black onyx layers, prized since antiquity for carved cameos.
gemstone
Cipollino Marble
A green-and-white banded metamorphic marble whose wavy mica layers resemble the rings of a sliced onion.
metamorphic
Zebra Agate
A banded chalcedony agate with bold alternating dark and light stripes resembling zebra markings, sometimes color-enhanced.
gemstone
Midnight Lace Obsidian
A black volcanic glass threaded with delicate grey, swirling lace-like bands of flow lines that show beautifully when polished.
igneous
Mahogany Obsidian
A natural volcanic glass with rich brown and black mahogany-like swirls created by iron oxide inclusions.
igneous
Lace Obsidian
Black volcanic glass laced with delicate web-like veins of contrasting color, formed by flow banding and fine crystallization.
igneous
Jaspillite
A banded, metamorphosed iron formation in which bright red jasper alternates with silvery hematite or magnetite layers.
metamorphic
Palagonite
A yellow-brown alteration material formed when basaltic volcanic glass reacts with water, common in hydrovolcanic tuffs and pillow lavas.
igneous
Norite
A coarse-grained mafic plutonic rock similar to gabbro but with orthopyroxene as the dominant pyroxene instead of clinopyroxene.
igneous
Variolite
A mafic volcanic rock speckled with pale spherical 'varioles,' typically formed in rapidly chilled basaltic pillow lavas.
igneous
Nordmarkite
A light-colored alkali quartz syenite dominated by perthitic feldspar with minor quartz, from the Oslo igneous province of Norway.
igneous
Lake 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