Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Pitchstone
A dull, resinous volcanic glass similar to obsidian but with higher water content and a waxy pitch-like luster.
igneous
Greenstone
A general field term for green, low-grade metamorphosed basaltic rocks colored by chlorite, epidote, and actinolite.
metamorphic
Diabase
A tough, dark, medium-grained igneous rock with the composition of basalt, common in dikes and sills.
igneous
Black Onyx
A solid jet-black chalcedony, usually a dyed and treated agate, prized for sleek polished beads, cabochons, and intaglios.
gemstone
Pumice
A frothy, lightweight volcanic glass so full of gas bubbles that it can float on water.
igneous
Rhyolite
A fine-grained, silica-rich volcanic rock that is the extrusive equivalent of granite, often pale, banded, or flow-textured.
igneous
Blue Obsidian
Blue-colored volcanic glass; genuine natural blue obsidian is very rare, while much blue obsidian on the market is manufactured glass.
crystal
Apricot Agate
A soft peachy-orange variety of banded chalcedony, naturally iron-tinted or dyed, popular for warm-toned beads and jewelry.
gemstone
Boninite
A rare high-magnesium andesite formed in young subduction zones, named for Japan's Bonin Islands.
igneous
Phonolite
A silica-poor volcanic rock of alkali feldspar and feldspathoids that rings when struck, hence 'clinkstone.'
igneous
Gondite
A metamorphic rock made chiefly of manganese-rich spessartine garnet and quartz, formed from ancient manganese-bearing sediments.
metamorphic
Soapstone
A soft, talc-rich metamorphic rock with a soapy feel, easily carved and highly heat-resistant for cookware and sculpture.
metamorphic
Black Agate
A deep black variety of banded chalcedony, often closely related to or treated like onyx, used for jewelry and carvings.
gemstone
Mariposite
A green, gold-associated metamorphic rock made of chrome-rich mica and quartz, named for Mariposa County in California's gold country.
metamorphic
Obsidian
A glassy, jet-black volcanic rock formed when lava cools too fast to crystallize, prized for razor-sharp conchoidal edges.
igneous
Epidosite
A hard, pistachio-green rock composed mainly of epidote and quartz, formed by hydrothermal alteration of mafic rocks.
metamorphic
Pseudotachylite
A dark, glassy rock formed when frictional heat from fault movement or impact melts rock along narrow veins.
metamorphic
Dragon Vein Agate
A treated chalcedony with a network of crackled veins, usually heated and dyed in vivid colors for affordable, eye-catching beads.
gemstone
Quartzite
An extremely hard metamorphic rock formed from sandstone, made of fused quartz grains that break across rather than between the grains.
metamorphic
Black Obsidian
Jet-black natural volcanic glass formed by rapidly cooled lava, prized for its glassy luster and razor-sharp conchoidal fracture.
igneous
Chert
A hard, fine-grained sedimentary silica rock that breaks with sharp conchoidal edges, prized by ancient toolmakers.
sedimentary
Monzonite
An intermediate plutonic rock with nearly equal alkali and plagioclase feldspar and very little quartz, sitting between diorite and syenite.
igneous
Zebra Agate
A banded chalcedony agate with bold alternating dark and light stripes resembling zebra markings, sometimes color-enhanced.
gemstone
Latite
The fine-grained volcanic equivalent of monzonite, an intermediate lava with nearly equal feldspars and little free quartz.
igneous