Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Slate
A fine-grained, low-grade metamorphic rock that splits into flat sheets along slaty cleavage, long used for roofing and flooring.
metamorphic
Basalt
A fine-grained, dark volcanic rock that erupts as fluid lava and forms most of the ocean floor and many lava plateaus.
igneous
Phyllite
A fine-grained foliated metamorphic rock between slate and schist, recognized by its silky silvery sheen and wavy, crinkled surfaces.
metamorphicLithographic Limestone
Extremely fine-grained, even-textured limestone famous for lithographic printing and for preserving exquisite fossils like Archaeopteryx.
sedimentary
Argillite
Hardened, fine-grained mudrock intermediate between shale and slate, dense and non-fissile, often carved into ornaments.
sedimentaryPipestone
A soft, fine-grained red metamorphosed claystone, sacred to many Native American peoples and carved into ceremonial pipes.
metamorphic
Siltstone
A fine-grained clastic rock of silt-sized grains, intermediate between sandstone and mudstone, with a gritty feel.
sedimentary
Ruin Marble
A fractured fine-grained limestone whose iron-stained crack networks form natural scenes resembling ruined cities and landscapes.
sedimentary
Novaculite
An extremely fine-grained, dense siliceous rock famous as Arkansas whetstone, prized for sharpening fine cutting tools.
sedimentary
Mudstone
A fine-grained sedimentary rock of compacted clay and silt that, unlike shale, breaks in blocks rather than thin layers.
sedimentary
Claystone
A very fine-grained sedimentary rock made mostly of clay minerals, smooth to the touch and lacking the gritty feel of siltstone.
sedimentary
Shale
The most common sedimentary rock, a fissile mudrock of compacted clay and silt that splits into thin layers.
sedimentary
Andesite
A fine-grained, intermediate volcanic rock common at subduction-zone volcanoes, between basalt and rhyolite in composition.
igneousAlabaster
A soft, fine-grained, translucent form of gypsum (or banded calcite) long prized as a carving and ornamental stone.
mineralCarrara Marble
A famous white to blue-grey Italian marble from Carrara, prized for centuries by sculptors and architects for its purity and fine grain.
metamorphic
Pele's Hair
Fine, golden, hair-like strands of basaltic volcanic glass spun from fluid lava droplets during eruptions, named for the Hawaiian volcano goddess.
igneous
Felsite
A general term for light-colored, fine-grained volcanic rocks rich in quartz and feldspar, like rhyolite.
igneous
Porcelanite
A hard, fine-grained siliceous rock with a dull porcelain-like texture, intermediate between soft diatomite and dense chert.
sedimentarySpiderweb Jasper
A jasper crossed by fine dark veins forming a spiderweb-like network, often a brecciated stone cemented by darker matrix.
mineral