| IGNEOUS ROCK PICTURES (About Igneous Rocks) |
| Aa—Jagged form of basalt lava. |
| Andesite—The typical intermediate-silica arc lava. |
| Anorthosite—Rare plutonic rock of straight plagioclase feldspar. |
| Basalt—Widespread low-silica lava, the most common extrusive rock. (Picture Gallery) |
| Diorite—Plutonic rock between granite and gabbro. |
| Dunite—Plutonic rock made of straight olivine. |
| Felsite—Volcanic rock of the same composition as granite. |
| Gabbro—Coarse-crystaled plutonic version of basalt. |
| Granite—Familiar rock making up the bulk of the continents. (Picture Gallery) |
| Granodiorite—Plutonic rock like diorite but also with quartz. |
| Komatiite—Rare and ancient ultramafic lava. |
| Lapillistone—Volcanic rock formed of little ash balls. |
| Latite—Dark, low-quartz lava, extrusive version of monzonite. |
| Obsidian—High-silica volcanic glass. (Picture Gallery) |
| Pahoehoe—Smooth-skinned flows of basalt lava. |
| Pegmatite—Igneous rock with very large crystals. |
| Peridotite—Dark, dense, rarely seen rock from the Earth's mantle. (Picture Gallery) |
| Perlite—Lightweight high-silica volcanic rock. |
| Porphyry—Igneous rock with large mineral grains in a fine matrix. |
| Pumice—Light-colored, frothy high-silica volcanic rock. |
| Pyroxenite—Uncommon ultramafic rock from the deep sea crust. |
| Quartz Monzonite—Just like granite, except it's short on quartz. |
| Rhyolite—High-silica white or red lava. |
| Scoria—Dark, frothy low-silica volcanic rock. |
| Syenite—Plutonic, alkalic granitic rock without quartz. |
| Tonalite—Plutonic, felsic granitic rock without alkali feldspar. |
| Tuff—Rock made from volcanic ash. |
Special Galleries: Igneous Rock Classification Diagrams, Igneous Rock Textures, Phenocrysts, Pillow Lavas, Volcanic Rocks |
SEDIMENTARY ROCK PICTURES (About Sedimentary Rocks) |
| Agate—Semiprecious chert of infinite variety. |
| Alabaster—White gypsum stone long prized for sculpture. |
| Arkose—Raw sandstone made from eroded granite. |
| Asphalt—Natural tar from petroleum seeps. |
| Banded Iron Formation—Extremely ancient "tiger iron. |
| Breccia—Rock made from broken rocks. |
| Chert—Common silica-rich rock type with much variety. |
| Coal—The original fossil fuel. |
| Conglomerate—Rocks made with extra-big grains. (Picture Gallery) |
| Coquina—Limestone composed of shell fragments. (Picture Gallery) |
| Diamictite—Rock made of poorly sorted land sediment. |
| Dolomite—Carbonate rock, a near-twin of limestone. |
| Graywacke—Impure sandstone, also called wacke. |
| Gypsum Rock—Soft rock formed early in evaporating waters. |
| Limestone—Rock composed of calcite, Earth's greatest store of carbon. (Picture Gallery) |
| Peat—Brown, vegetative precursor to coal. |
| Rock Salt—Massive halite, the only edible stone. |
| Sandstone—Where sand goes to and comes from. |
| Shale—Rock made from mud and clay. |
| Siltstone—Made from sediment finer than sand. |
| Travertine—Type of limestone precipitated in springs. (Picture Gallery) |
Special Galleries: More Sedimentary Rocks, Sedimentary Rock Classification Diagrams, Sedimentary Structures |
METAMORPHIC ROCK PICTURES (About Metamorphic Rocks) |
| Amphibolite—High-grade rock, typically a hornblende schist. |
| Blueschist—Rock made by high-grade metamorphism in subduction zones. |
| Cataclasite—Ground-up rock found in fault zones. |
| Eclogite—The most extreme metamorphic rock you can find. (Picture Gallery) |
| Gneiss—Banded and tough, it forms the lower crust. |
| Greenschist—Rock made by low-grade metamorphism of various rock types. |
| Greenstone—Dark rock made by metamorphism of basalt. |
| Hornfels—Tough and fine-grained, it forms where igneous rocks cook it. |
| Marble—Coarse-grained, metamorphosed limestone. |
| Migmatite—Swirly-banded rock produced by extreme metamorphism. |
| Mylonite—Milled and melted rock from deep in fault zones. |
| Phyllite—Shiny, colorful metamorphosed slate. (Picture Gallery) |
| Quartzite—Rugged metamorphosed sandstone. |
| Schist—Finely striped rock made by metamorphism of mudstones. |
| Serpentinite—Green, scaly metamorphosed ocean crust. (Picture Gallery) |
| Slate—Platy rock made by early metamorphism of shale. (Picture Gallery) |
| Soapstone—Soft and carvable, hydrothermally altered lava. |
Special Galleries: More Metamorphic Rocks, Porphyroblasts |
OTHER ROCKS |
| Artificial Rocks Gallery—Brick, concrete and other geotechnical products. |
| Concretions Gallery—Odd sedimentary lumps often mistaken for fossils. |
| Fulgurite Gallery—Lightning striking the ground makes these curious objects. |
| Geode Gallery—Sedimentary features with hollow, glittering interiors. |
| Meteorite Gallery—Various stones from interplanetary space. |
| Official State Rocks of the United States—Twenty-five states have one. |
| Pet Rocks—Favorite stones from me and other contributors. |
| Thunder Egg—Solid, agate-filled lump found in certain volcanic lands. |
You may also want to use the Rock Type Identification Key.
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