Rock Identification Learn Your Rocks Rock ID Practice Test Click Here to take a practice Rock ID Test Click Here to Learn more about a specific rock. Learn Your Rocks Rock ID Practice Test Quartz Sandstone Obsidian Garnet Mica Schist

Select a rock to learn more about it. Learn Your Rocks Select a rock to learn more about it. Gneiss Granite Conglomerate Obsidian Rhyolite Garnet Mica Schist Pumice Quartzite Quartz Sandstone Gabbro Breccia Fossillferous Limestone Coquina Andisite Mica Schist Rock Salt Scoria Marble Basalt Diorite Chalk Slate Shale Chert Agate

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Gneiss A banded or foliated rock usually made from some type of granite. Color will vary considerably based on the amount and kind of minerals found in the original granitic rock. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Metamorphic Particle Size, Texture Foliated, Crystalline Mineral Composition Amphibole, Feldspar, Quartz

Obsidian A black, banded, or spotted hard volcanic glass that is formed by very rapid cooling of lava. Historically, many different peoples have used the glass rock to fashion sharp tools such as knives and spear points. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Igneous, Extrusive Particle Size, Texture Compact Glassy Mineral Composition Silica Rich

Pumice A light, porous, fibrous, glassy lava, used in solid form as an abrasive and in powdered form as a polish and an abrasive. Sometimes it’s density is low enough that it will float in water. Pumice is lava that had a lot of gases in it and cooled quickly on the surface of the earth. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Igneous, Extrusive Particle Size, Texture Compact, Fibrous, Glassy Mineral Composition Silica Rich

Conglomerate A rock consisting of heterogeneous pebbles and gravel embeded in a cement made of clay, silt and sand particles. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Sedimentary Particle Size, Texture Gravel and smaller sized particles Mineral Composition Varied, heterogeneous mixture

Garnet Mica Schist A mica rich leafed foliated rock that is formed under great heat and pressure. Garnet crystals have developed on the rock as it was being formed. The rock may be silvery white to various shades of grey and exhibit yellow to brown tones depending on the oxidation of the various minerals in the rock sample. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Metamorphic Particle Size, Texture Leaf like foliation Mineral Composition Muscovite and Garnet

Quartz Sandstone A rock formed by the consolidation and compaction of generally rounded sand particles cemented together by clay, silt, or silica particles. The color will vary based on the trace elements present in the quartz sand particles. The rock may show color banding and cross-bedding patterns. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Sedimentary Particle Size, Texture Sand size, crystalline Mineral Composition Quartz

Fossillferous Limestone A common sedimentary rock consisting mostly of calcium carbonate which contains fossils of various fresh and or salt water shell fish. It is used as a building stone, and in the manufacture of lime, carbon dioxide, and cement. Acid Test Reacts with Acid Scratch Test Will not scratch glass Rock Type Sedimentary Particle Size, Texture Sand size, smooth Mineral Composition Calcite

Quartzite A rock formed by the metamorphism of quartz sandstone. Quartz is a very hard mineral composed of silica. Quartzite can be a wide variety of colors depending on what elements are present in small amounts. Quartzite is very prevalent and is found worldwide. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Metamorphic Particle Size, Texture Non-foliated, Crystalline Mineral Composition Quartz

Granite A common hard igneous rock consisting mostly of quartz, orthoclase or microcline, and mica. Granite is used for building and paving. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Igneous, Intrusive Particle Size, Texture Course grained, Crystalline Mineral Composition Quartz, Potassium Feldspar

Rhyolite A volcanic rock similar to granite in composite that cooled much more rapidly than granite that usually exhibits flow lines. Color may vary. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Igneous, Extrusive Particle Size, Texture Fine grained Mineral Composition Light color indicates a felsic composition

Any of various intermediate to dark granite textured crystalline rocks Diorite Any of various intermediate to dark granite textured crystalline rocks rich in plagioclase. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Igneous, Intrusive Particle Size, Texture Course grained Crystalline Mineral Composition Amphibole, Intermediate Feldspar

Breccia Rock composed of sharp angled fragments embedded in a fine grained matrix of sand, silt, and clay particles. The sharp edged rock generally are from a talus slope. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Sedimentary Particle Size, Texture Gravel size to smaller angular broken rock Mineral Composition Large variety

Shale A rock composed of fine grained layers of sediment. Shale is often embedded with Fossils of plant and animal material. Acid Test No Reaction Scratch Test Will not scratch glass Rock Type Sedimentary Particle Size, Texture Clay sized particles Mineral Composition Clay minerals

Slate A fine grained, grayish metamorphic rock that splits into smooth surfaced layers. It has been used for blackboards, roofing material and paving stones. It is generally made of metamorphosed shale. . Acid Test No Reaction Scratch Test Will not scratch glass Rock Type Metamorphic Particle Size, Texture Foliated, fairly smooth Mineral Composition Clay minerals

Basalt A hard dense igneous rock composed chiefly of plagioclase, pyroxene And olivine and often having a glassy appearance. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Igneous, Extrusive Particle Size, Texture Fine grained Crystalline Mineral Composition Amphibole, pyroxene Intermediate Feldspar

A rock containing mostly halite, table salt, as its main constituent. Rock Salt A rock containing mostly halite, table salt, as its main constituent. The color of the rock salt can vary depending on the trace mineral present In the sample. This is an evaporite in that it is the salt left after the salt has evaporated from saltwater. It is very tasty. Acid Test No Reaction Scratch Test Will not scratch glass Chemical Sedimentary, Evaporite Rock Type Particle Size, Texture Solid mass of inter-grown crystals. Mineral Composition Halite, trace minerals

Agate A fine grained variety of quartz with colored banding. The colored banding results from the presence of various trace elements. Agates have been cut and polished to use for jewelry for some time. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Chemical Sedimentary Particle Size, Texture Micro-crystalline Mineral Composition Quartz, Trace minerals

Marble A metamorphic rock formed from limestone or dolomite. Irregular Coloring is often present because of trace elements in the marble. Marble is often used for sculpting and as a building material. Acid Test Reacts with acid Scratch Test Will scratch glass Rock Type Metamorphic Particle Size, Texture Non-foliated Crystalline Mineral Composition Calcite, Trace Elements

Mica Schist Medium to course grained metamorphic rocks composed of laminated often flaky parallel layers of micaceous rock. Acid Test No Reaction Scratch Test Will not scratch glass Rock Type Metamorphic Particle Size, Texture Foliated Mineral Composition Muscovite, Biotite

Coquina Cream to pale brown, porous, poorly cemented organic limestone composed of marine or freshwater mollusk shells and shell fragments. Acid Test Reacts with acid Scratch Test Will not scratch glass Rock Type Sedimentary, Organic Particle Size, Texture Gravel size and smaller shell material Mineral Composition Calcite, Calcium Carbonate

Chalk A soft compact calcite with varying amounts of quartz, silica, feldspar, and other mineral impurities. Chalk is generally grey-white to yellow- White in color. It is derived chiefly from fossil sea shells. Acid Test Reacts with acid Scratch Test Will not scratch glass Rock Type Sedimentary, Organic Particle Size, Texture Fine particles, very soft Mineral Composition Calcium Carbonate, Calcite, Trace minerals

Gabbro A course grained igneous rock composed chiefly of calcic plagioclase and pyroxene Acid Test No Reaction Scratch Test Will scratch glass Rock Type Igneous, Intrusive Particle Size, Texture Course grained, Crystalline Mineral Composition Calcic plagioclase, pyroxene

Chert A siliceous rock of chalcedonic or opaline silica occurring in limestone. Color may vary considerably. White to grey to black sample will probably be flint. Yellow green brown and red will probably be Jasper. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Sedimentary Particle Size, Texture Dense & smooth Fine Particles Mineral Composition Chalcedonic, opaline silica, color varies

Scoria A volcanic rock having vesicular structure due to the gases that are moving through the lava as it cools and solidifies. Scoria has basaltic composition. It can vary in color from dark grey to black or dark brown to reddish rust. Acid Test No Reaction Scratch Test Will scratch glass Rock Type Igneous, Extrusive Particle Size, Texture Rough grained, fine crystalline Mineral Composition Plagioclase feldspar, pyroxine

Andesite A A white to grey igneous rock that usually forms on the surface in lava flows (extrusive) or sometimes as dikes and sills (intrusive) under. Acid Test No Reaction Scratch Test Will scratch glass Igneous, Extrusive or Dikes & sills Intrusive Rock Type Particle Size, Texture Fine grained, Crystalline Plagioclase, Feldspar, amphibole, Pyroxene, Biotite Mineral Composition