rock identification

Rock IdentificationRock Identification

Learn Your Rocks

Rock ID Practice Test

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Quartz Sandstone

Garnet Mica Schist

Obsidian

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Learn Your RocksLearn Your Rocks

Gneiss

Obsidian

Pumice

Slate

Mica Schist

Conglomerate

Garnet Mica Schist

Quartz Sandstone

Fossillferous Limestone

Quartzite

Granite

Rhyolite

Diorite

Breccia

Shale

Basalt

Rock Salt

Agate

Marble

Coquina

Gabbro

Chert

Scoria

Andisite

Chalk

Select a rock to learn more about it.

Rock Review Practice Test

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GneissGneissA 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

ObsidianObsidian



Rock Type Igneous, Extrusive

Particle Size, Texture

Compact Glassy

Mineral Composition

Silica Rich

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.

PumicePumice





Compact, Fibrous, Glassy

Mineral Composition

Silica Rich

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.

ConglomerateConglomerate



Rock Type Sedimentary


Gravel and smaller sized particles

Mineral Composition

Varied, heterogeneous mixture

A rock consisting of heterogeneous pebbles and gravel embeded in a cement made of clay, silt and sand particles.

Garnet Mica SchistGarnet Mica Schist





Leaf like foliation

Mineral Composition

Muscovite and Garnet

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.

Quartz SandstoneQuartz Sandstone





Sand size, crystalline

Mineral Composition

Quartz

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.

Fossillferous LimestoneFossillferous Limestone

Acid Test Reacts with Acid

Scratch Test Will not scratch glass



Sand size, smooth

Mineral Composition

Calcite

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.

QuartziteQuartzite





Non-foliated, Crystalline

Mineral Composition

Quartz

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.

GraniteGranite



Rock Type Igneous, Intrusive


Course grained, Crystalline

Mineral Composition

Quartz, Potassium Feldspar

A common hard igneous rock consisting mostly of quartz, orthoclase or microcline, and mica. Granite is used for building and paving.

RhyoliteRhyolite





Fine grained

Mineral Composition

Light color indicates a felsic composition

A volcanic rock similar to granite in composite that cooled much more rapidly than granite that usually exhibits flow lines. Color may vary.

DioriteDiorite





Course grained Crystalline

Mineral Composition

Amphibole, Intermediate Feldspar

Any of various intermediate to dark granite textured crystalline rocks rich in plagioclase.

BrecciaBreccia





Gravel size to smaller angular broken rock

Mineral Composition

Large variety

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.

ShaleShale





Clay sized particles

Mineral Composition

Clay minerals

A rock composed of fine grained layers of sediment. Shale is often embedded with Fossils of plant and animal material.

SlateSlate




Particle Size, Texture Foliated, fairly smooth

Mineral Composition

Clay minerals

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. .

BasaltBasalt





Fine grained Crystalline

Mineral Composition

Amphibole, pyroxene Intermediate Feldspar

A hard dense igneous rock composed chiefly of plagioclase, pyroxeneAnd olivine and often having a glassy appearance.

Rock SaltRock Salt



Rock TypeChemical Sedimentary, Evaporite


Solid mass of inter-grown crystals.

Mineral Composition

Halite, trace minerals

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.

AgateAgate



Rock Type Chemical Sedimentary


Micro-crystalline

Mineral Composition

Quartz, Trace minerals

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.

MarbleMarble

Acid Test Reacts with acid




Non-foliated Crystalline

Mineral Composition

Calcite, Trace Elements

A metamorphic rock formed from limestone or dolomite. IrregularColoring is often present because of trace elements in the marble.

Marble is often used for sculpting and as a building material.

Mica SchistMica Schist




Particle Size, Texture Foliated

Mineral Composition

Muscovite, Biotite

Medium to course grained metamorphic rocks composed of laminated often flaky parallel layers of micaceous rock.

CoquinaCoquina



Rock Type Sedimentary, Organic


Gravel size and smaller shell material

Mineral Composition

Calcite, Calcium Carbonate

Cream to pale brown, porous, poorly cemented organic limestone composed of marine or

freshwater mollusk shells and shell fragments.

ChalkChalk



Rock Type Sedimentary, Organic


Fine particles, very soft

Mineral Composition

Calcium Carbonate, Calcite, Trace minerals

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.

GabbroGabbro





Course grained, Crystalline

Mineral Composition

Calcic plagioclase, pyroxene

A course grained igneous rock composed chiefly of calcic plagioclase and pyroxene

ChertChert





Dense & smooth Fine Particles

Mineral Composition

Chalcedonic, opaline silica, color varies

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.

ScoriaScoria





Rough grained, fine crystalline

Mineral Composition

Plagioclase feldspar, pyroxine

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.

AndesiteAndesite



Rock TypeIgneous, Extrusive or Dikes & sills Intrusive


Fine grained, Crystalline

Mineral Composition

Plagioclase, Feldspar, amphibole, Pyroxene, Biotite

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.

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