Rock (Geology) - Wikipedia, The Free Encyclopedia

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Balanced Rockstands in Garden of

the Gods park in Colorado Springs,CO.

Rock (geology)From Wikipedia, the free encyclopedia

"Rocks", "Stone", and"Thestone" redirect here. For other uses, see Rock (disambiguation), Stone

(disambiguation), and The Stone (disambiguation), respectively.

In geology, a rockis a naturally occurring solid aggregate of one or more

minerals or mineraloids. For example, the common rock granite is acombination of the quartz, feldspar and biotite minerals. The Earth's outer

solid layer, the lithosphere, is made of rock.

Rocks have been used by mankind throughout history. From the Stone

Age rocks have been used for tools. The minerals and metals we find in

rocks have been essential to human civilization.[1]

Three major groups of rocks are defined: igneous, sedimentary, and

metamorphic. The scientific study of rocks is called petrology, which is

an essential component of geology.

Contents

1 Classification

1.1 Igneous

1.2 Sedimentary

1.3 Metamorphic

2 Human use2.1 Mining

3 See also

4 References

5 External links

Classification

See also: Formation of rocks

At a granular level, rocks are composed of grains of minerals, which, in turn, are homogeneous solids formed from

a chemical compound that is arranged in an orderly manner. The aggregate minerals forming the rock are held

together by chemical bonds. The types and abundance of minerals in a rock are determined by the manner in whic

the rock was formed. Many rocks contain silica (SiO2); a compound of silicon and oxygen that forms 74.3% of th

Earth's crust. This material forms crystals with other compounds in the rock. The proportion of silica in rocks and

minerals is a major factor in determining their name and properties.[2]
http://en.wikipedia.org/wiki/Crystalhttp://en.wikipedia.org/wiki/Silicon_dioxidehttp://en.wikipedia.org/wiki/Chemical_compoundhttp://en.wikipedia.org/wiki/Chemical_compoundhttp://en.wikipedia.org/wiki/Chemical_compoundhttp://en.wikipedia.org/wiki/Aggregate_%28composite%29http://en.wikipedia.org/wiki/Formation_of_rockshttp://en.wikipedia.org/wiki/Metamorphic_rockhttp://en.wikipedia.org/wiki/Stone_Agehttp://en.wikipedia.org/wiki/Stone_Agehttp://en.wikipedia.org/wiki/Quartzhttp://en.wikipedia.org/wiki/Stone_%28disambiguation%29http://en.wikipedia.org/wiki/Crystalhttp://en.wikipedia.org/wiki/Silicon_dioxidehttp://en.wikipedia.org/wiki/Chemical_bondhttp://en.wikipedia.org/wiki/Aggregate_%28composite%29http://en.wikipedia.org/wiki/Chemical_compoundhttp://en.wikipedia.org/wiki/Homogeneity_and_heterogeneityhttp://en.wikipedia.org/wiki/Formation_of_rockshttp://en.wikipedia.org/wiki/Petrologyhttp://en.wikipedia.org/wiki/Metamorphic_rockhttp://en.wikipedia.org/wiki/Sedimentaryhttp://en.wikipedia.org/wiki/Igneoushttp://en.wikipedia.org/wiki/Stone_Agehttp://en.wikipedia.org/wiki/Lithospherehttp://en.wikipedia.org/wiki/Biotitehttp://en.wikipedia.org/wiki/Feldsparhttp://en.wikipedia.org/wiki/Quartzhttp://en.wikipedia.org/wiki/Granitehttp://en.wikipedia.org/wiki/Mineraloidhttp://en.wikipedia.org/wiki/Mineralhttp://en.wikipedia.org/wiki/Geologyhttp://en.wikipedia.org/wiki/The_Stone_%28disambiguation%29http://en.wikipedia.org/wiki/Stone_%28disambiguation%29http://en.wikipedia.org/wiki/Rock_%28disambiguation%29http://en.wikipedia.org/wiki/Colorado_Springs,_COhttp://en.wikipedia.org/wiki/Garden_of_the_Godshttp://en.wikipedia.org/wiki/File:Balanced_Rock.jpg


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Rock outcrop along a mountain creek

near Oros, Costa Rica.

Sample of igneous gabbro

Rocks are geologically classified according to characteristics such as mineral and chemical composition,

permeability, the texture of the constituent particles, and particle size. These physical properties are the end result

the processes that formed the rocks.[3] Over the course of time, rocks can transform from one type into another, a

described by the geological model called the rock cycle. These events produce three general classes of rock:

igneous, sedimentary, and metamorphic.

The three classes of rocks are subdivided into many groups. However, there are no hard and fast boundaries

between allied rocks. By increase or decrease in the proportions of their constituent minerals they pass by every

gradation into one another, the distinctive structures also of one kind of rock may often be traced gradually mergin

into those of another. Hence the definitions adopted in establishing rock

nomenclature merely correspond to more or less arbitrary selected poin

in a continuously graduated series.[4]

Igneous

Main article: Igneous rock

Igneous rock (derived from the

Latin word igneus meaning of

fire, from ignis meaning fire)

forms through the cooling and

solidification of magma or lava.

This magma can be derived from partial melts of pre-existing rocks in

either a planet's mantle or crust. Typically, the melting of rocks is caused

by one or more of three processes: an increase in temperature, a

decrease in pressure, or a change in composition.

Igneous rocks are divided into two main categories: plutonic rock and

volcanic. Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earth's crust. Acommon example of this type is granite. Volcanic or extrusive rocks result from magma reaching the surface either

as lava orfragmental ejecta, forming minerals such as pumice or basalt.[3] The chemical abundance and the rate

of cooling of magma typically forms a sequence known as Bowen's reaction series, after the Canadian petrologist

Norman L. Bowen. Most major igneous rocks are found along this scale.[2]

About 64.7% of the Earth's crust by volume consists of igneous rocks; making it the most plentiful category. Of

these, 66% are basalts and gabbros, 16% are granite, and 17% granodiorites and diorites. Only 0.6% are syenite

and 0.3% peridotites and dunites. The oceanic crust is 99% basalt, which is an igneous rock of mafic composition

Granites and similar rocks, known as meta-granitoids, form much of the continental crust.[5] Over 700 types of

igneous rocks have been described, most of them having formed beneath the surface of Earth's crust. These have

diverse properties, depending on their composition and how they were formed.

Sedimentary

Main article: Sedimentary rock

Sedimentary rocks are formed by sedimentation of particles at or near the Earth's surface and within bodies of

water. This process causes clastic sediments or organic particles (detritus) to settle and accumulate, or for mineral

to chemically precipitate (evaporite) from a solution. The particulate matter then undergoes compaction and
http://en.wikipedia.org/wiki/Solutionhttp://en.wikipedia.org/wiki/Evaporitehttp://en.wikipedia.org/wiki/Precipitation_%28chemistry%29http://en.wikipedia.org/wiki/Detritushttp://en.wikipedia.org/wiki/Organic_matterhttp://en.wikipedia.org/wiki/Sedimenthttp://en.wikipedia.org/wiki/Clastichttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Sedimentationhttp://en.wikipedia.org/wiki/Sedimentary_rockhttp://en.wikipedia.org/wiki/Sedimentary_rockhttp://en.wikipedia.org/wiki/Crust_%28geology%29http://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Dunitehttp://en.wikipedia.org/wiki/Peridotitehttp://en.wikipedia.org/wiki/Syenitehttp://en.wikipedia.org/wiki/Dioritehttp://en.wikipedia.org/wiki/Granodioritehttp://en.wikipedia.org/wiki/Gabbrohttp://en.wikipedia.org/wiki/Norman_L._Bowenhttp://en.wikipedia.org/wiki/Petrologisthttp://en.wikipedia.org/wiki/Bowen%27s_reaction_serieshttp://en.wikipedia.org/wiki/Basalthttp://en.wikipedia.org/wiki/Pumicehttp://en.wikipedia.org/wiki/Lavahttp://en.wikipedia.org/wiki/Extrusive_%28geology%29http://en.wikipedia.org/wiki/Granitehttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Crystallizationhttp://en.wikipedia.org/wiki/Intrusionhttp://en.wikipedia.org/wiki/Plutonichttp://en.wikipedia.org/wiki/Volcanic_rockhttp://en.wikipedia.org/wiki/Plutonhttp://en.wikipedia.org/wiki/Crust_%28geology%29http://en.wikipedia.org/wiki/Mantle_%28geology%29http://en.wikipedia.org/wiki/Planethttp://en.wikipedia.org/wiki/Lavahttp://en.wikipedia.org/wiki/Magmahttp://en.wikipedia.org/wiki/Freezinghttp://en.wikipedia.org/wiki/Latinhttp://en.wikipedia.org/wiki/Igneous_rockhttp://en.wikipedia.org/wiki/Igneous_rockhttp://en.wikipedia.org/wiki/Metamorphic_rockhttp://en.wikipedia.org/wiki/Sedimentary_rockhttp://en.wikipedia.org/wiki/Igneous_rockhttp://en.wikipedia.org/wiki/Rock_cyclehttp://en.wikipedia.org/wiki/Particle_size_%28grain_size%29http://en.wikipedia.org/wiki/Texture_%28geology%29http://en.wikipedia.org/wiki/Permeability_%28earth_sciences%29http://en.wikipedia.org/wiki/Gabbrohttp://en.wikipedia.org/wiki/File:GabbroRockCreek1.jpghttp://en.wikipedia.org/wiki/Costa_Ricahttp://en.wikipedia.org/wiki/Oros%C3%ADhttp://en.wikipedia.org/wiki/File:DirkvdM_rocks.jpg


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Sedimentary sandstone with iron

oxide bands

Metamorphic banded gneiss

cementation during diagenesis.

Before being deposited, sediment was formed by weathering and erosion in a source area, and then transported to

the place of deposition by water, wind, ice, mass movement or glaciers

which are called agents of denudation. Mud rocks comprise 65%

(mudstone, shale and siltstone); sandstones 20 to 25% and carbonate

rocks 10 to 15% (limestone and dolostone).[3] About 7.9% of the crust

by volume is composed of sedimentary rocks, with 82% of those being

shales, while the remainder consist of limestone (6%), sandstone and

arkoses (12%).[5]

Metamorphic

Main article: Metamorphic rock

Metamorphic rocks are formed by subjecting any rock type

sedimentary rock, igneous rock or another older metamorphic rock

to different temperature and pressure conditions than those in which the

original rock was formed. This process is called metamorphism; meaning

to "change in form". The result is a profound change in physical properties

and chemistry of the stone. The original rock, known as the protolith,

transforms into other mineral types or else into other forms of the same

minerals, such as by recrystallization.[3] The temperatures and pressures

required for this process are always higher than those found at the Earth's

surface: temperatures greater than 150 to 200 C and pressures of

1500 bars.[6] Metamorphic rocks compose 27.4% of the crust by

volume.[5]

The three major classes of metamorphic rock are based upon the

formation mechanism. An intrusion of magma that heats the surrounding

rock causes contact metamorphisma temperature-dominated

transformation. Pressure metamorphism occurs when sediments are

buried deep under the ground; pressure is dominant and temperature

plays a smaller role. This is termed burial metamorphism, and it can result

in rocks such as jade. Where both heat and pressure play a role, the

mechanism is termed regional metamorphism. This is typically found in

mountain-building regions.[2]

Depending on the structure, metamorphic rocks are divided into two general categories. Those that possess a

texture are referred to as foliated; the remainder are termed non-foliated. The name of the rock is then determined

based on the types of minerals present. Schists are foliated rocks that are primarily composed of lamellar minerals

such as micas. A gneiss has visible bands of differing lightness, with a common example being the granite gneiss.

Other varieties of foliated rock include slates, phyllites, and mylonite. Familiar examples of non-foliated

metamorphic rocks include marble, soapstone, and serpentine. This branch contains quartzitea metamorphosed

form of sandstoneand hornfels.[2]

Human use
http://en.wikipedia.org/wiki/Hornfelshttp://en.wikipedia.org/wiki/Sandstonehttp://en.wikipedia.org/wiki/Quartzitehttp://en.wikipedia.org/wiki/Serpentine_grouphttp://en.wikipedia.org/wiki/Soapstonehttp://en.wikipedia.org/wiki/Marblehttp://en.wikipedia.org/wiki/Mylonitehttp://en.wikipedia.org/wiki/Phyllitehttp://en.wikipedia.org/wiki/Slatehttp://en.wikipedia.org/wiki/Lightnesshttp://en.wikipedia.org/wiki/Gneisshttp://en.wikipedia.org/wiki/Lamella_%28materials%29http://en.wikipedia.org/wiki/Schisthttp://en.wikipedia.org/wiki/Foliation_%28geology%29http://en.wikipedia.org/wiki/Jadehttp://en.wikipedia.org/wiki/Recrystallization_%28geology%29http://en.wikipedia.org/wiki/Protolithhttp://en.wikipedia.org/wiki/Metamorphismhttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Igneous_rockhttp://en.wikipedia.org/wiki/Sedimentary_rockhttp://en.wikipedia.org/wiki/Metamorphic_rockhttp://en.wikipedia.org/wiki/Metamorphic_rockhttp://en.wikipedia.org/wiki/Arkosehttp://en.wikipedia.org/wiki/Dolostonehttp://en.wikipedia.org/wiki/Limestonehttp://en.wikipedia.org/wiki/Carbonate_rockhttp://en.wikipedia.org/wiki/Sandstonehttp://en.wikipedia.org/wiki/Siltstonehttp://en.wikipedia.org/wiki/Shalehttp://en.wikipedia.org/wiki/Mudstonehttp://en.wikipedia.org/wiki/Denudationhttp://en.wikipedia.org/wiki/Glacierhttp://en.wikipedia.org/wiki/Mass_wastinghttp://en.wikipedia.org/wiki/Icehttp://en.wikipedia.org/wiki/Windhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Erosionhttp://en.wikipedia.org/wiki/Weatheringhttp://en.wikipedia.org/wiki/Diagenesishttp://en.wikipedia.org/wiki/File:Skagit-gneiss-Cascades.jpghttp://en.wikipedia.org/wiki/File:SandstoneUSGOV.jpg


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Ceremonial cairn of rocks, an ovoo,

from Mongolia

Uranium mine near Moab, Utah

The use of rocks has had a

huge impact on the cultural and

technological development of

the human race. Rocks have

been used by humans and

other hominids for more than

2 million years.[7] Lithic

technology marks some of the

oldest and continuously used

technologies. The mining of

rocks for their metal ore

content has been one of the

most important factors of

human advancement, which has progressed at different rates in different

places in part because of the kind of metals available from the rocks of a region.[8]

Mining

Main article: Mining

Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein o

(coal) seam. This term also includes the removal of soil. Materials recovered by mining include base metals,

precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock salt and potash. Mining is required to

obtain any material that cannot be grown through agricultural processes, or created artificially in a laboratory or

factory. Mining in a wider sense comprises extraction of any non-renewable resource (e.g., petroleum, natural gas

or even water).

Mining of stone and metal has been done since pre-historic times. Modern mining processes involve prospecting fo

ore bodies, analysis of the profit potential of a proposed mine, extraction of the desired materials and finally

reclamation of the land to prepare it for other uses once the mine is closed.

The nature of mining processes creates a potential negative impact on the environment both during the mining

operations and for years after the mine is closed. This impact has led to most of the world's nations adopting

regulations to moderate the negative effects of mining operations. Safety has long been a concern as well, though

modern practices have improved safety in mines significantly.[9]

See also

Geologic time scale

Geomorphology

List of rocks on Mars

List of rock types

Oldest rock

Quarry

Riprap

Rock balancing
http://en.wikipedia.org/wiki/Rock_balancinghttp://en.wikipedia.org/wiki/Ripraphttp://en.wikipedia.org/wiki/Quarryhttp://en.wikipedia.org/wiki/Oldest_rockhttp://en.wikipedia.org/wiki/List_of_rock_typeshttp://en.wikipedia.org/wiki/List_of_rocks_on_Marshttp://en.wikipedia.org/wiki/Geomorphologyhttp://en.wikipedia.org/wiki/Geologic_time_scalehttp://en.wikipedia.org/wiki/Prospectinghttp://en.wikipedia.org/wiki/Prehistoryhttp://en.wikipedia.org/wiki/Fossil_waterhttp://en.wikipedia.org/wiki/Natural_gashttp://en.wikipedia.org/wiki/Petroleumhttp://en.wikipedia.org/wiki/Non-renewable_resourcehttp://en.wikipedia.org/wiki/Factoryhttp://en.wikipedia.org/wiki/Laboratoryhttp://en.wikipedia.org/wiki/Chemical_synthesishttp://en.wikipedia.org/wiki/Agriculturehttp://en.wikipedia.org/wiki/Potashhttp://en.wikipedia.org/wiki/Sodium_chloridehttp://en.wikipedia.org/wiki/Oil_shalehttp://en.wikipedia.org/wiki/Limestonehttp://en.wikipedia.org/wiki/Diamondhttp://en.wikipedia.org/wiki/Coalhttp://en.wikipedia.org/wiki/Uraniumhttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Precious_metalshttp://en.wikipedia.org/wiki/Base_metalshttp://en.wikipedia.org/wiki/Coal_mininghttp://en.wikipedia.org/wiki/Vein_%28geology%29http://en.wikipedia.org/wiki/Orehttp://en.wikipedia.org/wiki/Geologyhttp://en.wikipedia.org/wiki/Mineralhttp://en.wikipedia.org/wiki/Value_%28economics%29http://en.wikipedia.org/wiki/Mininghttp://en.wikipedia.org/wiki/Orehttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Mininghttp://en.wikipedia.org/wiki/Lithic_technologyhttp://en.wikipedia.org/wiki/Paleolithichttp://en.wikipedia.org/wiki/Hominidshttp://en.wikipedia.org/wiki/Moab,_Utahhttp://en.wikipedia.org/wiki/Uraniumhttp://en.wikipedia.org/wiki/File:UraniumMineUtah.JPGhttp://en.wikipedia.org/wiki/Mongoliahttp://en.wikipedia.org/wiki/Ovoohttp://en.wikipedia.org/wiki/Cairnhttp://en.wikipedia.org/wiki/File:TallOvoo.JPG


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References

1. ^ Roberts, Dar. "Rocks and classifications" (http://earth.rice.edu/mtpe/geo/geosphere/topics/rocks_a.html).

Department of Geography, University of California, Santa Barbara. Retrieved November 11, 2012.

2. ^ abcd Wilson, James Robert (1995), A collector's guide to rock, mineral & fossil localities of Utah

(http://books.google.com/books?id=t-XvE8DTiW0C&pg=PA1), Utah Geological Survey, pp. 122,

ISBN 1557913366.

3. ^ abcd Blatt, Harvey; Tracy, Robert J. (1996). Petrology (2nd ed.). W. H. Freeman. ISBN 0-7167-2438-3.

4. ^ This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911).

"Petrology".Encyclopdia Britannica (11th ed.). Cambridge University Press.

5. ^ abc Bucher, Kurt; Grapes, Rodney (2011), Petrogenesis of Metamorphic Rocks

(http://books.google.com/books?id=FFcHarai9GEC&pg=PA24), Springer, pp. 2324, ISBN 3540741682.

6. ^ Blatt, Harvey and Robert J. Tracy, Petrology, W.H.Freeman, 2nd ed., 1996, p.355 ISBN 0-7167-2438-3

7. ^ "Prominent Hominid Fossils" (http://www.talkorigins.org/faqs/homs/specimen.html). Jim Foley. Retrieved June

8, 2012.

8. ^ "Overview of mining and impacts" (https://www.elaw.org/files/mining-eia-guidebook/Chapter1.pdf). Retrieved

June 8, 2012.

9. ^ "Sarwatch" (http://www.sarwatch.org/resources-topics.html). Retrieved June 8, 2012.

External links

Media related to rocks at Wikimedia Commons

The dictionary definition of rock at Wiktionary

Retrieved from "http://en.wikipedia.org/w/index.php?title=Rock_(geology)&oldid=570269387"

Categories: Petrology Rocks Stone Materials

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