In geology, rock is a naturally occurring aggregate of minerals and/or mineraloids. Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit Nature, in the broadest sense is equivalent to the natural world, physical universe, material world or material universe. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific A mineraloid is a Mineral -like substance that does not demonstrate Crystallinity. The Earth's lithosphere is made of rock. The lithosphere (IPA, from the Greek λίθος for "rocky" + σφαίρα for "sphere" is the solid outermost shell of a rocky Planet. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change Petrology is the scientific study of rocks. In Geology, petrology (from Greek πέτρα petra, rock and λόγος logos, knowledge is the study of rocks and the conditions on which
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Rock classification
- See also: formation of rocks
Rocks are classified by mineral and chemical composition, by the texture of the constituent particles and by the processes that formed them. This article discusses how rocks are formed There are also articles on physical rock formations also known as strata, and the formal naming of Geologic formations A chemical substance is a Material with a definite chemical composition. Texture in Geology refers to the physical appearance or character of a rock such as grain size shape arrangement and pattern at both the megascopic or microscopic surface These indicators separate rocks into igneous, sedimentary and metamorphic. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change They may also be classified according to particle size, in the case of conglomerates and breccias or in the case of individual stones. A conglomerate (kɒnˈglɒmərət is a rock consisting of individual stones that have become cemented together Breccia (ˈbrɛtʃiə ˈbrɛʃiə breach is a rock composed of angular fragments of several Minerals or rocks in a matrix, that is a cementing material The transformation of one rock type to another is described by the geological model called the rock cycle. rock cycle is a fundamental concept in Geology that describes the dynamic transitions through Geologic time among the three main rock types Sedimentary
Igneous rocks are formed when molten magma cools and are divided into two main categories: plutonic rock and volcanic. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Magma (Plurals magmas and magmata) is molten rock that sometimes forms beneath the surface of the Earth (or any other Terrestrial planet In Geology, an intrusion is a body of Igneous rock that has Crystallized from molten Magma below the surface of the Earth. Plate tectonics and hotspots Divergent plate boundaries At the Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earth's crust (example granite), while volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta (examples pumice and basalt) . EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. Lava is molten rock expelled by a Volcano during an eruption When first expelled from a volcanic vent it is a Liquid at Temperatures Pumice is a textural term for a volcanic rock that is a solidified frothy lava composed of highly microvesicular glass Pyroclastic with very thin translucent Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. [1]
Sedimentary rocks are formed by deposition of either clastic sediments, organic matter, or chemical precipitates (evaporites), followed by compaction of the particulate matter and cementation during diagenesis. Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Clastic rocks are composed of fragments or clasts, of pre-existing rock. Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of Evaporites (iˈvæpəraɪt are water-soluble Mineral sediments that result from the Evaporation of bodies of surficial Water. In Geology and Oceanography, diagenesis is any chemical physical or biological change undergone by a Sediment after its initial deposition and during Sedimentary rocks form at or near the Earth's surface. Mud rocks comprise 65% (mudstone, shale and siltstone); sandstones 20 to 25% and carbonate rocks 10 to 15% (limestone and dolostone). Mudstone (also called mudrock) is a fine grained Sedimentary rock whose original constituents were Clays or Muds Grain size is up Shale (also called mudstone) is a fine-grained Sedimentary rock whose original constituents were Clay minerals or Muds It is characterized by Siltstone is a Sedimentary rock which has a composition intermediate in grain size between the coarser Sandstones and the finer Mudstones and Sandstone is a Sedimentary rock composed mainly of Sand -size Mineral or rock grains. Carbonate rocks are a class of Sedimentary rocks composed primarily of Carbonate Minerals The two major types are Limestone and Dolomite Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3 Dolostone is a sedimentary Carbonate rock that contains a high percentage of the Mineral Dolomite. [1]
Metamorphic rocks are formed by subjecting any rock type (including previously-formed metamorphic rock) to different temperature and pressure conditions than those in which the original rock was formed. Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface These temperatures and pressures are always higher than those at the Earth's surface and must be sufficiently high so as to change the original minerals into other mineral types or else into other forms of the same minerals (e. g. by recrystallisation). Recrystallization (see also Crystallization) is a physical process that has meanings in Chemistry, Metallurgy and Geology. [1]
The three classes of rocks: the igneous, the sedimentary and the metamorphic — are subdivided into many groups. There are, however, no hard and fast boundaries between allied rocks. By increase or diminution 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 merging into those of another. Hence the definitions adopted in establishing rock nomenclature merely correspond to selected points (more or less arbitrary) in a continuously graduated series. This is frequently urged as a reason for reducing rock classification to its simplest possible terms, and using only a few generalized rock designations. But it is clear that many apparently trivial differences tend regularly to recur, and have a real significance, and so long as any variation can be shown to be of this nature it deserves recognition. [2]
Coloration
Iron oxides and carbonates play a large part in many sedimentary rocks and are especially important as coloring agents. Altogether there are sixteen known Iron Oxides and oxyhydroxides In Chemistry, a carbonate is a salt or Ester of Carbonic acid. The red sands and limestones, for example, which are so abundant, contain small amounts of iron(III) oxide (hematite), which in a finely divided state gives a red hue to all rocks in which it is present. Iron(III oxide —also known as ferric oxide, Hematite, red iron oxide, synthetic maghemite, colcothar, or simply Rust —is Hematite, also spelt hæmatite, is the Mineral form of Iron(III oxide (Fe2O3 one of several Iron oxides Limonite and goethite, on the other hand, makes rocks yellow or brown; manganese oxides, asphalt and other carbonaceous substances are the cause of the black color of many sediments. Limonite is an ore consisting in a mixture of hydrated Iron(III oxide-hydroxide of varying composition Goethite, named after the German Polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low temperature environments Manganese (ˈmæŋgəniːz is a Chemical element, designated by the symbol Mn. Asphalt ( is a sticky black and highly viscous liquid or semi-solid that is present in most crude Petroleums and in some natural deposits sometimes termed asphaltum Carbonaceous is the defining attribute of a substance rich in Carbon. Bluish tints result sometimes from the presence of phosphates or of fluorite; while green is most frequently seen in rocks which contain glauconite or chlorite. A phosphate, an Inorganic chemical, is a salt of Phosphoric acid. Fluorite (also called fluorspar) is a Mineral composed of Calcium fluoride, Ca[[Fluorine F2]] Glauconite is a phyllosilicate ( Mica group Mineral. It can also be referred to as an iron silicate The chlorites are a group of phyllosilicate Minerals Chlorites can be described by the following four endmembers based on their chemistry via substitution [2]
Impact on society
Rocks have had a huge impact on the cultural and technological advancement of the human race. Rocks have been used by Homo sapiens and other hominids for millions of years. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus A hominid is any member of the biological family Hominidae (the "great apes" including the extinct and extant Humans Chimpanzees Lithic technology marks some of the oldest and continuously used technologies. In Archeology, lithic technology refers to a broad array of techniques and styles to produce usable tools from various types of stone The mining of rocks for their metal ore content has been one of the most important factors of human advancement. Mining is the extraction of valuable Minerals or other geological materials from the earth usually (but not always from an Ore body The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across An ore is a volume of rock containing components or Minerals in a mode of occurrence that renders it valuable for mining Humanity's advancement has been decided by the kind of metals available from the rocks of a region. The prehistory and early history of civilization is classified into the stone age, Bronze Age, and Iron Age. The Stone Age is a broad prehistoric time period during which Humans widely used stone for toolmaking The term Bronze Age refers to a period in human cultural development when the most advanced Metalworking (at least in systematic and widespread use included techniques for This article is about the archaeological period known as the Iron Age for the mythological Iron Age see Ages of Man. Rocks have been and continue to be used to construct buildings and infrastructure. Infrastructure typically refers to the technical structures that support a society such as Roads Water supply, Wastewater, Power grids When so used, they are dimension stone. Dimension stone is natural stone or rock that has been selected and fabricated (i
See also
References
- ^ a b c Blatt, Harvey and Robert J. Dimension stone is natural stone or rock that has been selected and fabricated (i The geologic time scale is a chronologic schema (or idealized Model) relating Stratigraphy to time that is used by Geologists and other Geomorphology (from Greek: γη ge, "earth" μορφή morfé, "form" and λόγος Logos, "knowledge" The oldest rock or rocks on Earth, as an aggregate of Minerals that have not undergone subsequent metamorphosis, are from the Archean A quarry is a type of open-pit mine from which rock or Minerals are extracted Riprap — also known as rip rap, rubble, shot rock or rock armour — is rock or other material used to armor Tracy, 1996, Petrology, W. H. Freeman, 2nd ed. ISBN 0-7167-2438-3
- ^ a b This article incorporates text from the Encyclopædia Britannica Eleventh Edition article "Petrology", a publication now in the public domain. The Encyclopædia Britannica Eleventh Edition (1910–1911 is a 29-volume reference work that marked the beginning of the Encyclopædia Britannica The public domain is a range of abstract materials &ndash commonly referred to as Intellectual property &ndash which are not owned or controlled by anyone
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