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Latite
Latite is an igneous, volcanic rock, with aphanitic- aphyric to aphyric-porphyritic texture. Its mineral assemblage is usually alkali feldspar and plagioclase in approximately equal amounts. Quartz is less than five percent and is absent in a feldspathoid-bearing latite, and olivine is absent in a quartz-bearing latite. When quartz content is greater than five percent the rock is classified as quartz latite.Classification of Igneous Rocks , , ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quartz Latite
A quartz latite is a volcanic rock or fine grained extrusive rock composed mostly of alkali feldspar and plagioclase with some quartz. It forms from the rapid cooling of magma of intermediate composition but moderately enriched in alkali metal oxides. Quartz latite is intermediate between latite and rhyolite in its mineralogy. Description Quartz latite is the fine-grained equivalent of a quartz monzonite, containing approximately equal amounts of plagioclase and alkali feldspar and between 5% and 20% quartz and with plagioclase making up 35% to 65% of its total feldspar content. Quartz latite is not a recognized rock type in the TAS classification used to chemically classify glassy or very fine-grained volcanic rock. Occurrence Quartz latite is found in the 130-135 Mya Etendeka Formation of Namibia, where it forms extensive sheets in association with tholeiitic basalt. These are interpreted as densely welded ash flow tuffs. Some of the quartz latite flows were enormous, with e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Latite Nicol Parallei
Latite is an igneous, volcanic rock, with aphanitic- aphyric to aphyric-porphyritic texture. Its mineral assemblage is usually alkali feldspar and plagioclase in approximately equal amounts. Quartz is less than five percent and is absent in a feldspathoid-bearing latite, and olivine is absent in a quartz-bearing latite. When quartz content is greater than five percent the rock is classified as quartz latite.Classification of Igneous Rocks , , an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Rock
Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and metamorphic rocks and constitute an important element of some sediments and sedimentary rocks. For these reasons, in geology, volcanics and shallow hypabyssal rocks are not always treated as distinct. In the context of Precambrian shield geology, the term "volcanic" is often applied to what are strictly metavolcanic rocks. Volcanic rocks and sediment that form from magma erupted into the air are called "volcaniclastics," and these are technically sedimentary rocks. Volcanic rocks are among the most common rock types on Earth's surface, particularly in the oceans. On land, they are very common at plate boundaries and in flood basalt provinces. It has been est ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Rock Types
The following is a list of rock types recognized by geologists. There is no agreed number of specific types of rocks. Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe a rock type. Additionally, different classification systems exist for each major type of rock. There are three major types of rock: igneous rock, metamorphic rock, and sedimentary rock. Igneous rocks * * * * * * ** – Basaltic lava with a crumpled appearance ** – Basaltic lava with a flowing, often ropy appearance * ** ** * * * * * ** * * * ** * * * * * * * * * * * * * * * * * – An ultramafic, ultrapotassic intrusive rock dominated by mafic phenocrysts in a feldspar groundmass * – A silica-undersaturated form of andesite * – An ultramafic rock, essentially a peridotite * – A silica-undersaturated granite with 90% pyroxene * – A diorite with >5% modal quartz * – An in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhomb Porphyry
Porphyry ( ) is a textural term for an igneous rock consisting of coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate-rich, generally aphanitic matrix or groundmass. The larger crystals are called phenocrysts. In its non-geologic, traditional use, the term ''porphyry'' refers to the purple-red form of this stone, valued for its appearance. The term ''porphyry'' is from the Ancient Greek (), meaning "purple". Purple was the color of royalty, and the "imperial porphyry" was a deep purple igneous rock with large crystals of plagioclase. Some authors claimed the rock was the hardest known in antiquity. Thus, "imperial"-grade porphyry was prized for monuments and building projects in Imperial Rome and thereafter. Subsequently, the name was given to any igneous rocks with large crystals. The adjective ''porphyritic'' now refers to a certain texture of igneous rock regardless of its chemical and mineralogical composition. Its chief characteris ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porphyry (geology)
Porphyry ( ) is a textural term for an igneous rock consisting of coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate-rich, generally aphanitic matrix or groundmass. The larger crystals are called phenocrysts. In its non-geologic, traditional use, the term ''porphyry'' refers to the purple-red form of this stone, valued for its appearance. The term ''porphyry'' is from the Ancient Greek (), meaning "purple". Purple was the color of royalty, and the "imperial porphyry" was a deep purple igneous rock with large crystals of plagioclase. Some authors claimed the rock was the hardest known in antiquity. Thus, "imperial"-grade porphyry was prized for monuments and building projects in Imperial Rome and thereafter. Subsequently, the name was given to any igneous rocks with large crystals. The adjective ''porphyritic'' now refers to a certain texture of igneous rock regardless of its chemical and mineralogical composition. Its chief charact ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Igneous Rock
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks, or without crystallization to form natural glasses. Igneous rocks occur in a wide range of geological settings: shields, platforms, orogens, basins, large igneous provinces, extended crust and oceanic crust. Geological significance Igneous and metamorphic rocks make up 90–95% of the top ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Minerals'; p. 1. In the series ''Geology: Landforms, Minerals, and Rocks''. Rosen Publishing Group. The geological definition of mineral normally excludes compounds that occur only in living organisms. However, some minerals are often biogenic (such as calcite) or are organic compounds in the sense of chemistry (such as mellite). Moreover, living organisms often synthesize inorganic minerals (such as hydroxylapatite) that also occur in rocks. The concept of mineral is distinct from rock, which is any bulk solid geologic material that is relatively homogeneous at a large enough scale. A rock may consist of one type of mineral, or may be an aggregate of two or more different types of minerals, spacially segregated into disti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenocryst
300px, Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coins, 1 euro coin (diameter 2.3 cm) for scale. A phenocryst is an early forming, relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous rock. Such rocks that have a distinct difference in the size of the crystals are called porphyries, and the adjective porphyritic is used to describe them. Phenocrysts often have euhedral forms, either due to early growth within a magma, or by post-emplacement recrystallization. Normally the term ''phenocryst'' is not used unless the crystals are directly observable, which is sometimes stated as greater than .5 millimeter in diameter. Phenocrysts below this level, but still larger than the groundmass crystals, are termed ''microphenocrysts''. Very large phenocrysts are termed '' megaphenocrysts''. Some rocks contain both ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benmoreite
Benmoreite is a silica-undersaturated volcanic rock of intermediate composition. It is a sodium-rich variety of trachyandesite and belongs to the alkalic suite of igneous rocks. Nepheline benmoreite An origin by fractionation from basanite through nepheline hawaiite to nepheline benmoreite has been demonstrated for a volcanic suite in the McMurdo Volcanic Group of late Cenozoic age in McMurdo Sound area of Antarctica. Nepheline benmoreite magmas derived from mantle sources, containing lherzolite xenoliths, display similarities to some plutonic nepheline syenite Nepheline syenite is a holocrystalline plutonic rock that consists largely of nepheline and alkali feldspar. The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varieties are ...s. See also * References Petrology Intermediate rocks Volcanic rocks {{petrology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
USGS
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization's work spans the disciplines of biology, geography, geology, and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility. The agency was founded on March 3, 1879. The USGS is a bureau of the United States Department of the Interior; it is that department's sole scientific agency. The USGS employs approximately 8,670 people and is headquartered in Reston, Virginia. The USGS also has major offices near Lakewood, Colorado, at the Denver Federal Center, and Menlo Park, California. The current motto of the USGS, in use since August 1997, is "science for a changing world". The agency's previous slogan, adopted on the occasion of its hundredth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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