Petrology Petrology Amphibolite is the name given to a rock consisting mainly of hornblende amphibole, the use of the term being restricted, however, to metamorphic rocks. The modern terminology for a holocrystalline plutonic igneous rocks rock composed primarily of hornblende amphibole is a hornblendite, which are usually crystal cumulates. Rocks with >90% amphibole which have a feldspar groundmass may be a lamprophyre. ...more on Wikipedia about "Amphibolite"
Amygdules form when the vesicular cavities (created by expanding gas bubbles in volcanic lava) are filled with a secondary mineral such as calcite, quartz, or one of the zeolites, which are deposited by having minerals "wash" through the pores in the rock (see Porosity/Permeability). They are filled from the outside, making the amygdules concentrically layered. ...more on Wikipedia about "Amygdule"
Aphanite (from the Greek αφανης, invisible) is a name given to certain typically dark-coloured igneous rocks which are so fine-grained that their component mineral crystals are not detected by the unaided eye. ...more on Wikipedia about "Aphanite"
Aplite in petrology, the name given to intrusive rock in which quartz and felspar are the dominant minerals. Aplites are usually very fine-grained, white, grey or flesh-coloured, and their constituents are visible only with the help of a magnifying lens. Dykes and threads of aplite are very frequently to be observed traversing granitic bosses; they occur also, though in less numbers, in syenites, diorites, quartz-diabases and gabbros. ...more on Wikipedia about "Aplite"
A batholith is a large emplacement of igneous intrusive (also called plutonic) rock that forms from cooled magma deep in the Earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock-types, such as granite, quartz monzonite, or diorite. ...more on Wikipedia about "Batholith"
Within the field of geology, Bowen's reaction series is the work of the petrologist, Norman L. Bowen who was able to explain why certain types of minerals tend to be found together while others are almost never associated with one another. He experimented in the early 1900's with powdered rock material that was heated until it melted and then allowed to cool to a certain temperature whereupon he observed the types of minerals that formed in the rocks produced. He repeated this process with progressively cooler temperatures and the results he obtained led him to formulate his reaction series which is still accepted today as the idealized progression of minerals produced by cooling magma. Based upon Bowen's work, one can infer from the minerals present in a rock the relative conditions under which the material had formed. ...more on Wikipedia about "Bowen's reaction series"
Breccia, derived from the Latin word for "broken," is typically a sedimentary rock composed of angular fragments in a matrix that may be of a similar or a different material. A conglomerate by contrast is a sedimentary rock composed of rounded fragments or clasts of pre-existing rocks. Both breccias and conglomerates are composed of fragments averaging greater than 2 mm in size. The angular shape of the fragments indicate that the material has not been transported far from its source. Breccias indicate accumulation in a juvenile stream channel or accumulations due to gravity erosion. Talus slopes may become buried and the talus cemented in a similar manner. ...more on Wikipedia about "Breccia"
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Carbonatites are intrusive igneous rocks defined by a mineralogy which is greater than than 50% carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification. ...more on Wikipedia about "Carbonatite"
The Central Atlantic magmatic province (CAMP) was formed during the breakup of Pangaea during the Mesozoic Era. The initial breakup of Pangaea in early Jurassic time provided a legacy of basaltic dikes, sills, and lavas over a vast area around the present central North Atlantic Ocean. Although some connections among these basalts had long been recognized, in 1988 they were linked as constituting a single major flood basalt province(Rampino and Stothers). The basaltic sills of similar age (near 200 Ma, or earliest Jurassic) and composition (intermediate-Ti quartz tholeiite) which occur across the vast Amazon River basin of Brazil were linked to the province in 1999(Marzoli et al.). ...more on Wikipedia about "Central Atlantic Magmatic Province"
Chert is a fine-grained silica-rich cryptocrystalline sedimentary rock that may contain small fossils. It varies greatly in color from white to black, but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements present in the rock, and both red and green are most often related to traces of iron (in its oxidized and reduced forms respectively). Jasper is basically chert which owes its red color to iron(III) inclusions. ...more on Wikipedia about "Chert"
A cryptocrystal is a rock whose texture is so finely crystalline—that is, made up of such minute crystals—that its crystalline nature is only vaguely revealed even in a thin section by transmitted polarized light. Among the sedimentary rocks, chert and flint are cryptocrystalline. Also a form of diamond, known as carbonado, is cryptocyrstalline. Lava flows, especially of the acidic type such as felsites and rhyolites, may have a cryptocrystalline ground mass as distinguished from pure obsidian (acidic) or tachylite (basic), which are natural rock glasses. ...more on Wikipedia about "Cryptocrystal"
Cumulate rocks are igneous rocks formed by the accumulation of crystals from a magma either by settling or floating. ...more on Wikipedia about "Cumulate rocks"
A dike or dyke in geology refers to a tabular intrusive igneous body. The thickness is usually much smaller than the other two dimensions. Thickness can vary from sub-centimeter scale to many meters in thickness and the lateral dimensions can extend over many kilometers. A dike is an intrusion into a cross-cutting fissure, meaning a dike cuts across other pre-existing layers or bodies of rock, this means that a dike is always younger than the rocks that contain it. Dikes are usually high angle to near vertical in orientation, but subsequent tectonic deformation may rotate the including sequence. Near horizontal or conformable intrusions along bedding planes between strata are called intrusive sills. ...more on Wikipedia about "Dike (geology)"
Dolerite (from the Greek word doleros meaning deceptive), in petrology is the name given by Hauy to those basaltic rocks which are comparatively coarse grained. Dolerite is a synonym for diabase. ...more on Wikipedia about "Dolerite" Connect with http://www.shortopedia.com.
In coal geology, exinite is an umbrella term, used when referring to the finely-ground and macrerated remains, originally formed by spores, pollen, dinoflagellate cysts, leaf cuticles, plant resins and waxes, as found in coal deposits. Exinite is one of the four categories of kerogen. ...more on Wikipedia about "Exinite"
Extrusive refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. ...more on Wikipedia about "Extrusive (geology)"
Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements, such as silica, oxygen, aluminium, sodium, and potassium. The term combines the words " feldspar" and " silica." ...more on Wikipedia about "Felsic"
Felsite is a very fine to cryptocrystalline igneous rock that may or may not contain larger crystals, called phenocrysts, that are typical of many porphyritic igneous rocks. The mass of the rock consists of a fine-grained matrix of felsic materials, particularly quartz, sodium and potassium feldspar, and may be termed a quartz felsite or quartz porphyry if the quartz phenocrysts are present. This rock is typically of volcanic origin, and may be found in association with obsidian and rhyolite. In some cases, it is sufficiently fine-grained for use in making stone tools. ...more on Wikipedia about "Felsite"
Fluid inclusions are microscopic bubbles of liquid and gas that are trapped within crystals. As minerals often form from a liquid or aqueous medium, tiny blebs of that liquid can become trapped within the crystal structure or in healed fractures wirhin a crystal. These small inclusions range in size from 0.1 to 1 mm and are usually only visible in detail by microscopic study. ...more on Wikipedia about "Fluid inclusions"
The three main ways rocks are formed: ...more on Wikipedia about "Formation of rocks"
Geodes ( Greek geoides, "earthlike") are geological rock formations which occur in sedimentary and certain volcanic rocks. Geodes are essentially rock cavities or vugs with internal crystal formations or concentric banding. The exterior of the most common geodes is generally limestone or a related rock, while the interior contains quartz crystals and/or chalcedony deposits. Other geodes are completely filled with crystal, being solid all the way though. These types of geodes are called nodules. ...more on Wikipedia about "Geode"
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The Gibbs-Thomson effect (not to be confused with the Thomson effect) relates surface curvature to vapor pressure and chemical potential. It is named after Josiah Willard Gibbs and three Thomsons: James Thomson , William Thomson, 1st Baron Kelvin, and Sir Joseph John Thomson. ...more on Wikipedia about "Gibbs-Thomson effect"
Glaciated Rocks are rocks which show evidence of having been exposed to a glacier. Generally they show striations or deep scratches caused more by the debris being carried by the glacier than by the ice itself. They may also be themselves, erratics, that is not belonging to the local rocks but having been transported there by the glacier. ...more on Wikipedia about "Glaciated Rocks"
Granophyre (from granite and porphyry) is an igneous rock similar to granite in which irregular crystals of intergrown quartz and alkali feldspar are embedded in a groundmass of these minerals. ...more on Wikipedia about "Granophyre"
Greenschist is a general field petrologic term applied to metamorphic and/or altered mafic volcanic rock. The green is due to abundant green chlorite, actinolite and epidote minerals that dominate the rock. However, basalts may remain quite black if primary pyroxene does not revert to chlorite or actinolite. To qualify for the name a rock must also exhibit schistocity or some foliation or layering. An alternate term for these rocks is greenstone. ...more on Wikipedia about "Greenschist"
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