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Aegirine
Aegirine is a member of the clino pyroxene group of inosilicate minerals. Aegirine is the sodium endmember of the aegirine- augite series. Aegirine has the chemical formula Na Fe Si2 O6 in which the iron is present as Fe3+. In the aegirine-augite series the sodium is variably replaced by calcium with iron(II) and magnesium replacing the iron(III) to balance the charge. Aluminium also substitutes for the iron(III). Acmite is a fibrous, green-colored variety. Aegirine occurs as dark green monoclinic prismatic crystals. It has a glassy luster and perfect cleavage. Its Mohs hardness varies from 5 to 6, and its specific gravity is between 3.2 and 3.4. This mineral commonly occurs in alkalic igneous rocks, nepheline syenites, carbonatites and pegmatites. It also appears in regionally metamorphosed schists, gneisses, and iron formations; in blueschist facies rocks, and from sodium metasomatism in granulites. It may occur as an authigenic mineral in shales and marls. It occurs in ass ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aegirine - Acmite In Syenite Sodium Iron Silicate Magnet Cove Hot Springs County Arkansas 2000
Aegirine is a member of the clino pyroxene group of inosilicate minerals. Aegirine is the sodium endmember of the aegirine- augite series. Aegirine has the chemical formula Na Fe Si2 O6 in which the iron is present as Fe3+. In the aegirine-augite series the sodium is variably replaced by calcium with iron(II) and magnesium replacing the iron(III) to balance the charge. Aluminium also substitutes for the iron(III). Acmite is a fibrous, green-colored variety. Aegirine occurs as dark green monoclinic prismatic crystals. It has a glassy luster and perfect cleavage. Its Mohs hardness varies from 5 to 6, and its specific gravity is between 3.2 and 3.4. This mineral commonly occurs in alkalic igneous rocks, nepheline syenites, carbonatites and pegmatites. It also appears in regionally metamorphosed schists, gneisses, and iron formations; in blueschist facies rocks, and from sodium metasomatism in granulites. It may occur as an authigenic mineral in shales and marls. It occurs in ass ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 also known. Phonolite is the fine-grained extrusive equivalent. Petrology Nepheline syenites are silica-undersaturated and some are peralkaline (terms discussed in igneous rock). Nepheline is a feldspathoid, a solid-solution mineral, that does not coexist with quartz; rather, nepheline would react with quartz to produce alkali feldspar. They are distinguished from ordinary basic syenites not only by the presence of nepheline but also by the occurrence of many other minerals rich in alkalis and in rare earths and other incompatible elements. Alkali feldspar dominates, commonly represented by orthoclase and the exsolved lamellar albite, form perthite. In some rocks the potash feldspar, in others the soda feldspar predominates. Fresh clear m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyroxene
The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) or magnesium (Mg) and more rarely zinc, manganese or lithium, and Y represents ions of smaller size, such as chromium (Cr), aluminium (Al), magnesium (Mg), cobalt (Co), manganese (Mn), scandium (Sc), titanium Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ... (Ti), vanadium (V) or even iron (Fe II) or (Fe III). Although aluminium substitutes extensively for silicon in silicates such as feldspars and amphiboles, the substitution occurs only to a limited extent in most pyroxenes. They share a common structure consisting of single chains of si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophyllite
Astrophyllite is a very rare, brown to golden-yellow hydrous potassium iron titanium silicate mineral. Belonging to the astrophyllite group, astrophyllite may be classed either as an inosilicate, phyllosilicate, or an intermediate between the two. It forms an isomorphous series with kupletskite, to which it is visually identical and often intimately associated. Astrophyllite is of interest primarily to scientists and collectors. Heavy, soft and fragile, astrophyllite typically forms as ''bladed'', radiating ''stellate'' aggregates. It is this crystal habit that gives astrophyllite its name, from the Greek words ''astron'' meaning " star" and ''phyllon'' meaning "leaf". Its great submetallic gleam and darkness contrast sharply with the light ( felsic) matrix the mineral is regularly found within. Astrophyllite is usually opaque to translucent, but may be transparent in thin specimens. As the crystals themselves possess perfect cleavage, they are typically left ''in situ'', the e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arfvedsonite
Arfvedsonite () is a sodium amphibole mineral with composition: aNa2] Fe2+)4Fe3+(OH)2, Si8O22]. It crystallizes in the monoclinic prismatic crystal system and typically occurs as greenish black to bluish grey fibrous to radiating or stellate prisms. It is a rather rare mineral occurring in nepheline syenite intrusions and agpaitic (peralkaline) pegmatites and granites as the Golden Horn batholith in Okanogan County, Washington (type locality for zektzerite). Occurrences include Mont Saint-Hilaire, Quebec, Canada; the Ilímaussaq complex in Southern Greenland; and in pegmatites of the Kola Peninsula, Russia. Its mineral association includes nepheline, albite, aegirine, riebeckite, katophorite and quartz. Arfvedsonite was discovered in 1823 and named for the Swedish chemist Johan August Arfwedson (1792–1841). See also * List of minerals * List of minerals named after people This is a list of minerals named after people. The chemical composition follows name. A *Abe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Riebeckite
Riebeckite is a sodium-rich member of the amphibole group of silicate minerals, chemical formula Na2(Fe2+3Fe3+2)Si8O22(OH)2. It forms a solid solution series with magnesioriebeckite. It crystallizes in the monoclinic system, usually as long prismatic crystals showing a diamond-shaped cross section, but also in fibrous, bladed, acicular, columnar, and radiating forms. Its Mohs hardness is 5.0–6.0, and its specific gravity is 3.0–3.4. Cleavage is perfect, two directions in the shape of a diamond; fracture is uneven, splintery. It is often translucent to nearly opaque. Name and discovery Riebeckite was first described in 1888 for an occurrence on Socotra Island, Aden Governorate, Yemen, and named for German explorer Emil Riebeck (1853–1885). The mineral is also known as crocidolite. Occurrence Riebeckite typically forms dark-blue elongated to fibrous crystals in highly alkali granites, syenites, rarely in felsic volcanics, granite pegmatites and schist. It occurs in banded i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nepheline
Nepheline, also called nephelite (), is a rock-forming mineral in the feldspathoid groupa silica-undersaturated aluminosilicate, Na3 K Al4 Si4 O16, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatites. It is used in glass and ceramic manufacturing and other industries, and has been investigated as an ore of aluminium. Description and properties Nepheline crystals are rare and belong to the hexagonal system, usually having the form of a short, six-sided prism terminated by the basal plane. The crystals appear to have more symmetry than they actually possess, but unsymmetrical etched figures produced artificially on the prism faces indicate that the crystals are hemimorphic and tetartohedral, the only element of symmetry being a polar hexad axis. Nepheline is found in compact, granular aggregates, and can be white, yellow, gray, green, or reddish. Its hardness on the Mohs scale is 5.5–6, and its specific gravity 2.60–2.65. It i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Feldspar
Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldspars and the ''alkali'' (potassium-sodium) feldspars. Feldspars make up about 60% of the Earth's crust, and 41% of the Earth's continental crust by weight. Feldspars crystalize from magma as both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock. Rock formed almost entirely of calcic plagioclase feldspar is known as anorthosite. Feldspars are also found in many types of sedimentary rocks. Compositions The feldspar group of minerals consists of tectosilicates, silicate minerals in which silicon ions are linked by shared oxygen ions to form a three-dimensional network. Compositions of major elements in common feldspars can be expressed in terms of three endmembers: * potassium feldspar (K-spar) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marl
Marl is an earthy material rich in carbonate minerals, clays, and silt. When hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae. Marl makes up the lower part of the cliffs of Dover, and the Channel Tunnel follows these marl layers between France and the United Kingdom. Marl is also a common sediment in post-glacial lakes, such as the marl ponds of the northeastern United States. Marl has been used as a soil conditioner and neutralizing agent for acid soil and in the manufacture of cement. Description Marl or marlstone is a carbonate-rich mud or mudstone which contains variable amounts of clays and silt. The term was originally loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay and calcium carbonate, formed under freshwater conditions. These typically contain 35–65% clay and 65–35% carbonate. The te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metamorphism
Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of chemically active fluids, but the rock remains mostly solid during the transformation. Metamorphism is distinct from weathering or diagenesis, which are changes that take place at or just beneath Earth's surface. Various forms of metamorphism exist, including regional, contact, hydrothermal, shock, and dynamic metamorphism. These differ in the characteristic temperatures, pressures, and rate at which they take place and in the extent to which reactive fluids are involved. Metamorphism occurring at increasing pressure and temperature conditions is known as ''prograde metamorphism'', while decreasing temperature and pressure characterize ''retrograde metamorphism''. Metamorphic petrology is the study of metamorphism. Metamorphic petrologists re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Granulite
Granulites are a class of high-grade metamorphic rocks of the granulite facies that have experienced high-temperature and moderate-pressure metamorphism. They are medium to coarse–grained and mainly composed of feldspars sometimes associated with quartz and anhydrous ferromagnesian minerals, with granoblastic texture and gneissose to massive structure.D.R. Bowes (1989), ''The Encyclopedia of Igneous and Metamorphic Petrology''; Van Nostrand Reinhold They are of particular interest to geologists because many granulites represent samples of the deep continental crust. Some granulites experienced decompression from deep in the Earth to shallower crustal levels at high temperature; others cooled while remaining at depth in the Earth. The minerals present in a granulite will vary depending on the parent rock of the granulite and the temperature and pressure conditions experienced during metamorphism. A common type of granulite found in high-grade metamorphic rocks of the continent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metasomatism
Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is the replacement of one rock by another of different mineralogical and chemical composition. The minerals which compose the rocks are dissolved and new mineral formations are deposited in their place. Dissolution and deposition occur simultaneously and the rock remains solid. Synonyms to the word metasomatism are metasomatose and metasomatic process. The word metasomatose can also be used as a name for specific varieties of metasomatism (for example '' Mg-metasomatose'' and '' Na-metasomatose''). Metasomatism can occur via the action of hydrothermal fluids from an igneous or metamorphic source. In the igneous environment, metasomatism creates skarns, greisen, and may affect hornfels in the contact metamorphic aureole adjacent to an intrusive rock mass. In the metamorphic environment, metasomatism is created by mass ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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