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Orbicular Granite
Orbicular granite (also known as orbicular rock or orbiculite) is an uncommon plutonic rock type which is usually granitic in composition. These rocks have a unique appearance due to ''orbicules'' - concentrically layered, spheroidal structures, probably formed through nucleation around a grain in a cooling magma chamber due to rapid physical changes. Almost one third of known orbicular rock occurrences are from Finland. The occurrences are usually very small. Occurrences Chile *On the coastline eleven kilometres north of Caldera, Northern Chile, there is a body of Jurassic orbicular granite which is dyke-like with an exposed surface area of approximately 375 m2, enclosed in a tonalitic batholith. Where visible, the contact between country rock and the orbicular body is characterized by a zone of comb layering. The orbicular body has a porphyritic granodiorite matrix. The surface ratio of matrix/orbicules is 35/65; orbicules are mainly ellipsoidal with an average axis of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mount Magnet, Western Australia
Mount Magnet is a town in the Mid West region of Western Australia. It is one of the region's original gold mining towns, and the longest surviving gold mining settlement in the state. The prominent hill that is adjacent to the current townsite was called West Mount Magnet in 1854 by explorer Robert Austin, having named a smaller hill 64 km away, East Mount Magnet (now called Carron Hill). Both hills had an extremely high iron content which affected the readings of his compass. West Mount Magnet had its Aboriginal name reinstated by the Surveyor General in 1972, "Warramboo," meaning campfire camping place. The magnetic variation at Mount Magnet is zero: magnetic north equals true north. Overview Surrounding the town are remnants of old gold mining operations, and to the north east are significant Aboriginal sites being preserved jointly by the local community and the Western Australian Museum. Its history is sustained through the Wirnda Barna Arts Centre, and the Mount M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porphyritic
Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning all types of igneous rocks can display some degree of porphyritic texture. Most Porphyritic rocks have bimodal size ranges, meaning the rock is composed of two distinct sizes of crystal. In extrusive rocks, the phenocrysts are surrounded by a fine-grained (aphanitic) matrix or groundmass of volcanic glass or non-visible crystals, commonly seen in porphyritic basalt. Porphyritic intrusive rocks have a matrix with individual crystals easily distinguished with the eye, but one group of crystals appearing clearly much bigger than the rest, as in a porphyritic granite. The term comes 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 pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pluton (geology)
In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and compositions, illustrated by examples like the Palisades Sill of New York and New Jersey; the Henry Mountains of Utah; the Bushveld Igneous Complex of South Africa; Shiprock in New Mexico; the Ardnamurchan intrusion in Scotland; and the Sierra Nevada Batholith of California. Because the solid country rock into which magma intrudes is an excellent insulator, cooling of the magma is extremely slow, and intrusive igneous rock is coarse-grained (phaneritic). Intrusive igneous rocks are classified separately from extrusive igneous rocks, generally on the basis of their mineral content. The relative amounts of quartz, alkali feldspar, plagioclase, and feldspathoid is particularly important in classifying intrusive igneous rocks. Intrusions m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salar De Atacama
Salar de Atacama is the largest salt flat in Chile. It is located south of San Pedro de Atacama, is surrounded by mountains, and has no drainage outlets. In the east it is enclosed by the main chain of the Andes, while to the west lies a secondary mountain range of the Andes called Cordillera de Domeyko. Large volcanoes dominate the landscape, including the Licancabur, Acamarachi, Aguas Calientes and the Láscar. The last is one of the most active volcanoes in Chile. All of them are located along the eastern side of the Salar de Atacama, forming a generally north-south trending line of volcanoes that separate it from smaller endorheic basins. Features The salt flat encompasses , is about long and wide, which makes it the third largest in the world, after Salar de Uyuni in Bolivia (). and Salinas Grandes in Argentina (). Its average elevation is about 2,300 m above sea level. The topography of the core portion of the ''salar'' exhibits a high level of roughness, the result of e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cordón De Lila
{{Antofagasta-geo-stub ...
Cordón de Lila is a mountain range of the Andes located in northern Chile, south of Salar de Atacama. Geologically it is made up of a batholith of Cambrian and Ordovician age. The rocks of Cordón de Lila are the result of pre-Andean magmatism that occurred during the Famatinian orogeny. The compositions of the plutonic rocks are granodiorite and monzogranite that are either metaluminous or marginally peraluminous. These rocks are remnants of the magmatism along the western rim of the Famatinian orogeny. References Landforms of Antofagasta Region Lila Lila or LILA may refer to: Arts and entertainment * ''Lila'' (album), debut album by American country music singer Lila McCann * ''Lila'' (movie), a 1968 sexploitation film * The Meaning of Lila, a comic strip written by John Forgetta and L. A. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
K-feldspar
Orthoclase, or orthoclase feldspar (endmember formula K Al Si3 O8), is an important tectosilicate mineral which forms igneous rock. The name is from the Ancient Greek for "straight fracture," because its two cleavage planes are at right angles to each other. It is a type of potassium feldspar, also known as K-feldspar. The gem known as moonstone (see below) is largely composed of orthoclase. Formation and subtypes Orthoclase is a common constituent of most granites and other felsic igneous rocks and often forms huge crystals and masses in pegmatite. Typically, the pure potassium endmember of orthoclase forms a solid solution with albite, the sodium endmember (NaAlSi3O8), of plagioclase. While slowly cooling within the earth, sodium-rich albite lamellae form by exsolution, enriching the remaining orthoclase with potassium. The resulting intergrowth of the two feldspars is called perthite. The higher-temperature polymorph of KAlSi3O8 is sanidine. Sanidine is common in rapidly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at . Since the transformation is accompanied by a significant change in volume, it can easily induce microfracturing of ceramics or rocks passing through this temperature threshold. There are many different varieties of quartz, several of which are classified as gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia. Quartz is the mineral defining the val ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetite
Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the exception of extremely rare native iron deposits, it is the most magnetic of all the naturally occurring minerals on Earth. Naturally magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, which is how ancient peoples first discovered the property of magnetism. Magnetite is black or brownish-black with a metallic luster, has a Mohs hardness of 5–6 and leaves a black streak. Small grains of magnetite are very common in igneous and metamorphic rocks. The chemical IUPAC name is iron(II,III) oxide and the common chemical name is ''ferrous-ferric oxide''. Properties In addition to igneous rocks, magnetite also occurs in sedimentary rocks, including banded iron formations and in lake and marine sediments ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biotite
Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous end-members include siderophyllite and eastonite. Biotite was regarded as a mineral ''species'' by the International Mineralogical Association until 1998, when its status was changed to a mineral ''group''. The term ''biotite'' is still used to describe unanalysed dark micas in the field. Biotite was named by J.F.L. Hausmann in 1847 in honor of the French physicist Jean-Baptiste Biot, who performed early research into the many optical properties of mica. Members of the biotite group are sheet silicates. Iron, magnesium, aluminium, silicon, oxygen, and hydrogen form sheets that are weakly bound together by potassium ions. The term "iron mica" is sometimes used for iron-rich biotite, but the term also refers to a flaky micaceous form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clinopyroxene
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 (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 silica tetrahedra. Pyroxenes that crystallize in the monoclinic system are known as clinopyroxenes and those that crystallize in the orthorhombic system are known as orthopyroxenes. The name ''pyroxene'' is derived from the Ancient Greek words for 'fire' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amphibole
Amphibole () is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is Amp. Amphiboles can be green, black, colorless, white, yellow, blue, or brown. The International Mineralogical Association currently classifies amphiboles as a mineral supergroup, within which are two groups and several subgroups. Mineralogy Amphiboles crystallize into two crystal systems, monoclinic and orthorhombic. In chemical composition and general characteristics they are similar to the pyroxenes. The chief differences from pyroxenes are that (i) amphiboles contain essential hydroxyl (OH) or halogen (F, Cl) and (ii) the basic structure is a double chain of tetrahedra (as opposed to the single chain structure of pyroxene). Most apparent, in hand specimens, is that amphiboles form oblique cleavage planes (at around 120 degrees), whe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plagioclase
Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more properly known as the plagioclase feldspar series. This was first shown by the German mineralogist Johann Friedrich Christian Hessel (1796–1872) in 1826. The series ranges from albite to anorthite endmembers (with respective compositions NaAlSi3O8 to CaAl2Si2O8), where sodium and calcium atoms can substitute for each other in the mineral's crystal lattice structure. Plagioclase in hand samples is often identified by its polysynthetic crystal twinning or 'record-groove' effect. Plagioclase is a major constituent mineral in the Earth's crust, and is consequently an important diagnostic tool in petrology for identifying the composition, origin and evolution of igneous rocks. Plagioclase is also a major constituent of rock in the highlan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
