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Siderite
Siderite is a mineral composed of iron(II) carbonate (FeCO3). It takes its name from the Greek word σίδηρος ''sideros,'' "iron". It is a valuable iron mineral, since it is 48% iron and contains no sulfur or phosphorus. Zinc, magnesium and manganese commonly substitute for the iron resulting in the siderite-smithsonite, siderite- magnesite and siderite-rhodochrosite solid solution series. Siderite has Mohs hardness of 3.75-4.25, a specific gravity of 3.96, a white streak and a vitreous lustre or pearly luster. Siderite is antiferromagnetic below its Néel temperature of 37 K which can assist in its identification. It crystallizes in the trigonal crystal system, and are rhombohedral in shape, typically with curved and striated faces. It also occurs in masses. Color ranges from yellow to dark brown or black, the latter being due to the presence of manganese. Siderite is commonly found in hydrothermal veins, and is associated with barite, fluorite, galena, and others. It i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concretion
A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin "(act of) compacting, condensing, congealing, uniting", itself from ''con'' meaning 'together' and ''crescere'' meaning "to grow". Concretions form within layers of sedimentary strata that have already been deposited. They usually form early in the burial history of the sediment, before the rest of the sediment is hardened into rock. This concretionary cement often makes the concretion harder and more resistant to weathering than the host stratum. There is an important distinction to draw between concretions and nodules. Concretions are formed from mineral precipitation around some kind of nucleus while a nodule is a replacement body. Descriptions dating from the 18th ce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnesite
Magnesite is a mineral with the chemical formula (magnesium carbonate). Iron, manganese, cobalt, and nickel may occur as admixtures, but only in small amounts. Occurrence Magnesite occurs as veins in and an alteration product of ultramafic rocks, serpentinite and other magnesium rich rock types in both contact and regional metamorphic terrains. These magnesites are often cryptocrystalline and contain silica in the form of opal or chert. Magnesite is also present within the regolith above ultramafic rocks as a secondary carbonate within soil and subsoil, where it is deposited as a consequence of dissolution of magnesium-bearing minerals by carbon dioxide in groundwaters. Isotopic structure: clumped isotope The recent advancement in the field of stable isotope geochemistry is the study of isotopic structure of minerals and molecules. This requires study of molecules with high resolutions looking at bonding scenario (how heavy isotopes are bonded to each other)- leading to kno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diagenesis
Diagenesis () is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play a role as sediments become buried much deeper in the Earth's crust. In the early stages, the transformation of poorly consolidated sediments into sedimentary rock (lithification) is simply accompanied by a reduction in porosity and water expulsion (clay sediments), while their main mineralogical assemblages remain unaltered. As the rock is carried deeper by further deposition above, its organic content is progressively transformed into kerogens and bitumens. The process of diagenesis excludes surface alteration (weathering) and deep metamorphism. There is no sharp boundary between diagenesis and metamorphism, but the latter occurs at higher temperatures and pressures. Hydrothermal solutions, meteoric groundwater, rock porosity, permeability, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Smithsonite
Smithsonite, also known as zinc spar, is the mineral form of zinc carbonate ( Zn CO3). Historically, smithsonite was identified with hemimorphite before it was realized that they were two different minerals. The two minerals are very similar in appearance and the term calamine has been used for both, leading to some confusion. The distinct mineral smithsonite was named in 1832 by François Sulpice Beudant in honor of English chemist and mineralogist James Smithson (c.1765–1829), who first identified the mineral in 1802. Smithsonite is a variably colored trigonal mineral which only rarely is found in well formed crystals. The typical habit is as earthy botryoidal masses. It has a Mohs hardness of 4.5 and a specific gravity of 4.4 to 4.5. Smithsonite occurs as a secondary mineral in the weathering or oxidation zone of zinc-bearing ore deposits. It sometimes occurs as replacement bodies in carbonate rocks and as such may constitute zinc ore. It commonly occurs in association with he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron(II) Carbonate
Iron(II) carbonate, or ferrous carbonate, is a chemical compound with formula , that occurs naturally as the mineral siderite. At ordinary ambient temperatures, it is a green-brown ionic solid consisting of iron(II) cations and carbonate anions . Preparation Ferrous carbonate can be prepared by reacting solution of the two ions, such as iron(II) chloride and sodium carbonate: : + → + 2 Ferrous carbonate can be prepared also from solutions of an iron(II) salt, such as iron(II) perchlorate, with sodium bicarbonate, releasing carbon dioxide: : ()2 + 2 → + 2 + + Sel and others used this reaction (but with instead of ()2) at 0.2 M to prepare amorphous . Care must be taken to exclude oxygen from the solutions, because the ion is easily oxidized to , especially at pH above 6.0. Ferrous carbonate also forms directly on steel or iron surfaces exposed to solutions of carbon dioxide, forming an "iron carbonate" scale: : + + → + Properties The dependency of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhodochrosite
Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO3. In its (rare) pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown. It streaks white, and its Mohs hardness varies between 3.5 and 4. Its specific gravity is between 3.5 and 3.7. It crystallizes in the trigonal system, and cleaves with rhombohedral carbonate cleavage in three directions. Crystal twinning often is present. It is transparent to translucent with refractive indices of ''nω''=1.814 to 1.816, ''nε''=1.596 to 1.598. It is often confused with the manganese silicate, rhodonite, but is distinctly softer. It is officially listed as one of the National symbols of Argentina. Rhodochrosite forms a complete solid solution series with iron carbonate (siderite). Calcium, (as well as magnesium and zinc, to a limited extent) frequently substitutes for manganese in the structure, leading to lighter shades of red and pink, depending on the degree of substit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trigonal Crystal System
In crystallography, the hexagonal crystal family is one of the six crystal families, which includes two crystal systems (hexagonal and trigonal) and two lattice systems (hexagonal and rhombohedral). While commonly confused, the trigonal crystal system and the rhombohedral lattice system are not equivalent (see section crystal systems below). In particular, there are crystals that have trigonal symmetry but belong to the hexagonal lattice (such as α-quartz). The hexagonal crystal family consists of the 12 point groups such that at least one of their space groups has the hexagonal lattice as underlying lattice, and is the union of the hexagonal crystal system and the trigonal crystal system. There are 52 space groups associated with it, which are exactly those whose Bravais lattice is either hexagonal or rhombohedral. __TOC__ Lattice systems The hexagonal crystal family consists of two lattice systems: hexagonal and rhombohedral. Each lattice system consists of one Bravais la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhombohedral
In geometry, a rhombohedron (also called a rhombic hexahedron or, inaccurately, a rhomboid) is a three-dimensional figure with six faces which are rhombus, rhombi. It is a special case of a parallelepiped where all edges are the same length. It can be used to define the rhombohedral lattice system, a Honeycomb (geometry), honeycomb with rhombohedral cells. A cube is a special case of a rhombohedron with all sides square. In general a ''rhombohedron'' can have up to three types of rhombic faces in congruent opposite pairs, ''C''''i'' symmetry, Order (group theory), order 2. Four points forming non-adjacent vertices of a rhombohedron necessarily form the four vertices of an orthocentric tetrahedron, and all orthocentric tetrahedra can be formed in this way. Rhombohedral lattice system The rhombohedral lattice system has rhombohedral cells, with 6 congruent rhombic faces forming a trigonal trapezohedron: : Special cases by symmetry * Cube: with Octahedral symmetry, Oh symm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrothermal Circulation
Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with the assistance of. Roderick McKenzie.'' Oxford: Clarendon Press. and θέρμη, ''heat'' ). Hydrothermal circulation occurs most often in the vicinity of sources of heat within the Earth's crust. In general, this occurs near volcanic activity, but can occur in the shallow to mid crust along deeply penetrating fault irregularities or in the deep crust related to the intrusion of granite, or as the result of orogeny or metamorphism. Seafloor hydrothermal circulation Hydrothermal circulation in the oceans is the passage of the water through mid-oceanic ridge systems. The term includes both the circulation of the well-known, high-temperature vent waters near the ridge crests, and the much-lower-temperature, diffuse flow of water through sedim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barite
Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate ( Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), anglesite (lead sulfate), and anhydrite (calcium sulfate). Baryte and celestine form a solid solution (Ba,Sr)SO4. Names and history The radiating form, sometimes referred to as ''Bologna Stone'', attained some notoriety among alchemists for specimens found in the 17th century near Bologna by Vincenzo Casciarolo. These became phosphorescent upon being calcined. Carl Scheele determined that baryte contained a new element in 1774, but could not isolate barium, only barium oxide. Johan Gottlieb Gahn also isolated barium oxide two years later in similar studies. Barium was first isolated by electrolysis of molten barium salts in 1808 by Sir Humphry Davy in England. The American Petroleum Institute specification API 13/ISO 13500, which gover ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vein (geology)
In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation. The hydraulic flow involved is usually due to hydrothermal circulation. Veins are classically thought of as being the ones in the body not the rock veins and arteries planar fractures in rocks, with the crystal growth occurring normal to the walls of the cavity, and the crystal protruding into open space. This certainly is the method for the formation of some veins. However, it is rare in geology for significant open space to remain open in large volumes of rock, especially several kilometers below the surface. Thus, there are two main mechanisms considered likely for the formation of veins: ''open-space filling'' and ''crack-seal growth''. Open space filling Open space filling is the hallmark of epithermal vein systems, such as a stockwork, in greisens or in cert ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antiferromagnetism
In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions. This is, like ferromagnetism and ferrimagnetism, a manifestation of ordered magnetism. The phenomenon of antiferromagnetism was first introduced by Lev Landau in 1933. Generally, antiferromagnetic order may exist at sufficiently low temperatures, but vanishes at and above the Néel temperature – named after Louis Néel, who had first identified this type of magnetic ordering. Above the Néel temperature, the material is typically paramagnetic. Measurement When no external field is applied, the antiferromagnetic structure corresponds to a vanishing total magnetization. In an external magnetic field, a kind of ferrimagnetic behavior may be displayed in the antiferromagnetic phase, with the absolute value of one of the sublattice magneti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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