|
Potash 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 alkali feldspar, also known as potassium feldspar or K-spar. The gem known as moonstone (see below) is largely composed of orthoclase. Formation and subtypes left, Orthoclase Organ_Mountains.html" ;"title="crystal twinning from the Organ Mountains">crystal twinning from the Organ Mountains in New Mexico 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 p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tectosilicate
Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, the crystalline forms of silica (silicon dioxide, ) are usually considered to be tectosilicates, and they are classified as such in the Dana system (75.1). However, the Nickel-Strunz system classifies them as oxide minerals (4.DA). Silica is found in nature as the mineral quartz, and its polymorphs. On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes that have been forming and re-working the crust for billions of years. These processes include partial melting, crystallization, fractionation, metamorphism, weathering, and diagenesis. Living organisms also contribute to this geologic cycle. For example, a type of plankton known as diatoms construct their exoskeletons ("frustules") from silica extracted from sea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lamella (materials)
A lamella (: lamellae) is a small plate or flake, from the Latin, and may also refer to collections of fine sheets of material held adjacent to one another in a gill-shaped structure, often with fluid in between though sometimes simply a set of "welded" plates. The term is used in biological contexts for thin membranes of plates of tissue. In the context of materials science, the microscopic structures in bone and nacre are called lamellae. Moreover, the term lamella is often used to describe crystal structure of some materials. Uses of the term In surface chemistry (especially mineralogy and materials science), lamellar structures are fine layers, alternating between different materials. They can be produced by chemical effects (as in eutectic solidification), biological means, or a deliberate process of lamination, such as pattern welding. Lamellae can also describe the layers of atoms in the crystal lattices of materials such as metals. In surface anatomy, a lamella is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plagioclase
Plagioclase ( ) is a series of Silicate minerals#Tectosilicates, 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 F. C. Hessel, 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 crystallography, crystal lattice structure. Plagioclase in hand samples is often identified by its polysynthetic crystal twinning or "phonograph record, record-groove" effect. Plagioclase is a major constituent mineral in Earth's crust and is consequently an important diagnostic tool in petrology for identifying the composition, origin and evolutio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Albite
Albite is a plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series. It represents a plagioclase with less than 10% anorthite content. The pure albite endmember has the formula . It is a tectosilicate. Its color is usually pure white, hence its name from Latin, . It is a common constituent in felsic rocks. Properties Albite crystallizes with triclinic pinacoidal forms. Its specific gravity is about 2.62 and it has a Mohs hardness of 6 to 6.5. Albite almost always exhibits crystal twinning often as minute parallel striations on the crystal face. Albite often occurs as fine parallel segregations alternating with pink microcline in perthite as a result of exolution on cooling. There are two variants of albite, which are referred to as 'low albite' and 'high albite'; the latter is also known as 'analbite'. Although both variants are triclinic, they differ in the volume of their unit cell, which is slightly larger for the 'high' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solid Solution
A solid solution, a term popularly used for metals, is a homogeneous mixture of two compounds in solid state and having a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The word "solution" is used to describe the intimate mixing of components at the atomic level and distinguishes these homogeneous materials from physical mixtures of components. Two terms are mainly associated with solid solutions – ''solvents'' and ''solutes,'' depending on the relative abundance of the atomic species. In general if two compounds are isostructural then a solid solution will exist between the end members (also known as parents). For example sodium chloride and potassium chloride have the same cubic crystal structure so it is possible to make a pure compound with any ratio of sodium to potassium (Na1-xKx)Cl by dissolving that ratio of NaCl and KCl in water and then evaporating the solution. A member of this family is sold under the bra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pegmatite
A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic composition to granite. However, rarer intermediate composition and mafic pegmatites are known. Many of the world's largest crystals are found within pegmatites. These include crystals of microcline, quartz, mica, spodumene, beryl, and tourmaline. Some individual crystals are over long. Most pegmatites are thought to form from the last fluid fraction of a large crystallizing magma body. This residual fluid is highly enriched in volatiles and trace elements, and its very low viscosity allows components to migrate rapidly to join an existing crystal rather than coming together to form new crystals. This allows a few very large crystals to form. While most pegmatites have a simple composition of minerals common in ordinary igneous rock ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Felsic
In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted with mafic rocks, which are richer in magnesium and iron. Felsic refers to silicate minerals, magma, and rock (geology), rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Molten felsic magma and lava is more viscosity, viscous than molten mafic magma and lava. Felsic magmas and lavas have lower temperatures of melting and solidification than mafic magmas and lavas. Felsic rocks are usually light in color and have specific gravity, specific gravities less than 3. The most common felsic rock is granite. Common felsic minerals include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars (albite-rich). Terminology Acid rock In modern usage, the term ''acid rock ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Granite
Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground. It is common in the continental crust of Earth, where it is found in igneous intrusions. These range in size from dike (geology), dikes only a few centimeters across to batholiths exposed over hundreds of square kilometers. Granite is typical of a larger family of ''granitic rocks'', or ''granitoids'', that are composed mostly of coarse-grained quartz and feldspars in varying proportions. These rocks are classified by the relative percentages of quartz, alkali feldspar, and plagioclase (the QAPF diagram, QAPF classification), with true granite representing granitic rocks rich in quartz and alkali feldspar. Most granitic rocks also contain mica or amphibole minerals, though a few (known as leucogranites) conta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moonstone (gemstone)
Moonstone is a sodium potassium aluminium silicate minerals, silicate ((Na,K)AlSi3O8) of the feldspar group that displays a pearly and opalescence, opalescent Lustre (mineralogy)#Schiller, schiller. An alternative name for moonstone is hecatolite (from goddess Hecate). Etymology The name ''moonstone'' derives from the stone's characteristic visual effect, called adularescence (or schiller), which produces a milky, bluish interior light. This effect is caused by light diffraction through alternating layers of orthoclase and albite within the stone. The diffracted light varies from white to blue, depending on the thinness of the albite layers. More technically, this micro-structure consists of regular exsolution layers (lamellae) of different alkali feldspars (orthoclase and sodium-rich plagioclase). Polished moonstones often display chatoyancy ("cat's eye" effect), where a luminous streak appears through the stone. Asterism (gemology), Asterism is rare and produces four-legged ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Feldspar
Feldspar ( ; sometimes spelled felspar) is 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 crystallize 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. Etymology The name ''feldspar'' derives from the German , a compound of the words ' ("field") and ("flake"). had long been used as the word for "a rock easily cleaved into flakes"; was introduced in the 18th century as a more specific term, referring perhaps to its comm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
