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Chiastolite
Chiastolite ( ) is a variety of the mineral andalusite with the chemical composition Al2SiO5. It is noted for its distinctive cross-shaped black inclusions of graphite. The presence of these crosses caused the mineral to be used as a gem. Chiastolite specimens were distributed throughout Europe from the 16th century, as an amulet or souvenir provided by the pilgrims returning from Santiago de Compostela (Saint James of Compostella), in Spain. In the old books of mineralogy, chiastolite appears it is cited with the name of l''apis crucifer'' or ''lapis cruciatur'', cross stone. The first figure of a chiastolite appears in Laet's book ''De Gemmis et Lapidibus'', published in 1648. The chiastolite specimens sold to the pilgrims came from Asturias, where it is very abundant, in large specimens, in the area of Boal. In areas around Georgetown, California, US, metamorphosed sediments contained andalusite and chiastolite in a graphite-rich metasediment. The chiastolite crystals have be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andalusite
Andalusite is an aluminium nesosilicate mineral with the chemical formula Al2SiO5. This mineral was called andalousite by Delamétherie, who thought it came from Andalusia, Spain. It soon became clear that it was a locality error, and that the specimens studied were actually from El Cardoso de la Sierra, in the Spanish province of Guadalajara, not Andalusia. Andalusite is trimorphic with kyanite and sillimanite, being the lower pressure mid temperature polymorph. At higher temperatures and pressures, andalusite may convert to sillimanite. Thus, as with its other polymorphs, andalusite is an aluminosilicate index mineral, providing clues to depth and pressures involved in producing the host rock. Varieties The variety chiastolite commonly contains dark inclusions of carbon or clay which form a cruciform pattern when shown in cross-section. This stone was known at least from the sixteenth century, being taken to many European countries, as a souvenir, by pilgrims returning fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Margarite
Margarite is a calcium rich member of the mica group of the phyllosilicates with formula: Ca Al2(Al2 Si2) O10(O H)2. It forms white to pinkish or yellowish gray masses or thin laminae. It crystallizes in the monoclinic crystal system. It typically has a specific gravity of around 3 and a Mohs hardness of 4. It is translucent with perfect 010 cleavage and exhibits crystal twinning. It occurs commonly as an alteration product of corundum, andalusite and other aluminous minerals. It has been reported as forming alteration pseudomorphs of chiastolite along with muscovite and paragonite. The margarite in this occurrence forms preferentially along the dark graphite rich inclusions with the chiastolite crystals. Margarite is found in the emery deposits of Turkey and the Aegean islands, and with corundum at several localities in the United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North Amer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muscovite
Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated phyllosilicate mineral of aluminium and potassium with formula KAl2(Al Si3 O10)( F,O H)2, or ( KF)2( Al2O3)3( SiO2)6( H2O). It has a highly perfect basal cleavage yielding remarkably thin laminae (sheets) which are often highly elastic. Sheets of muscovite have been found in Nellore, India. Muscovite has a Mohs hardness of 2–2.25 parallel to the 01face, 4 perpendicular to the 01and a specific gravity of 2.76–3. It can be colorless or tinted through grays, violet or red, and can be transparent or translucent. It is anisotropic and has high birefringence. Its crystal system is monoclinic. The green, chromium-rich variety is called fuchsite; mariposite is also a chromium-rich type of muscovite. Muscovite is the most common mica, found in granites, pegmatites, gneisses, and schists, and as a contact metamorphic rock or as a secondary mineral resulting from the alteration of topaz, feldspar, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nesosilicates
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 seawat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aluminium Minerals
Aluminium (or aluminum in North American English) is a chemical element; it has symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has a great affinity towards oxygen, forming a protective layer of oxide on the surface when exposed to air. It visually resembles silver, both in its color and in its great ability to reflect light. It is soft, nonmagnetic, and ductile. It has one stable isotope, 27Al, which is highly abundant, making aluminium the 12th-most abundant element in the universe. The radioactivity of 26Al leads to it being used in radiometric dating. Chemically, aluminium is a post-transition metal in the boron group; as is common for the group, aluminium forms compounds primarily in the +3 oxidation state. The aluminium cation Al3+ is small and highly charged; as such, it has more polarizing power, and bonds formed by aluminium have a more covalent character. The s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prentice Hall
Prentice Hall was a major American publishing#Textbook_publishing, educational publisher. It published print and digital content for the 6–12 and higher-education market. It was an independent company throughout the bulk of the twentieth century. In its last few years it was owned by, then absorbed into, Savvas Learning Company. In the Web era, it distributed its technical titles through the Safari Books Online e-reference service for some years. History On October 13, 1913, law professor Charles Gerstenberg and his student Richard Ettinger founded Prentice Hall. Gerstenberg and Ettinger took their mothers' maiden names, Prentice and Hall, to name their new company. At the time the name was usually styled as Prentice-Hall (as seen for example on many title pages), per an orthographic norm for Dash#Relationships and connections, coordinate elements within such compounds (compare also ''McGraw-Hill'' with later styling as ''McGraw Hill''). Prentice-Hall became known as a publi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Mineralogist
''American Mineralogist: An International Journal of Earth and Planetary Materials'' is a peer-reviewed scientific journal covering the general fields of mineralogy, crystallography, geochemistry, and petrology. It is an official journal of the Mineralogical Society of America, publishing both subscription and open access articles. The journal is a hybrid open-access journal. The editors-in-chief are Hongwu Xu (Los Alamos National Laboratory), and Don Baker (McGill University). History The journal was established in 1916, with the first issue appearing in July of that year, under the auspices of the ''Philadelphia Mineralogical Society'', the ''New York Mineralogical Club'', and the ''Mineral Collectors' Association''. On December 30, 1919, the Mineralogical Society of America was formed and ''American Mineralogist'' became the society's journal. Abstracting and indexing The ''American Mineralogist'' is abstracted and indexed in Chemical Abstracts, the Science Citation Index, Ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paragonite
Paragonite is a mineral, related to muscovite. Its empirical formula is . A wide solvus separates muscovite from paragonite, such that there is little solid solution along the vector Na+ K+ and apparent micas of intermediate composition is most commonly a microscopic (or even sub-microscopic) intergrowth of two distinct micas, one rich in K, and the other in Na. Paragonite is a common mineral in rocks metamorphosed under blueschist facies conditions along with other sodic minerals such as albite, jadeite and glaucophane. During the transition from blueschist to greenschist facies, paragonite and glaucophane are transformed into chlorite and albite. Jadeite bearing pyroxene minerals have suggested clinozoisite and paragonite are associated and derived from lawsonite releasing quartz and water via the following reaction: 4CaAl2Si2O8(H2O)2 + NaAlSi2O6 2Ca2Al3Si3O12(OH) + NaAl3Si3O10(OH)2 + SiO2 + 6H2O It was first described in 1843 for an occurrence at Mt. Campione, Tessin, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Georgetown, California
Georgetown (formerly Growlersburg) is a census-designated place (CDP) in El Dorado County, California, United States. It is the northeasternmost town in the California Mother Lode. The population was 2,546 in the 2020 census, up from 2,367 in 2010, and 962 in 2000. The town is registered as California Historical Landmark #484. History Founded August 7, 1849, by George Phipps and party, Georgetown was nicknamed "Growlersburg" due to the heavy, gold-laden quartz rocks that "growled" in the miners' pants as they walked around town. Georgetown is named for George Washington. The first post office was established in 1851. After a disastrous fire in 1852, the old town was moved from the canyon in lower Main Street to its present site, and, unique in early-day planning, Main Street was laid out wide, with side streets . After this new reconstruction, the residents of the city proclaimed their town as the "Pride of the Mountains". The hub of an immensely rich gold mining area, Georget ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudomorph
In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form (crystal system), resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced by another due to alteration, or chemical substitution, dissolution and refilling, structural changes or incrustation. The name literally means "false form". Terminology for pseudomorphs is "''replacer'' after ''original''", as in ''brookite'' after ''rutile''. The term ''pseudomorphoses'' was initially used by Haüy. Substitution pseudomorph A substitution pseudomorph is a pseudomorph in which one mineral or other material is replaced by another. The original shape of the mineral remains unchanged, but chemical composition, color, hardness, and other properties change to those of the replacing mineral. This happens typically when a mineral of one composition changes by chemical reaction to another of similar composition, retaining t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Minerals'; p. 1. In the series ''Geology: Landforms, Minerals, and Rocks''. Rosen Publishing Group. The Geology, geological definition of mineral normally excludes compounds that occur only in living organisms. However, some minerals are often biogenic (such as calcite) or organic compounds in the sense of chemistry (such as mellite). Moreover, living organisms often synthesize inorganic minerals (such as hydroxylapatite) that also occur in rocks. The concept of mineral is distinct from rock (geology), rock, which is any bulk solid geologic material that is relatively homogeneous at a large enough scale. A rock may consist of one type of mineral or may be an aggregate (geology), aggregate of two or more different types of minerals, spaci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
