Hornblende is a complex inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende is an isomorphous mixture of three molecules; the general formula can be given as 2–358O222. Some metals vary in their occurrence and magnitude: Manganese and titanium are present. Sodium and potassium are present and fluorine substitutes for the hydroxyl in the crystalline structure. Hornblende has a hardness of 5–6, a specific gravity of 2.9–3.4 and is an opaque green, greenish-brown, brown or black color. Its cleavage angles are at 124 degrees, it is most confused with various pyroxene minerals and biotite mica, which are black and can be found in granite and in charnockite. Hornblende is a common constituent of many igneous and metamorphic rocks such as granite, diorite, basalt, andesite and schist, it is the principal mineral of amphibolites. Dark brown to black hornblendes that contain titanium are ordinarily called basaltic hornblende, from the fact that they are a constituent of basalt and related rocks.
Hornblende alters to chlorite and epidote. A rare variety of hornblende contains less than 5% of iron oxide, is gray to white in color, named edenite, from its locality in Edenville, Orange County, New York. Other minerals in the hornblende series include: pargasite hastingsite tschermakite edenite The word hornblende is derived from the German horn and blenden, to'deceive' in allusion to its similarity in appearance to metal-bearing ore minerals. List of minerals – A list of minerals for which there are articles on Wikipedia Hurlbut, Cornelius S..
Quartz is a mineral composed of silicon and oxygen atoms 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 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 573 °C. Since the transformation is accompanied by a significant change in volume, it can induce fracturing of ceramics or rocks passing through this temperature threshold. There are many different varieties of quartz. Since antiquity, varieties of quartz have been the most used minerals in the making of jewelry and hardstone carvings in Eurasia; the word "quartz" is derived from the German word "Quarz", which had the same form in the first half of the 14th century in Middle High German in East Central German and which came from the Polish dialect term kwardy, which corresponds to the Czech term tvrdý.
The Ancient Greeks referred to quartz as κρύσταλλος derived from the Ancient Greek κρύος meaning "icy cold", because some philosophers believed the mineral to be a form of supercooled ice. Today, the term rock crystal is sometimes used as an alternative name for the purest form of quartz. Quartz belongs to the trigonal crystal system; the ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end. In nature quartz crystals are twinned, distorted, or so intergrown with adjacent crystals of quartz or other minerals as to only show part of this shape, or to lack obvious crystal faces altogether and appear massive. Well-formed crystals form in a'bed' that has unconstrained growth into a void. However, doubly terminated crystals do occur where they develop without attachment, for instance within gypsum. A quartz geode is such a situation where the void is spherical in shape, lined with a bed of crystals pointing inward. Α-quartz crystallizes in the trigonal crystal system, space group P3121 or P3221 depending on the chirality.
Β-quartz belongs to space group P6222 and P6422, respectively. These space groups are chiral. Both α-quartz and β-quartz are examples of chiral crystal structures composed of achiral building blocks; the transformation between α- and β-quartz only involves a comparatively minor rotation of the tetrahedra with respect to one another, without change in the way they are linked. Although many of the varietal names arose from the color of the mineral, current scientific naming schemes refer to the microstructure of the mineral. Color is a secondary identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties. Pure quartz, traditionally called rock crystal or clear quartz, is colorless and transparent or translucent, has been used for hardstone carvings, such as the Lothair Crystal. Common colored varieties include citrine, rose quartz, smoky quartz, milky quartz, others; these color differentiation's arise from chromophores which have been incorporated into the crystal structure of the mineral.
Polymorphs of quartz include: α-quartz, β-quartz, moganite, cristobalite and stishovite. The most important distinction between types of quartz is that of macrocrystalline and the microcrystalline or cryptocrystalline varieties; the cryptocrystalline varieties are either translucent or opaque, while the transparent varieties tend to be macrocrystalline. Chalcedony is a cryptocrystalline form of silica consisting of fine intergrowths of both quartz, its monoclinic polymorph moganite. Other opaque gemstone varieties of quartz, or mixed rocks including quartz including contrasting bands or patterns of color, are agate, carnelian or sard, onyx and jasper. Amethyst is a form of quartz that ranges from a dull purple color; the world's largest deposits of amethysts can be found in Brazil, Uruguay, France and Morocco. Sometimes amethyst and citrine are found growing in the same crystal, it is referred to as ametrine. An amethyst is formed. Blue quartz contains inclusions of fibrous crocidolite. Inclusions of the mineral dumortierite within quartz pieces result in silky-appearing splotches with a blue hue, shades giving off purple and/or grey colors additionally being found.
"Dumortierite quartz" will sometimes feature contrasting light and dark color zones across the material. Interest in the certain quality forms of blue quartz as a collectible gemstone arises in India and in the United States. Citrine is a variety of quartz whose color ranges from a pale yellow to brown due to ferric impurities. Natural citrines are rare. However, a heat-treated amethyst will have small lines in the crystal, as opposed to a natural citrine's cloudy or smokey appearance, it is nearly impossible to differentiate between cut citrine and yellow topaz visually, but they differ in hardness. Brazil is the leading producer of citrine, with much
The alkali metals are a group in the periodic table consisting of the chemical elements lithium, potassium, rubidium and francium. This group lies in the s-block of the periodic table of elements as all alkali metals have their outermost electron in an s-orbital: this shared electron configuration results in their having similar characteristic properties. Indeed, the alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterised homologous behaviour; the alkali metals are all shiny, soft reactive metals at standard temperature and pressure and lose their outermost electron to form cations with charge +1. They can all be cut with a knife due to their softness, exposing a shiny surface that tarnishes in air due to oxidation by atmospheric moisture and oxygen; because of their high reactivity, they must be stored under oil to prevent reaction with air, are found only in salts and never as the free elements. Caesium, the fifth alkali metal, is the most reactive of all the metals.
In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, excluding hydrogen, nominally a group 1 element but not considered to be an alkali metal as it exhibits behaviour comparable to that of the alkali metals. All the alkali metals react with water, with the heavier alkali metals reacting more vigorously than the lighter ones. All of the discovered alkali metals occur in nature as their compounds: in order of abundance, sodium is the most abundant, followed by potassium, rubidium and francium, rare due to its high radioactivity. Experiments have been conducted to attempt the synthesis of ununennium, to be the next member of the group, but they have all met with failure. However, ununennium may not be an alkali metal due to relativistic effects, which are predicted to have a large influence on the chemical properties of superheavy elements. Most alkali metals have many different applications. One of the best-known applications of the pure elements is the use of rubidium and caesium in atomic clocks, of which caesium atomic clocks are the most accurate and precise representation of time.
A common application of the compounds of sodium is the sodium-vapour lamp, which emits light efficiently. Table salt, or sodium chloride, has been used since antiquity. Lithium finds use as an anode in lithium batteries. Sodium and potassium are essential elements, having major biological roles as electrolytes, although the other alkali metals are not essential, they have various effects on the body, both beneficial and harmful. Sodium compounds have been known since ancient times. While potash has been used since ancient times, it was not understood for most of its history to be a fundamentally different substance from sodium mineral salts. Georg Ernst Stahl obtained experimental evidence which led him to suggest the fundamental difference of sodium and potassium salts in 1702, Henri-Louis Duhamel du Monceau was able to prove this difference in 1736; the exact chemical composition of potassium and sodium compounds, the status as chemical element of potassium and sodium, was not known and thus Antoine Lavoisier did not include either alkali in his list of chemical elements in 1789.
Pure potassium was first isolated in 1807 in England by Sir Humphry Davy, who derived it from caustic potash by the use of electrolysis of the molten salt with the newly invented voltaic pile. Previous attempts at electrolysis of the aqueous salt were unsuccessful due to potassium's extreme reactivity. Potassium was the first metal, isolated by electrolysis; that same year, Davy reported extraction of sodium from the similar substance caustic soda by a similar technique, demonstrating the elements, thus the salts, to be different. Petalite was discovered in 1800 by the Brazilian chemist José Bonifácio de Andrada in a mine on the island of Utö, Sweden. However, it was not until 1817 that Johan August Arfwedson working in the laboratory of the chemist Jöns Jacob Berzelius, detected the presence of a new element while analysing petalite ore; this new element was noted by him to form compounds similar to those of sodium and potassium, though its carbonate and hydroxide were less soluble in water and more alkaline than the other alkali metals.
Berzelius gave the unknown material the name "lithion/lithina", from the Greek word λιθoς, to reflect its discovery in a solid mineral, as opposed to potassium, discovered in plant ashes, sodium, known for its high abundance in animal blood. He named the metal inside the material "lithium". Lithium and potassium were part of the discovery of periodicity, as they are among a series of triads of elements in the same group that were noted by Johann Wolfgang Döbereiner in 1850 as having similar properties. Rubidium and caesium were the first elements to be discovered using the spectroscope, invented in 1859 by Robert Bunsen and Gustav Kirchhoff; the next year, they discovered caesiu
The Danube is Europe's second longest river, after the Volga. It is located in Eastern Europe; the Danube was once a long-standing frontier of the Roman Empire, today flows through 10 countries, more than any other river in the world. Originating in Germany, the Danube flows southeast for 2,850 km, passing through or bordering Austria, Hungary, Serbia, Bulgaria and Ukraine before draining into the Black Sea, its drainage basin extends into nine more countries. The Danube river basin is home to fish species such as pike, huchen, Wels catfish and tench, it is home to a large diversity of carp and sturgeon, as well as salmon and trout. A few species of euryhaline fish, such as European seabass and eel, inhabit the Danube Delta and the lower portion of the river. Since ancient times, the Danube has become a traditional trade route in Europe, nowadays 2,415 km of its total length being navigable; the river is an important source of energy and drinking water. Danube is an Old European river name derived from a Proto-Indo-European *dānu.
Other river names from the same root include the Dunaj, Dzvina/Daugava, Donets, Dniestr, Dysna and Tuoni. In Rigvedic Sanskrit, dānu means "fluid, drop", in Avestan, the same word means "river". In the Rigveda, Dānu once appears as the mother of Vrtra, "a dragon blocking the course of the rivers"; the Finnish word for Danube is Tonava, most derived from the word for the river in Swedish and German, Donau. Its Sámi name Deatnu means "Great River", it is possible that dānu in Scythian as in Avestan was a generic word for "river": Dnieper and Dniestr, from Danapris and Danastius, are presumed to continue Scythian *dānu apara "far river" and *dānu nazdya- "near river", respectively. The river was known to the ancient Greeks as the Istros a borrowing from a Daco-Thracian name meaning "strong, swift", from a root also encountered in the ancient name of the Dniester and akin to Iranic turos “swift” and Sanskrit iṣiras "swift", from the PIE *isro-, *sreu “to flow”. In the Middle Ages, the Greek Tiras was borrowed into Italian as Tyrlo and into Turkic languages as Tyrla, the latter further borrowed into Romanian as a regionalism.
The Thraco-Phrygian name was Matoas, "the bringer of luck". In Latin, the Danube was variously known as Ister; the Latin name is masculine, except Slovenian. The German Donau is feminine, as it has been re-interpreted as containing the suffix -ouwe "wetland". Romanian differs from other surrounding languages in designating the river with a feminine term, Dunărea; this form was not inherited from Latin. To explain the loss of the Latin name, scholars who suppose that Romanian developed near the large river propose that the Romanian name descends from a hypotetical Thracian *Donaris that shares the same PIE root with the Iranic don-/dan-, with the suffix -aris encountered in the ancient name of the Ialomița River, in the unidentified Miliare river mentioned by Jordanes in his Getica. Gábor Vékony says that this hypothesis is not plausible, because the Greeks borrowed the Istros form from the native Thracians, he proposes. The modern languages spoken in the Danube basin all use names related to Dānuvius: German: Donau.
Dunav. Dunai. Classified as an international waterway, it originates in the town of Donaueschingen, in the Black Forest of Germany, at the confluence of the rivers Brigach and Breg; the Danube flows southeast for about 2,730 km, passing through four capital cities before emptying into the Black Sea via the Danube Delta in Romania and Ukraine. Once a long-standing frontier of the Roman Empire, the river passes through or touches the borders of 10 countries: Romania, Serbia, Germany, Slovakia, Croatia and Moldova, its drainage basin extends into nine more. In addition to the bordering countries, the drainage basin includes parts of nine more countries: Bosnia and Herzegovina, the Czech Republic, Montenegro, Italy, North Macedonia and Albania, its total drainage basin is 801,463 km2. The highest point of the drainage basin is the summit of Piz Bernina at the Italy–Switzerland border, at 4,049 metres; the land drained by the Danube extends into many other countries. Many Danubian tributaries are important rivers in their own right, navigable by barges and other shallow-draught boats.
From its source to its outlet into the Black Sea, its main tribu
Andesine is a silicate mineral, a member of the plagioclase feldspar solid solution series. Its chemical formula is 4O8, where Ca/ is between 30%-50%; the formula may be written as Na0.7-0.5Ca0.3-0.5Al1.3-1.5Si2.7-2.5O8. The plagioclase feldspars are a continuous solid solution series and as such the accurate identification of individual members requires detailed optical study, chemical analysis or density measurements. Refractive indices and specific gravity increase directly with calcium content, it is sometimes used as a gemstone. Andesine was first described in 1841 for an occurrence in the Marmato mine, Cauca, Chocó Department, Colombia; the name is for the Andes due to its abundance in the andesite lavas in those mountains. In the early 2000s, red and green gemstones began to be marketed under the name of'andesine'. After some controversy, these gemstones were subsequently discovered to have been artificially-colored. Andesine occurs in intermediate igneous rocks such as diorite and andesite.
It characteristically occurs in metamorphic rocks of granulite to amphibolite facies exhibiting antiperthite texture. It occurs as detrital grains in sedimentary rocks, it is associated with quartz, potassium feldspar, biotite and magnetite
Porphyritic is an adjective used in geology for igneous rocks, for a rock that has a distinct difference in the size of the crystals, with at least one group of crystals larger than another group. Porphyritic rocks may be aphanites or extrusive rock, with large crystals or phenocrysts floating in a fine-grained groundmass of non-visible crystals, as in a porphyritic basalt, or phanerites or intrusive rock, with individual crystals of the groundmass distinguished with the eye, but one group of crystals much bigger than the rest, as in a porphyritic granite. Most types of igneous rocks may display some degree of porphyritic texture. One main type of rock that has a porphyritic texture are porphyry, though not all porphyritic rocks are porphyries. Porphyritic rocks are formed. In the first stage, the magma is cooled deep in the crust, creating the large crystal grains, with a diameter of 2mm or more. In the final stage, the magma is cooled at shallow depth or as it erupts from a volcano, creating small grains that are invisible to the unaided eye referred to as the ground mass
A phenocryst is an early forming large and conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous rock. Such rocks that have a distinct difference in the size of the crystals are called porphyries, the adjective porphyritic is used to describe them. Phenocrysts have euhedral forms, either due to early growth within a magma, or by post-emplacement recrystallization; the term phenocryst is not used unless the crystals are directly observable, sometimes stated as greater than.5 millimeter in diameter. Phenocrysts below this level, but still larger than the groundmass crystals, are termed microphenocrysts. Large phenocrysts are termed megaphenocrysts; some rocks contain both megaphenocrysts. In metamorphic rocks, crystals similar to phenocrysts are called porphyroblasts. Phenocrysts are more found in the lighter igneous rocks such as felsites and andesites, although they occur throughout the igneous spectrum including in the ultramafics; the largest crystals found in some pegmatites are phenocrysts being larger than the other minerals.
Rocks can be classified according to the nature and abundance of phenocrysts, the presence or absence of phenocrysts is noted when a rock name is determined. Aphyric is a term used to describe rocks that have no phenocrysts, or more where the rock consists of less than 1% phenocrysts. Porphyritic rocks are named using mineral name modifiers in decreasing order of abundance, thus when olivine forms the primary phenocrysts in a basalt, the name may be refined from basalt to porphyritic olivine basalt or olivine phyric basalt. A basalt with olivine as the dominate phenocrysts, but with lesser amounts of plagioclase phenocrysts, might be termed a olivine-plagioclase phyric basalt. In more complex nomenclature, a basalt with 1% plagioclase phenocrysts, but 4% olivine microphenocrysts, might be termed an aphyric to sparsely plagioclase-olivine phyric basalt, where plagioclase is listed before the olivine, because of its larger crystals. Categorizing a rock as aphyric or as sparsely phyric is a question of whether a significant number of crystals exceed the minimum size.
Geologists use phenocrysts to help determine rock origins and transformations, as when and whether crystals form depends on pressure and on temperature. Fumiko Shido first applied this technique to oceanic basalts, further development came from Tsugio Shibata, from W. B. Bryan. Plagioclase phenocrysts exhibit zoning with a more calcic core surrounded by progressively more sodic rinds; this zoning reflects the change in magma composition. In rapakivi granites, phenocrysts of orthoclase are enveloped within rinds of sodic plagioclase such as oligoclase. In shallow intrusives or volcanic flows phenocrysts which formed before eruption or shallow emplacement are surrounded by a fine-grained to glassy matrix; these volcanic phenocrysts show flow banding, a parallel arrangement of lath-shaped crystals. These characteristics provide clues to the rocks' origins. Intragranular microfractures and any intergrowth among crystals provide additional clues. Best, Myron. Igneous and Metamorphic Petrology. Oxford, England: Blackwell Publishing.
ISBN 978-1-4051-0588-0. Williams, Howel. Petrography: An introduction to the study of rocks in thin sections. San Francisco: W. H. Freeman. ISBN 978-0-7167-0206-1; the Integrated Ocean Drilling Program. Proceedings of the Ocean Drilling Program, Vol. 187 Initial Reports