Intrusive rock is formed when magma crystallizes and solidifies underground to form intrusions, for example plutons, dikes, sills and volcanic necks. Intrusive rock forms within Earth's crust from the crystallization of magma. Many mountain ranges, such as the Sierra Nevada in California, are formed from large granite intrusions. Intrusions are one of the two ways igneous rock. Technically an intrusion is any formation of intrusive igneous rock. In contrast, an extrusion consists of extrusive rock. Large bodies of magma that solidify underground before they reach the surface of the crust are called plutons. Plutonic rocks form 7% of the Earth's current land surface. Coarse-grained intrusive igneous rocks that form at depth within the earth are called abyssal while those that form near the surface are called subvolcanic or hypabyssal. Intrusive structures are classified according to whether or not they are parallel to the bedding planes or foliation of the country rock: if the intrusion is parallel the body is concordant, otherwise it is discordant.
An intrusive suite is a group of plutons related in time and space.. Intrusions vary from mountain-range-sized batholiths to thin veinlike fracture fillings of aplite or pegmatite. Intrusions can be classified according to the shape and size of the intrusive body and its relation to the other formations into which it intrudes: Batholith: a large irregular discordant intrusion Chonolith: an irregularly-shaped intrusion with a demonstrable base Cupola: a dome-shaped projection from the top of a large subterranean intrusion Dike: a narrow tabular discordant body nearly vertical Laccolith: concordant body with flat base and convex top with a feeder pipe below Lopolith: concordant body with flat top and a shallow convex base, may have a feeder dike or pipe below Phacolith: a concordant lens-shaped pluton that occupies the crest of an anticline or trough of a syncline Volcanic pipe or volcanic neck: tubular vertical body that may have been a feeder vent for a volcano Sill: a thin tabular concordant body intruded along bedding planes Stock: a smaller irregular discordant intrusive Boss: a small stock A body of intrusive igneous rock which crystallizes from magma cooling underneath the surface of the Earth is called a pluton.
If the pluton is large, it may be called a stock. Intrusive rocks are characterized by large crystal sizes, as the individual crystals are visible, the rock is called phaneritic; this is as the magma cools underground, while cooling may be fast or slow, cooling is slower than on the surface, so larger crystals grow. If it runs parallel to rock layers, it is called a sill. If an intrusion makes rocks above rise to form a dome, it is called a laccolith. How deep-seated intrusions burst through the overlying strata causes intrusive rock to be recognized: Veins spread out into branches, or branchlike parts result from filled cracks, the high temperature is evident in how they alter country rock; as heat dissipation is slow, as the rock is under pressure, crystals form, no vitreous chilled matter is present. The intrusions did not flow. Contained gases could not escape through the thick strata, thus form cavities, which can be observed; because their crystals are of the rough equal size, these rocks are said to be equigranular.
There is no distinction between a first generation of large well-shaped crystals and a fine-grained ground-mass. The minerals of each have formed in a definite order, each has had a period of crystallization that may be distinct or may have coincided with or overlapped the period of formation of some of the other ingredients. Earlier crystals originated at a time when most of the rock was still liquid and are more or less perfect. Crystals are less regular in shape because they were compelled to occupy the spaces left between the already-formed crystals; the former case is said to be idiomorphic. There are many other characteristics that serve to distinguish the members of these two groups. For example, orthoclase is feldspar from granite, while its modifications occur in lavas of similar composition; the same distinction holds for nepheline varieties. Leucite is common in lavas but rare in plutonic rocks. Muscovite is confined to intrusions; these differences show the influence of the physical conditions under which consolidation takes place.
Intrusive rocks formed at greater depths are called abyssal. Some intrusive rocks solidified in fissures as dikes and intrusive sills at shallow depth and are called subvolcanic or hypabyssal, they show structures intermediate between those of plutonic rocks. They are commonly porphyritic and sometimes vesicular. In fact, many of them are petrologically indistinguishable from lavas of similar composition. Ellicott City Granodiorite Guilford Quartz Monzonite Methods of pluton emplacement Norbeck Intrusive Suite Volcanic rock Woodstock Quartz Monzonite
Hadrian's Villa is a large Roman archaeological complex at Tivoli, Italy. A UNESCO World Heritage Site, it is the property of the Republic of Italy, has been directed and run by the Polo Museale del Lazio since December 2014; the villa was constructed at Tibur as a retreat from Rome for Roman Emperor Hadrian during the second and third decades of the 2nd century AD. Hadrian is said to have disliked the palace on the Palatine Hill in Rome, leading to the construction of the retreat, it was traditional that the Roman emperor had constructed a villa as a place to relax from everyday life. Previous emperors and Romans with wealth, such as Trajan, had constructed villas. Many villas were self-sustaining with small farms and did not need to import food; the picturesque landscape around Tibur had made the area a popular choice for villas and rural retreats. It was reputedly popular with people from the Spanish peninsula who were residents in the city of Rome; this may have contributed to Hadrian's choice of the property – although born in Rome, his parents came from Spain and he may have been familiar with the area during his early life.
There may have been a connection through his wife Vibia Sabina, the niece of the Emperor Trajan. Sabina's family held large landholdings and it is speculated the Tibur property may have been one of them. A villa from the Republican era formed the basis for Hadrian's establishment. During the years of his reign, Hadrian governed the empire from the villa. Hadrian started using the villa as his official residence around AD 128. A large court therefore lived there permanently and large numbers of visitors and bureaucrats would have to have been entertained and temporarily housed on site; the postal service kept it in contact with Rome 29 kilometres away, where the various government departments were located. It isn't known if Hadrian's wife lived at the villa either on a temporary or permanent basis – his relations with her were rather strained or distant due to his ambiguous sexuality. Hadrian's parents had died when he was young, he and his sister were adopted by Trajan, it is possible that Hadrian's court at the villa was predominately male but it's that his childhood nurse Germana, to whom he had formed a deep attachment, was accommodated there.
After Hadrian, the villa was used by his various successors. Zenobia, the deposed queen of Palmyra lived here in the 270s. During the decline of the Roman Empire in the 4th century, the villa fell into disuse and was ruined as valuable statues and marble were taken away; the facility was used as a warehouse by both sides during the destructive Gothic War between the Ostrogoths and Byzantines. Remains of lime kilns have been found, where marble from the complex was burned to extract lime for building material. In the 16th century, Cardinal Ippolito II d'Este had much of the remaining marble and statues in Hadrian's Villa removed to decorate his own Villa d'Este located nearby. Since that period excavations have sporadically turned up more fragments and sculptures, some of which have been kept in situ or housed on site in the display buildings. Hadrian's Villa is a vast area of land with many pools, baths and classical Greek architecture set in what would have been a mixture of landscaped gardens, wilderness areas and cultivated farmlands.
The buildings are constructed in travertine, lime and tufa. The complex contains over 30 buildings, covering an area of at least a square kilometre of which much is still unexcavated; the site was chosen due to its abundant waters and available aqueducts that passed through Rome, including Anio Vetus, Anio Nobus, Aqua Marcia, Aqua Claudia. The area was known as the location of villas before Hadrian obtained the property - it was, still is, a picturesque area conveniently close to Rome but detached and separate; the villa was the greatest Roman example of an Alexandrian garden, recreating a sacred landscape. The villa shows echoes of many different architectural styles Greek and Egyptian. Hadrian, a well-traveled emperor, borrowed these designs, such as the caryatids by the Canopus, along with the statues beside them depicting the Egyptian dwarf and fertility god, Bes. A Greek so called "Maritime Theatre" known as the Island Enclosure, exhibits classical ionic style, whereas the domes of the main buildings as well as the Corinthian arches of the Canopus and Serapeum show clear Roman architecture.
Hadrian's biography states that areas in the villa were named after places Hadrian saw during his travels. Only a few places mentioned in the biography can be correlated with the present-day ruins. One of the most striking and best preserved parts of the Villa consists of a pool named Canopus and an artificial grotto named Serapeum. An Egyptian city named. However, the architecture is Greek influenced as seen in the Corinthian columns and the copies of famous Greek statues that surround the pool; the pool measured 119 by 18 metres. Each column surrounding the pool was connected to each other with marble. One anecdote involves its peculiarly-shaped dome. A prominent architect of the day, Apollodorus of Damascus, dismisses Hadrian's designs, comparing the dome on Serapeum to a "pumpkin"; the full quote is "draw your pumpkins. You know noth
The mica group of sheet silicate minerals includes several related materials having nearly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, are similar in chemical composition; the nearly perfect cleavage, the most prominent characteristic of mica, is explained by the hexagonal sheet-like arrangement of its atoms. The word mica is derived from the Latin word mica, meaning a crumb, influenced by micare, to glitter. Chemically, micas can be given the general formula X2Y4–6Z8O204,in which X is K, Na, or Ca or less Ba, Rb, or Cs. Structurally, micas can be classed as trioctahedral. If the X ion is K or Na, the mica is a common mica, whereas if the X ion is Ca, the mica is classed as a brittle mica. Muscovite Common micas: Biotite Lepidolite Phlogopite ZinnwalditeBrittle micas: Clintonite Very fine-grained micas, which show more variation in ion and water content, are informally termed "clay micas", they include: Hydro-muscovite with H3O+ along with K in the X site.
Mica is distributed and occurs in igneous and sedimentary regimes. Large crystals of mica used for various applications are mined from granitic pegmatites; until the 19th century, large crystals of mica were quite rare and expensive as a result of the limited supply in Europe. However, their price dropped when large reserves were found and mined in Africa and South America during the early 19th century; the largest documented single crystal of mica was found in Lacey Mine, Canada. Similar-sized crystals were found in Karelia, Russia; the British Geological Survey reported that as of 2005, Koderma district in Jharkhand state in India had the largest deposits of mica in the world. China was the top producer of mica with a third of the global share followed by the US, South Korea and Canada. Large deposits of sheet mica were mined in New England from the 19th century to the 1970s. Large mines existed in Connecticut, New Hampshire, Maine. Scrap and flake mica is produced all over the world. In 2010, the major producers were Russia, United States, South Korea and Canada.
The total global production was 350,000 t. Most sheet mica was produced in Russia. Flake mica comes from several sources: the metamorphic rock called schist as a byproduct of processing feldspar and kaolin resources, from placer deposits, from pegmatites. Sheet mica is less abundant than flake and scrap mica, is recovered from mining scrap and flake mica; the most important sources of sheet mica are pegmatite deposits. Sheet mica prices vary with grade and can range from less than $1 per kilogram for low-quality mica to more than $2,000 per kilogram for the highest quality; the mica group represents 37 phyllosilicate minerals that have a platy texture. The commercially important micas are muscovite and phlogopite, which are used in a variety of applications. Mica’s value is based on several of its unique physical properties; the crystalline structure of mica forms layers that can be split or delaminated into thin sheets causing foliation in rocks. These sheets are chemically inert, elastic, hydrophilic, lightweight, reflective, refractive and range in opacity from transparent to opaque.
Mica is stable when exposed to electricity, light and extreme temperatures. It has superior electrical properties as an insulator and as a dielectric, can support an electrostatic field while dissipating minimal energy in the form of heat. Muscovite, the principal mica used by the electrical industry, is used in capacitors that are ideal for high frequency and radio frequency. Phlogopite mica remains stable at higher temperatures and is used in applications in which a combination of high-heat stability and electrical properties is required. Muscovite and phlogopite are used in ground forms; the leading use of dry-ground mica in the US is in the joint compound for filling and finishing seams and blemishes in gypsum wallboard. The mica acts as a filler and extender, provides a smooth consistency, improves the workability of the compound, provides resistance to cracking. In 2008, joint compound accounted for 54% of dry-ground mica consumption. In the paint industry, ground mica is used as a pigment extender that facilitates suspension, reduces chalking, prevents shrinking and shearing of the paint film, increases the resistance of the paint film to water penetration and weathering and brightens the tone of colored pigments.
Mica promotes paint adhesion in aqueous and oleoresinous formulations. Consumption of dry-ground mica in paint, the second-ranked use, accounted for 22% of the dry-ground mica used in 2008. Ground mica is used in the well-drilling industry as an additive to drilling fluids; the coarsely ground mica flakes help prevent the loss of circulation by sealing po
A glacial erratic is a piece of rock that differs from the size and type of rock native to the area in which it rests. "Erratics" take their name from the Latin word errare, are carried by glacial ice over distances of hundreds of kilometres. Erratics can range in size from pebbles to large boulders such as Big Rock in Alberta. Geologists identify erratics by studying the rocks surrounding the position of the erratic and the composition of the erratic itself. Erratics are significant because: They can be transported by glaciers, they are thereby one of a series of indicators which mark the path of prehistoric glacier movement, their lithographic origin can be traced to the parent bedrock, allowing for confirmation of the ice flow route. They can be transported by ice rafting; this allows quantification of the extent of glacial flooding resulting from ice dam failure which release the waters stored in proglacial lakes such as Lake Missoula. Erratics released by ice-rafts that were stranded and subsequently melt, dropping their load, allow characterization of the high-water marks for transient floods in areas like temporary Lake Lewis.
Erratics dropped by icebergs melting in the ocean can be used to track Antarctic and Arctic-region glacial movements for periods prior to record retention. Known as dropstones, these can be correlated with ocean temperatures and levels to better understand and calibrate models of the global climate; the term "erratic" is used to refer to erratic blocks, which Geikie describes as: "large masses of rock as big as a house, that have been transported by glacier-ice, have been lodged in a prominent position in the glacier valleys or have been scattered over hills and plains. And examination of their mineralogical character leads the identification of their sources…". In geology, an erratic is material moved by geologic forces from one location to another by a glacier. Erratics are formed by glacial ice erosion resulting from the movement of ice. Glaciers erode by multiple processes: abrasion/scouring, ice thrusting and glacially-induced spalling. Glaciers crack pieces of bedrock off in the process of producing the larger erratics.
In an abrasion process, debris in the basal ice scrapes along the bed and gouging the underlying rocks, similar to sandpaper on wood, producing smaller glacial till. In ice thrusting, the glacier freezes to its bed as it surges forward, it moves large sheets of frozen sediment at the base along with the glacier. Glacially-induced spalling occurs when ice lens formation with the rocks below the glacier spall off layers of rock, providing smaller debris, ground into the glacial basal material to become till. Evidence supports another option for creation of erratics as well, rock avalanches onto the upper surface of the glacier. Rock avalanche–supraglacial transport occurs when the glacier undercuts a rock face, which fails by avalanche onto the upper surface of the glacier; the characteristics of rock avalanche–supraglacial transport includes: Monolithologic composition – a cluster of boulders of similar composition are found in close proximity. Commingling of the multiple lithologies present throughout the glaciated basin, has not occurred.
Angularity – the supraglacially transported rocks tend to be rough and irregular, with no sign of subglacial abrasion. The sides of boulders are planar, suggesting that some surfaces may be original fracture planes. Great size – the size distribution of the boulders tends to be skewed toward larger boulders than those produced subglacially. Surficial positioning of the boulders – the boulders are positioned on the surface of glacial deposits, as opposed to or buried. Restricted areal extents – the boulder fields tend to have limited areal extent. Orientations – the boulders may be close enough that original fracture planes can be matched. Locations of the boulder trains – the boulders appear in rows, trains or clusters along the lateral moraines as opposed to being located on the terminal moraine or in the general glacial field. Erratics provide an important tool in characterizing the directions of glacier flows, which are reconstructed used on a combination of moraines, drumlins, meltwater channels, similar data.
Erratic distributions and glacial till properties allow for identification of the source rock from which they derive, which confirms the flow direction when the erratic source outcrop is unique to a limited locality. Erratic materials may be transported by multiple glacier flows prior to their deposition, which can complicate the reconstruction of the glacial flow. Glacial ice entrains debris of varying sizes from small particles to large masses of rock; this debris is transported to the coast by glacier ice and released during the production and melting of icebergs. The rate of debris release by ice depends upon the size of the ice mass in which it is carried as well as the temperature of the ocean through which the ice floe passes. Sediments from the late Pleistocene period lying on the floor of the North Atlantic show a series of layers which contain ice-rafted debris, they were formed between 70,000 years before the present. The deposited debris can be traced back to the origin by both the nature of the materials released and the continuous path of debris release.
Some paths extend more than 3,000 kilometres distant from the point at which the ice floes broke free. The location and altitude of ice-rafted boulders r
The Rosetta Stone is a granodiorite stele, found in 1799, inscribed with three versions of a decree issued at Memphis, Egypt, in 196 BC during the Ptolemaic dynasty on behalf of King Ptolemy V. The top and middle texts are in Ancient Egyptian using hieroglyphic script and Demotic script while the bottom is in Ancient Greek; as the decree has only minor differences between the three versions, the Rosetta Stone proved to be the key to deciphering Egyptian hieroglyphs, thereby opening a window into ancient Egyptian history. The stone, carved during the Hellenistic period, is believed to have been displayed within a temple at nearby Sais, it was moved during the early Christian or medieval period, was used as building material in the construction of Fort Julien near the town of Rashid in the Nile Delta. It was rediscovered there in July 1799 by a French soldier named Pierre-François Bouchard during the Napoleonic campaign in Egypt, it was the first Ancient Egyptian bilingual text recovered in modern times, it aroused widespread public interest with its potential to decipher this untranslated hieroglyphic language.
Lithographic copies and plaster casts began circulating among European scholars. British troops having meanwhile defeated the French, under the Capitulation of Alexandria in 1801 the original stone came into British possession and was transported to London, it has been on public display at the British Museum continuously since 1802 and is the most-visited object there. Study of the decree was under way when the first full translation of the Greek text appeared in 1803, it was 20 years, before the transliteration of the Egyptian scripts was announced by Jean-François Champollion in Paris in 1822. Major advances in the decoding were recognition that the stone offered three versions of the same text. Since its rediscovery, the stone has been the focus of nationalist rivalries, including its transfer from French to British possession during the Napoleonic Wars, a long-running dispute over the relative value of Young and Champollion's contributions to the decipherment and, since 2003, demands for the stone's return to Egypt.
Two other fragmentary copies of the same decree were discovered and several similar Egyptian bilingual or trilingual inscriptions are now known, including two earlier Ptolemaic decrees. The Rosetta Stone is, therefore, no longer unique, but it was the essential key to modern understanding of Ancient Egyptian literature and civilisation; the term Rosetta Stone is now used in other contexts as the name for the essential clue to a new field of knowledge. The Rosetta Stone is listed as "a stone of black granodiorite, bearing three inscriptions... found at Rosetta" in a contemporary catalogue of the artefacts discovered by the French expedition and surrendered to British troops in 1801. At some period after its arrival in London, the inscriptions on the stone were coloured in white chalk to make them more legible, the remaining surface was covered with a layer of carnauba wax designed to protect the Rosetta Stone from visitors' fingers; this gave a dark colour to the stone. These additions were removed when the stone was cleaned in 1999, revealing the original dark grey tint of the rock, the sparkle of its crystalline structure, a pink vein running across the top left corner.
Comparisons with the Klemm collection of Egyptian rock samples showed a close resemblance to rock from a small granodiorite quarry at Gebel Tingar on the west bank of the Nile, west of Elephantine in the region of Aswan. The Rosetta Stone is 1,123 millimetres high at its highest point, 757 mm wide, 284 mm thick, it weighs 760 kilograms. It bears three inscriptions: the top register in Ancient Egyptian hieroglyphs, the second in the Egyptian Demotic script, the third in Ancient Greek; the front surface is polished and the inscriptions incised on it. The Rosetta Stone is a fragment of a larger stele. No additional fragments were found in searches of the Rosetta site. Owing to its damaged state, none of the three texts is complete; the top register, composed of Egyptian hieroglyphs, suffered the most damage. Only the last 14 lines of the hieroglyphic text can be seen; the following register of demotic text has survived best. The final register of Greek text contains 54 lines; the stele was erected after the coronation of King Ptolemy V and was inscribed with a decree that established the divine cult of the new ruler.
The decree was issued by a congress of priests. The date is given as "4 Xandicus" in the Macedonian calendar and "18 Meshir" in the Egyptian calendar, which corres
Calcium is a chemical element with symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air, its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust and the third most abundant metal, after iron and aluminium; the most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life. The name derives from Latin calx "lime", obtained from heating limestone; some calcium compounds were known to the ancients, though their chemistry was unknown until the seventeenth century. Pure calcium was isolated in 1808 via electrolysis of its oxide by Humphry Davy, who named the element. Calcium compounds are used in many industries: in foods and pharmaceuticals for calcium supplementation, in the paper industry as bleaches, as components in cement and electrical insulators, in the manufacture of soaps.
On the other hand, the metal in pure form has few applications due to its high reactivity. Calcium is the fifth-most abundant element in the human body; as electrolytes, calcium ions play a vital role in the physiological and biochemical processes of organisms and cells: in signal transduction pathways where they act as a second messenger. Calcium ions outside cells are important for maintaining the potential difference across excitable cell membranes as well as proper bone formation. Calcium is a ductile silvery metal whose properties are similar to the heavier elements in its group, strontium and radium. A calcium atom has twenty electrons, arranged in the electron configuration 4s2. Like the other elements placed in group 2 of the periodic table, calcium has two valence electrons in the outermost s-orbital, which are easily lost in chemical reactions to form a dipositive ion with the stable electron configuration of a noble gas, in this case argon. Hence, calcium is always divalent in its compounds, which are ionic.
Hypothetical univalent salts of calcium would be stable with respect to their elements, but not to disproportionation to the divalent salts and calcium metal, because the enthalpy of formation of MX2 is much higher than those of the hypothetical MX. This occurs because of the much greater lattice energy afforded by the more charged Ca2+ cation compared to the hypothetical Ca+ cation. Calcium, strontium and radium are always considered to be alkaline earth metals. Beryllium and magnesium are different from the other members of the group in their physical and chemical behaviour: they behave more like aluminium and zinc and have some of the weaker metallic character of the post-transition metals, why the traditional definition of the term "alkaline earth metal" excludes them; this classification is obsolete in English-language sources, but is still used in other countries such as Japan. As a result, comparisons with strontium and barium are more germane to calcium chemistry than comparisons with magnesium.
Calcium metal melts at 842 °C and boils at 1494 °C. It crystallises in the face-centered cubic arrangement like strontium, its density of 1.55 g/cm3 is the lowest in its group. Calcium can be cut with a knife with effort. While calcium is a poorer conductor of electricity than copper or aluminium by volume, it is a better conductor by mass than both due to its low density. While calcium is infeasible as a conductor for most terrestrial applications as it reacts with atmospheric oxygen, its use as such in space has been considered; the chemistry of calcium is that of a typical heavy alkaline earth metal. For example, calcium spontaneously reacts with water more than magnesium and less than strontium to produce calcium hydroxide and hydrogen gas, it reacts with the oxygen and nitrogen in the air to form a mixture of calcium oxide and calcium nitride. When finely divided, it spontaneously burns in air to produce the nitride. In bulk, calcium is less reactive: it forms a hydration coating in moist air, but below 30% relative humidity it may be stored indefinitely at room temperature.
Besides the simple oxide CaO, the peroxide CaO2 can be made by direct oxidation of calcium metal under a high pressure of oxygen, there is some evidence for a yellow superoxide Ca2. Calcium hydroxide, Ca2, is a strong base, though it is not as strong as the hydroxides of strontium, barium or the alkali metals. All four dihalides of calcium are known. Calcium carbonate and calcium sulfate are abundant minerals. Like strontium and barium, as well as the alkali metals and the divalent lanthanides europium and ytterbium, calcium metal dissolves directly in liquid ammonia to give a dark blue solution. Due to the large size of the Ca2+ ion, high coordination numbers are common, up to 24 in some intermetallic compounds such as CaZn13. Calcium is complexed by oxygen chelates such as EDTA and polyphosphates, which are useful in an
In geology, felsic refers to igneous rocks that are rich in elements that form feldspar and quartz. It is contrasted with mafic rocks, which are richer in magnesium and iron. Felsic refers to silicate minerals and rocks which are enriched in the lighter elements such as silicon, aluminium and potassium. Felsic magma or lava is higher in viscosity than mafic magma/lava. Felsic rocks are light in color and have specific gravities less than 3; the most common felsic rock is granite. Common felsic minerals include quartz, muscovite and the sodium-rich plagioclase feldspars. In modern usage, the term acid rock, although sometimes used as a synonym now refers to a high-silica-content volcanic rock, such as rhyolite. Older, broader usage is now considered archaic; that usage, with the contrasting term "basic rock", was based on an incorrect idea, dating from the 19th century, that "silicic acid" was the chief form of silicon occurring in rocks. The term "felsic" combines the words "feldspar" and "silica".
The similarity of the resulting term felsic to the German felsig, "rocky", is purely accidental. Feldspar is linked to German, it is a borrowing of Feldspat. The link is therefore to German Feld, meaning "field". In order for a rock to be classified as felsic, it needs to contain more than 75% felsic minerals. Rocks with greater than 90% felsic minerals can be called leucocratic, from the Greek words for white and dominance. Felsite is a petrologic field term used to refer to fine-grained or aphanitic, light-colored volcanic rocks which might be reclassified after a more detailed microscopic or chemical analysis. In some cases, felsic volcanic rocks may contain phenocrysts of mafic minerals hornblende, pyroxene or a feldspar mineral, may need to be named after their phenocryst mineral, such as'hornblende-bearing felsite'; the chemical name of a felsic rock is given according to the TAS classification of Le Maitre. However, this only applies to volcanic rocks. If the rock is analyzed and found to be felsic but is metamorphic and has no definite volcanic protolith, it may be sufficient to call it a'felsic schist'.
There are examples known of sheared granites which can be mistaken for rhyolites. For phaneritic felsic rocks, the QAPF diagram should be used, a name given according to the granite nomenclature; the species of mafic minerals is included in the name, for instance, hornblende-bearing granite, pyroxene tonalite or augite megacrystic monzonite, because the term "granite" assumes content with feldspar and quartz. The rock texture thus determines the basic name of a felsic rock. QAPF diagram List of minerals List of rock types Bowen's reaction series Archean felsic volcanic rocks Le Maitre, L. E. ed. 2002. Igneous Rocks: A Classification and Glossary of Terms 2nd edition, Cambridge