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Encyclopedia > Tuff
Welded tuff at Golden Gate in Yellowstone National Park

Tuff (from the Italian "tufo") is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. (Note that tuff is a type of rock entirely different from tufa.) Photo taken by Daniel Mayer and released under terms of the GNU FDL. File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Photo taken by Daniel Mayer and released under terms of the GNU FDL. File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Yellowstone National Park is the centerpiece of the Greater Yellowstone Ecosystem, the largest intact ecosystem in the Earths northern temperate zone. ... The rocky side of a mountain creek near Orosí, Costa Rica. ... Diamond Head, a well_known backdrop to Waikiki in Hawaii, is an ash cone that solidified into tuff Volcanic ash is the term for very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. ... Tufa is the name for an unusual geological formation. ...

Contents

Volcanic ash

The products of a volcanic eruption are volcanic gases, lava, steam, and tephra. Magma is blown apart when it interacts violently with volcanic gases and steam. Solid material produced and thrown into the air by such volcanic eruptions is called tephra, regardless of composition or fragment size. If the resulting pieces of ejecta are small enough, the material is called volcanic ash, defined as such particles less than 2 mm in diameter, sand-sized or smaller. These particles are small, slaggy pieces of magma and rock that have been tossed into the air by outbursts of steam and other gases; magma may have been torn apart as it became vesicular by the expansion of the gases within it. For other uses, see Volcano (disambiguation). ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... It has been suggested that this article be split into articles entitled steam and water vapor, accessible from a disambiguation page. ... Tephra refers to air-fall material produced by a volcanic eruption regardless of composition or fragment size. ... Tephra refers to air-fall material produced by a volcanic eruption regardless of composition or fragment size. ... Patterns in the sand Sand is a granular material made up of fine rock particles. ... Slag is also an early play by David Hare. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... Vesicular texture is a volcanic rock texture characterised by, or containing, many vesicles. ...


Breccias

Among the loose beds of ash that cover the slopes of many volcanoes, three classes of materials are represented. In addition to true ashes of the kind described above, there are lumps of the old lavas and tuffs forming the walls of the crater, etc., which have been torn away by the violent outbursts of steam, and pieces of sedimentary rocks from the deeper parts of the volcano that were dislodged by the rising lava and are often intensely baked and recrystallized by the heat to which they have been subjected. For other uses, see Volcano (disambiguation). ... Two types of sedimentary rock: limey shale overlaid by limestone. ... Insulin crystals Recrystallization is an essentially physical process that has meanings in chemistry, metallurgy and geology. ...


In some great volcanic explosions nothing but materials of the second kind were emitted, as at Mount Bandaisan in Japan in 1888. There have been many eruptions also in which the quantity of broken sedimentary rocks that mingled with the ash is very great; as instances we may cite the volcanoes of the Eifel and the Devonian tuffs, known as "Schalsteins," in Germany. In the Scottish coalfields some old volcanoes are plugged with masses consisting entirely of sedimentary debris: in such a case we must suppose that no lava was ejected, but the cause of the eruption was the sudden liberation and expansion of a large quantity of steam. These accessory or adventitious materials, however, as distinguished from the true ashes, tend to occur in angular fragments; and when they form a large part of the mass the rock is more properly a "volcanic breccia" than a tuff. The ashes vary in size from large blocks twenty feet or more in diameter to the minutest impalpable dust. The large masses are called "volcanic bombs"; they have mostly a rounded, elliptical or pear-shaped form owing to rotation in the air while they were still viscous. Many of them have ribbed or nodular surfaces, and sometimes they have a crust intersected by many cracks like the surface of a loaf of bread. Any ash in which they are very abundant is called an agglomerate. Year 1888 (MDCCCLXXXVIII) was a leap year starting on Sunday (click on link for calendar) of the Gregorian calendar (or a leap year starting on Tuesday of the 12-day slower Julian calendar). ... The Eifel is a hilly region in Germany. ... The Devonian is a major division of the geologic timescale that extends from the end of the Silurian period (360 million years ago (mya)) to the beginning of the Mississippian subperiod of the Carboniferous (408. ... Motto (Latin) No one provokes me with impunity Cha togar mfhearg gun dioladh (Scottish Gaelic) Wha daur meddle wi me?(Scots)1 Anthem (Multiple unofficial anthems) Scotlands location in Europe Capital Edinburgh Largest city Glasgow Official languages English, Gaelic and Scots1 Government Constitutional monarchy  -  Monarch Queen Elizabeth II... Breccia, derived from the Latin word for broken, is a sedimentary rock composed of angular fragments in a matrix that may be of a similar or a different material. ... A volcanic bomb is a globule of molten rock (tephra) larger than 2. ... Agglomerate - Wikipedia /**/ @import /skins-1. ...


In those layers and beds of tuff that have been spread out over considerable tracts of country and which are most frequently encountered among the sedimentary rocks, smaller fragments preponderate greatly and bombs more than a few inches in diameter may be absent altogether. A tuff of recent origin is generally loose and incoherent, but the older tuffs have been, in most cases, cemented together by pressure and the action of infiltrating water, making rocks which, while not very hard, are strong enough to be extensively used for building purposes (e.g. in the neighborhood of Rome). If they have accumulated subaerially, like the ash beds found on Mt. Etna or Vesuvius at the present day, tuffs consist almost wholly of volcanic materials of different degrees of fineness with pieces of wood and vegetable matter, land shells, etc. But many volcanoes stand near the sea, and the ashes cast out by them are mingled with the sediments that are gathering at the bottom of the waters. In this way ashy muds or sands or even in some cases ashy limestones are being formed. As a matter of fact most of the tuffs found in the older formations contain admixtures of clay, sand, and sometimes fossil shells, which prove that they were beds spread out under water. Nickname: Motto: SPQR: Senatus Populusque Romanus Location of the city of Rome (yellow) within the Province of Rome (red) and region of Lazio (grey) Coordinates: Region Lazio Province Province of Rome Founded 21 April 753 BC Government  - Mayor Walter Veltroni Area  - City 1,285 km²  (580 sq mi)  - Urban 5... The term subaerial, mainly used in geology, describes events or structures located at the Earths surface, under the air. This is to be contrasted with submarine events or structures, those located under the sea. ... For other meanings of Etna, see Etna (disambiguation). ... Mount Vesuvius (Italian: Monte Vesuvio) is a volcano east of Naples, Italy, located at 40°49′N 14°26′ E. It is the only active volcano on the European mainland, although it is not currently erupting. ... In computer gaming, a MUD (Multi-User Dungeon, Domain or Dimension) is a multi-player computer game that combines elements of role-playing games, hack and slash style computer games and social chat rooms. ... Patterns in the sand Sand is a granular material made up of fine rock particles. ... -1... The Gay Head cliffs in Marthas Vineyard are made almost entirely of clay. ... FOSSIL is a standard for allowing serial communication for telecommunications programs under DOS. FOSSIL is an acronym for Fido Opus Seadog Standard Interface Layer. ... Various seashells Danielle A shell is the hard, rigid outer covering, or integument, allanimals. ...


During some volcanic eruptions a layer of ashes several feet in thickness is deposited over a considerable district, but such beds thin out rapidly as the distance from the crater increases, and ash deposits covering many square miles are usually very thin. The showers of ashes often follow one another after longer or shorter intervals, and hence thick masses of tuff, whether of subaerial or of marine origin, have mostly a stratified character. The coarsest materials or agglomerates show this least distinctly; in the fine beds it is often developed in great perfection. This article does not cite any references or sources. ...


Igneous rock

Apart from adventitious material, such as fragments of the older rocks, pieces of trees, etc., the contents of an ash deposit may be described as consisting of more or less crystalline igneous rocks. If the lava within the crater has been at such a temperature that solidification has commenced, crystals are usually present. They may be of considerable size like the grey, rounded leucite crystals found on the sides of Vesuvius. Many of these are very perfect and rich in faces because they grew in a medium that was liquid and not very viscous. Good crystals of augite and olivine are also to be obtained in the ash beds of Vesuvius and of many other volcanoes, ancient and modern. Blocks of these crystalline minerals (anorthite, olivine, augite and hornblende) are common objects in the tuffs of many of the West Indian volcanoes. Where crystals are very abundant the ashes are called "crystal tuffs." In St. Vincent and Martinique in 1902, much of the dust was composed of minute crystals enclosed in thin films of glass because the lava at the moment of eruption had very nearly solidified as a crystalline mass. Some basaltic volcanoes, on the other hand, have ejected great quantities of black glassy scoria, which, after consolidation, weather to a red soft rock known as palagonite; tuffs of this kind occur in Iceland and Sicily. In the Lipari Islands and Hungary there are acid (rhyolitic) tuffs, of pale grey or yellow color, largely composed of lumps and fragments of pumice. Over a large portion of the sea bottom the beds of fine mud contain small, water-worn, rounded pebbles of very spongy volcanic glass; these have been floated from the shore or cast out by submarine volcanoes, and may have travelled for hundreds of miles before sinking; it has been proved by experiment that some kinds of pumice will float on sea-water for more than a year. The deep sea-deposit known as the "red clay" is largely of volcanic origin and might be suitably described as a "submarine tuff-bed." Quartz crystal Synthetic bismuth hopper crystal Insulin crystals Gallium, a metal that easily forms large single crystals A huge monocrystal of potassium dihydrogen phosphate grown from solution by Saint-Gobain for the megajoule laser of CEA. In chemistry and mineralogy, a crystal is a solid in which the constituent atoms... Volcanic rock on North America Plutonic rock on North America Igneous rocks form when rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Leucite or amphigene is a rock-forming mineral composed of potassium and aluminium metasilicate KAl(SiO3)2. ... Augite is a single chain inosilicate mineral described chemically as (Ca,Mg,Fe)SiO3 or calcium magnesium iron silicate. ... The mineral olivine (also called chrysolite and, when gem-quality, peridot) is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. ... Anorthite is one of the plagioclase feldspars, an important group of minerals abundant in the Earths crust. ... Amphibole (Hornblende) Hornblende is a complex inosilicate series of minerals. ... 1902 (MCMII) was a common year starting on Wednesday (see link for calendar). ... Glass can be made transparent and flat, or into other shapes and colors as shown in this sphere from the Verrerie of Brehat in Brittany. ... Basalt Basalt (IPA: ) is a common gray to black extrusive volcanic rock. ... Scoria Scoria is the vesicular ejecta of mafic to intermediate magmas such as basalt and andesite. ... Palagonite is a form of volcanic glass similar to obsidian but with a chemical composition more closely related to basalt. ... Sicily (Sicilia in Italian and Sicilian) is an autonomous region of Italy and the largest island in the Mediterranean Sea, with an area of 25,708 km² (9,926 sq. ... The Aeolian Islands (Italian Isole Eolie) lie to the north of Sicily and are in the summer a main tourist resort, attracting up to 200,000 visitors. ... Acidity redirects here. ... Rhyolite This page is about a volcanic rock. ... // Specimen of highly porous pumice from Teide volcano on Tenerife, Canary Islands. ...


Welded tuff

Welded tuff is basically a product of pyroclastic flows hot enough to fuse or "weld" still-hot ash into a single uniform layer called a cooling unit. Ignimbrite is another term commonly used for this type of tuff. The glass fragments that make up much of the erupted ash flow and deform readily, and their curving shapes are flattened and deformed during the welding process (see image and contrast with the ash shapes in unwelded tuff). Ignimbrite is a volcanic pyroclastic rock, often of dacitic or rhyolitic composition. ...

Light microscope image of a welded tuff (ignimbrite) as seen in thin section (Long dimension is several mm). The glass shards (mostly brown) were deformed by flow and compaction about crystal fragments (clear).
Light microscope image of a welded tuff (ignimbrite) as seen in thin section (Long dimension is several mm). The glass shards (mostly brown) were deformed by flow and compaction about crystal fragments (clear).

Welded tuff deposits can be highly voluminous, such as the Lava Creek Tuff erupted from Yellowstone Caldera in Wyoming 640,000 years ago. Lava Creek Tuff is known to be at least 1000 times as large as the deposits of Mount St. Helens's May 18, 1980 eruption, and it had a Volcanic Explosivity Index (VEI) of 8 -- greater than any eruption known in the last 10,000 years. Such deposits may be represented by welded tuff near the eruption source, tuff at greater distances, and unconsolidated ash yet further away. Welded tuff is commonly rhyolitic in composition. Image File history File linksMetadata Download high-resolution version (600x627, 320 KB) Microscope image of part of a thin section of an ignimbrite (welded tuff) showing shards (mostly brown glass) deformed during flow and compaction about crystal fragments (clear). ... Image File history File linksMetadata Download high-resolution version (600x627, 320 KB) Microscope image of part of a thin section of an ignimbrite (welded tuff) showing shards (mostly brown glass) deformed during flow and compaction about crystal fragments (clear). ... Tuff Cliff showing the Lava Creek Tuff formation. ... It has been suggested that Yellowstone Plateau be merged into this article or section. ... Official language(s) English Capital Cheyenne Largest city Cheyenne Area  Ranked 10th  - Total 97,818 sq mi (253,348 km²)  - Width 280 miles (450 km)  - Length 360 miles (580 km)  - % water 0. ... Tuff Cliff showing the Lava Creek Tuff formation. ... For the mountain in California see Mount Saint Helena. Mount St. ... VEI and ejecta volume correlation The Volcanic Explosivity Index (VEI) was devised by Chris Newhall of the U.S. Geological Survey and Steve Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions. ...


Rhyolite tuffs

For petrographical purposes tuffs are generally classified according to the nature of the volcanic rock of which they consist; this may be the same as the accompanying lavas if any were emitted during an eruption, and if there is a change in the kind of lava which is poured out, the tuffs also indicate this equally clearly. Rhyolite tuffs contain pumiceous, glassy fragments and small scoriae with quartz, alkali feldspar, biotite, etc. Iceland, Lipari, Hungary, the Basin and Range of the American southwest, and New Zealand are among the areas where such tuffs are prominent. The broken pumice is clear and isotropic, and very small particles commonly have crescentic, sickle-shaped, or biconcave outlines, showing that they are produced by the shattering of a vesicular glass, sometimes described as ash-structure. The tiny glass fragments derived from broken pumice are called shards; the glass shards readily deform and flow when the deposits are sufficiently hot, as shown in the accompanying image of welded tuff. Petrology is a field of geology which focuses on the study of rocks and the conditions by which they form. ... Quartz is one of the most common minerals in the Earths continental crust. ... In chemistry, an alkali (from Arabic: al-qalyالقلوي, القالي ) is a basic, ionic salt of an alkali metal or alkali earth metal element. ... This article does not cite any references or sources. ... A Biotite slice Biotite is a common phyllosilicate mineral that contains potassium, magnesium, iron and aluminium. ... Basin and Range index map - USGS The Basin and Range Province is a particular type of topography that covers much of the southwestern United States and northwestern Mexico that is typified by elongate north-south trending arid valleys bounded by mountain ranges which also bound adjacent valleys. ...

Light microscope image of tuff as seen in thin section (Long dimension is several mm). The curved shapes of altered glass shards (ash fragments) are well-preserved, although the glass is partly altered. The shapes were formed about bubbles of expanding water-rich gas.
Light microscope image of tuff as seen in thin section (Long dimension is several mm). The curved shapes of altered glass shards (ash fragments) are well-preserved, although the glass is partly altered. The shapes were formed about bubbles of expanding water-rich gas.

In the ancient rocks of Wales, Charnwood, the Pentland Hills, etc., similar tuffs are known, but in all cases they are greatly changed by silicification (which has filled them with opal, chalcedony and quartz) and by devitrification. The frequent presence of rounded corroded quartz crystals, such as occur in rhyolitic lavas, helps to demonstrate their real nature. Image File history File linksMetadata Tuff_shards. ... Image File history File linksMetadata Tuff_shards. ... This article is about the sub-division of the United Kingdom. ... Charnwood may refer to: Charnwood (borough), a local government district in England Charnwood Forest, located within the borough Operation Charnwood, a failed operation during the Battle of Normandy in World War II Charnwood (UK Parliament constituency), electorate in the British House of Commons Charnwood, Australian Capital Territory, a suburb of... The Pentland Hills is a range of hills to the south west of Edinburgh, Scotland. ... For other articles with similar names, see Opal (disambiguation). ... Chalcedony knife, AD 1000-1200 Bloodstone redirects here. ...


Trachyte tuffs

Trachyte tuffs contain little or no quartz but much sanidine or anorthoclase and sometimes oligoclase feldspar, with occasional biotite, augite and hornblende. In weathering they often change to soft red or yellow clay-stones, rich in kaolin with secondary quartz. Recent trachyte tuffs are found on the Rhine (at Siebengebirge), in Ischia, near Naples, Hungary, etc. Sanidine is the high temperature form of potassium feldspar ((K,Na)(Si,Al)4O8) which occurs in felsic volcanic rocks such as rhyolite and trachyte. ... Feldspar (from the German Feld, field, and Spat, a rock that does not contain ore) is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earths crust. ... Kaolin Kaolinite (Aluminium Silicate Hydroxide) Kaolinite is a mineral with the chemical composition Al2Si2O5(OH)4. ... It has been suggested that River Rhine Pollution: November 1986 be merged into this article or section. ... The castle Schloß Drachenburg belongs among the emblems of the Siebengebirge The Siebengebirge (lit. ... The island of Ischia near Naples, Italy. ... “Napoli” redirects here. ...


Andesitic tuffs

Andesitic tuffs are exceedingly common. They occur along the whole chain of the Cordilleras and Andes, in the West Indies, New Zealand, Japan, etc. In the Lake district, North Wales, Lorne, the Pentland Hills, the Cheviots and many other districts of Great Britain, ancient rocks of exactly similar nature are abundant. In color they are red or brown; their scoriae fragments are of all sizes from huge blocks down to minute granular dust. The cavities are filled up with many secondary minerals, such as calcite, chlorite, quartz, epidote, chalcedony: but in microscopic sections the nature of the original lava can nearly always be made out from the shapes and properties of the little crystals which occur in the decomposed glassy base. Even in the smallest details these ancient tuffs have a complete resemblance to the modern ash beds of Cotopaxi, Krakatoa and Mont Pelé. The American cordillera consists of an essentially continuous sequence of mountain ranges that form the western backbone of both North America and South America. ... Planes view of the Andes, Peru. ... The Caribbean or the West Indies is a group of islands in the Caribbean Sea. ... Doubly refracting Calcite from Iceberg claim, Dixon, New Mexico. ... Chlorite is a group of phyllosilicate minerals often classified as clays. ... Epidote from Slovakia Epidote is a calcium aluminium iron sorosilicate mineral, Ca2(Al, Fe)3(SiO4)3(OH), crystallizing in the monoclinic system. ... Cotopaxi is a volcano located about 50 km south of Quito, Ecuador. ... Krakatoa or Krakatau or Krakatao is a volcanic island in the Sunda Strait between Java and Sumatra in Indonesia. ...


Basaltic tuffs

Basaltic tuffs are also of wide spread occurrence both in districts where volcanoes are now active and in lands where eruptions have long since ended. In the British Isles they are found in Skye, Mull, Antrim and other places, where there are Tertiary volcanic rocks; in Scotland, Derbyshire, Ireland among the carboniferous strata; and among the still older rocks of the Lake District, southern uplands of Scotland and Wales. They are black, dark green or red in colour; vary greatly in coarseness, some being full of round spongy bombs a foot or more in diameter, and, being often submarine, may contain shale, sandstone, grit and other sedimentary material, and are occasionally fossiliferous. Recent basaltic tuffs are found in Iceland, the Faroe Islands, Jan Mayen, Sicily, Vesuvius, Sandwich Islands, Samoa, etc. When weathered they are filled with calcite, chlorite, serpentine and, especially where the lavas contain nepheline or leucite, are often rich in zeolites, such as analcite, prehnite, natrolite, scolecite, chabazite, heulandite, etc. The British Isles in relation to mainland Europe The British Isles (French: , Irish: [1] or Oileáin Iarthair Eorpa,[2] Manx: Ellanyn Goaldagh, Scottish Gaelic: , Welsh: ), is a group of islands off the northwest coast of continental Europe comprising Great Britain, Ireland and a number of smaller islands. ... Looking towards Quiraing, Skye. ... Tobermory with 700 people, the largest settlement on Mull, is home to the only whisky distillery on the island. ... Statistics Province: Ulster County Town: Antrim Area: 2,844 km² Population (est. ... Tertiary geological time interval covers roughly the time span between the demise of the non-avian dinosaurs and beginning of the most recent Ice Age, approximately 65 million to 1. ... Motto (Latin) No one provokes me with impunity Cha togar mfhearg gun dioladh (Scottish Gaelic) Wha daur meddle wi me?(Scots)1 Anthem (Multiple unofficial anthems) Scotlands location in Europe Capital Edinburgh Largest city Glasgow Official languages English, Gaelic and Scots1 Government Constitutional monarchy  -  Monarch Queen Elizabeth II... Derbyshire is a county in the East Midlands of England. ... The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... The Sandwich Islands was the name given to Hawaii by Captain James Cook on his discovery of the islands on January 18, 1778. ... Serpentine Serpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg, Fe)3Si2O5(OH)4) minerals; it may contain minor amounts of other elements including chromium, manganese, cobalt and nickel. ... A big crystal of Nepheline from Canaã Massif, Brazil Nepheline, also called nephelite (from Greek: nephos, cloud), is a feldspathoid: a silica-undersaturated aluminosilicate, Na3KAl4Si4O16, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatites. ... Leucite or amphigene is a rock-forming mineral composed of potassium and aluminium metasilicate KAl(SiO3)2. ... Zeolite The micro-porous molecular structure of a zeolite, ZSM-5 Zeolites (Greek, zein, to boil; lithos, a stone) are minerals that have a micro-porous structure. ... Analcite or analcime (from the Greek analkimos - weak) is a white, grey, or colourless tectosilicate mineral. ... Prehnite is a phyllosilicate of calcium and aluminium with the formula: Ca2Al(AlSi3O10)(OH)2. ... Natrolite is a mineral species belonging to the zeolite group. ... A sample of scolecite Scolecite is a tectosilicate mineral belonging to the zeolite group; a hydrated calcium silicate, CaAl2Si3O10·3H2O. Its name came from the Greek word, skolec = worm because of its reaction to the blowpipe flame. ... Categories: Silicate minerals | Mineral stubs ... Heulandite - Wikipedia /**/ @import /skins-1. ...


Ultramafic tuffs

Ultramafic tuffs are extremely rare; their characteristic is the abundance of olivine or serpentine and the scarcity or absence of feldspar and quartz. Rare occurrences may include unusual surface deposits of maars of kimberlites of the diamond-fields of southern Africa and other regions. The principal rock of kimberlite is a dark bluish green serpentine-rich breccia (blue-ground) which when thoroughly oxidized and weathered becomes a friable brown or yellow mass (the "yellow-ground"). These breccias were emplaced as gas-solid mixtures and are typically preserved and mined in diatremes that form intrusive pipe-like structures. At depth, some kimberlite breccias grade into root zones of dikes made of unfragmented rock. At the surface, ultramafic tuffs may occur in maar deposits. Because kimberlites are the most common igneous source of diamonds, the transitions from maar to diatreme to root-zone dikes have been studied in detail. Diatreme-facies kimberlite is more properly called an ultramafic breccia rather than a tuff. The mineral olivine (also called chrysolite and, when gem-quality, peridot) is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. ... Serpentine Serpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg, Fe)3Si2O5(OH)4) minerals; it may contain minor amounts of other elements including chromium, manganese, cobalt and nickel. ... This article does not cite any references or sources. ... Quartz is one of the most common minerals in the Earths continental crust. ... Ukinrek Maars, Alaska; the result of a 10-day eruption in 1977. ... Hewn kimberlite core sample from the James Bay Lowlands region of Northern Ontario, Canada. ... This article is about the gemstone. ... Hewn kimberlite core sample from the James Bay Lowlands region of Northern Ontario, Canada. ... A Diatreme is a volcanic pipe or feature formed by a gas or volatile rich explosive magma. ... Ukinrek Maars, Alaska; the result of a 10-day eruption in 1977. ...


Folding and metamorphosis

In course of time other changes than weathering may overtake tuff deposits. Sometimes they are involved in folding and become sheared and cleaved. Many of the green slates of the lake district in Cumberland are fine cleaved ashes. In Charnwood forest also the tuffs are slaty and cleaved. The green color is due to the large development of chlorite. Among the crystalline schists of many regions green beds or green schists occur, which consist of quartz, hornblende, chlorite or biotite, iron oxides, feldspar, etc., and are probably recrystallized or metamorphosed tuffs. They often accompany masses of epidiorite and hornblende-schists which are the corresponding lavas and sills. Some chlorite-schists also are probably altered beds of volcanic tuff. The "Schalsteins" of Devon and Germany include many cleaved and partly recrystallized ash-beds, some of which still retain their fragmental structure though their lapilli are flattened and drawn out. Their steam cavities are usually filled with calcite, but sometimes with quartz. The more completely altered forms of these rocks are platy, green chloritic schists; in these, however, structures indicating their original volcanic nature only sparingly occur. These are intermediate stages between cleaved tuffs and crystalline schists. Slate Thick slate fragment Slate roof Slate is a fine-grained, homogeneous, metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low grade regional metamorphism. ... Cumberland is one of the 39 traditional counties of England. ... Schist The schists form a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. ... Iron oxide pigment There are a number of iron oxides: Iron oxides Iron(II) oxide or ferrous oxide (FeO) The black-coloured powder in particular can cause explosions as it readily ignites. ... Metamorphism can be defined as the mineralogical, chemical and crystallographic changes in a solid-state rock, i. ... In geology, a sill is a tabular, often horizontal mass of igneous rock that has been intruded laterally between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. ... “Devonshire” redirects here. ...


Economic importance

Yucca Mountain Repository, a U.S. Department of Energy terminal storage facility for spent nuclear reactor and other radioactive waste, is in tuff and ignimbrite in the Basin and Range Province in Nevada. Yucca Mountain Yucca Mountain is a Ridge line in Nye County, south-central Nevada, composed of volcanic material (mostly tuff) ejected from a now-extinct caldera-forming supervolcano. ... Ignimbrite is a volcanic pyroclastic rock, often of dacitic or rhyolitic composition. ... Basin and Range index map - USGS The Basin and Range Province is a particular type of topography that covers much of the southwestern United States and northwestern Mexico that is typified by elongate north-south trending arid valleys bounded by mountain ranges which also bound adjacent valleys. ... there is a jungle in nevada by the park This article is about the U. S. state of Nevada. ...


In the Napa and Sonoma valleys of California areas made out of tuff are routinely excavated for storage of wine barrels.


Otherwise, tuffs are not of much importance in an economic sense. The peperino, much used at Rome and Naples as a building stone, is a trachyte tuff. Puzzolana also is a decomposed tuff, but of basic character, originally obtained near Naples and used as a cement, but this name is now applied to a number of substances not always of identical character. In the Eifel a trachytic, pumiceous tuff called trass has been extensively worked as a hydraulic mortar. Peperino is an Italian name applied to a brown or grey volcanic tuff, containing fragments of basalt and limestone, with disseminated crystals of augite, mica, magnetite, leucite, and other similar minerals. ... A sample of trachyte Trachyte is an igneous, volcanic rock with an aphanitic to porphyritic texture. ... “Napoli” redirects here. ... In the most general sense of the word, cement is a binder, a substance which sets and hardens independently, and can bind other materials together. ... Trass is the local name of a volcanic tuff occurring in the Eifel, where it is worked for hydraulic mortar. ... Mortar holding weathered bricks. ...


See also


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Tuff - LoveToKnow 1911 (1809 words)
A tuff of recent origin is generally loose and incoherent, but the older tuffs have been, in most cases, cemented together by pressure and the action of infiltrating water, making rocks which, while not very hard, are strong enough to be extensively used for building purposes (e.g.
Where crystals are very abundant the ashes are called "crystal tuffs." In St Vincent and Martinique in 1902 much of the dust was composed of minute crystals enclosed in thin films of glass, because the lava at the moment of eruption had very nearly solidified as a crystalline mass.
Puzzuolana also is a decomposed tuff, but of basic character, originally obtained near Naples and used as a cement, but this name is now applied to a number of substances not always of identical character.
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