Obsidian is a occurring volcanic glass formed as an extrusive igneous rock. Obsidian is produced when felsic lava extruded from a volcano cools with minimal crystal growth, it is found within the margins of rhyolitic lava flows known as obsidian flows, where the chemical composition causes a high viscosity which, upon rapid cooling, forms a natural glass from the lava. The inhibition of atomic diffusion through this viscous lava explains the lack of crystal growth. Obsidian is hard and amorphous. In the past it was used to manufacture cutting and piercing tools and it has been used experimentally as surgical scalpel blades.... among the various forms of glass we may reckon Obsidian glass, a substance similar to the stone found by Obsidius in Ethiopia. The translation into English of Natural History written by Pliny the Elder of Rome shows a few sentences on the subject of a volcanic glass called obsidian, discovered in Ethiopia by Obsidius, a Roman explorer. Obsidian is the rock formed as a result of cooled lava, the parent material.
Extrusive formation of obsidian may occur when felsic lava cools at the edges of a felsic lava flow or volcanic dome or when lava cools during sudden contact with water or air. Intrusive formation of obsidian may occur. Tektites were once thought by many to be obsidian produced by lunar volcanic eruptions, though few scientists now adhere to this hypothesis. Obsidian is mineral-like, but not a true mineral, it is sometimes classified as a mineraloid. Though obsidian is dark in color, similar to mafic rocks such as basalt, obsidian's composition is felsic. Obsidian consists of SiO2 70% or more. Crystalline rocks with obsidian's composition include rhyolite; because obsidian is metastable at the Earth's surface, no obsidian has been found, older than Cretaceous age. This breakdown of obsidian is accelerated by the presence of water. Having a low water content when newly formed less than 1% water by weight, obsidian becomes progressively hydrated when exposed to groundwater, forming perlite. Pure obsidian is dark in appearance, though the color varies depending on the presence of impurities.
Iron and other transition elements may give the obsidian a dark brown to black color. Few samples are nearly colorless. In some stones, the inclusion of small, radially clustered crystals spherulites of the mineral cristobalite in the black glass produce a blotchy or snowflake pattern. Obsidian may contain patterns of gas bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled; these bubbles can produce interesting effects such as a golden sheen. An iridescent, rainbow-like sheen is caused by inclusions of magnetite nanoparticles. Obsidian can be found in locations, it can be found in Argentina, Azerbaijan, Canada, Georgia, Greece, El Salvador, Iceland, Japan, Mexico, New Zealand, Papua New Guinea, Scotland and the United States. Obsidian flows which may be hiked on are found within the calderas of Newberry Volcano and Medicine Lake Volcano in the Cascade Range of western North America, at Inyo Craters east of the Sierra Nevada in California.
Yellowstone National Park has a mountainside containing obsidian located between Mammoth Hot Springs and the Norris Geyser Basin, deposits can be found in many other western U. S. states including Arizona, New Mexico, Utah, Washington and Idaho. Obsidian can be found in the eastern U. S. states of Virginia, as well as North Carolina. There are only four major deposit areas in the central Mediterranean: Lipari, Pantelleria and Monte Arci. Ancient sources in the Aegean were Gyali. Acıgöl town and the Göllü Dağ volcano were the most important sources in central Anatolia, one of the more important source areas in the prehistoric Near East; the first known archaeological evidence of usage was in Kariandusi and other sites of the Acheulian age dated 700,000 BC, although the number of objects found at these sites were low relative to the Neolithic. Use of obsidian in pottery of the Neolithic in the area around Lipari was found to be less at a distance representing two weeks journeying. Anatolian sources of obsidian are known to have been the material used in the Levant and modern-day Iraqi Kurdistan from a time beginning sometime about 12,500 BC.
The first attested civilized use is dated to the late fifth millennium BC, known from excavations at Tell Brak. Obsidian was valued in Stone Age cultures because, like flint, it could be fractured to produce sharp blades or arrowheads. Like all glass and some other types of occurring rocks, obsidian breaks with a characteristic conchoidal fracture, it was polished to create early mirrors. Modern archaeologists have developed a relative dating system, obsidian hydration dating, to calculate the age of obsidian artifacts. In the Ubaid in the 5th millennium BC, blades were manufactured from obsidian extracted from outcrops located in modern-day Turkey. Ancient Egyptians used obsidian imported from the eastern Mediterranean and southern Red Sea regions. Obsidian was used in ritual circumcisions because of its deftness and sharpness. In the eastern Mediterranean
Asphalt known as bitumen, is a sticky and viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, is classed as a pitch. Before the 20th century, the term asphaltum was used; the word is derived from the Ancient Greek ἄσφαλτος ásphaltos. The primary use of asphalt is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete, its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs. The terms "asphalt" and "bitumen" are used interchangeably to mean both natural and manufactured forms of the substance. In American English, "asphalt" is used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is called "bitumen", geologists worldwide prefer the term for the occurring variety. Common colloquial usage refers to various forms of asphalt as "tar", as in the name of the La Brea Tar Pits.
Occurring asphalt is sometimes specified by the term "crude bitumen". Its viscosity is similar to that of cold molasses while the material obtained from the fractional distillation of crude oil boiling at 525 °C is sometimes referred to as "refined bitumen"; the Canadian province of Alberta has most of the world's reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres, an area larger than England. The word "asphalt" is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, the latinisation of the Greek ἄσφαλτος, a word meaning "asphalt/bitumen/pitch", which derives from ἀ-, "without" and σφάλλω, "make fall"; the first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, it thus seems that the name itself was expressive of this application. Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall. From the Greek, the word passed into late Latin, thence into French and English.
In French, the term asphalte is used for occurring asphalt-soaked limestone deposits, for specialised manufactured products with fewer voids or greater bitumen content than the "asphaltic concrete" used to pave roads. The expression "bitumen" originated in the Sanskrit words jatu, meaning "pitch", jatu-krit, meaning "pitch creating" or "pitch producing"; the Latin equivalent is claimed by some to be gwitu-men, by others, subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu, the German word Kitt and the old Norse word kvada. In British English, "bitumen" is used instead of "asphalt"; the word "asphalt" is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself. Bitumen mixed with clay was called "asphaltum", but the term is less used today. In Australian English, the word "asphalt" is used to describe a mix of construction aggregate. "Bitumen" refers to the liquid derived from the heavy-residues from crude oil distillation.
In American English, "asphalt" is equivalent to the British "bitumen". However, "asphalt" is commonly used as a shortened form of "asphalt concrete". In Canadian English, the word "bitumen" is used to refer to the vast Canadian deposits of heavy crude oil, while "asphalt" is used for the oil refinery product. Diluted bitumen is known as "dilbit" in the Canadian petroleum industry, while bitumen "upgraded" to synthetic crude oil is known as "syncrude", syncrude blended with bitumen is called "synbit"."Bitumen" is still the preferred geological term for occurring deposits of the solid or semi-solid form of petroleum. "Bituminous rock" is a form of sandstone impregnated with bitumen. The oil sands of Alberta, Canada are a similar material. Neither of the terms "asphalt" or "bitumen" should be confused with coal tars. Tar is the thick liquid product of the dry distillation and pyrolysis of organic hydrocarbons sourced from vegetation masses, whether fossilized as with coal, or freshly harvested; the majority of bitumen, on the other hand, was formed when vast quantities of organic animal materials were deposited by water and buried hundreds of metres deep at the diagenetic point, where the disorganized fatty hydrocarbon molecules joined together in long chains in the absence of oxygen.
Bitumen occurs as a solid or viscous liquid. It may be mixed in with coal deposits. Bitumen, coal using the Bergius process, can be refined into petrols such as gasoline, bitumen may be distilled into tar, not the other way around; the components of asphalt include four main classes of compounds: Naphthene aromatics, consisting of hydrogenated polycyclic aromatic compounds Polar aromatics, consisting of high molecular weight phenols and carboxylic acids produced by partial oxidation of the material Saturated hydrocarbons. Most natural bitumens a
The Uinta Basin is a physiographic section of the larger Colorado Plateaus province, which in turn is part of the larger Intermontane Plateaus physiographic division. It is a geologic structural basin in eastern Utah, east of the Wasatch Mountains and south of the Uinta Mountains; the Uinta Basin is fed by rivers flowing south from the Uinta Mountains. Many of the principal rivers flow into the Duchesne River which feeds the Green River—a tributary of the Colorado River; the Uinta Mountains forms the northern border of the Uinta Basin. They contain the highest point in Kings Peak, with a summit 13,528 feet above sea level; the climate of the Uinta Basin is semi-arid, with severe winter cold. Father Escalante's expedition visited the Uinta Basin in September 1776. 1822–1840 French Canadian trappers Étienne Provost, François le Clerc, Antoine Robidoux entered the Uinta Basin by way of the Old Spanish Trail and made their fortunes by trapping the many beaver and trading with the Uintah tribe. The Northern Ute Indian Reservation was established in 1861 by presidential decree.
The United States opened the reservation for homesteading by non-Native Americans in 1905. During the early decades of the twentieth century, both Native and non-Native irrigation systems were constructed—the Uinta Indian Irrigation Project, the Moon Lake Project, the Central Utah Project; the largest community in the Utah part of the Uinta Basin is Vernal. According to the U. S. Census, the community's population in 2010 was 9,089. Other communities in the Utah part of the region include Duchesne, Altamont, a number of small unincorporated communities; the Uinta Basin is the location of the Uintah and Ouray Indian Reservation, home to the Ute Tribe of the Uintah and Ouray Agency. The Ute Tribe is the source of Utah's state name. Local attractions include Dinosaur National Monument, Starvation Reservoir State Park, Flaming Gorge National Recreation Area, Raven Ridge and Fantasy Canyon; the local economy, once based on agriculture and mining, has diversified, energy extraction and tourism are now major industries as well.
In order to move oil out of the region, a new railroad is proposed to be constructed into the basin. In addition, Utah State University operates Branch campuses at Vernal and Roosevelt, expanding educational opportunities in a underserved region of Utah; the Uinta Basin is the most northerly section of the Colorado Plateau sections. The basin is 5,000 to 10,000 feet above sea level and corresponding to this depression is a broad east-west strip of higher plateau that rises above the denuded country to the south. On the south side of the plateau the descent of 3,000 feet, to the general level of eastern Utah on the south, is made in two steps; the first is the second, the Book Cliffs. Eastward in Colorado the two lines of cliffs are poorly distinguished; the Green River flows southward out of the Uinta Mountains to the north, crossing the Uinta Basin, flows in a 5,000 feet deep gorge known as Desolation Canyon. The Colorado River crosses the eastern portion of this section, cutting off an area of some 40 miles in diameter in which are preserved fragments of a lofty lava cap forming Grand Mesa and Battlement Mesa.
The Uinta Basin forms a geologic structural basin, is the source of commercial oil and gas production. Separated from the Piceance Basin by the Douglas Creek Arch, both basins formed during the Laramide Orogeny, are bounded by the Charleston-Nebo thrust fault, the Uinta Basin boundary fault, the Grand Hogback monocline; the Uinta Basin includes the Wasatch Plateau. According to the USGS Uinta-Piceance Assessment Team, "The black-shale facies of the Green River Formation is the main petroleum system of Tertiary age whereas the Mahogany zone of the Green River Formation is a minor component; the Cretaceous Mancos Group and equivalent rocks are the main source of Cretaceous oil and a major contributor of gas in the basin, whereas the Upper Cretaceous Mesaverde is a lesser contributor of oil but a significant source for gas. Ferron Sandstone coals are known to be a source of coalbed methane; the most prominent source of oil from Paleozoic rocks is the Permian Phosphoria Formation. During the Laramide Orogeny along the Wasatch Mountains, the north-south trending coast during the Late Cretaceous was receding eastward, at the same time the area where the basin is located was subsiding, creating a lacustrine environment.
A clastic wedge consisting of the North Horn and Wasatch was deposited northwards. These sediments interfingered with organic-rich lacustrine clays and carbonate muds of the Green River and Flagstaff facies. Deposits originated from the Uinta Mountains from the north, forming a southward-thinning clastic wedge. A carbonate sediment consisting of an organic-rich oil shale was deposited from the middle Eocene into the Oligocene; the basin is known for solid-hydrocarbon-filled fractures consisting of ozocerite and wurtzilite. In 1948, oil was discovered in the Paleozoic portion of the basin at Ashley Valley. Tertiary discoveries followed in 1948 at Roosevelt, the Red Wash Field and Duchesne Field in 1951; the Bluebell Field was discovered in 1967 and the Altamont Field in 1970. The Altamont-Bluebell structural trap occurs. Billie Untermann Utah -- Place. Population, Housing Units and Density: 2000. U. S. Census Bureau Utah History to Go The Uintah Basin Standard Utah State University, Uintah Basin Campus "Uinta Basin".
Geographic Names Info
Ford Model T
The Ford Model T is an automobile produced by Ford Motor Company from October 1, 1908, to May 26, 1927. It is regarded as the first affordable automobile, the car that opened travel to the common middle-class American; the Ford Model T was named the most influential car of the 20th century in the 1999 Car of the Century competition, ahead of the BMC Mini, Citroën DS, Volkswagen Type 1. Ford's Model T was successful not only because it provided inexpensive transportation on a massive scale, but because the car signified innovation for the rising middle class and became a powerful symbol of America's age of modernization. With 16.5 million sold it stands eighth on the top ten list of most sold cars of all time as of 2012. Although automobiles had existed for decades, they were still scarce and unreliable at the Model T's introduction in 1908. Positioned as reliable maintained, mass-market transportation, it was a runaway success. In a matter of days after the release, 15,000 orders were placed.
The first production Model T was produced on August 12, 1908 and left the factory on September 27, 1908, at the Ford Piquette Avenue Plant in Detroit, Michigan. On May 26, 1927, Henry Ford watched the 15 millionth Model T Ford roll off the assembly line at his factory in Highland Park, Michigan. Henry Ford conceived a series of cars between the founding of the company in 1903 and the introduction the Model T. Ford named his first car the Model A and proceeded through the alphabet up through the Model T, twenty models in all. Not all the models went into production; the production model before the Model T was the Model S, an upgraded version of the company's largest success to that point, the Model N. The follow-up was the Ford Model A; the company publicity said this was because the new car was such a departure from the old that Henry wanted to start all over again with the letter A. The Model T was Ford's first automobile mass-produced on moving assembly lines with interchangeable parts, marketed to the middle class.
Henry Ford said of the vehicle: I will build a motor car for the great multitude. It will be small enough for the individual to run and care for, it will be constructed of the best materials, by the best men to be hired, after the simplest designs that modern engineering can devise. But it will be so low in price that no man making a good salary will be unable to own one – and enjoy with his family the blessing of hours of pleasure in God's great open spaces. Although credit for the development of the assembly line belongs to Ransom E. Olds, with the first mass-produced automobile, the Oldsmobile Curved Dash, having begun in 1901, the tremendous advancements in the efficiency of the system over the life of the Model T can be credited entirely to the vision of Ford and his engineers; the Model T was designed by Childe Harold Wills, Hungarian immigrants Joseph A. Galamb and Eugene Farkas. Henry Love, C. J. Smith, Gus Degner and Peter E. Martin were part of the team. Production of the Model T began in the third quarter of 1908.
Collectors today sometimes classify Model Ts by build years and refer to these as "model years", thus labeling the first Model Ts as 1909 models. This is a retroactive classification scheme; the nominal model designation was "Model T", although design revisions did occur during the car's two decades of production. The Model T had a front-mounted 177-cubic-inch inline four-cylinder engine, producing 20 hp, for a top speed of 40–45 mph. According to Ford Motor Company, the Model T had fuel economy on the order of 13–21 mpg‑US; the engine was capable of running on gasoline, kerosene, or ethanol, although the decreasing cost of gasoline and the introduction of Prohibition made ethanol an impractical fuel for most users. The engines of the first 2,447 units were cooled with water pumps; the ignition system used in the Model T was an unusual one, with a low-voltage magneto incorporated in the flywheel, supplying alternating current to trembler coils to drive the spark plugs. This was closer to that used for stationary gas engines than the expensive high-voltage ignition magnetos that were used on some other cars.
This ignition made the Model T more flexible as to the quality or type of fuel it used. The system did not need a starting battery, since proper hand-cranking would generate enough current for starting. Electric lighting powered by the magneto was adopted in 1915, replacing acetylene and oil lamps, but electric starting was not offered until 1919; the Model T engine was produced for replacement needs, as well as stationary and marine applications until 1941, well after production of the Model T had ended. The Fordson Model F tractor engine, designed about a decade was similar to, but larger than, the Model T engine; the Model T was a rear-wheel drive vehicle. Its transmission was a planetary gear type billed as "three speed". In today's terms it would be considered a two-speed; the Model T's transmission was controlled with three floor-mounted pedals and a lever mounted to the road side of the driver's seat. The throttle was controlled with a lever on the steering wheel; the left pedal was used to engage the transmission.
With the floor lever in either the mid position or forward an
Colorado is a state of the Western United States encompassing most of the southern Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains. It is the 8th most extensive and 21st most populous U. S. state. The estimated population of Colorado was 5,695,564 on July 1, 2018, an increase of 13.25% since the 2010 United States Census. The state was named for the Colorado River, which early Spanish explorers named the Río Colorado for the ruddy silt the river carried from the mountains; the Territory of Colorado was organized on February 28, 1861, on August 1, 1876, U. S. President Ulysses S. Grant signed Proclamation 230 admitting Colorado to the Union as the 38th state. Colorado is nicknamed the "Centennial State" because it became a state one century after the signing of the United States Declaration of Independence. Colorado is bordered by Wyoming to the north, Nebraska to the northeast, Kansas to the east, Oklahoma to the southeast, New Mexico to the south, Utah to the west, touches Arizona to the southwest at the Four Corners.
Colorado is noted for its vivid landscape of mountains, high plains, canyons, plateaus and desert lands. Colorado is part of the western and southwestern United States, is one of the Mountain States. Denver is most populous city of Colorado. Residents of the state are known as Coloradans, although the antiquated term "Coloradoan" is used. Colorado is notable for its diverse geography, which includes alpine mountains, high plains, deserts with huge sand dunes, deep canyons. In 1861, the United States Congress defined the boundaries of the new Territory of Colorado by lines of latitude and longitude, stretching from 37°N to 41°N latitude, from 102°02'48"W to 109°02'48"W longitude. After 158 years of government surveys, the borders of Colorado are now defined by 697 boundary markers and 697 straight boundary lines. Colorado and Utah are the only states that have their borders defined by straight boundary lines with no natural features; the southwest corner of Colorado is the Four Corners Monument at 36°59'56"N, 109°2'43"W.
This is the only place in the United States where four states meet: Colorado, New Mexico and Utah. The summit of Mount Elbert at 14,440 feet elevation in Lake County is the highest point in Colorado and the Rocky Mountains of North America. Colorado is the only U. S. state that lies above 1,000 meters elevation. The point where the Arikaree River flows out of Yuma County and into Cheyenne County, Kansas, is the lowest point in Colorado at 3,317 feet elevation; this point, which holds the distinction of being the highest low elevation point of any state, is higher than the high elevation points of 18 states and the District of Columbia. A little less than half of Colorado is flat and rolling land. East of the Rocky Mountains are the Colorado Eastern Plains of the High Plains, the section of the Great Plains within Nebraska at elevations ranging from 3,350 to 7,500 feet; the Colorado plains are prairies but include deciduous forests and canyons. Precipitation averages 15 to 25 inches annually. Eastern Colorado is presently farmland and rangeland, along with small farming villages and towns.
Corn, hay and oats are all typical crops. Most villages and towns in this region boast both a grain elevator. Irrigation water is available from subterranean sources. Surface water sources include the South Platte, the Arkansas River, a few other streams. Subterranean water is accessed through artesian wells. Heavy use of wells for irrigation caused underground water reserves to decline. Eastern Colorado hosts considerable livestock, such as hog farms. 70% of Colorado's population resides along the eastern edge of the Rocky Mountains in the Front Range Urban Corridor between Cheyenne and Pueblo, Colorado. This region is protected from prevailing storms that blow in from the Pacific Ocean region by the high Rockies in the middle of Colorado; the "Front Range" includes Denver, Fort Collins, Castle Rock, Colorado Springs, Pueblo and other townships and municipalities in between. On the other side of the Rockies, the significant population centers in Western Colorado are the cities of Grand Junction and Montrose.
The Continental Divide of the Americas extends along the crest of the Rocky Mountains. The area of Colorado to the west of the Continental Divide is called the Western Slope of Colorado. West of the Continental Divide, water flows to the southwest via the Colorado River and the Green River into the Gulf of California. Within the interior of the Rocky Mountains are several large parks which are high broad basins. In the north, on the east side of the Continental Divide is the North Park of Colorado; the North Park is drained by the North Platte River, which flows north into Nebraska. Just to the south of North Park, but on the western side of the Continental Divide, is the Middle Park of Colorado, drained by the Colorado River; the South Park of Colorado is the region of the headwaters of the South Platte River. In southmost Colorado is the large San Luis Valley, where the headwaters of the Rio Grande are located; the valley sits between the Sangre De Cristo Mountains and San Juan Mountains, consists of large desert lands that run into the mountains.
The Rio Grande drains due south into New Mexico and Texas. Across the Sangre de Cristo Range to the east of the S
In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation; the hydraulic flow involved is due to hydrothermal circulation. Veins are classically thought of as being the result of growth of crystals on the walls of planar fractures in rocks, with the crystal growth occurring normal to the walls of the cavity, the crystal protruding into open space; this is the method for the formation of some veins. However, it is rare in geology for significant open space to remain open in large volumes of rock several kilometers below the surface. Thus, there are two main mechanisms considered for the formation of veins: open-space filling and crack-seal growth. Open space filling is the hallmark of epithermal vein systems, such as a stockwork, in greisens or in certain skarn environments. For open space filling to take effect, the confining pressure is considered to be below 0.5 GPa, or less than 3–5 km.
Veins formed in this way may exhibit a colloform, agate-like habit, of sequential selvages of minerals which radiate out from nucleation points on the vein walls and appear to fill up the available open space. Evidence of fluid boiling is present. Vugs and geodes are all examples of open-space filling phenomena in hydrothermal systems. Alternatively, hydraulic fracturing may create a breccia, filled with vein material; such breccia vein systems may be quite extensive, can form the shape of tabular dipping sheets, diatremes or laterally extensive mantos controlled by boundaries such as thrust faults, competent sedimentary layers, or cap rocks. When the confining pressure is too great, or when brittle-ductile rheological conditions predominate, vein formation occurs via crack-seal mechanisms. Crack-seal veins are thought to form quite during deformation by precipitation of minerals within incipient fractures; this happens swiftly by geologic standards, because pressures and deformation mean that large open spaces cannot be maintained.
Veins grow in thickness by reopening of the vein fracture and progressive deposition of minerals on the growth surface. Veins need either hydraulic pressure in excess of hydrostatic pressure or they need open spaces or fractures, which requires a plane of extension within the rock mass. In all cases except brecciation, therefore, a vein measures the plane of extension within the rock mass, give or take a sizeable bit of error. Measurement of enough veins will statistically form a plane of principal extension. In ductilely deforming compressional regimes, this can in turn give information on the stresses active at the time of vein formation. In extensionally deforming regimes, the veins occur normal to the axis of extension. Veins are of prime importance to mineral deposits, because they are the source of mineralisation either in or proximal to the veins. Typical examples include gold lodes, as well as skarn mineralisation. Hydrofracture breccias are classic targets for ore exploration as there is plenty of fluid flow and open space to deposit ore minerals.
Ores related to hydrothermal mineralisation, which are associated with vein material, may be composed of vein material and/or the rock in which the vein is hosted. In many gold mines exploited during the gold rushes of the 19th century, vein material alone was sought as ore material. In most of today's mines, ore material is composed of the veins and some component of the wall rocks which surrounds the veins; the difference between 19th-century and 21st-century mining techniques and the type of ore sought is based on the grade of material being mined and the methods of mining which are used. Hand-mining of gold ores permitted the miners to pick out the lode quartz or reef quartz, allowing the highest-grade portions of the lodes to be worked, without dilution from the unmineralised wall rocks. Today's mining, which uses larger machinery and equipment, forces the miners to take low-grade waste rock in with the ore material, resulting in dilution of the grade. However, today's mining and assaying allows the delineation of lower-grade bulk tonnage mineralisation, within which the gold is invisible to the naked eye.
In these cases, veining is the subordinate host to mineralisation and may only be an indicator of the presence of metasomatism of the wall-rocks which contains the low-grade mineralisation. For this reason, veins within hydrothermal gold deposits are no longer the exclusive target of mining, in some cases gold mineralisation is restricted to the altered wall rocks within which barren quartz veins are hosted. Boudinage Ore genesis Shear
Ceres (dwarf planet)
Ceres is the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter closer to Mars's orbit. With a diameter of 945 km, Ceres is the largest of the minor planets and the only dwarf planet inside Neptune's orbit, it is the 33rd-largest known body in the Solar System. Ceres comprises rock and ice, contains one-third of the mass of the entire asteroid belt. Ceres is the only object in the asteroid belt known to be rounded by its own gravity, although detailed analysis was required to exclude Vesta. From Earth, the apparent magnitude of Ceres ranges from 6.7 to 9.3, peaking once at opposition every 15 to 16 months, its synodic period. Thus at its brightest, it is too dim to be seen by the naked eye, except under dark skies. Ceres was the first asteroid to be discovered, it was considered a planet, but was reclassified as an asteroid in the 1850s after many other objects in similar orbits were discovered. Ceres appears to be differentiated into a rocky core and an icy mantle, may have a remnant internal ocean of liquid water under the layer of ice.
The surface is various hydrated minerals such as carbonates and clay. In January 2014, emissions of water vapor were detected from several regions of Ceres; this was unexpected because large bodies in the asteroid belt do not emit vapor, a hallmark of comets. The robotic NASA spacecraft Dawn entered orbit around Ceres on 6 March 2015. Pictures with a resolution unattained were taken during imaging sessions starting in January 2015 as Dawn approached Ceres, showing a cratered surface. Two distinct bright spots inside a crater were seen in a 19 February 2015 image, leading to speculation about a possible cryovolcanic origin or outgassing. On 3 March 2015, a NASA spokesperson said the spots are consistent with reflective materials containing ice or salts, but that cryovolcanism is unlikely. However, on 2 September 2016, scientists from the Dawn team claimed in a Science paper that a massive cryovolcano called Ahuna Mons is the strongest evidence yet for the existence of these mysterious formations.
On 11 May 2015, NASA released a higher-resolution image showing that, instead of one or two spots, there are several. On 9 December 2015, NASA scientists reported that the bright spots on Ceres may be related to a type of salt a form of brine containing magnesium sulfate hexahydrite. In June 2016, near-infrared spectra of these bright areas were found to be consistent with a large amount of sodium carbonate, implying that recent geologic activity was involved in the creation of the bright spots. In July 2018, NASA released a comparison of physical features found on Ceres with similar ones present on Earth. From June to October, 2018, Dawn orbited Ceres from as close as 35 km and as far away as 4,000 km; the Dawn mission ended on 1 November 2018. In October 2015, NASA released a true-color portrait of Ceres made by Dawn. In February 2017, organics were detected on Ceres in Ernutet crater. Johann Elert Bode, in 1772, first suggested that an undiscovered planet could exist between the orbits of Mars and Jupiter.
Kepler had noticed the gap between Mars and Jupiter in 1596. Bode based his idea on the Titius–Bode law, a now-discredited hypothesis, first proposed in 1766. Bode observed that there was a regular pattern in the semi-major axes of the orbits of known planets, that the pattern was marred only by the large gap between Mars and Jupiter; the pattern predicted that the missing planet ought to have an orbit with a semi-major axis near 2.8 astronomical units. William Herschel's discovery of Uranus in 1781 near the predicted distance for the next body beyond Saturn increased faith in the law of Titius and Bode, in 1800, a group headed by Franz Xaver von Zach, editor of the Monatliche Correspondenz, sent requests to twenty-four experienced astronomers, asking that they combine their efforts and begin a methodical search for the expected planet. Although they did not discover Ceres, they found several large asteroids. One of the astronomers selected for the search was Giuseppe Piazzi, a Catholic priest at the Academy of Palermo, Sicily.
Before receiving his invitation to join the group, Piazzi discovered Ceres on 1 January 1801. He was searching for "the 87th of the Catalogue of the Zodiacal stars of Mr la Caille", but found that "it was preceded by another". Instead of a star, Piazzi had found a moving star-like object. Piazzi observed Ceres a total of 24 times, the final time on 11 February 1801, when illness interrupted his observations, he announced his discovery on 24 January 1801 in letters to only two fellow astronomers, his compatriot Barnaba Oriani of Milan and Johann Elert Bode of Berlin. He reported it as a comet but "since its movement is so slow and rather uniform, it has occurred to me several times that it might be something better than a comet". In April, Piazzi sent his complete observations to Oriani, Jérôme Lalande in Paris; the information was published in the September 1801 issue of the Monatliche Correspondenz. By this time, the apparent position of Ceres had changed, was too close to the Sun's glare for other astronomers to confirm Piazzi's observations.
Toward the end of the year, Ceres should have been vis