Feldspars are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight. Feldspars crystallize from magma as veins in both intrusive and extrusive igneous rocks and are present in many types of metamorphic rock. Rock formed entirely of calcic plagioclase feldspar is known as anorthosite. Feldspars are found in many types of sedimentary rocks; the name feldspar derives from the German Feldspat, a compound of the words Feld, "field", Spat meaning "a rock that does not contain ore". The change from Spat to -spar was influenced by the English word spar, meaning a non-opaque mineral with good cleavage. Feldspathic refers to materials; the alternate spelling, has fallen out of use. This group of minerals consists of tectosilicates. Compositions of major elements in common feldspars can be expressed in terms of three endmembers: potassium feldspar endmember KAlSi3O8, albite endmember NaAlSi3O8, anorthite endmember CaAl2Si2O8. Solid solutions between K-feldspar and albite are called "alkali feldspar".
Solid solutions between albite and anorthite are called "plagioclase", or more properly "plagioclase feldspar". Only limited solid solution occurs between K-feldspar and anorthite, in the two other solid solutions, immiscibility occurs at temperatures common in the crust of the Earth. Albite is considered both alkali feldspar. Alkali feldspars are grouped into two types: those containing potassium in combination with sodium, aluminum, or silicon; the first of these include: orthoclase KAlSi3O8, sanidine AlSi3O8, microcline KAlSi3O8, anorthoclase AlSi3O8. Potassium and sodium feldspars are not miscible in the melt at low temperatures, therefore intermediate compositions of the alkali feldspars occur only in higher temperature environments. Sanidine is stable at the highest temperatures, microcline at the lowest. Perthite is a typical texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition; the perthitic textures in the alkali feldspars of many granites can be seen with the naked eye.
Microperthitic textures in crystals are visible using a light microscope, whereas cryptoperthitic textures can be seen only with an electron microscope. Barium feldspars are considered alkali feldspars. Barium feldspars form as the result of the substitution of barium for potassium in the mineral structure; the barium feldspars are monoclinic and include the following: celsian BaAl2Si2O8, hyalophane 4O8. The plagioclase feldspars are triclinic; the plagioclase series follows: albite NaAlSi3O8, oligoclase AlSi2O8, andesine NaAlSi3O8—CaAl2Si2O8, labradorite AlSi2O8, bytownite AlSi2O8, anorthite CaAl2Si2O8. Intermediate compositions of plagioclase feldspar may exsolve to two feldspars of contrasting composition during cooling, but diffusion is much slower than in alkali feldspar, the resulting two-feldspar intergrowths are too fine-grained to be visible with optical microscopes; the immiscibility gaps in the plagioclase solid solutions are complex compared to the gap in the alkali feldspars. The play of colours visible in some feldspar of labradorite composition is due to fine-grained exsolution lamellae.
The specific gravity in the plagioclase series increases from albite to anorthite. Chemical weathering of feldspars results in the formation of clay minerals such as illite and kaolinite. About 20 million tonnes of feldspar were produced in 2010 by three countries: Italy and China. Feldspar is a common raw material used in glassmaking, to some extent as a filler and extender in paint and rubber. In glassmaking, alumina from feldspar improves product hardness and resistance to chemical corrosion. In ceramics, the alkalis in feldspar act as a flux. Fluxes melt at an early stage in the firing process, forming a glassy matrix that bonds the other components of the system together. In the US, about 66% of feldspar is consumed in glassmaking, including glass containers and glass fiber. Ceramics and other uses, such as fillers, accounted for the remainder. In earth sciences and archaeology, feldspars are used for K-Ar dating, argon-argon dating, luminescence dating. In October 2012, the Mars Curiosity rover analyzed a rock that turned out to have a high feldspar content.
List of minerals – A list of minerals for which there are articles on Wikipedia List of countries by feldspar production This article incorporates public domain material from the United States Geological Survey document: "Feldspar and nepheline syenite". Bonewitz, Ronald Louis. Rock and Gem. New York: DK Publishing. ISBN 978-0-7566-3342-4. Media related to Feldspar at Wikimedia Commons
Maryland is a state in the Mid-Atlantic region of the United States, bordering Virginia, West Virginia, the District of Columbia to its south and west. The state's largest city is Baltimore, its capital is Annapolis. Among its occasional nicknames are Old Line State, the Free State, the Chesapeake Bay State, it is named after the English queen Henrietta Maria, known in England as Queen Mary. Sixteen of Maryland's twenty-three counties border the tidal waters of the Chesapeake Bay estuary and its many tributaries, which combined total more than 4,000 miles of shoreline. Although one of the smallest states in the U. S. it features a variety of climates and topographical features that have earned it the moniker of America in Miniature. In a similar vein, Maryland's geography and history combines elements of the Mid-Atlantic and South Atlantic regions of the country. One of the original Thirteen Colonies of Great Britain, Maryland was founded by George Calvert, a Catholic convert who sought to provide a religious haven for Catholics persecuted in England.
In 1632, Charles I of England granted Calvert a colonial charter, naming the colony after his wife, Queen Mary. Unlike the Pilgrims and Puritans, who enforced religious conformity in their settlements, Calvert envisioned a colony where people of different religious sects would coexist under the principle of toleration. Accordingly, in 1649 the Maryland General Assembly passed an Act Concerning Religion, which enshrined this principle by penalizing anyone who "reproached" a fellow Marylander based on religious affiliation. Religious strife was common in the early years, Catholics remained a minority, albeit in greater numbers than in any other English colony. Maryland's early settlements and population centers clustered around rivers and other waterways that empty into the Chesapeake Bay, its economy was plantation-based, centered on the cultivation of tobacco. The need for cheap labor led to a rapid expansion of indentured servants, penal labor, African slaves. In 1760, Maryland's current boundaries took form following the settlement of a long-running border dispute with Pennsylvania.
Maryland was an active participant in the events leading up to the American Revolution, by 1776 its delegates signed the Declaration of Independence. Many of its citizens subsequently played key military roles in the war. In 1790, the state ceded land for the establishment of the U. S. capital of Washington, D. C. Although a slave state, Maryland remained in the Union during the U. S. Civil War, its strategic location giving it a significant role in the conflict. After the war, Maryland took part in the Industrial Revolution, driven by its seaports, railroad networks, mass immigration from Europe. Since the Second World War, the state's population has grown to six million residents, it is among the most densely populated states in the nation; as of 2015, Maryland had the highest median household income of any state, owing in large part to its close proximity to Washington, D. C. and a diversified economy spanning manufacturing, higher education, biotechnology. Maryland has been ranked as one of the best governed states in the country.
The state's central role in American history is reflected by its hosting of some of the highest numbers of historic landmarks per capita. Maryland is comparable in overall area with Belgium, it is the 42nd largest and 9th smallest state and is closest in size to the state of Hawaii, the next smaller state. The next larger state, its neighbor West Virginia, is twice the size of Maryland. Maryland possesses a variety of topography within its borders, contributing to its nickname America in Miniature, it ranges from sandy dunes dotted with seagrass in the east, to low marshlands teeming with wildlife and large bald cypress near the Chesapeake Bay, to rolling hills of oak forests in the Piedmont Region, pine groves in the Maryland mountains to the west. Maryland is bounded on its north by Pennsylvania, on its west by West Virginia, on its east by Delaware and the Atlantic Ocean, on its south, across the Potomac River, by West Virginia and Virginia; the mid-portion of this border is interrupted by District of Columbia, which sits on land, part of Montgomery and Prince George's counties and including the town of Georgetown, Maryland.
This land was ceded to the United States Federal Government in 1790 to form the District of Columbia.. The Chesapeake Bay nearly bisects the state and the counties east of the bay are known collectively as the Eastern Shore. Most of the state's waterways are part of the Chesapeake Bay watershed, with the exceptions of a tiny portion of extreme western Garrett County, the eastern half of Worcester County, a small portion of the state's northeast corner. So prominent is the Chesapeake in Maryland's geography and economic life that there has been periodic agitation to change the state's official nickname to the "Bay State", a nickname, used by Massachusetts for decades; the highest point in Maryland, with an elevation of 3,360 feet, is Hoye Crest on Backbone Mountain, in the southwest corner of Garrett County, near the bo
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic rock is artificial, in nature volcanic rocks grade into hypabyssal and metamorphic rocks and constitute an important element of some sediments and sedimentary rocks. For these reasons, in geology and shallow hypabyssal rocks are not always treated as distinct. In the context of Precambrian shield geology, the term "volcanic" is applied to what are metavolcanic rocks. Volcanic rocks and sediment that form from magma erupted into the air are called "volcaniclastics," and these are technically sedimentary rocks. Volcanic rocks are among the most common rock types on Earth's surface in the oceans. On land, they are common at plate boundaries and in flood basalt provinces, it has been estimated. Lava Tephra Volcanic bomb Lapilli Volcanic ash Volcanic rocks are fine-grained or aphanitic to glass in texture, they contain clasts of other rocks and phenocrysts.
Phenocrysts are crystals that are identifiable with the unaided eye. Rhomb porphyry is an example with large rhomb shaped phenocrysts embedded in a fine grained matrix. Volcanic rocks have a vesicular texture caused by voids left by volatiles trapped in the molten lava. Pumice is a vesicular rock produced in explosive volcanic eruptions. Most modern petrologists classify igneous rocks, including volcanic rocks, by their chemistry when dealing with their origin; the fact that different mineralogies and textures may be developed from the same initial magmas has led petrologists to rely on chemistry to look at a volcanic rock's origin. The chemistry of volcanic rocks is dependent on two things: the initial composition of the primary magma and the subsequent differentiation. Differentiation of most volcanic rocks tends to increase the silica content by crystal fractionation; the initial composition of most volcanic rocks is basaltic, albeit small differences in initial compositions may result in multiple differentiation series.
The most common of these series are tholeiitic, calc-alkaline, alkaline. Most volcanic rocks share a number of common minerals. Differentiation of volcanic rocks tends to increase the silica content by fractional crystallization. Thus, more evolved volcanic rocks tend to be richer in minerals with a higher amount of silica such as phyllo and tectosilicates including the feldspars, quartz polymorphs and muscovite. While still dominated by silicates, more primitive volcanic rocks have mineral assemblages with less silica, such as olivine and the pyroxenes. Bowen's reaction series predicts the order of formation of the most common minerals in volcanic rocks. A magma may pick up crystals that crystallized from another magma. Diamonds found in kimberlites are well-known xenocrysts. Volcanic rocks are named according to both texture. Basalt is a common volcanic rock with low silica content. Rhyolite is a volcanic rock with high silica content. Rhyolite has silica content similar to that of granite while basalt is compositionally equal to gabbro.
Intermediate volcanic rocks include andesite, dacite and latite. Pyroclastic rocks are the product of explosive volcanism, they are felsic. Pyroclastic rocks are the result of volcanic debris, such as ash and tephra, other volcanic ejecta. Examples of pyroclastic rocks are ignimbrite. Shallow intrusions, which possess structure similar to volcanic rather than plutonic rocks, are considered to be volcanic, shading into subvolcanic; the terms lava stone and lava rock are more used by marketers than geologists, who would say "volcanic rock". "Lava stone" may describe anything from a friable silicic pumice to solid mafic flow basalt, is sometimes used to describe rocks that were never lava, but look as if they were. To convey anything about the physical or chemical properties of the rock, a more specific term should be used; the sub-family of rocks that form from volcanic lava are called igneous volcanic rocks. The lavas of different volcanoes, when cooled and hardened, differ much in their appearance and composition.
If a rhyolite lava-stream cools it can freeze into a black glassy substance called obsidian. When filled with bubbles of gas, the same lava may form the spongy appearing pumice. Allowed to cool it forms a light-colored, uniformly solid rock called rhyolite; the lavas, having cooled in contact with the air or water, are finely crystalline or have at least fine-grained ground-mass representing that part of the viscous semi-crystalline lava flow, still liquid at the moment of eruption. At this time they were exposed only to atmospheric pressure, the steam and other gases, which they contained in great quantity were free to escape; as crystal
Joshua Tree National Park
Joshua Tree National Park is an American national park in southeastern California, east of Los Angeles, near San Bernardino and Palm Springs. The park is named for the Joshua trees native to the Mojave Desert. Declared a national monument in 1936, Joshua Tree was redesignated as a national park in 1994 when the U. S. Congress passed the California Desert Protection Act. Encompassing a total of 790,636 acres —an area larger than the state of Rhode Island—the park includes 429,690 acres of designated wilderness. Straddling the border between San Bernardino County and Riverside County, the park includes parts of two deserts, each an ecosystem whose characteristics are determined by elevation: the higher Mojave Desert and the lower Colorado Desert; the Little San Bernardino Mountains traverse the southwest edge of the park. The earliest known residents of the land in and around what became Joshua Tree National Park were the people of the Pinto Culture, who lived and hunted here between 8000 and 4000 BCE.
Their stone tools and spear points, discovered in the Pinto Basin in the 1930s, suggest that they hunted game and gathered seasonal plants, but little else is known about them. Residents included the Serrano, the Cahuilla, the Chemehuevi peoples. All three lived at times in small villages in or near water the Oasis of Mara in what non-aboriginals called Twentynine Palms, they were hunter-gatherers who subsisted on plant foods supplemented by small game and reptiles while using other plants for making medicines and arrows, other articles of daily life. A fourth group, the Mojaves, used the local resources as they traveled along trails between the Colorado River and the Pacific coast. In the 21st century, small numbers of all four peoples live in the region near the park. In 1772, a group of Spaniards led by Pedro Fages, made the first European sightings of Joshua trees while pursuing native converts to Christianity who had run away from a mission in San Diego. By 1823, the year Mexico achieved independence from Spain, a Mexican expedition from Los Angeles, in what was Alta California, is thought to have explored as far east as the Eagle Mountains in what became the park.
Three years Jedediah Smith led a group of American fur trappers and explorers along the nearby Mojave Trail, others soon followed. Two decades after that, the United States defeated Mexico in the Mexican–American War and took over about half of Mexico's original territory, including California and the future parkland. In 1870, white settlers began grazing cattle on the tall grasses. In 1888, a gang of cattle rustlers moved into the region near the Oasis of Mara. Led by brothers James. B. and William S. McHaney, they hid stolen cattle in a box canyon at Cow Camp. Throughout the region, ranchers dug wells and built rainwater catchments called "tanks", such as White Tank and Barker Dam. In 1900, C. O. Barker, a miner and cattleman, built the original Barker Dam improved by William "Bill" Keys, a rancher. Grazing continued in the park through 1945. Barker Dam was added to the National Register of Historic Places in 1975. Between the 1860s and the 1940s, miners worked about 300 pit mines small, in what became the park.
The most successful, the Lost Horse Mine, produced gold and silver worth about $5 million in today's currency. Johnny Lang and others, the original owners of the Lost Horse Mine, installed a two-stamp mill to process ore at the site, the next owner, J. D. Ryan, replaced it with a 10-stamp steam-powered mill. Ryan pumped water from his ranch to the mill and cut timber from the nearby hills to heat water to make steam. Most of the structures associated with the mine fell apart, for safety reasons the National Park Service plugged the mine, which had collapsed; the Desert Queen Mine on Keys' Desert Queen Ranch was another productive gold mine. In the early 1930s, Keys bought a gasoline-powered two-stamp mill, the Wall Street Mill, moved it to his ranch to process ore; the ranch and mill were added to the NRHP in 1975 and the mine in 1976. Some of the mines in the park yielded copper and iron. On August 10, 1936, after Minerva Hoyt and others persuaded the state and federal governments to protect the area, president Franklin D. Roosevelt used the power of the 1906 Antiquities Act to establish Joshua Tree National Monument, protecting about 825,000 acres.
In 1950, the size of the park was reduced by about 290,000 acres to open the land to more mining. The monument was redesignated as a national park on October 31, 1994, by the Desert Protection Act, which added 234,000 acres. In 2019, the park expanded by 4,518 acres under a bill included in the John D. Dingell, Jr. Conservation and Recreation Act; the higher and cooler Mojave Desert is the special habitat of Yucca brevifolia, the Joshua tree for which the park is named. It occurs in patterns from dense forests to distantly spaced specimens. In addition to Joshua tree forests, the western part of the park includes some of the most interesting geologic displays found in California's deserts; the dominant geologic features of this landscape are hills of bare rock broken up into loose boulders. These hills are popular among rock scrambling enthusiasts; the flatland between these hills is sparsely forested with Joshua trees. Together with the boulder piles and Skull Rock, the trees make the landscape otherworldly.
Temperatures are most comfortable
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula K3AlSi3O102. More it refers to the dark mica series a solid-solution series between the iron-endmember annite, the magnesium-endmember phlogopite. Biotite was named by J. F. L. Hausmann in 1847 in honor of the French physicist Jean-Baptiste Biot, who performed early research into the many optical properties of mica. Biotite is a sheet silicate. Iron, aluminium, silicon and hydrogen form sheets that are weakly bound together by potassium ions, it is sometimes called "iron mica". It is sometimes called "black mica" as opposed to "white mica" – both form in the same rocks, in some instances side-by-side. Like other mica minerals, biotite has a perfect basal cleavage, consists of flexible sheets, or lamellae, which flake off, it has a monoclinic crystal system, with tabular to prismatic crystals with an obvious pinacoid termination. It has four prism faces and two pinacoid faces to form a pseudohexagonal crystal.
Although not seen because of the cleavage and sheets, fracture is uneven. It appears greenish to brown or black, yellow when weathered, it can be transparent to opaque, has a vitreous to pearly luster, a grey-white streak. When biotite is found in large chunks, they are called "books" because it resembles a book with pages of many sheets; the color of biotite is black and the mineral has a hardness of 2.5–3 on the Mohs scale of mineral hardness. Biotite dissolves in both acid and alkaline aqueous solutions, with the highest dissolution rates at low pH. However, biotite dissolution is anisotropic with crystal edge surfaces reacting 45 to 132 times faster than basal surfaces. In thin section, biotite exhibits moderate relief and a pale to deep greenish brown or brown color, with moderate to strong pleochroism. Biotite has a high birefringence which can be masked by its deep intrinsic color. Under cross-polarized light, biotite exhibits extinction parallel to cleavage lines, can have characteristic bird's eye extinction, a mottled appearance caused by the distortion of the mineral's flexible lamellae during grinding of the thin section.
Basal sections of biotite in thin section are approximately hexagonal in shape and appear isotropic under cross-polarized light. Biotite is found in a wide variety of metamorphic rocks. For instance, biotite occurs in the lava of Mount Vesuvius and in the Monzoni intrusive complex of the western Dolomites. Biotite in granite tends to be poorer in magnesium than the biotite found in its volcanic equivalent, rhyolite. Biotite is an essential phenocryst in some varieties of lamprophyre. Biotite is found in large cleavable crystals in pegmatite veins, as in New England and North Carolina USA. Other notable occurrences include Ontario Canada, it is an essential constituent of many metamorphic schists, it forms in suitable compositions over a wide range of pressure and temperature. It has been estimated. An igneous rock composed entirely of dark mica is known as a glimmerite or biotitite. Biotite may be found in association with its common alteration product chlorite; the largest documented single crystals of biotite were 7 m2 sheets found in Iveland, Norway.
Biotite is used extensively to constrain ages of rocks, by either potassium-argon dating or argon–argon dating. Because argon escapes from the biotite crystal structure at high temperatures, these methods may provide only minimum ages for many rocks. Biotite is useful in assessing temperature histories of metamorphic rocks, because the partitioning of iron and magnesium between biotite and garnet is sensitive to temperature
Utah is a state in the western United States. It became the 45th state admitted to the U. S. on January 4, 1896. Utah is the 13th-largest by area, 31st-most-populous, 10th-least-densely populated of the 50 United States. Utah has a population of more than 3 million according to the Census estimate for July 1, 2016. Urban development is concentrated in two areas: the Wasatch Front in the north-central part of the state, which contains 2.5 million people. Utah is bordered by Colorado to the east, Wyoming to the northeast, Idaho to the north, Arizona to the south, Nevada to the west, it touches a corner of New Mexico in the southeast. 62% of Utahns are reported to be members of The Church of Jesus Christ of Latter-day Saints, making Utah the only state with a majority population belonging to a single church. This influences Utahn culture and daily life; the LDS Church's world headquarters is located in Salt Lake City. The state is a center of transportation, information technology and research, government services, a major tourist destination for outdoor recreation.
In 2013, the U. S. Census Bureau estimated. St. George was the fastest-growing metropolitan area in the United States from 2000 to 2005. Utah has the 14th highest median average income and the least income inequality of any U. S. state. A 2012 Gallup national survey found Utah overall to be the "best state to live in" based on 13 forward-looking measurements including various economic and health-related outlook metrics. A common folk etymology is that the name "Utah" is derived from the name of the Ute tribe, purported to mean "people of the mountains" in the Ute language. However, the word for people in Ute is'núuchiu' while the word for mountain is'káav', offering no linguistic connection to the words'Ute' or'Utah'. According to other sources "Utah" is derived from the Apache name "yuttahih" which means "One, Higher up" or "Those that are higher up". In the Spanish language it was said as "Yuta", subsequently the English-speaking people adapted the word "Utah". Thousands of years before the arrival of European explorers, the Ancestral Puebloans and the Fremont people lived in what is now known as Utah, some of which spoke languages of the Uto-Aztecan group.
Ancestral Pueblo peoples built their homes through excavations in mountains, the Fremont people built houses of straw before disappearing from the region around the 15th century. Another group of Native Americans, the Navajo, settled in the region around the 18th century. In the mid-18th century, other Uto-Aztecan tribes, including the Goshute, the Paiute, the Shoshone, the Ute people settled in the region; these five groups were present. The southern Utah region was explored by the Spanish in 1540, led by Francisco Vásquez de Coronado, while looking for the legendary Cíbola. A group led by two Catholic priests—sometimes called the Dominguez-Escalante Expedition—left Santa Fe in 1776, hoping to find a route to the coast of California; the expedition encountered the native residents. The Spanish made further explorations in the region, but were not interested in colonizing the area because of its desert nature. In 1821, the year Mexico achieved its independence from Spain, the region became known as part of its territory of Alta California.
European trappers and fur traders explored some areas of Utah in the early 19th century from Canada and the United States. The city of Provo, Utah was named for one, Étienne Provost, who visited the area in 1825; the city of Ogden, Utah was named after Peter Skene Ogden, a Canadian explorer who traded furs in the Weber Valley. In late 1824, Jim Bridger became the first known English-speaking person to sight the Great Salt Lake. Due to the high salinity of its waters, He thought. After the discovery of the lake, hundreds of American and Canadian traders and trappers established trading posts in the region. In the 1830s, thousands of migrants traveling from the Eastern United States to the American West began to make stops in the region of the Great Salt Lake known as Lake Youta. Following the death of Joseph Smith in 1844, Brigham Young, as president of the Quorum of the Twelve, became the effective leader of the LDS Church in Nauvoo, Illinois. To address the growing conflicts between his people and their neighbors, Young agreed with Illinois Governor Thomas Ford in October 1845 that the Mormons would leave by the following year.
Young and the first band of Mormon pioneers reached the Salt Lake Valley on July 24, 1847. Over the next 22 years, more than 70,000 pioneers settled in Utah. For the first few years, Brigham Young and the thousands of early settlers of Salt Lake City struggled to survive; the arid desert land was deemed by the Mormons as desirable as a place where they could practice their religion without harassment. The Mormon settlements provided pioneers for other settlements in the West. Salt Lake City became the hub of a "far-flung commonwealth" of Mormon settlements. With new church converts coming from the East and around the world, Church leaders assigned groups of church members as missionaries to establish other settlements throughout the West, they developed irrigation to support large pioneer populations along Utah's Wasatch front. Throughout the remainder of the 19th century, Mormon pioneers established hundreds of other settlements in Utah, Id
Monzonite is an igneous intrusive rock. It is composed of equal amounts of plagioclase and alkali feldspar, with less than 5% quartz by weight, it may contain minor amounts of hornblende and other minerals. If quartz constitutes greater than 5%, the rock is termed a quartz monzonite. If the rock has a greater percentage of alkali feldspar, it grades into a syenite. With an increase in calcic plagioclase and mafic minerals the rock type becomes a diorite; the volcanic equivalent is the latite. Monzonite was named after the Monzoni range in Val di Fassa where it is abundant; as rock definitions have been systematized and codified, this association has lost any relevance to the rock's definition. QAPF diagram – Classification system for igneous rocks