Washington Monument
The Washington Monument is an obelisk on the National Mall in Washington, D. C. built to commemorate George Washington, once commander-in-chief of the Continental Army and the first President of the United States. Located due east of the Reflecting Pool and the Lincoln Memorial, the monument, made of marble and bluestone gneiss, is both the world's tallest predominantly stone structure and the world's tallest obelisk, standing 554 feet 7 11⁄32 inches tall according to the National Geodetic Survey or 555 feet 5 1⁄8 inches tall according to the National Park Service, it is the tallest monumental column in the world if all are measured above their pedestrian entrances. It was the tallest structure in the world from 1884 to 1889, when it was overtaken by the Eiffel Tower in Paris. Construction of the monument began in 1848 and was halted from 1854 to 1877 due to a lack of funds, a struggle for control over the Washington National Monument Society, the intervention of the American Civil War. Although the stone structure was completed in 1884, internal ironwork, the knoll, other finishing touches were not completed until 1888.
A difference in shading of the marble, visible 150 feet or 27% up, shows where construction was halted and resumed with marble from a different source. The original design was by Robert Mills, but he did not include his proposed colonnade due to a lack of funds, proceeding only with a bare obelisk; the cornerstone was laid on July 4, 1848. The Washington Monument is a hollow Egyptian style stone obelisk with a 500-foot tall column and a 55-foot tall pyramidion, its walls are 1 1⁄2 feet thick at their top. The marble pyramidion has thin walls only 7 inches thick supported by six arches, two between opposite walls that cross at the center of the pyramidion and four smaller corner arches; the top of the pyramidion is a large marble capstone with a small aluminum pyramid at its apex with inscriptions on all four sides. The lowest 150 feet of the walls, constructed during the first phase 1848–1854, are composed of a pile of bluestone gneiss rubble stones held together by a large amount of mortar with a facade of semi-finished marble stones about 1 1⁄4 feet thick.
The upper 350 feet of the walls, constructed during the second phase 1880–1884, are composed of finished marble surface stones, half of which project into the walls backed by finished granite stones. The interior is occupied by iron stairs that spiral up the walls, with an elevator in the center, each supported by four iron columns, which do not support the stone structure; the stairs contain fifty sections, most on the north and south walls, with many long landings stretching between them along the east and west walls. These landings allowed many inscribed memorial stones of various materials and sizes to be viewed while the stairs were accessible, plus one memorial stone between stairs, difficult to view; the pyramidion has eight observation windows, two per side, eight red aircraft warning lights, two per side. Two aluminum lightning rods connected via the elevator support columns to ground water protect the monument; the monument's present foundation is 37 feet thick, consisting of half of its original bluestone gneiss rubble encased in concrete.
At the northeast corner of the foundation, 21 feet below ground, is the marble cornerstone, including a zinc case filled with memorabilia. Fifty American flags fly 24 hours a day on a large circle of flag poles centered on the monument. In 2001, a temporary screening facility was added to the entrance to prevent a terrorist attack. In 2011, an earthquake damaged the monument the pyramidion. George Washington, hailed as the father of his country, as the leader, "first in war, first in peace and first in the hearts of his countrymen", was the dominant military and political leader of the new United States of America from 1775 to 1799, his former enemy King George III called him "the greatest character of the age."At his death in 1799, he left a critical legacy. Washington was the unchallenged public icon of American civic patriotism, he was identified with the Federalist Party, which lost control of the national government in 1800 to the Jeffersonian Republicans, who were reluctant to celebrate the hero of the opposition party.
Starting with victory in the Revolution, there were many proposals to build a monument to Washington. After his death, Congress authorized a suitable memorial in the national capital, but the decision was reversed when the Democratic-Republican Party took control of Congress in 1801; the Republicans were dismayed. They blocked his image on coins or the celebration of his birthday. Further political squabbling, along with the North–South division on the Civil War, blocked the completion of the Washington Monument until the late 19th century. By that time, Washington had the image of a national hero who could be celebrated by both North and South, memorials to him were no longer contr
Egyptian pyramids
The Egyptian pyramids are ancient pyramid-shaped masonry structures located in Egypt. As of November 2008, sources cite either 138 as the number of identified Egyptian pyramids. Most were built as tombs for the country's pharaohs and their consorts during the Old and Middle Kingdom periods; the earliest known Egyptian pyramids are found at Saqqara, northwest of Memphis. The earliest among these is the Pyramid of Djoser, built c. 2630–2610 BC during the Third Dynasty. This pyramid and its surrounding complex were designed by the architect Imhotep, are considered to be the world's oldest monumental structures constructed of dressed masonry; the most famous Egyptian pyramids are those found on the outskirts of Cairo. Several of the Giza pyramids are counted among the largest structures built; the Pyramid of Khufu at Giza is the largest Egyptian pyramid. It is the only one of the Seven Wonders of the Ancient World still in existence. By the time of the Early Dynastic Period, those with sufficient means were buried in bench-like structures known as mastabas.
The second historically-documented Egyptian pyramid is attributed to the architect Imhotep, who planned what Egyptologists believe to be a tomb for the pharaoh Djoser. Imhotep is credited with being the first to conceive the notion of stacking mastabas on top of each other, creating an edifice composed of a number of "steps" that decreased in size towards its apex; the result was the Pyramid of Djoser, designed to serve as a gigantic stairway by which the soul of the deceased pharaoh could ascend to the heavens. Such was the importance of Imhotep's achievement that he was deified by Egyptians; the most prolific pyramid-building phase coincided with the greatest degree of absolutist rule. It was during this time of the Old Kingdom of Egypt that the most famous pyramids, the Giza pyramid complex, were built. Over time, as authority became less centralized, the ability and willingness to harness the resources required for construction on a massive scale decreased, pyramids were smaller, less well-built and hastily constructed.
Long after the end of Egypt's own pyramid-building period, a burst of pyramid-building occurred in what is present-day Sudan, after much of Egypt came under the rule of the Kingdom of Kush, based at Napata. While Napatan rule was brief, ending in 661 BC, Egyptian culture made an indelible impression; the Meroitic period of Kushite history, when the kingdom was centered on Meroë, saw a full-blown pyramid-building revival, which saw more than two hundred Egyptian-inspired indigenous royal pyramid-tombs constructed in the vicinity of the kingdom's capital cities. Al-Aziz Uthman tried to destroy the Giza pyramid complex, he gave up after damaging the Pyramid of Menkaure. The shape of Egyptian pyramids is thought to represent the primordial mound from which the Egyptians believed the earth was created; the shape of a pyramid is thought to be representative of the descending rays of the sun, most pyramids were faced with polished reflective white limestone, in order to give them a brilliant appearance when viewed from a distance.
Pyramids were also named in ways that referred to solar luminescence. For example, the formal name of the Bent Pyramid at Dahshur was The Southern Shining Pyramid, that of Senwosret at el-Lahun was Senwosret is Shining. While it is agreed that pyramids were burial monuments, there is continued disagreement on the particular theological principles that might have given rise to them. One suggestion is that they were designed as a type of "resurrection machine."The Egyptians believed the dark area of the night sky around which the stars appear to revolve was the physical gateway into the heavens. One of the narrow shafts that extend from the main burial chamber through the entire body of the Great Pyramid points directly towards the center of this part of the sky; this suggests the pyramid may have been designed to serve as a means to magically launch the deceased pharaoh's soul directly into the abode of the gods. All Egyptian pyramids were built on the west bank of the Nile, which, as the site of the setting sun, was associated with the realm of the dead in Egyptian mythology.
In 1842, Karl Richard Lepsius produced the first modern list of pyramids – now known as the Lepsius list of pyramids – in which he counted 67. A great many more have since been discovered; as of November 2008, 118 Egyptian pyramids have been identified. The location of Pyramid 29, which Lepsius called the "Headless Pyramid", was lost for a second time when the structure was buried by desert sands after Lepsius's survey, it was found again only during an archaeological dig conducted in 2008. Many pyramids are in a poor state of preservation or buried by desert sands. If visible at all, they may appear as little more than mounds of rubble; as a consequence, archaeologists are continuing to identify and study unknown pyramid structures. The most recent pyramid to be discovered was that of Sesheshet at Saqqara, mother of the Sixth Dynasty pharaoh Teti, announced on 11 November 2008. All of Egypt's pyramids, except the small Third Dynasty pyramid of Zawyet el-Amwat, are sited on the west bank of the Nile, most are grouped together in a number of pyramid fields.
The most important of these are listed geographically, from north to south, below. Abu Rawash is the site of Egypt's most northerly pyramid — the ruined Pyramid of Djedefre and successor of Khufu, it was thought that this pyramid had never been completed, but the current archaeological consensus is that not only was it completed, but that it was orig
Cairo
Cairo is the capital of Egypt. The city's metropolitan area is one of the largest in Africa, the largest in the Middle East, the 15th-largest in the world, is associated with ancient Egypt, as the famous Giza pyramid complex and the ancient city of Memphis are located in its geographical area. Located near the Nile Delta, modern Cairo was founded in 969 CE by the Fatimid dynasty, but the land composing the present-day city was the site of ancient national capitals whose remnants remain visible in parts of Old Cairo. Cairo has long been a centre of the region's political and cultural life, is titled "the city of a thousand minarets" for its preponderance of Islamic architecture. Cairo is considered a World City with a "Beta +" classification according to GaWC. Cairo has the oldest and largest film and music industries in the Middle East, as well as the world's second-oldest institution of higher learning, Al-Azhar University. Many international media and organizations have regional headquarters in the city.
With a population of over 9 million spread over 3,085 square kilometers, Cairo is by far the largest city in Egypt. An additional 9.5 million inhabitants live in close proximity to the city. Cairo, like many other megacities, suffers from high levels of traffic. Cairo's metro, one of two in Africa, ranks among the fifteen busiest in the world, with over 1 billion annual passenger rides; the economy of Cairo was ranked first in the Middle East in 2005, 43rd globally on Foreign Policy's 2010 Global Cities Index. Egyptians refer to Cairo as Maṣr, the Egyptian Arabic name for Egypt itself, emphasizing the city's importance for the country, its official name al-Qāhirah means "the Vanquisher" or "the Conqueror" due to the fact that the planet Mars, an-Najm al-Qāhir, was rising at the time when the city was founded also in reference to the much awaited arrival of the Fatimid Caliph Al-Mu'izz who reached Cairo in 973 from Mahdia, the old Fatimid capital. The location of the ancient city of Heliopolis is the suburb of Ain Shams.
The Coptic name of the city is Kashromi which means "man breaker", akin to Arabic al-Qāhirah . Sometimes the city is informally referred to as Kayro by people from Alexandria; the area around present-day Cairo Memphis, the old capital of Egypt, had long been a focal point of Ancient Egypt due to its strategic location just upstream from the Nile Delta. However, the origins of the modern city are traced back to a series of settlements in the first millennium. Around the turn of the 4th century, as Memphis was continuing to decline in importance, the Romans established a fortress town along the east bank of the Nile; this fortress, known as Babylon, was the nucleus of the Roman and the Byzantine city and is the oldest structure in the city today. It is situated at the nucleus of the Coptic Orthodox community, which separated from the Roman and Byzantine churches in the late 4th century. Many of Cairo's oldest Coptic churches, including the Hanging Church, are located along the fortress walls in a section of the city known as Coptic Cairo.
Following the Muslim conquest in 640 AD, the conqueror Amr ibn As settled to the north of the Babylon in an area that became known as al-Fustat. A tented camp Fustat became a permanent settlement and the first capital of Islamic Egypt. In 750, following the overthrow of the Umayyad caliphate by the Abbasids, the new rulers created their own settlement to the northeast of Fustat which became their capital; this was known as al-Askar. A rebellion in 869 by Ahmad ibn Tulun led to the abandonment of Al Askar and the building of another settlement, which became the seat of government; this was al-Qatta ` closer to the river. Al Qatta'i was centred around a ceremonial mosque, now known as the Mosque of ibn Tulun. In 905, the Abbasids re-asserted control of the country and their governor returned to Fustat, razing al-Qatta'i to the ground. Since 1860s, Cairo expanded west as far as what is called now In 968, the Fatimids were led by general Jawhar al-Siqilli to establish a new capital for the Fatimid dynasty.
Egypt was conquered from their base in Ifriqiya and a new fortified city northeast of Fustat was established. It took four years to build the city known as al-Manṣūriyyah, to serve as the new capital of the caliphate. During that time, Jawhar commissioned the construction of the al-Azhar Mosque by order of the Caliph, which developed into the third-oldest university in the world. Cairo would become a centre of learning, with the library of Cairo containing hundreds of thousands of books; when Caliph al-Mu'izz li Din Allah arrived from the old Fatimid capital of Mahdia in Tunisia in 973, he gave the city its present name, al-Qāhiratu. For nearly 200 years after Cairo was established, the administrative centre of Egypt remained in Fustat. However, in 1168 the Fatimids under the leadership of vizier Shawar set fire to Fustat to prevent Cairo's capture by the Crusaders. Egypt's capital was permanently moved to Cairo, expanded to include the ruins of Fustat and the previous capitals of
Pyramid of Khendjer
The Pyramid of Khendjer was a pyramid built for the burial of the 13th dynasty pharaoh Khendjer, who ruled Egypt c. 1760 BC during the Second Intermediate Period. The pyramid, part of larger complex comprising a mortuary temple, a chapel, two enclosure walls and a subsidiary pyramid stood around 37 m high and is now ruined; the pyramidion was discovered during excavations under the direction of Gustave Jéquier in 1929, indicating that the pyramid was finished during Khendjer's lifetime. It is the only pyramid known to have been completed during the 13th dynasty; the first investigations of the pyramid of Khendjer were undertaken in the mid 19th century by Karl Richard Lepsius who included the pyramid in his list under the number XLIV. The pyramid was excavated by Gustave Jéquier from 1929 until 1931 with the excavation report published 2 years in 1933; the pyramid complex of Khendjer is located between the pyramid of Pepi II and the pyramid of Senusret III in South Saqqara. The main pyramid lies in ruins, due in part to the damaging excavations by G. Jéquier and now rises only about one meter above the desert sand.
The pyramid complex comprises the main pyramid enclosed by two walls. The outer one, made of mudbrick, contained in the north-east corner a small subsidiary pyramid, the only one known dating to the 13th dynasty; the inner enclosure wall was patterned with niches and panels. This replaced an earlier mudbrick wavy-wall, which led Rainer Stadelmann to suggest that the wavy-wall was constructed as a provisional and abbreviated substitute to the more time consuming but preferred niched-wall. At the south-east corner of the outer wall is a blocked unfinished stairway, which could be part of earlier plans for the pyramid substructure or part of an unfinished south tomb, meant for the Ka of the deceased king. A small chapel was built adjacent to the north side of the main pyramid, inside the inner enclosure wall; the chapel could be reached by two stairways. The north wall of the chapel housed a yellow quartzite false door; the location of this door was unusual as it should have stood on the wall closest to the pyramid, i.e. the south wall rather than the north one.
The few surviving fragments of relief from the chapel show standard scenes with offering bearers. On the eastern side of the pyramid lay a mortuary temple which spread across both enclosure walls; this allowed for the outer section of the temple to be placed outside the inner wall, with the inner sanctuary on the inside of the inner wall. Little remains of the temple, except for pieces of reliefs and columns and parts of its pavement; the pyramid stood at 105 royal cubits in height, about 37 metres. The pyramid was constructed with a mudbrick core and a limestone outer casing with its backing stones; these and the limestone casing were both quarried by stone robbers. The core fared badly with time and the pyramid now stands only one meter tall due to the its disintegration. A fragmented black granite pyramidion was discovered on the east side of the complex and has been restored by G. Jéquier, it is now on display at Cairo. The pyramidion is decorated by reliefs showing Khendjer making offerings and is inscribed with the prenomen "Userkare", thus known to be a throne name of Khendjer.
The entrance to the substructures is located at the base of the southern end of the pyramid west side. A stairway with 13 steps leads to a chamber housing a large granite portcullis similar to those encountered in the Mazghuna pyramids dated from the Middle Kingdom; the portcullis was destined to block the way to the burial chamber but was never put into place across the passage. Beyond the portcullis chamber, a further stairway with 39 steps continued down to a closed double-leaf wooden door. Beyond the door is a second portcullis chamber, left open. In turn this leads to a small antechamber and from there on to a further corridor whose access was concealed beneath the paving of the antechamber floor; this corridor leads to the burial chamber. Khendjer's second portcullis chamber and corridor were constructed in the corner of a large trench dug in the ground; the burial chamber, made of a colossal monolithic quartzite block, was placed in the trench before the pyramid construction started, in a manner similar to the burial chamber of Amenemhet III at Hawara.
The weight of the quartzite block was estimated at 150 tons by G. Jéquier; the block was carved into two compartments destined to receive the king's coffin, canopic chest and funerary goods. Two large quartzite beams weighing 60 tons formed its roof. Once the block and its roof had been put into position, the workers built a gabled roof of limestone beams and a brick vault above it to relieve the weight of the pyramid; the mechanism for closing the vault consisted of sand-filled shafts on which rested the props of the northern ceiling slab. This would be lowered on the vault on draining the sand. After draining all the sand, the workmen escaped through the corridor which they filled with masonry and paved over its opening in the antechamber. At the north eastern corner of Khendjer's pyramid complex is a small subsidiary pyramid, thought to have been prepared for the burials of two of Khendjer's queens. G. Jéquier found shaft tombs nearby, which may have been prepared for other royal family members.
The entrance to the substructures of this pyramid lie at the base of its eastern base. A small stairway leads to two portcullis chambers similar to those found in the main pyramid. Here too the portcullises were left open. Beyond is an antechamber branching to the north and south t
Saqqara
Saqqara spelled Sakkara or Saccara in English, is a vast, ancient burial ground in Egypt, serving as the necropolis for the Ancient Egyptian capital, Memphis. Saqqara features numerous pyramids, including the world-famous Step pyramid of Djoser, sometimes referred to as the Step Tomb due to its rectangular base, as well as a number of mastabas. Located some 30 km south of modern-day Cairo, Saqqara covers an area of around 7 by 1.5 km. At Saqqara, the oldest complete stone building complex known in history was built: Djoser's step pyramid, built during the Third Dynasty. Another 16 Egyptian kings built pyramids at Saqqara, which are now in various states of preservation or dilapidation. High officials added private funeral monuments to this necropolis during the entire pharaonic period, it remained an important complex for non-royal burials and cult ceremonies for more than 3,000 years, well into Ptolemaic and Roman times. North of the area known as Saqqara lies Abusir; the area running from Giza to Dahshur has been used as a necropolis by the inhabitants of Memphis at different times, it was designated as a World Heritage Site by UNESCO in 1979.
Some scholars believe that the name Saqqara is not derived from the ancient Egyptian funerary deity, but from a local Berber Tribe called Beni Saqqar. The earliest burials of nobles can be traced back to the First Dynasty, at the northern side of the Saqqara plateau. During this time, the royal burial ground was at Abydos; the first royal burials at Saqqara, comprising underground galleries, date to the Second Dynasty. The last Second Dynasty king, was buried in his tomb at Abydos, but built a funerary monument at Saqqara consisting of a large rectangular enclosure, known as Gisr el-Mudir, it inspired the monumental enclosure wall around the Step Pyramid complex. Djoser's funerary complex, built by the royal architect Imhotep, further comprises a large number of dummy buildings and a secondary mastaba. French architect and Egyptologist Jean-Philippe Lauer spent the greater part of his life excavating and restoring Djoser's funerary complex. Tomb of king Hotepsekhemwy tomb of king Nynetjer Buried Pyramid, funerary complex of king Sekhemkhet Gisr el-Mudir, funerary complex of king Khasekhemwy Step Pyramid, funerary complex of king Djoser Nearly all Fourth Dynasty kings chose a different location for their pyramids.
During the second half of the Old Kingdom, under the Fifth and Sixth Dynasties, Saqqara was again the royal burial ground. The Fifth and Sixth Dynasty pyramids are not built wholly of massive stone blocks, but instead with a core consisting of rubble, they are less well preserved than the world-famous pyramids built by the Fourth Dynasty kings at Giza. Unas, the last ruler of the Fifth Dynasty, was the first king to adorn the chambers in his pyramid with Pyramid Texts. During the Old Kingdom, it was customary for courtiers to be buried in mastaba tombs close to the pyramid of their king. Thus, clusters of private tombs were formed in Saqqara around the pyramid complexes of Unas and Teti. Mastabet el-Fara'un, tomb of king Shepseskaf Pyramid complex of king Userkaf Haram el-Shawaf, pyramid complex of king Djedkare Pyramid of king Menkauhor Mastaba of Ti Mastaba of the Two Brothers Pyramid complex of king Unas Mastaba of Ptahhotep Pyramid complex of king Teti Mastaba of Mereruka Mastaba of Kagemni Mastaba of Akhethetep Pyramid complex of king Pepi I Pyramid complex of king Merenre Pyramid complex of king Pepi II Tomb of Perneb Pyramid of king Ibi From the Middle Kingdom onward, Memphis was no longer the capital of the country, kings built their funerary complexes elsewhere.
Few private monuments from this period have been found at Saqqara. Pyramid of king Khendjer Pyramid of an unknown king During the New Kingdom Memphis was an important administrative and military centre, being the capital after the Amaran Period. From the Eighteenth Dynasty onward many high officials built tombs at Saqqara. While still a general, Horemheb built a large tomb here, although he was buried as pharaoh in the Valley of the Kings at Thebes. Other important tombs belong to the vizier Aperel, the vizier Neferrenpet, the artist Thutmose, the wet-nurse of Tutankhamun, Maia. Many monuments from earlier periods were still standing, but dilapidated by this period. Prince Khaemweset, son of Pharaoh Ramesses II, made repairs to buildings at Saqqara. Among other things, he restored the Pyramid of Unas and added an inscription to its south face to commemorate the restoration, he enlarged the Serapeum, the burial site of the mummified Apis bulls, was buried in the catacombs. The Serapeum, containing one undisturbed interment of an Apis bull and the tomb of Khaemweset, were rediscovered by the French Egyptologist Auguste Mariette in 1851.
Several clusters of tombs of high officials, among which the tombs of Horemheb and of Maya and Merit. Reliefs and statues from these two tombs are on display in the National Museum of Antiquities at Leiden, the Netherlands, in the British Museum, London. During the periods after the New Kingdom, when several cities in the Delta served as capital of Egypt, Saqqara remained in use as a burial ground for nobles. Moreover, the area became an important destination for pilgrims to a number of cult centres. Activities sprang up around the Serapeum, extensive underground galleries were cut into the rock as burial sites for large numbers of mummified ibises, cats and falcons. Several shaft tombs of officials o
Granite
Granite is a common type of felsic intrusive igneous rock, granular and phaneritic in texture. Granites can be predominantly white, pink, or gray depending on their mineralogy; the word "granite" comes from the Latin granum, a grain, in reference to the coarse-grained structure of such a holocrystalline rock. Speaking, granite is an igneous rock with between 20% and 60% quartz by volume, at least 35% of the total feldspar consisting of alkali feldspar, although the term "granite" is used to refer to a wider range of coarse-grained igneous rocks containing quartz and feldspar; the term "granitic" means granite-like and is applied to granite and a group of intrusive igneous rocks with similar textures and slight variations in composition and origin. These rocks consist of feldspar, quartz and amphibole minerals, which form an interlocking, somewhat equigranular matrix of feldspar and quartz with scattered darker biotite mica and amphibole peppering the lighter color minerals; some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic.
A granitic rock with a porphyritic texture is known as a granite porphyry. Granitoid is a descriptive field term for lighter-colored, coarse-grained igneous rocks. Petrographic examination is required for identification of specific types of granitoids; the extrusive igneous rock equivalent of granite is rhyolite. Granite is nearly always massive and tough; these properties have made granite a widespread construction stone throughout human history. The average density of granite is between 2.65 and 2.75 g/cm3, its compressive strength lies above 200 MPa, its viscosity near STP is 3–6·1019 Pa·s. The melting temperature of dry granite at ambient pressure is 1215–1260 °C. Granite has poor primary permeability overall, but strong secondary permeability through cracks and fractures if they are present. Granite is classified according to the QAPF diagram for coarse grained plutonic rocks and is named according to the percentage of quartz, alkali feldspar and plagioclase feldspar on the A-Q-P half of the diagram.
True granite contains both alkali feldspars. When a granitoid is devoid or nearly devoid of plagioclase, the rock is referred to as alkali feldspar granite; when a granitoid contains less than 10% orthoclase, it is called tonalite. A granite containing both muscovite and biotite micas is called two-mica granite. Two-mica granites are high in potassium and low in plagioclase, are S-type granites or A-type granites. A worldwide average of the chemical composition of granite, by weight percent, based on 2485 analyses: Granite containing rock is distributed throughout the continental crust. Much of it was intruded during the Precambrian age. Outcrops of granite tend to form rounded massifs. Granites sometimes occur in circular depressions surrounded by a range of hills, formed by the metamorphic aureole or hornfels. Granite occurs as small, less than 100 km2 stock masses and in batholiths that are associated with orogenic mountain ranges. Small dikes of granitic composition called aplites are associated with the margins of granitic intrusions.
In some locations coarse-grained pegmatite masses occur with granite. Granite is more common in continental crust than in oceanic crust, they are crystallized from felsic melts which are less dense than mafic rocks and thus tend to ascend toward the surface. In contrast, mafic rocks, either basalts or gabbros, once metamorphosed at eclogite facies, tend to sink into the mantle beneath the Moho. Granitoids have crystallized from felsic magmas that have compositions near a eutectic point. Magmas are composed of minerals in variable abundances. Traditionally, magmatic minerals are crystallized from the melts that have separated from their parental rocks and thus are evolved because of igneous differentiation. If a granite has a cooling process, it has the potential to form larger crystals. There are peritectic and residual minerals in granitic magmas. Peritectic minerals are generated through peritectic reactions, whereas residual minerals are inherited from parental rocks. In either case, magmas will evolve to the eutectic for crystallization upon cooling.
Anatectic melts are produced by peritectic reactions, but they are much less evolved than magmatic melts because they have not separated from their parental rocks. The composition of anatectic melts may change toward the magmatic melts through high-degree fractional crystallization. Fractional crystallisation serves to reduce a melt in iron, titanium and sodium, enrich the melt in potassium and silicon – alkali feldspar and quartz, are two of the defining constituents of granite; this process operates regardless of the origin of parental magmas to granites, regardless of their chemistry. The composition and origin of any magma that differentiates into granite leave certain petrological evidence as to what the granite's parental rock was; the final texture and composition of a granite are distinctive as to its parental rock. For instance, a granite, derived from partial melting of meta
Gold
Gold is a chemical element with symbol Au and atomic number 79, making it one of the higher atomic number elements that occur naturally. In its purest form, it is a bright reddish yellow, soft and ductile metal. Chemically, gold is a group 11 element, it is solid under standard conditions. Gold occurs in free elemental form, as nuggets or grains, in rocks, in veins, in alluvial deposits, it occurs in a solid solution series with the native element silver and naturally alloyed with copper and palladium. Less it occurs in minerals as gold compounds with tellurium. Gold is resistant to most acids, though it does dissolve in aqua regia, a mixture of nitric acid and hydrochloric acid, which forms a soluble tetrachloroaurate anion. Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to refine gold and to confirm the presence of gold in metallic objects, giving rise to the term acid test. Gold dissolves in alkaline solutions of cyanide, which are used in mining and electroplating.
Gold dissolves in mercury, forming amalgam alloys. A rare element, gold is a precious metal, used for coinage and other arts throughout recorded history. In the past, a gold standard was implemented as a monetary policy, but gold coins ceased to be minted as a circulating currency in the 1930s, the world gold standard was abandoned for a fiat currency system after 1971. A total of 186,700 tonnes of gold exists above ground, as of 2015; the world consumption of new gold produced is about 50% in jewelry, 40% in investments, 10% in industry. Gold's high malleability, resistance to corrosion and most other chemical reactions, conductivity of electricity have led to its continued use in corrosion resistant electrical connectors in all types of computerized devices. Gold is used in infrared shielding, colored-glass production, gold leafing, tooth restoration. Certain gold salts are still used as anti-inflammatories in medicine; as of 2017, the world's largest gold producer by far was China with 440 tonnes per year.
Gold is the most malleable of all metals. It can be drawn into a monoatomic wire, stretched about twice before it breaks; such nanowires distort via formation and migration of dislocations and crystal twins without noticeable hardening. A single gram of gold can be beaten into a sheet of 1 square meter, an avoirdupois ounce into 300 square feet. Gold leaf can be beaten thin enough to become semi-transparent; the transmitted light appears greenish blue, because gold reflects yellow and red. Such semi-transparent sheets strongly reflect infrared light, making them useful as infrared shields in visors of heat-resistant suits, in sun-visors for spacesuits. Gold is a good conductor of electricity. Gold has a density of 19.3 g/cm3 identical to that of tungsten at 19.25 g/cm3. By comparison, the density of lead is 11.34 g/cm3, that of the densest element, osmium, is 22.588±0.015 g/cm3. Whereas most metals are gray or silvery white, gold is reddish-yellow; this color is determined by the frequency of plasma oscillations among the metal's valence electrons, in the ultraviolet range for most metals but in the visible range for gold due to relativistic effects affecting the orbitals around gold atoms.
Similar effects impart a golden hue to metallic caesium. Common colored gold alloys include the distinctive eighteen-karat rose gold created by the addition of copper. Alloys containing palladium or nickel are important in commercial jewelry as these produce white gold alloys. Fourteen-karat gold-copper alloy is nearly identical in color to certain bronze alloys, both may be used to produce police and other badges. White gold alloys can be made with nickel. Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as green gold. Blue gold can be made by alloying with iron, purple gold can be made by alloying with aluminium. Less addition of manganese, aluminium and other elements can produce more unusual colors of gold for various applications. Colloidal gold, used by electron-microscopists, is red. Gold has only one stable isotope, 197Au, its only occurring isotope, so gold is both a mononuclidic and monoisotopic element. Thirty-six radioisotopes have been synthesized, ranging in atomic mass from 169 to 205.
The most stable of these is 195Au with a half-life of 186.1 days. The least stable is 171Au. Most of gold's radioisotopes with atomic masses below 197 decay by some combination of proton emission, α decay, β+ decay; the exceptions are 195Au, which decays by electron capture, 196Au, which decays most by electron capture with a minor β− decay path. All of gold's radioisotopes with atomic masses above 197 decay by β− decay. At least 32 nuclear isomers have been characterized, ranging in atomic mass from 170 to 200. Within that range, only 178Au, 180Au, 181Au, 182Au, 188Au do not have isomers. Gold's most stable isomer is 198m2Au with a half-life of 2.27 days. Gold's least stable isomer is 177m2Au with a half-life of only 7 ns. 184m1Au has three decay paths: β+ decay, isomeric
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