Misplaced Pages

#498501

83-520: The Gilo River flows mainly through the Baro Salient , a portion of Ethiopia that juts westward into Sudan. The river valley was subjected to much prospecting for gold before World War II and in the 1950s, but not enough was found to make commercial extraction viable. Burchard Heinrich Jessen, who was part of W.N. McMillan's expedition that traveled through this part of southwestern Ethiopia in 1904, estimated its length at 200 miles and noted that at flood

166-399: A fault . Water often lubricates faults, filling in fractures and jogs. About 10 kilometres (6.2 mi) below the surface, under very high temperatures and pressures, the water carries high concentrations of carbon dioxide, silica, and gold. During an earthquake, the fault jog suddenly opens wider. The water inside the void instantly vaporizes, flashing to steam and forcing silica, which forms

249-483: A dilute solution of gold(III) chloride or chlorauric acid . Unlike sulfur, phosphorus reacts directly with gold at elevated temperatures to produce gold phosphide (Au 2 P 3 ). Gold readily dissolves in mercury at room temperature to form an amalgam , and forms alloys with many other metals at higher temperatures. These alloys can be produced to modify the hardness and other metallurgical properties, to control melting point or to create exotic colors. Gold

332-572: A gold-from-seawater swindle in the United States in the 1890s, as did an English fraudster in the early 1900s. Fritz Haber did research on the extraction of gold from sea water in an effort to help pay Germany 's reparations following World War I . Based on the published values of 2 to 64 ppb of gold in seawater, a commercially successful extraction seemed possible. After analysis of 4,000 water samples yielding an average of 0.004 ppb, it became clear that extraction would not be possible, and he ended

415-830: 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 also important in commercial jewelry as these produce white gold alloys. Fourteen-karat gold-copper alloy is nearly identical in color to certain bronze alloys, and both may be used to produce police and other badges . 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 , and purple gold can be made by alloying with aluminium . Less commonly, addition of manganese , indium , and other elements can produce more unusual colors of gold for various applications. Colloidal gold , used by electron-microscopists,

498-552: A large alluvial deposit. The mines at Roşia Montană in Transylvania were also very large, and until very recently, still mined by opencast methods. They also exploited smaller deposits in Britain , such as placer and hard-rock deposits at Dolaucothi . The various methods they used are well described by Pliny the Elder in his encyclopedia Naturalis Historia written towards the end of

581-667: A more secular approach into historical study. According to John Tosh , "From the High Middle Ages (c.1000–1300) onwards, the written word survives in greater abundance than any other source for Western history." Western historians developed methods comparable to modern historiographic research in the 17th and 18th centuries, especially in France and Germany, where they began investigating these source materials to write histories of their past. Many of these histories had strong ideological and political ties to their historical narratives. In

664-462: A novel type of metal-halide perovskite material consisting of Au and Au cations in its crystal structure has been found. It has been shown to be unexpectedly stable at normal conditions. Gold pentafluoride , along with its derivative anion, AuF − 6 , and its difluorine complex , gold heptafluoride , is the sole example of gold(V), the highest verified oxidation state. Some gold compounds exhibit aurophilic bonding , which describes

747-464: A river in Ethiopia is a stub . You can help Misplaced Pages by expanding it . Gold Gold is a chemical element with the chemical symbol Au (from Latin aurum ) and atomic number 79. In its pure form, it is a bright , slightly orange-yellow, dense, soft, malleable , and ductile metal . Chemically, gold is a transition metal , a group 11 element , and one of the noble metals . It

830-401: A sheet of 1 square metre (11 sq ft), and an avoirdupois ounce into 28 square metres (300 sq ft). Gold leaf can be beaten thin enough to become semi-transparent. The transmitted light appears greenish-blue because gold strongly reflects yellow and red. Such semi-transparent sheets also strongly reflect infrared light, making them useful as infrared (radiant heat) shields in

913-517: A solution of Au(OH) 3 in concentrated H 2 SO 4 produces red crystals of gold(II) sulfate , Au 2 (SO 4 ) 2 . Originally thought to be a mixed-valence compound, it has been shown to contain Au 4+ 2 cations, analogous to the better-known mercury(I) ion, Hg 2+ 2 . A gold(II) complex, the tetraxenonogold(II) cation, which contains xenon as a ligand, occurs in [AuXe 4 ](Sb 2 F 11 ) 2 . In September 2023,

SECTION 10

#1732858718499

996-470: Is Au with a half-life of 2.27 days. Gold's least stable isomer is Au with a half-life of only 7 ns. Au has three decay paths: β decay, isomeric transition , and alpha decay. No other isomer or isotope of gold has three decay paths. The possible production of gold from a more common element, such as lead , has long been a subject of human inquiry, and the ancient and medieval discipline of alchemy often focused on it; however,

1079-696: Is Au , which decays by proton emission with a half-life of 30 μs. Most of gold's radioisotopes with atomic masses below 197 decay by some combination of proton emission , α decay , and β decay . The exceptions are Au , which decays by electron capture, and Au , which decays most often by electron capture (93%) with a minor β decay path (7%). All of gold's radioisotopes with atomic masses above 197 decay by β decay. At least 32 nuclear isomers have also been characterized, ranging in atomic mass from 170 to 200. Within that range, only Au , Au , Au , Au , and Au do not have isomers. Gold's most stable isomer

1162-648: Is also known, an example of a mixed-valence complex . Gold does not react with oxygen at any temperature and, up to 100 °C, is resistant to attack from ozone: Au + O 2 ⟶ ( no reaction ) {\displaystyle {\ce {Au + O2 ->}}({\text{no reaction}})} Au + O 3 → t < 100 ∘ C ( no reaction ) {\displaystyle {\ce {Au{}+O3->[{} \atop {t<100^{\circ }{\text{C}}}]}}({\text{no reaction}})} Some free halogens react to form

1245-520: Is also used in infrared shielding, the production of colored glass , gold leafing , and tooth restoration . Certain gold salts are still used as anti-inflammatory agents in medicine. Gold is the most malleable of all metals. It can be drawn into a wire of single-atom width, and then stretched considerably before it breaks. Such nanowires distort via the formation, reorientation, and migration of dislocations and crystal twins without noticeable hardening. A single gram of gold can be beaten into

1328-427: Is always richer at the exposed surface of gold-bearing veins, owing to the oxidation of accompanying minerals followed by weathering; and by washing of the dust into streams and rivers, where it collects and can be welded by water action to form nuggets. Gold sometimes occurs combined with tellurium as the minerals calaverite , krennerite , nagyagite , petzite and sylvanite (see telluride minerals ), and as

1411-427: Is an effective method for interpreting recorded history, is raised in the philosophy of history as a question of epistemology . The study of different historical methods is known as historiography , which focuses on examining how different interpreters of recorded history create different interpretations of historical evidence. Prehistory traditionally refers to the span of time before recorded history, ending with

1494-513: Is attributed to wind-blown dust or rivers. At 10 parts per quadrillion, the Earth's oceans would hold 15,000 tonnes of gold. These figures are three orders of magnitude less than reported in the literature prior to 1988, indicating contamination problems with the earlier data. A number of people have claimed to be able to economically recover gold from sea water , but they were either mistaken or acted in an intentional deception. Prescott Jernegan ran

1577-464: Is found in ores in rock formed from the Precambrian time onward. It most often occurs as a native metal , typically in a metal solid solution with silver (i.e. as a gold/silver alloy ). Such alloys usually have a silver content of 8–10%. Electrum is elemental gold with more than 20% silver, and is commonly known as white gold . Electrum's color runs from golden-silvery to silvery, dependent upon

1660-465: Is most often called the oldest since this treasure is the largest and most diverse. Gold artifacts probably made their first appearance in Ancient Egypt at the very beginning of the pre-dynastic period, at the end of the fifth millennium BC and the start of the fourth, and smelting was developed during the course of the 4th millennium; gold artifacts appear in the archeology of Lower Mesopotamia during

1743-528: Is now questioned. The gold-bearing Witwatersrand rocks were laid down between 700 and 950 million years before the Vredefort impact. These gold-bearing rocks had furthermore been covered by a thick layer of Ventersdorp lavas and the Transvaal Supergroup of rocks before the meteor struck, and thus the gold did not actually arrive in the asteroid/meteorite. What the Vredefort impact achieved, however,

SECTION 20

#1732858718499

1826-508: Is one of the earliest mentions of "pigtail of Brahmin boys". These poems also allude to historical incidents, ancient Tamil kings, the effect of war on loved ones and households. The Pattinappalai poem in the Ten Idylls group, for example, paints a description of the Chola capital, the king Karikala , the life in a harbor city with ships and merchandise for seafaring trade, the dance troupes,

1909-498: Is one of the few documents containing material relating to the Nāga and Yakkha peoples , indigenous inhabitants of Lanka prior to the legendary arrival of Prince Vijaya from Singha Pura of Kalinga. The Sangam literature offers a window into some aspects of the ancient South Indian culture, secular and religious beliefs, and the people. For example, in the Sangam era Ainkurunuru poem 202

1992-588: Is one of the least reactive chemical elements, being the second-lowest in the reactivity series . It is solid under standard conditions . Gold often occurs in free elemental ( native state ), as nuggets or grains, in rocks , veins , and alluvial deposits . It occurs in a solid solution series with the native element silver (as in electrum ), naturally alloyed with other metals like copper and palladium , and mineral inclusions such as within pyrite . Less commonly, it occurs in minerals as gold compounds, often with tellurium ( gold tellurides ). Gold

2075-427: Is red if the particles are small; larger particles of colloidal gold are blue. Gold has only one stable isotope , Au , which is also its only naturally 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 Au with a half-life of 186.1 days. The least stable

2158-553: Is resistant to most acids, though it does dissolve in aqua regia (a mixture of nitric acid and hydrochloric acid ), forming a soluble tetrachloroaurate anion . Gold is insoluble in nitric acid alone, which dissolves silver and base metals , a property long used to refine gold and confirm the presence of gold in metallic substances, giving rise to the term ' acid test '. Gold dissolves in alkaline solutions of cyanide , which are used in mining and electroplating . Gold also dissolves in mercury , forming amalgam alloys, and as

2241-484: Is similarly unaffected by most bases. It does not react with aqueous , solid , or molten sodium or potassium hydroxide . It does however, react with sodium or potassium cyanide under alkaline conditions when oxygen is present to form soluble complexes. Common oxidation states of gold include +1 (gold(I) or aurous compounds) and +3 (gold(III) or auric compounds). Gold ions in solution are readily reduced and precipitated as metal by adding any other metal as

2324-585: Is the soluble form of gold encountered in mining. The binary gold halides , such as AuCl , form zigzag polymeric chains, again featuring linear coordination at Au. Most drugs based on gold are Au(I) derivatives. Au(III) (referred to as auric) is a common oxidation state, and is illustrated by gold(III) chloride , Au 2 Cl 6 . The gold atom centers in Au(III) complexes, like other d compounds, are typically square planar , with chemical bonds that have both covalent and ionic character. Gold(I,III) chloride

2407-466: Is therefore limited based on the types of records kept. Because of this, recorded history in different contexts may refer to different periods of time depending on the topic. The interpretation of recorded history often relies on historical method , or the set of techniques and guidelines by which historians use primary sources and other evidence to research and then to write accounts of the past. The question of what constitutes history, and whether there

2490-634: Is thought to have been delivered to Earth by asteroid impacts during the Late Heavy Bombardment , about 4 billion years ago. Gold which is reachable by humans has, in one case, been associated with a particular asteroid impact. The asteroid that formed Vredefort impact structure 2.020 billion years ago is often credited with seeding the Witwatersrand basin in South Africa with the richest gold deposits on earth. However, this scenario

2573-505: Is thought to have been produced in supernova nucleosynthesis , and from the collision of neutron stars , and to have been present in the dust from which the Solar System formed. Traditionally, gold in the universe is thought to have formed by the r-process (rapid neutron capture) in supernova nucleosynthesis , but more recently it has been suggested that gold and other elements heavier than iron may also be produced in quantity by

Gilo River - Misplaced Pages Continue

2656-416: Is unaffected by most acids. It does not react with hydrofluoric , hydrochloric , hydrobromic , hydriodic , sulfuric , or nitric acid . It does react with selenic acid , and is dissolved by aqua regia , a 1:3 mixture of nitric acid and hydrochloric acid . Nitric acid oxidizes the metal to +3 ions, but only in minute amounts, typically undetectable in the pure acid because of the chemical equilibrium of

2739-600: The Culavamsa "Lesser Chronicle", compiled by Sinhala monks, covers the period from the 4th century to the British takeover of Sri Lanka in 1815. The Culavamsa was compiled by a number of authors of different time periods. The combined work, sometimes referred to collectively as the Mahavamsa , provides a continuous historical record of over two millennia, and is considered one of the world's longest unbroken historical accounts. It

2822-571: The Bronze Age in the late Neolithic of the late 4th millennium BCE . The Sumerian archaic cuneiform script and the Egyptian hieroglyphs are generally considered the earliest writing systems, both emerging out of their ancestral proto-literate symbol systems from 3400 to 3200 BCE, with earliest coherent texts from about 2600 BCE . The earliest chronologies date back to the earliest civilizations of Early Dynastic Period of Egypt , Mesopotamia and

2905-645: The Chu (state) circulated the Ying Yuan , one kind of square gold coin. In Roman metallurgy , new methods for extracting gold on a large scale were developed by introducing hydraulic mining methods, especially in Hispania from 25 BC onwards and in Dacia from 106 AD onwards. One of their largest mines was at Las Medulas in León , where seven long aqueducts enabled them to sluice most of

2988-449: The Jiahu symbols ( c.  6600 BCE ), Vinča signs ( c.  5300 BCE ), early Indus script ( c.  3500 BCE ) and Nsibidi script ( c.  before 500 CE ). There is disagreement concerning exactly when prehistory becomes history, and when proto-writing became "true writing". However, invention of the first writing systems is roughly contemporary with the beginning of

3071-583: The Old Testament , starting with Genesis 2:11 (at Havilah ), the story of the golden calf , and many parts of the temple including the Menorah and the golden altar. In the New Testament , it is included with the gifts of the magi in the first chapters of Matthew. The Book of Revelation 21:21 describes the city of New Jerusalem as having streets "made of pure gold, clear as crystal". Exploitation of gold in

3154-481: The Sumerians , which emerged independently of each other from roughly 3500 BCE. Earliest recorded history, which varies greatly in quality and reliability, deals with Pharaohs and their reigns , as preserved by ancient Egyptians . Much of the earliest recorded history was re-discovered relatively recently due to archaeological dig sites findings. A number of different traditions have developed in different parts of

3237-641: The Varna Necropolis near Lake Varna and the Black Sea coast, thought to be the earliest "well-dated" finding of gold artifacts in history. Several prehistoric Bulgarian finds are considered no less old – the golden treasures of Hotnitsa, Durankulak , artifacts from the Kurgan settlement of Yunatsite near Pazardzhik , the golden treasure Sakar, as well as beads and gold jewelry found in the Kurgan settlement of Provadia – Solnitsata ("salt pit"). However, Varna gold

3320-442: The invention of writing . For some geographic regions or cultures , written history is limited to a relatively recent period in human history because of the limited use of written records. Moreover, human cultures do not always record all of the information which is considered relevant by later historians, such as the full impact of natural disasters or the names of individuals. Recorded history for particular types of information

3403-470: The reducing agent . The added metal is oxidized and dissolves, allowing the gold to be displaced from solution and be recovered as a solid precipitate. Less common oxidation states of gold include −1, +2, and +5. The −1 oxidation state occurs in aurides, compounds containing the Au anion . Caesium auride (CsAu), for example, crystallizes in the caesium chloride motif; rubidium, potassium, and tetramethylammonium aurides are also known. Gold has

Gilo River - Misplaced Pages Continue

3486-562: The "father of history" composing his The Histories from the 450s to the 420s BCE. However, his contemporary Thucydides (c. 460 BCE – c. 400 BCE) is credited with having first approached history with a well-developed historical method in his work the History of the Peloponnesian War . Thucydides, unlike Herodotus, regarded history as being the product of the choices and actions of human beings, and looked at cause and effect, rather than as

3569-501: The 2000s this was done using analogue recording methods such as cassettes and reel-to-reel tapes . With the onset of new technologies, there are now digital recordings , which may be recorded to compact disks. Nevertheless, historical record and interpretation often relies heavily on written records, partially because it dominates the extant historical materials, and partially because historians are used to communicating and researching in that medium. The historical method comprises

3652-403: The 20th century, academic historians began focusing less on epic nationalistic narratives, which often tended to glorify the nation or great men , to attempt more objective and complex analyses of social and intellectual forces. A major trend of historical methodology in the 20th century was a tendency to treat history more as a social science rather than as an art , which traditionally had been

3735-511: The advancement of technology. History can now be recorded through photography , audio recordings , and video recordings . More recently, Internet archives have been saving copies of webpages, documenting the history of the Internet . Other methods of collecting historical information have also accompanied the change in technologies; for example, since at least the 20th century, attempts have been made to preserve oral history by recording it. Until

3818-508: The bards and artists, the worship of the Hindu god Murugan and the monasteries of Buddhism and Jainism. Indica is an account of Mauryan India by the Greek writer Megasthenes . The original book is now lost, but its fragments have survived in later Greek and Latin works. The earliest of these works are those by Diodorus Siculus , Strabo ( Geographica ), Pliny , and Arrian ( Indica ). In

3901-562: The case. French historians associated with the Annales School introduced quantitative history, using raw data to track the lives of typical individuals, and were prominent in the establishment of cultural history. The Zuo zhuan , attributed to Zuo Qiuming in the 5th century BCE covers the period from 722 to 468 BCE in a narrative form. The Book of Documents is one of the Five Classics of Chinese classic texts and one of

3984-1409: The corresponding gold halides. Gold is strongly attacked by fluorine at dull-red heat to form gold(III) fluoride AuF 3 . Powdered gold reacts with chlorine at 180 °C to form gold(III) chloride AuCl 3 . Gold reacts with bromine at 140 °C to form a combination of gold(III) bromide AuBr 3 and gold(I) bromide AuBr, but reacts very slowly with iodine to form gold(I) iodide AuI: 2 Au + 3 F 2 → Δ 2 AuF 3 {\displaystyle {\ce {2Au{}+3F2->[{} \atop \Delta ]2AuF3}}} 2 Au + 3 Cl 2 → Δ 2 AuCl 3 {\displaystyle {\ce {2Au{}+3Cl2->[{} \atop \Delta ]2AuCl3}}} 2 Au + 2 Br 2 → Δ AuBr 3 + AuBr {\displaystyle {\ce {2Au{}+2Br2->[{} \atop \Delta ]AuBr3{}+AuBr}}} 2 Au + I 2 → Δ 2 AuI {\displaystyle {\ce {2Au{}+I2->[{} \atop \Delta ]2AuI}}} Gold does not react with sulfur directly, but gold(III) sulfide can be made by passing hydrogen sulfide through

4067-424: The densest element, osmium , is 22.588 ± 0.015 g/cm . Whereas most metals are gray or silvery white, gold is slightly 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

4150-573: The earliest narratives of China. The Spring and Autumn Annals , the official chronicle of the State of Lu covering the period from 722 to 481 BCE, is arranged on annalistic principles. It is traditionally attributed to Confucius (551–479 BCE). Zhan Guo Ce was a renowned ancient Chinese historical compilation of sporadic materials on the Warring States period compiled between the 3rd and 1st centuries BCE. Sima Qian (around 100 BCE)

4233-664: The early 4th millennium. As of 1990, gold artifacts found at the Wadi Qana cave cemetery of the 4th millennium BC in West Bank were the earliest from the Levant. Gold artifacts such as the golden hats and the Nebra disk appeared in Central Europe from the 2nd millennium BC Bronze Age . The oldest known map of a gold mine was drawn in the 19th Dynasty of Ancient Egypt (1320–1200 BC), whereas

SECTION 50

#1732858718499

4316-427: The first century AD. Recorded history Recorded history or written history describes the historical events that have been recorded in a written form or other documented communication which are subsequently evaluated by historians using the historical method . For broader world history , recorded history begins with the accounts of the ancient world around the 4th millennium BCE, and it coincides with

4399-574: The first written reference to gold was recorded in the 12th Dynasty around 1900 BC. Egyptian hieroglyphs from as early as 2600 BC describe gold, which King Tushratta of the Mitanni claimed was "more plentiful than dirt" in Egypt. Egypt and especially Nubia had the resources to make them major gold-producing areas for much of history. One of the earliest known maps, known as the Turin Papyrus Map , shows

4482-403: The gold acts simply as a solute, this is not a chemical reaction . A relatively rare element, gold is a precious metal that has been used for coinage , jewelry , and other works of art throughout recorded history . In the past, a gold standard was often implemented as a monetary policy . Gold coins ceased to be minted as a circulating currency in the 1930s, and the world gold standard

4565-563: The highest electron affinity of any metal, at 222.8 kJ/mol, making Au a stable species, analogous to the halides . Gold also has a –1 oxidation state in covalent complexes with the group 4 transition metals, such as in titanium tetraauride and the analogous zirconium and hafnium compounds. These chemicals are expected to form gold-bridged dimers in a manner similar to titanium(IV) hydride . Gold(II) compounds are usually diamagnetic with Au–Au bonds such as [ Au(CH 2 ) 2 P(C 6 H 5 ) 2 ] 2 Cl 2 . The evaporation of

4648-606: The invention of writing systems . Prehistory refers to the past in an area where no written records exist, or where the writing of a culture is not understood. Protohistory refers to the transition period between prehistory and history, after the advent of literacy in a society but before the writings of the first historians . Protohistory may also refer to the period during which a culture or civilization has not yet developed writing, but other cultures have noted its existence in their own writings. More complete writing systems were preceded by proto-writing . Early examples are

4731-542: The mineral quartz, and gold out of the fluids and onto nearby surfaces. The world's oceans contain gold. Measured concentrations of gold in the Atlantic and Northeast Pacific are 50–150 femtomol /L or 10–30 parts per quadrillion (about 10–30 g/km ). In general, gold concentrations for south Atlantic and central Pacific samples are the same (~50 femtomol/L) but less certain. Mediterranean deep waters contain slightly higher concentrations of gold (100–150 femtomol/L), which

4814-411: The noble metals, it still forms many diverse compounds. The oxidation state of gold in its compounds ranges from −1 to +5, but Au(I) and Au(III) dominate its chemistry. Au(I), referred to as the aurous ion, is the most common oxidation state with soft ligands such as thioethers , thiolates , and organophosphines . Au(I) compounds are typically linear. A good example is Au(CN) − 2 , which

4897-432: The object of study." Historians use other types of sources to understand history as well. Secondary sources are written accounts of history based upon the evidence from primary sources. These are sources which, usually, are accounts, works, or research that analyse, assimilate, evaluate, interpret, and/or synthesize primary sources. Tertiary sources are compilations based upon primary and secondary sources and often tell

4980-563: The plan of a gold mine in Nubia together with indications of the local geology . The primitive working methods are described by both Strabo and Diodorus Siculus , and included fire-setting . Large mines were also present across the Red Sea in what is now Saudi Arabia . Gold is mentioned in the Amarna letters numbered 19 and 26 from around the 14th century BC. Gold is mentioned frequently in

5063-520: The preface to his book, the Muqaddimah (1377), the Arab historian and early sociologist , Ibn Khaldun , warned of seven mistakes that he thought that historians regularly committed. In this criticism, he approached the past as strange and in need of interpretation. Ibn Khaldun often criticised "idle superstition and uncritical acceptance of historical data." As a result, he introduced a scientific method to

SECTION 60

#1732858718499

5146-598: The prestigious Ban family of the Eastern Han dynasty era. In Sri Lanka , the oldest historical text is the Mahavamsa ( c. 5th century CE). Buddhist monks of the Anuradhapura Maha Viharaya maintained chronicles of Sri Lankan history starting from the 3rd century BCE. These annals were combined and compiled into a single document in the 5th century by the Mahanama of Anuradhapura while Dhatusena of Anuradhapura

5229-459: The project. The earliest recorded metal employed by humans appears to be gold, which can be found free or " native ". Small amounts of natural gold have been found in Spanish caves used during the late Paleolithic period, c.  40,000 BC . The oldest gold artifacts in the world are from Bulgaria and are dating back to the 5th millennium BC (4,600 BC to 4,200 BC), such as those found in

5312-681: The r-process in the collision of neutron stars . In both cases, satellite spectrometers at first only indirectly detected the resulting gold. However, in August 2017, the spectroscopic signatures of heavy elements, including gold, were observed by electromagnetic observatories in the GW170817 neutron star merger event, after gravitational wave detectors confirmed the event as a neutron star merger. Current astrophysical models suggest that this single neutron star merger event generated between 3 and 13 Earth masses of gold. This amount, along with estimations of

5395-620: The rare bismuthide maldonite ( Au 2 Bi ) and antimonide aurostibite ( AuSb 2 ). Gold also occurs in rare alloys with copper , lead , and mercury : the minerals auricupride ( Cu 3 Au ), novodneprite ( AuPb 3 ) and weishanite ( (Au,Ag) 3 Hg 2 ). A 2004 research paper suggests that microbes can sometimes play an important role in forming gold deposits, transporting and precipitating gold to form grains and nuggets that collect in alluvial deposits. A 2013 study has claimed water in faults vaporizes during an earthquake, depositing gold. When an earthquake strikes, it moves along

5478-420: The rate of occurrence of these neutron star merger events, suggests that such mergers may produce enough gold to account for most of the abundance of this element in the universe. Because the Earth was molten when it was formed , almost all of the gold present in the early Earth probably sank into the planetary core . Therefore, as hypothesized in one model, most of the gold in the Earth's crust and mantle

5561-935: The reaction. However, the ions are removed from the equilibrium by hydrochloric acid, forming AuCl − 4 ions, or chloroauric acid , thereby enabling further oxidation: 2 Au + 6 H 2 SeO 4 → 200 ∘ C Au 2 ( SeO 4 ) 3 + 3 H 2 SeO 3 + 3 H 2 O {\displaystyle {\ce {2Au{}+6H2SeO4->[{} \atop {200^{\circ }{\text{C}}}]Au2(SeO4)3{}+3H2SeO3{}+3H2O}}} Au + 4 HCl + HNO 3 ⟶ HAuCl 4 + NO ↑ + 2 H 2 O {\displaystyle {\ce {Au{}+4HCl{}+HNO3->HAuCl4{}+NO\uparrow +2H2O}}} Gold

5644-464: The rest of the gold on Earth is thought to have been incorporated into the planet since its very beginning, as planetesimals formed the mantle . In 2017, an international group of scientists established that gold "came to the Earth's surface from the deepest regions of our planet", the mantle, as evidenced by their findings at Deseado Massif in the Argentinian Patagonia . On Earth, gold

5727-608: The result of divine intervention. History developed as a popular form of literature in later Greek and Roman societies in the works of Polybius , Tacitus and others. Saint Augustine was influential in Christian and Western thought at the beginning of the medieval period. Through the Medieval and Renaissance periods, history was often studied through a sacred or religious perspective. Around 1800, German philosopher and historian Georg Wilhelm Friedrich Hegel brought philosophy and

5810-474: The same result and showing that the isotopes of gold produced by it were all radioactive . In 1980, Glenn Seaborg transmuted several thousand atoms of bismuth into gold at the Lawrence Berkeley Laboratory. Gold can be manufactured in a nuclear reactor, but doing so is highly impractical and would cost far more than the value of the gold that is produced. Although gold is the most noble of

5893-486: The silver content. The more silver, the lower the specific gravity . Native gold occurs as very small to microscopic particles embedded in rock, often together with quartz or sulfide minerals such as " fool's gold ", which is a pyrite . These are called lode deposits. The metal in a native state is also found in the form of free flakes, grains or larger nuggets that have been eroded from rocks and end up in alluvial deposits called placer deposits . Such free gold

5976-446: The south-east corner of the Black Sea is said to date from the time of Midas , and this gold was important in the establishment of what is probably the world's earliest coinage in Lydia around 610 BC. The legend of the golden fleece dating from eighth century BCE may refer to the use of fleeces to trap gold dust from placer deposits in the ancient world. From the 6th or 5th century BC,

6059-464: The study of history, and he often referred to it as his "new science". His historical method also laid the groundwork for the observation of the role of state , communication , propaganda and systematic bias in history, and he is thus considered to be the "father of historiography" or the "father of the philosophy of history". While recorded history begins with the invention of writing, over time new ways of recording history have come along with

6142-520: The techniques and guidelines by which historians use primary sources and other evidence to research and then to write history . Primary sources are first-hand evidence of history (usually written, but sometimes captured in other mediums) made at the time of an event by a present person. Historians think of those sources as the closest to the origin of the information or idea under study. These types of sources can provide researchers with, as Dalton and Charnigo put it, "direct, unmediated information about

6225-436: The tendency of gold ions to interact at distances that are too long to be a conventional Au–Au bond but shorter than van der Waals bonding . The interaction is estimated to be comparable in strength to that of a hydrogen bond . Well-defined cluster compounds are numerous. In some cases, gold has a fractional oxidation state. A representative example is the octahedral species {Au( P(C 6 H 5 ) 3 )} 2+ 6 . Gold

6308-403: The transmutation of the chemical elements did not become possible until the understanding of nuclear physics in the 20th century. The first synthesis of gold was conducted by Japanese physicist Hantaro Nagaoka , who synthesized gold from mercury in 1924 by neutron bombardment. An American team, working without knowledge of Nagaoka's prior study, conducted the same experiment in 1941, achieving

6391-417: The visors of heat-resistant suits and in sun visors for spacesuits . Gold is a good conductor of heat and electricity . Gold has a density of 19.3 g/cm , almost identical to that of tungsten at 19.25 g/cm ; as such, tungsten has been used in the counterfeiting of gold bars , such as by plating a tungsten bar with gold. By comparison, the density of lead is 11.34 g/cm , and that of

6474-663: The width of the Gilo reaches 80 to 100 yards, with a depth of about 20 feet. Jessen further wrote that at the time of his visit: The river abounds with fish, and as a natural consequence, the crocodiles are very numerous and large. At midday, practically every sandbank is covered with them. It is a remarkable fact that the hippopotami are conspicuous by their absence, only one having been seen and killed many years ago, as these animals are plentiful everywhere in these countries. 8°08′N 33°12′E  /  8.133°N 33.200°E  / 8.133; 33.200 This article related to

6557-427: The world as to how to interpret these ancient accounts. Dionysius of Halicarnassus knew of seven predecessors of Herodotus , including Hellanicus of Lesbos , Xanthus of Lydia and Hecataeus of Miletus . He described their works as simple, unadorned accounts of their own and other cities and people, Greek or foreign, including popular legends. Herodotus (484 BCE – c. 425 BCE) has generally been acclaimed as

6640-783: Was abandoned for a fiat currency system after the Nixon shock measures of 1971. In 2020, the world's largest gold producer was China, followed by Russia and Australia. As of 2020 , a total of around 201,296 tonnes of gold exist above ground. This is equal to a cube, with each side measuring roughly 21.7 meters (71 ft). The world's consumption of new gold produced is about 50% in jewelry, 40% in investments , and 10% in industry . Gold's high malleability, ductility, resistance to corrosion and most other chemical reactions, as well as conductivity of electricity have led to its continued use in corrosion-resistant electrical connectors in all types of computerized devices (its chief industrial use). Gold

6723-679: Was ruling the Anuradhapura Kingdom . It was written based on prior ancient compilations known as the Atthakatha , which were commentaries written in Sinhala. An earlier document known as the Dipavamsa (4th century CE) "Island Chronicles" is much simpler and contains less information than the Mahavamsa and was probably compiled using the Atthakatha on the Mahavamsa as well. A companion volume,

6806-678: Was the first in China to lay the groundwork for professional historical writing. His written work was the Records of the Grand Historian , a monumental lifelong achievement in literature. Its scope extends as far back as the 16th century BCE, and it includes many treatises on specific subjects and individual biographies of prominent people, and also explores the lives and deeds of commoners, both contemporary and those of previous eras. His work influenced every subsequent author of history in China, including

6889-605: Was to distort the Witwatersrand basin in such a way that the gold-bearing rocks were brought to the present erosion surface in Johannesburg , on the Witwatersrand , just inside the rim of the original 300 km (190 mi) diameter crater caused by the meteor strike. The discovery of the deposit in 1886 launched the Witwatersrand Gold Rush . Some 22% of all the gold that is ascertained to exist today on Earth has been extracted from these Witwatersrand rocks. Much of

#498501