Misplaced Pages

#756243

54-660: In recent years, the archeological sites have attracted a growing number of tourists. At the same time, looting and illicit trafficking of antiquities continue as a serious problem in the area. Angkor Borei is particularly challenging area to perform archaeological research on due to the fact that the site is inhabited today. Various areas have been heavily damaged by bulldozing, gardening, and other daily activities. Like many ancient Asian sites, any initial information came from Chinese documents and accounts. Much archeology has uncovered various previously unknown artifacts and locations. Research has uncovered brick architecture, post holes for

108-458: A centimeter over several million years. The average diameter of a polymetallic nodule is between 3 and 10 cm (1 and 4 in) in diameter and are characterized by enrichment in iron, manganese, heavy metals , and rare earth element content when compared to the Earth's crust and surrounding sediment. The proposed mining of these nodules via remotely operated ocean floor trawling robots has raised

162-421: A direct result of metamorphism. These are the leading source of copper ore. Porphyry copper deposits form along convergent boundaries and are thought to originate from the partial melting of subducted oceanic plates and subsequent concentration of Cu, driven by oxidation. These are large, round, disseminated deposits containing on average 0.8% copper by weight. Hydrothermal Hydrothermal deposits are

216-511: A higher concentration of hydroxide (OH-) in ground water . This alkalinity promotes the mineralization of dissolved CO 2 (from the atmosphere) to produce calcite (CaCO 3 ), which can accumulate to as thick as 20 cm. This can also lead to the dissolution of other metals in slag, such as iron (Fe), manganese (Mn), nickel (Ni), and molybdenum (Mo), which become insoluble in water and mobile as particulate matter . The most effective method to detoxify alkaline ground water discharge

270-431: A highly abrasive dust that has caused car parts to wear at significantly greater than normal rates. Dissolution of slags generate alkalinity that can be used to precipitate out metals, sulfates, and excess nutrients (nitrogen and phosphorus) in wastewater treatment. Similarly, ferrous slags have been used as soil conditioners to re-balance soil pH and fertilizers as sources of calcium and magnesium.   Because of

324-449: A large source of ore. They form as a result of the precipitation of dissolved ore constituents out of fluids. Laterites form from the weathering of highly mafic rock near the equator. They can form in as little as one million years and are a source of iron (Fe), manganese (Mn), and aluminum (Al). They may also be a source of nickel and cobalt when the parent rock is enriched in these elements. Banded iron formations (BIFs) are

378-502: A large wooden structure, and a temple containing two Vishnu statues. Brick was not thought to have been used as early as 400 BC. Evidence suggests there may have been a moat or some kind of man made hydraulic system. Artifacts include ceramics, brick fragments, animal bone, vessels, clay pellets, slag , and stone statues. An analysis of the pottery shows it contains fine orange wares, cord marked earthenware , burnished earthenware, gray wares , and slipped wheel made earthenware. Based on

432-644: A number of ecological concerns. The extraction of ore deposits generally follows these steps. Progression from stages 1–3 will see a continuous disqualification of potential ore bodies as more information is obtained on their viability: With rates of ore discovery in a steady decline since the mid 20th century, it is thought that most surface level, easily accessible sources have been exhausted. This means progressively lower grade deposits must be turned to, and new methods of extraction must be developed. Some ores contain heavy metals , toxins, radioactive isotopes and other potentially negative compounds which may pose

486-824: A risk to the environment or health. The exact effects an ore and its tailings have is dependent on the minerals present. Tailings of particular concern are those of older mines, as containment and remediation methods in the past were next to non-existent, leading to high levels of leaching into the surrounding environment. Mercury and arsenic are two ore related elements of particular concern. Additional elements found in ore which may have adverse health affects in organisms include iron, lead, uranium, zinc, silicon, titanium, sulfur, nitrogen, platinum, and chromium. Exposure to these elements may result in respiratory and cardiovascular problems and neurological issues. These are of particular danger to aquatic life if dissolved in water. Ores such as those of sulphide minerals may severely increase

540-413: A series of experiments testing the reactivity of a specific slag material (i.e., dissolution ) or using the topological constraint theory (TCT) to account for its complex chemical network. Slags are transported along with slag tailings to "slag dumps", where they are exposed to weathering, with the possibility of leaching of toxic elements and hyperalkaline runoffs into the soil and water, endangering

594-513: A single mineral, but it is mixed with other valuable minerals and with unwanted or valueless rocks and minerals. The part of an ore that is not economically desirable and that cannot be avoided in mining is known as gangue . The valuable ore minerals are separated from the gangue minerals by froth flotation , gravity concentration, electric or magnetic methods, and other operations known collectively as mineral processing or ore dressing . Mineral processing consists of first liberation, to free

SECTION 10

#1732802445757

648-552: A sizeable portion of international trade in raw materials both in value and volume. This is because the worldwide distribution of ores is unequal and dislocated from locations of peak demand and from smelting infrastructure. Most base metals (copper, lead, zinc, nickel) are traded internationally on the London Metal Exchange , with smaller stockpiles and metals exchanges monitored by the COMEX and NYMEX exchanges in

702-486: A variety of geological processes generally referred to as ore genesis and can be classified based on their deposit type. Ore is extracted from the earth through mining and treated or refined , often via smelting , to extract the valuable metals or minerals. Some ores, depending on their composition, may pose threats to health or surrounding ecosystems. The word ore is of Anglo-Saxon origin, meaning lump of metal . In most cases, an ore does not consist entirely of

756-542: Is air sparging . Fine slags and slag dusts generated from milling slags to be recycled into the smelting process or upcycled in a different industry (e.g. construction) can be carried by the wind, affecting a larger ecosystem. It can be ingested and inhaled, posing a direct health risk to the communities near the plants , mines, disposal sites, etc. Ore Ore is natural rock or sediment that contains one or more valuable minerals , typically including metals , concentrated above background levels, and that

810-483: Is a mineral deposit occurring in high enough concentration to be economically viable. An ore deposit is one occurrence of a particular ore type. Most ore deposits are named according to their location, or after a discoverer (e.g. the Kambalda nickel shoots are named after drillers), or after some whimsy, a historical figure, a prominent person, a city or town from which the owner came, something from mythology (such as

864-410: Is considered alluvial if formed via river, colluvial if by gravity, and eluvial when close to their parent rock. Polymetallic nodules , also called manganese nodules, are mineral concretions on the sea floor formed of concentric layers of iron and manganese hydroxides around a core. They are formed by a combination of diagenetic and sedimentary precipitation at the estimated rate of about

918-896: Is designed to minimize iron loss, which gives out the significant amount of iron, following by oxides of calcium , silicon , magnesium , and aluminium. As the slag is cooled down by water, several chemical reactions from a temperature of around 2,600 °F (1,430 °C) (such as oxidization ) take place within the slag. Based on a case study at the Hopewell National Historical Site in Berks and Chester counties, Pennsylvania , US, ferrous slag usually contains lower concentration of various types of trace elements than non-ferrous slag . However, some of them, such as arsenic (As), iron, and manganese , can accumulate in groundwater and surface water to levels that can exceed environmental guidelines. Non-ferrous slag

972-547: Is economically viable to mine and process. The grade of ore refers to the concentration of the desired material it contains. The value of the metals or minerals a rock contains must be weighed against the cost of extraction to determine whether it is of sufficiently high grade to be worth mining and is therefore considered an ore. A complex ore is one containing more than one valuable mineral. Minerals of interest are generally oxides , sulfides , silicates , or native metals such as copper or gold . Ore bodies are formed by

1026-467: Is produced from non-ferrous metals of natural ores. Non-ferrous slag can be characterized into copper, lead, and zinc slags due to the ores' compositions, and they have more potential to impact the environment negatively than ferrous slag. The smelting of copper, lead and bauxite in non-ferrous smelting, for instance, is designed to remove the iron and silica that often occurs with those ores, and separates them as iron-silicate-based slags. Copper slag,

1080-526: Is slags) are generated per tonne of steel produced. Slag is usually a mixture of metal oxides and silicon dioxide . However, slags can contain metal sulfides and elemental metals. It is important to note, the oxide form may or may not be present once the molten slag solidifies and forms amorphous and crystalline components. The major components of these slags include the oxides of calcium , magnesium , silicon , iron, and aluminium, with lesser amounts of manganese , phosphorus , and others depending on

1134-459: Is the Triad of Phnom Da, a stone statue set of Vishnu and two of his avatars –  Rama and Balarama (related to Krishna). Vishnu appears as an eight armed figure over 30 meters tall holding attributes in six hands, though it is suspected there were two other attributes that are now lost. Each of the attributes is associated with one of the eight Lokapalas (gods who guard regions of space). While

SECTION 20

#1732802445757

1188-593: Is used in the manufacture of high-performance concretes, especially those used in the construction of bridges and coastal features, where its low permeability and greater resistance to chlorides and sulfates can help to reduce corrosive action and deterioration of the structure. Slag can also be used to create fibers used as an insulation material called slag wool . Slag is also used as aggregate in asphalt concrete for paving roads . A 2022 study in Finland found that road surfaces containing ferrochrome slag release

1242-667: The alumina and silica separated from the metal, and assisting in the removal of sulfur and phosphorus from the steel. As a co-product of steelmaking , slag is typically produced either through the blast furnace – oxygen converter route or the electric arc furnace – ladle furnace route. To flux the silica produced during steelmaking, limestone and/or dolomite are added, as well as other types of slag conditioners such as calcium aluminate or fluorspar . There are three types of slag: ferrous , ferroalloy , non-ferrous slags, which are produced through different smelting processes. Ferrous slags are produced in different stages of

1296-598: The temperature control of the smelting, and minimizing any re-oxidation of the final liquid metal product before the molten metal is removed from the furnace and used to make solid metal. In some smelting processes, such as ilmenite smelting to produce titanium dioxide , the slag can be the valuable product. During the Bronze Age of the Mediterranean area there were a vast number of differential metallurgical processes in use. A slag by-product of such workings

1350-944: The Cultural category. The submission has been renewed on March 27, 2020. Slag The general term slag may be a by-product or co-product of smelting ( pyrometallurgical ) ores and recycled metals depending on the type of material being produced. Slag is mainly a mixture of metal oxides and silicon dioxide . Broadly, it can be classified as ferrous (co-products of processing iron and steel), ferroalloy (a by-product of ferroalloy production) or non-ferrous / base metals (by-products of recovering non-ferrous materials like copper , nickel , zinc and phosphorus ). Within these general categories, slags can be further categorized by their precursor and processing conditions (e.g., blast furnace slags, air-cooled blast furnace slag, granulated blast furnace slag, basic oxygen furnace slag, and electric arc furnace slag). Slag generated from

1404-494: The EAF process can contain toxic metals, which can be hazardous to human and environmental health. Due to the large demand for ferrous, ferralloy, and non-ferrous materials, slag production has increased throughout the years despite recycling (most notably in the iron and steelmaking industries) and upcycling efforts. The World Steel Association (WSA) estimates that 600 kg of co-materials (co-products and by-products)(about 90 wt%

1458-553: The Triad is made from schist, other free standing stone statues found here – such as the Trivikrama, Krishna Govardhana and Hari Kambujendra – are made of sandstone and also relate to Hinduism and perhaps Buddhism. They display style and iconography similar to the late or post-Gupta Empire period and are said to be remarkably lifelike. Most of these statues have been moved to the Phnom Penh National Museum, in

1512-752: The United States and the Shanghai Futures Exchange in China. The global Chromium market is currently dominated by the United States and China. Iron ore is traded between customer and producer, though various benchmark prices are set quarterly between the major mining conglomerates and the major consumers, and this sets the stage for smaller participants. Other, lesser, commodities do not have international clearing houses and benchmark prices, with most prices negotiated between suppliers and customers one-on-one. This generally makes determining

1566-553: The acidity of their immediate surroundings and of water, with numerous, long lasting impacts on ecosystems. When water becomes contaminated it may transport these compounds far from the tailings site, greatly increasing the affected range. Uranium ores and those containing other radioactive elements may pose a significant threat if leaving occurs and isotope concentration increases above background levels. Radiation can have severe, long lasting environmental impacts and cause irreversible damage to living organisms. Metallurgy began with

1620-412: The bones implies a lack of starvation and extreme stress. The teeth themselves lack common features associated with the consumption of sugars and starches. The cemetery also contained some objects, including beads that are believed to have originated from across southeast Asia like India. The Phnom Da is a granite outcrop and a historic site about 3 kilometers southeast from Angkor Borei. It is notable for

1674-453: The capital of Cambodia. The statues appear to predate the stone temple The oldest standing Khmer stone temple (6th-century CE) on the site and may have been preceded by wooden Hindu temples. The inscriptions include 11 Sanskrit lines and 21 Khmer lines which describe the forms of Vishnu and King Rudravarman, along with a ceremony detailing the allocation of land. King Rudravaram included in the temple means that he could have been associated with

Angkor Borei and Phnom Da - Misplaced Pages Continue

1728-417: The direct working of native metals such as gold, lead and copper. Placer deposits, for example, would have been the first source of native gold. The first exploited ores were copper oxides such as malachite and azurite, over 7000 years ago at Çatalhöyük . These were the easiest to work, with relatively limited mining and basic requirements for smelting. It is believed they were once much more abundant on

1782-458: The highest concentration of any single metal available. They are composed of chert beds alternating between high and low iron concentrations. Their deposition occurred early in Earth's history when the atmospheric composition was significantly different from today. Iron rich water is thought to have upwelled where it oxidized to Fe (III) in the presence of early photosynthetic plankton producing oxygen. This iron then precipitated out and deposited on

1836-624: The iron and steelmaking processes resulting in varying physiochemical properties. Additionally, the rate of cooling of the slag material affects its degree of crystallinity further diversifying its range of properties. For example, slow cooled blast furnace slags (or air-cooled slags) tend have more crystalline phases than quenched blast furnace slags ( ground granulated blast furnace slags ) making it denser and better suited as an aggregate. It may also have higher free calcium oxide and magnesium oxide content, which are often converted to its hydrated forms if excessive volume expansions are not desired. On

1890-429: The later strength gain of concrete. This leads to concrete with reduced permeability and better durability. Careful consideration of the slag type used is required, as the high calcium oxide and magnesium oxide content can lead to excessive volume expansion and cracking in concrete. These hydraulic properties have also been used for soil stabilization in roads and railroad constructions . Granulated blast furnace slag

1944-513: The local ecological communities. Leaching concerns are typically around non-ferrous or base metal slags, which tend to have higher concentrations of toxic elements. However, ferrous and ferroalloy slags may also have them, which raises concerns about highly weathered slag dumps and upcycled materials. Dissolution of slags can produce highly alkaline groundwater with pH values above 12. The calcium silicates (CaSiO 4 ) in slags react with water to produce calcium hydroxide ions that leads to

1998-626: The main tin source, began. Some 3000 years ago, the smelting of iron ores began in Mesopotamia . Iron oxide is quite abundant on the surface and forms from a variety of processes. Until the 18th century gold, copper, lead, iron, silver, tin, arsenic and mercury were the only metals mined and used. In recent decades, Rare Earth Elements have been increasingly exploited for various high-tech applications. This has led to an ever-growing search for REE ore and novel ways of extracting said elements. Ores (metals) are traded internationally and comprise

2052-461: The molten metal and can be removed. Slag is the collection of compounds that are removed. In many smelting processes, oxides are introduced to control the slag chemistry, assisting in the removal of impurities and protecting the furnace refractory lining from excessive wear. In this case, the slag is termed synthetic . A good example is steelmaking slag: quicklime (CaO) and magnesite (MgCO 3 ) are introduced for refractory protection, neutralizing

2106-526: The name of a god or goddess) or the code name of the resource company which found it (e.g. MKD-5 was the in-house name for the Mount Keith nickel sulphide deposit ). Ore deposits are classified according to various criteria developed via the study of economic geology, or ore genesis . The following is a general categorization of the main ore deposit types: Magmatic deposits are ones who originate directly from magma These are ore deposits which form as

2160-582: The ocean floor. The banding is thought to be a result of changing plankton population. Sediment Hosted Copper forms from the precipitation of a copper rich oxidized brine into sedimentary rocks. These are a source of copper primarily in the form of copper-sulfide minerals. Placer deposits are the result of weathering, transport, and subsequent concentration of a valuable mineral via water or wind. They are typically sources of gold (Au), platinum group elements (PGE), sulfide minerals , tin (Sn), tungsten (W), and rare-earth elements (REEs). A placer deposit

2214-553: The oldest surviving temples, Khmer and Sanskrit inscriptions as a source, as well as perhaps the earliest Cambodian stone statues, based on the epigraphical evidence, iconography, and style, in Cambodia. These items are often attributed to the reign of King Rudravarman (514–539 CE). The statues confirm the adoption of ideas from what is now Vietnam and India, along with the Cambodian creativity and innovation with design. Among these

Angkor Borei and Phnom Da - Misplaced Pages Continue

2268-403: The ore from the gangue, and concentration to separate the desired mineral(s) from it. Once processed, the gangue is known as tailings , which are useless but potentially harmful materials produced in great quantity, especially from lower grade deposits. An ore deposit is an economically significant accumulation of minerals within a host rock. This is distinct from a mineral resource in that it

2322-653: The other hand, water quenched blast furnace slags have greater amorphous phases giving it latent hydraulic properties (as discovered by Emil Langen in 1862) similar to Portland cement . During the process of smelting iron, ferrous slag is created, but dominated by calcium and silicon compositions. Through this process, ferrous slag can be broken down into blast furnace slag (produced from iron oxides of molten iron), then steel slag (forms when steel scrap and molten iron combined). The major phases of ferrous slag contain calcium-rich olivine -group silicates and melilite -group silicates. Slag from steel mills in ferrous smelting

2376-439: The plastic, and concrete industries and leached for metals to be used in the electronic industries. However, high physical and chemical variability across different types of slags results in performance and yield inconsistencies. Moreover, stoichiometric -based calculation of the carbonation potential can lead to overestimation that can further obfuscate the material's true potential. To this end, some have proposed performing

2430-431: The price of ores of this nature opaque and difficult. Such metals include lithium , niobium - tantalum , bismuth , antimony and rare earths . Most of these commodities are also dominated by one or two major suppliers with >60% of the world's reserves. China is currently leading in world production of Rare Earth Elements. The World Bank reports that China was the top importer of ores and metals in 2005 followed by

2484-557: The religion and seen as an incarnation. He is rumored to have murdered his half-brother for the throne and to strengthen his claim to it, he relied on religion. According to one source however, the dating for the statues could be inaccurate, throwing off the current accepted timeline. The base of the site is also surrounded by the remains of small caves. This site was originally added to the UNESCO World Heritage Tentative List on September 1, 1992, in

2538-713: The slowly released phosphate content in phosphorus -containing slag, and because of its liming effect, it is valued as fertilizer in gardens and farms in steel making areas. However, the most important application is construction. Slags have one of the highest carbonation potential among the industrial alkaline waste due their high calcium oxide and magnesium oxide content, inspiring further studies to test its feasibility in CO 2 capture and storage ( CCS ) methods (e.g., direct aqueous sequestration, dry gas-solid carbonation among others). Across these CCS methods, slags can be transformed into precipitated calcium carbonates to be used in

2592-403: The specifics of the raw materials used. Furthermore, slag can be classified based on the abundance of iron among other major components. In nature, iron, copper, lead, nickel , and other metals are found in impure states called ores , often oxidized and mixed in with silicates of other metals. During smelting, when the ore is exposed to high temperatures, these impurities are separated from

2646-571: The style of artifacts and carbon dating, there were three general layers of occupation. The dates also suggest that Óc Eo was also inhabited at the time of Angkor Borei. Vat Komnou cemetery is also a notable feature which was excavated and found to contain roughly 60 bodies ranging from 200 BC - AD 400. Out of these bodies, 25 were children below 19, 36 were adults, and the remaining were elders. Males were found to be more than twice as common as females, many of which had stress fractures in their lower backs suggesting some sort of heavy labor. An analysis of

2700-413: The surface than today. After this, copper sulphides would have been turned to as oxide resources depleted and the Bronze Age progressed. Lead production from galena smelting may have been occurring at this time as well. The smelting of arsenic-copper sulphides would have produced the first bronze alloys. The majority of bronze creation however required tin, and thus the exploitation of cassiterite,

2754-472: The waste product of smelting copper ores, was studied in an abandoned Penn Mine in California, US. For six to eight months per year, this region is flooded and becomes a reservoir for drinking water and irrigation . Samples collected from the reservoir showed the higher concentration of cadmium (Cd) and lead (Pb) that exceeded regulatory guidelines. Slags can serve other purposes, such as assisting in

SECTION 50

#1732802445757

2808-423: Was a colorful, glassy material found on the surfaces of slag from ancient copper foundries. It was primarily blue or green and was formerly chipped away and melted down to make glassware products and jewelry. It was also ground into powder to add to glazes for use in ceramics. Some of the earliest such uses for the by-products of slag have been found in ancient Egypt . Historically, the re-smelting of iron ore slag

2862-439: Was also used as an aggregate and had begun being integrated into the cement industry as a geopolymer . Today, ground granulated blast furnace slags are used in combination with Portland cement to create " slag cement ". Granulated blast furnace slags react with portlandite ( Ca(OH) 2 ), which is formed during cement hydration, via the pozzolanic reaction to produce cementitious properties that primarily contribute to

2916-442: Was common practice, as improved smelting techniques permitted greater iron yields—in some cases exceeding that which was originally achieved. During the early 20th century, iron ore slag was also ground to a powder and used to make agate glass , also known as slag glass. Use of slags in the construction industry dates back to the 1800s, where blast furnace slags were used to build roads and railroad ballast. During this time, it

#756243