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91-462: While most grinding in the mineral industry is achieved using devices containing a steel grinding medium, the IsaMill uses inert grinding media such as silica sand , waste smelter slag or ceramic balls. The use of steel grinding media can cause problems in the subsequent flotation processes that are used to separate the various minerals in an ore, because the iron from the grinding medium can affect

182-531: A 2600 kW drive. The mill used silica, crushed and screened, as the grinding medium. The new mill was commissioned in late 2003 and met Anglo Platinum's performance expectations, including almost perfect scale-up. It had lower operating costs than the smaller M3000 unit installed in a similar duty at Lonmin's operation. Like the McArthur River mine before it, the WLTR project was only possible because of

273-405: A ball mill using 9 mm balls, but only 40 kWh/t in an IsaMill using a 2 mm grinding medium. The IsaMill usually consists of a series of eight disks mounted on a rotating shaft inside a cylindrical shell (see Figure 2). The mill is 70–80% filled with the grinding medium, and is operated under a pressure of 100 to 200 kilopascals . The disks contain slots to allow the ore slurry to pass from

364-420: A carrier gas at 200–500 °C. Silicon dioxide is a relatively inert material (hence its widespread occurrence as a mineral). Silica is often used as inert containers for chemical reactions. At high temperatures, it is converted to silicon by reduction with carbon. McArthur River zinc mine The McArthur River mine is a zinc-lead mine, situated about 70 kilometres southwest of Borroloola , near

455-414: A conversation between chief geologist Syd Carter and fellow geologist Ron Beresford who were reviewing the progress of the survey party in 1956. Bemoaning that Beresford was naming all the prospects, Carter asked him what the specific area of the zinc deposit was going to be named. Bereford replied "here's your chance Syd" to which Carter replied, "that will do." Drilling continued during the 1960s. By 1977

546-407: A glass with no true melting point, can be used as a glass fibre for fibreglass. Silicon dioxide is mostly obtained by mining, including sand mining and purification of quartz . Quartz is suitable for many purposes, while chemical processing is required to make a purer or otherwise more suitable (e.g. more reactive or fine-grained) product. Precipitated silica or amorphous silica is produced by

637-494: A heat capacity minimum. Its density decreases from 2.08 g/cm at 1950 °C to 2.03 g/cm at 2200 °C. The molecular SiO 2 has a linear structure like CO 2 . It has been produced by combining silicon monoxide (SiO) with oxygen in an argon matrix. The dimeric silicon dioxide, (SiO 2 ) 2 has been obtained by reacting O 2 with matrix isolated dimeric silicon monoxide, (Si 2 O 2 ). In dimeric silicon dioxide there are two oxygen atoms bridging between

728-449: A high-cost and short-lived grinding medium would be uneconomic in an industry processing hundreds of tonnes of ore an hour. Subsequent test work focussed on finding a cheaper grinding medium that might make the bead mill viable for mineral processing. This work included using glass beads (about US$ 4/kg) and screened river sand (about US$ 0.10/kg) before it was found that the rounded beads produced by granulating reverberatory furnace slag from

819-685: A joint venture of Newmont Australia Pty Ltd and Barrick Australia Pacific that operates the Kalgoorlie "super pit" gold mine in Western Australia and the Gidji Roaster, north of Kalgoorlie. The first of two IsaMills bought by KCGM was commissioned at the Gidji Roaster in February 2001 to supplement the treatment capacity of the roaster. A change in the ore type had resulted in an increase in its sulfur content, which in turn increased

910-481: A larger M50000 model IsaMill, with an internal volume of 50,000 L, with a drive up to 8 MW. The advantages of the IsaMill include: The development of an economic ultrafine grinding technology has made possible atmospheric leaching of minerals for which this was previously impossible. MIM Holdings also developed, through its research facility located in Albion, a suburb of Brisbane, an atmospheric leaching process called

1001-550: A larger M6000 unit at the Gidgi Roaster and was able to subsequently decommission the two Lurgi roasters. A slight decrease in gold recovery was more than offset by increased availability, with the operation of the Gidgi plant no longer being constrained by air quality control requirements. Removal of the roasters was completed early in 2017, although the impressive stack still remains as a landmark. The initial development of

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1092-450: A low value of 140° in α-tridymite, up to 180° in β-tridymite. In α-quartz, the Si–O–Si angle is 144°. Alpha quartz is the most stable form of solid SiO 2 at room temperature. The high-temperature minerals, cristobalite and tridymite, have both lower densities and indices of refraction than quartz. The transformation from α-quartz to beta-quartz takes place abruptly at 573 °C. Since

1183-523: A motor size of 1120 kW and allowed the new design and grinding medium to be proven at a commercial scale. This model of the IsaMill was designated the "M3000". This was the first application of stirred mills in the metals mining industry. The development of the IsaMill gave the MIM Holdings Board of Directors the confidence to authorise construction of the McArthur River mine and concentrator. The next four M3000 IsaMills were installed in

1274-400: A patented product separator that consists of a rotor and a displacement body (see Figure 2 and Figure 4). The relatively short distance between the last disk results in a centrifugal action that forces coarse particles towards the mill shell, from where they flow back towards the feed end. This action retains the grinding medium within the mill. The product separator is a very important part of

1365-402: A rate equal to the mill's feed rate. The design of the IsaMill results in a sharp product size distribution, meaning that the IsaMill can operate in open circuit (i.e. without the need for an external separation of the discharged particles in screens or hydrocyclones to allow coarse over-size product to be returned to the mill for a second pass). It also means that there is less overgrinding at

1456-564: A result, the Mount Isa lead–zinc concentrator was forced to produce a bulk concentrate from the beginning of 1986 until late 1996. Bulk concentrates cannot be treated in electrolytic zinc smelters , due to their lead content, and are typically treated in blast furnaces using the Imperial Smelting Process . The Imperial Smelting Process has higher operating costs than the more common electrolytic zinc process, and therefore

1547-453: A separator that would retain the oversize grinding medium within the mill while allowing the fine ore slurry to exit. With the development of the product separator and changes to reduce the wear rate of the mill, the first two full-scale IsaMills were put into production in the Mount Isa lead–zinc concentrator in 1994. With 3000 liter ("L") volumes, they were six times larger than the largest standard mill previously produced by Netzsch. They had

1638-410: A silicon wafer enables it to overcome the surface states that otherwise prevent electricity from reaching the semiconducting layer. The process of silicon surface passivation by thermal oxidation (silicon dioxide) is critical to the semiconductor industry . It is commonly used to manufacture metal–oxide–semiconductor field-effect transistors (MOSFETs) and silicon integrated circuit chips (with

1729-446: A stirred-medium grinding mill, in which the grinding medium and the ore being ground are stirred rather than being subjected to the tumbling action of older high-throughput mills (such as ball mills and rod mills ). Stirred mills often consist of stirrers mounted on a rotating shaft located along the central axis of the mill. The mixing chamber is filled with the grinding medium (normally sand, smelter slag, or ceramic or steel beads) and

1820-445: A suspension of water and ore particles, referred to in the minerals industry as a slurry . In contrast, ball mills, rod mills and other tumbling mills are only partially filled by the grinding medium and the ore. In stirred-medium mills, the stirrers set the contents of the mixing chamber in motion, causing intensive collisions between the grinding medium and the ore particles and between the ore particles themselves. The grinding action

1911-477: A very shallow layer of about 1 nm or 10 Å of so-called native oxide. Higher temperatures and alternative environments are used to grow well-controlled layers of silicon dioxide on silicon, for example at temperatures between 600 and 1200 °C, using so-called dry oxidation with O 2 or wet oxidation with H 2 O. The native oxide layer is beneficial in microelectronics , where it acts as electric insulator with high chemical stability. It can protect

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2002-524: A white powder with extremely low bulk density (0.03-0.15 g/cm ) and thus high surface area. The particles act as a thixotropic thickening agent, or as an anti-caking agent, and can be treated to make them hydrophilic or hydrophobic for either water or organic liquid applications. Silica fume is an ultrafine powder collected as a by-product of the silicon and ferrosilicon alloy production. It consists of amorphous (non-crystalline) spherical particles with an average particle diameter of 150 nm, without

2093-439: Is also the primary component of rice husk ash , which is used, for example, in filtration and as supplementary cementitious material (SCM) in cement and concrete manufacturing. Silicification in and by cells has been common in the biological world and it occurs in bacteria, protists, plants, and animals (invertebrates and vertebrates). Prominent examples include: About 95% of the commercial use of silicon dioxide (sand)

2184-399: Is an oxide of silicon with the chemical formula SiO 2 , commonly found in nature as quartz . In many parts of the world, silica is the major constituent of sand . Silica is one of the most complex and abundant families of materials , existing as a compound of several minerals and as a synthetic product. Examples include fused quartz , fumed silica , opal , and aerogels . It

2275-423: Is based on one of the world's largest zinc , lead and silver deposits. Tom Lynott, the manager of McArthur River station is attributed with identifying the valuable metals in the area as early as 1887. Small mining ventures were attempted and failed due to the cost of transport. The deposit was proven in 1955 by a survey party from Mount Isa Mines (MIM) and named 'HYC' or 'Here's Your Chance'. The name came out of

2366-411: Is by attrition and abrasion, in which very fine particles are chipped from the surfaces of larger particles, rather than impact breakage. This results in the generation of fine particles at greater energy efficiency than tumbling mills. For example, grinding a pyrite concentrate so that 80% of the particles are less than 12 μm (0.012 mm) consumes over 120 kilowatt-hours per tonne (kWh/t) of ore in

2457-486: Is contaminating stream sediments in both Barney Creek and Surprise Creek, affecting macroinvertebrate species. An extreme risk of embankment failure, or "overtopping", of the spillway in the Tailings Storage Facility due to water volumes has also been identified, requiring immediate action. Local Indigenous people have also raised concerns about contamination of fish in the McArthur River. Testing by

2548-604: Is covalently bonded in a tetrahedral manner to 4 oxygen atoms. In contrast, CO 2 is a linear molecule. The starkly different structures of the dioxides of carbon and silicon are a manifestation of the double bond rule . Based on the crystal structural differences, silicon dioxide can be divided into two categories: crystalline and non-crystalline (amorphous). In crystalline form, this substance can be found naturally occurring as quartz , tridymite (high-temperature form), cristobalite (high-temperature form), stishovite (high-pressure form), and coesite (high-pressure form). On

2639-465: Is in the construction industry, e.g. in the production of concrete ( Portland cement concrete ). Certain deposits of silica sand, with desirable particle size and shape and desirable clay and other mineral content, were important for sand casting of metallic products. The high melting point of silica enables it to be used in such applications such as iron casting; modern sand casting sometimes uses other minerals for other reasons. Crystalline silica

2730-651: Is obtained by the dealumination of a low-sodium, ultra-stable Y zeolite with combined acid and thermal treatment. The resulting product contains over 99% silica, and has high crystallinity and specific surface area (over 800 m /g). Faujasite-silica has very high thermal and acid stability. For example, it maintains a high degree of long-range molecular order or crystallinity even after boiling in concentrated hydrochloric acid . Molten silica exhibits several peculiar physical characteristics that are similar to those observed in liquid water : negative temperature expansion, density maximum at temperatures ~5000 °C, and

2821-421: Is rapidly cooled, it does not crystallize, but solidifies as a glass. Because of this, most ceramic glazes have silica as the main ingredient. The structural geometry of silicon and oxygen in glass is similar to that in quartz and most other crystalline forms of silicon and oxygen, with silicon surrounded by regular tetrahedra of oxygen centres. The difference between the glass and crystalline forms arises from

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2912-494: Is refined to make zinc and lead metal and alloys. The HYC ore body consists of an extremely fine dissemination of the valuable mineral grains intermeshed with the gangue. The technology to efficiently produce a marketable concentrate from this type of ore was not available until long after the deposit was identified. After Mount Isa Mines successfully introduced the IsaMill , the fine grinding necessary for mineral liberation

3003-426: Is the major constituent of sand . Even though it is poorly soluble, silica occurs in many plants such as rice . Plant materials with high silica phytolith content appear to be of importance to grazing animals, from chewing insects to ungulates . Silica accelerates tooth wear, and high levels of silica in plants frequently eaten by herbivores may have developed as a defense mechanism against predation. Silica

3094-457: Is the only polymorph of silica stable at the Earth's surface. Metastable occurrences of the high-pressure forms coesite and stishovite have been found around impact structures and associated with eclogites formed during ultra-high-pressure metamorphism . The high-temperature forms of tridymite and cristobalite are known from silica-rich volcanic rocks . In many parts of the world, silica

3185-504: Is the process by which a semiconductor surface is rendered inert, and does not change semiconductor properties as a result of interaction with air or other materials in contact with the surface or edge of the crystal. The formation of a thermally grown silicon dioxide layer greatly reduces the concentration of electronic states at the silicon surface . SiO 2 films preserve the electrical characteristics of p–n junctions and prevent these electrical characteristics from deteriorating by

3276-436: Is used as a fining agent for wine, beer, and juice, with the E number reference E551 . In cosmetics, silica is useful for its light-diffusing properties and natural absorbency. Diatomaceous earth , a mined product, has been used in food and cosmetics for centuries. It consists of the silica shells of microscopic diatoms ; in a less processed form it was sold as "tooth powder". Manufactured or mined hydrated silica

3367-489: Is used as the hard abrasive in toothpaste . Silicon dioxide is widely used in the semiconductor technology: Because silicon dioxide is a native oxide of silicon it is more widely used compared to other semiconductors like gallium arsenide or indium phosphide . Silicon dioxide could be grown on a silicon semiconductor surface. Silicon oxide layers could protect silicon surfaces during diffusion processes , and could be used for diffusion masking. Surface passivation

3458-418: Is used in hydraulic fracturing of formations which contain tight oil and shale gas . Silica is the primary ingredient in the production of most glass . As other minerals are melted with silica, the principle of freezing point depression lowers the melting point of the mixture and increases fluidity. The glass transition temperature of pure SiO 2 is about 1475 K. When molten silicon dioxide SiO 2

3549-498: Is used in structural materials , microelectronics , and as components in the food and pharmaceutical industries. All forms are white or colorless, although impure samples can be colored. Silicon dioxide is a common fundamental constituent of glass . In the majority of silicon dioxides, the silicon atom shows tetrahedral coordination , with four oxygen atoms surrounding a central Si atom ( see 3-D Unit Cell ). Thus, SiO 2 forms 3-dimensional network solids in which each silicon atom

3640-538: Is used to produce elemental silicon . The process involves carbothermic reduction in an electric arc furnace : Fumed silica , also known as pyrogenic silica, is prepared by burning SiCl 4 in an oxygen-rich hydrogen flame to produce a "smoke" of SiO 2 . It can also be produced by vaporizing quartz sand in a 3000 °C electric arc. Both processes result in microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles which then agglomerate into tertiary particles,

3731-544: The Albion Process . By using IsaMills to grind the particles of refractory minerals to ultrafine sizes, the Albion Process increases the activity of sulfide concentrates to the point where they can be readily oxidised in conventional open tanks. Thus, the oxidation is carried out without the need for high pressure, expensive reagents or bacteria. Silica Silicon dioxide , also known as silica ,

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3822-599: The Albion process . The technology has now been applied to both gold and base metal projects also. Bulk concentrate is trucked 120 km from the mine to a loading facility in the Gulf of Carpentaria. The concentrate is loaded onto a ship at the Bing Bong loading facility . From here the purpose-built barge called MV Aburri operates a shuttle service from the loading facility to a point fifteen nautical miles offshore where

3913-587: The Gulf of Carpentaria in the northeastern Northern Territory , Australia . It is operated by McArthur River Mining (MRM), a subsidiary of the Swiss mining company Glencore . Although discovered in the 1950s, when it was originally called the HYC or "Here's Your Chance" deposit, it only opened as a mine in 1995. Initially an underground mining operation, the mine has been converted to open-cut . The McArthur River zinc mine

4004-609: The McArthur River Project Agreement Ratification Act was passed by the Northern Territory Government and the mine was operational by 1995. By 2001, most of the accessible underground ore was extracted and MIM reported a $ 900,000 loss. It began looking at the feasibility of turning the mine into an open-cut operation. Terms of Reference for an Environmental Impact Statement (EIS) were released in 2003. MIM

4095-813: The Northern Land Council with the support of the traditional owners and the Environmental Defenders Office , through the Supreme Court of the Northern Territory . This decision was also overturned within days and the mine given the go-ahead once more by parliamentary vote. The traditional owners continued to protest, taking the matter to the Federal Court of Australia . They won the case, only to have this decision declared invalid. The final decision

4186-555: The planar process ). Hydrophobic silica is used as a defoamer component . In its capacity as a refractory , it is useful in fiber form as a high-temperature thermal protection fabric. Silica is used in the extraction of DNA and RNA due to its ability to bind to the nucleic acids under the presence of chaotropes . Silica aerogel was used in the Stardust spacecraft to collect extraterrestrial particles. Pure silica (silicon dioxide), when cooled as fused quartz into

4277-416: The IsaMill design. It avoids the need to use screens to separate the grinding medium from the ground particles. Using screens would make the mills high-maintenance, as they would be prone to blocking, necessitating frequent stoppages for cleaning. Fine particles are not as susceptible to the centrifugal forces and stay closer to the center of the mill, where they are discharged through the displacement body at

4368-461: The IsaMill was driven by problems encountered treating MIM's lead–zinc ore bodies. The next major leap was driven by problems experienced by South Africa's platinum producers, driving the development of larger mills and initiating the global penetration of the technology. Around the beginning of the 21st century, South African platinum mining companies were mining increasing quantities of more difficult platinum ore, resulting in decreasing recoveries of

4459-507: The IsaMills at Mount Isa, together with some other modifications to the lead–zinc concentrator, allowed MIM to stop producing the low-value bulk concentrate in 1996. The IsaMills made possible the development of the McArthur River mine. The first sales to external organisations of the M3000 mills were to Kalgoorlie Consolidated Gold Mines Pty Ltd ("KCGM"), Australia's largest gold producer and

4550-408: The McArthur River concentrator in 1995. The first mills installed at Mount Isa and McArthur River initially operated with six disks. The number was increased first to seven disks and finally to the eight disks that are now standard. The full-scale IsaMills allowed MIM to refine the mill design to allow improved ease of maintenance. For example, the shell design was changed to allow it to split along

4641-456: The Mount Isa copper smelter constituted an ideal grinding medium. As a result of the success of the laboratory tests, a larger-scale mill was tested in MIM's pilot flotation plant. It was found that the standard mill suffered a very high wear rate, with the disks being severely worn within 12 hours. MIM's development efforts focussed on finding a lining that could withstand the wear and on designing

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4732-578: The Northern Territory Government and the mine's consultant found that small species, including rainbow fish and bony bream, have been contaminated with lead above maximum-permitted concentrations, making them unsafe for human consumption. In 2015, reports showed that Glencore and the Northern Territory Health Department did not act on a recommendation from the Chief Health Officer to warn people living near

4823-496: The acidification of solutions of sodium silicate . The gelatinous precipitate or silica gel , is first washed and then dehydrated to produce colorless microporous silica. The idealized equation involving a trisilicate and sulfuric acid is: Approximately one billion kilograms/year (1999) of silica were produced in this manner, mainly for use for polymer composites – tires and shoe soles. Thin films of silica grow spontaneously on silicon wafers via thermal oxidation , producing

4914-462: The advantages conferred by the IsaMill technology. The success of the M10000 unit encouraged Anglo Platinum to look at other applications of the IsaMill technology and, following an extensive program of plant investigations and laboratory test work, it decided to install an M10000 IsaMill with a 3000 kW drive in a mainstream (rather than ultrafine) grinding application. The grinding medium selected

5005-552: The branching of the pyrogenic product. The main use is as pozzolanic material for high performance concrete. Fumed silica nanoparticles can be successfully used as an anti-aging agent in asphalt binders. Silica, either colloidal, precipitated, or pyrogenic fumed, is a common additive in food production. It is used primarily as a flow or anti- caking agent in powdered foods such as spices and non-dairy coffee creamer, or powders to be formed into pharmaceutical tablets. It can adsorb water in hygroscopic applications. Colloidal silica

5096-416: The concentrate is transferred on to overseas bulk carriers. There have been several transportation incidents. Seepage from the Tailings Storage Facility at the mine have been detected in the nearby Surprise Creek. Monitoring in 2005, 2007 and 2010 shows that soluble sulfate, zinc and, potentially, lead and cadmium are seeping into Surprise Creek. Dust from operations at the run of mine pad and crushing plant

5187-509: The connectivity of the tetrahedral units: Although there is no long-range periodicity in the glassy network, ordering remains at length scales well beyond the SiO bond length. One example of this ordering is the preference to form rings of 6-tetrahedra. The majority of optical fibers for telecommunications are also made from silica. It is a primary raw material for many ceramics such as earthenware , stoneware , and porcelain . Silicon dioxide

5278-488: The densest of the low-pressure forms, which has a density of 2.648 g/cm . The difference in density can be ascribed to the increase in coordination as the six shortest Si–O bond lengths in stishovite (four Si–O bond lengths of 176 pm and two others of 181 pm) are greater than the Si–O bond length (161 pm) in α-quartz. The change in the coordination increases the ionicity of the Si–O bond. Faujasite silica, another polymorph,

5369-415: The feed end to that opposite the drive end, the disks that required most frequent replacement were the first that were removed from the shaft rather than the last (see Figure 6 and Figure 7). While the IsaMills at Mount Isa were operated using screened copper smelter reverberatory furnace slag as the grinding medium, those at McArthur River used screened primary grinding mill fines as the grinding medium for

5460-405: The feed end to the discharge end (see Figure 3). The area between each disk is effectively an individual grinding chamber, and the grinding medium is set in motion by the rotation of the disks, which accelerate the medium toward the shell. This action is most pronounced close to the disks. The medium flows back toward the shaft in the zone near the midpoint between the disks, creating a circulation of

5551-541: The finer end of the size distribution, such as occurs during the operation of tower mills. The development of the IsaMill was driven by MIM Holdings’ desire to develop its McArthur River lead–zinc deposit in Australia's Northern Territory , and by the need for finer grinding at its Mount Isa lead–zinc concentrator. The mineral grains in the McArthur River deposit were much finer than those of operating mines. Test work had shown that it would be necessary to grind part of

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5642-617: The fire. After claiming the fire had been brought under control, photos of smoke coming from the mine emerged again in March 2015, sparking an investigation by the Environment Protection Authority. Sightings of smoke again in July 2016, turned out to be dust from the dump, causing the immediate closure of the site and an investigation into why dust mitigation measures were not being complied with. Rehabilitation of

5733-414: The first feasibility studies commenced and a pilot operation and temporary work camp were established. Costs prohibited further development at the time, but by 1989 MIM Holdings were issued the necessary leases to bring the mine into operation. In 1992 it joined forces with Japanese consortium ANT Minerals to develop the mine, forming McArthur River Mining Pty Ltd to operate on their behalf. In November 1993,

5824-513: The first seven years of their operation and, in 2004, switched to using screened river sand. The first sale outside the MIM Holdings group also occurred in 1995, with the sale of three smaller "M1000" IsaMills to Kemira for grinding calcium sulfate at one of its Finnish operations. A fifth M3000 IsaMill was installed in the McArthur River concentrator in 1998 and six more in the Mount Isa lead–zinc concentrator in 1999. The installation of

5915-411: The gaseous ambient environment. Silicon oxide layers could be used to electrically stabilize silicon surfaces. The surface passivation process is an important method of semiconductor device fabrication that involves coating a silicon wafer with an insulating layer of silicon oxide so that electricity could reliably penetrate to the conducting silicon below. Growing a layer of silicon dioxide on top of

6006-467: The grinding medium between each pair of disks, as shown in Figure 4. The average residence time of the ore in the mill is 30–60 seconds. There is negligible short-circuiting of the grinding zone by the feed, as a result of having multiple grinding chambers in series. The ground product is separated from the grinding medium at the discharge end of the mill. This is achieved without using screens by using

6097-414: The horizontal center-line (see Figure 5). This was done to allow the use of a replaceable slip-in liner, avoiding the need for the shell to be sent away for cold rubber lining and the need to have a stock of spare, lined shells. Also, the direction of flow of feed through the mill was reversed, because most of the disk wear occurred at the feed end, which was initially at the drive end of the mill. By changing

6188-482: The mass of sulfide concentrate produced, thus making the two Lurgi roasters a bottleneck in the gold production process. Studies by KCGM metallurgists had shown that ultrafine grinding was an alternative to roasting as a method of unlocking fine gold that could not be recovered without further treatment (so-called "refractory gold"), but until the development of the IsaMill, there was no economic method of ultrafine grinding available. In 2015 KCGM completed commissioning of

6279-423: The mills used in these industries were used on a small scale and were often batch operations. They used expensive grinding media that frequently needed to be removed, screened and replaced so that the mills would continue to operate properly. The traditional grinding medium consisted of silica-alumina-zirconium beads that, in those days, cost about US$ 25 per kilogram ("kg") and lasted for only a few hundred hours. Such

6370-428: The mine has been burning since 2013. Pyrite iron sulphide stacked in the dump overheated and ignited. The rock was misclassified in its Environmental Impact Statement as 12 per cent reactive potentially acid-forming rock and the rest non-acid-forming. Workers were allegedly told to cover up details of the extent of the fire and now claim to be suffering from respiratory conditions as a result of breathing toxic smoke from

6461-493: The mine to not eat fish from three locations. A small section of seagrass , which provides food for dugongs has also been destroyed by dredging at the Bing Bong Loading Facility. Potential for bioaccumulation of heavy metals in dugongs, a significant concern for Aboriginals from Borroloola who eat the meat, has been identified as a result from potential ore spillage at the facility. A waste dump at

6552-599: The mine's environmental impact was not being monitored. In 2012 mining giant Glencore bought the remaining 66% share in Xstrata, taking over the McArthur River Mine. In 2013, the Northern Territory Government approved another $ 360 million expansion that would double its size and production, extending the life of the mine to 2038. Following an environmental impact study, the expansion is expected to increase production to 5.5 million tonnes per year and increase

6643-425: The mining industry. He found that fine grinding was well established for such high-value manufactured products as printer inks, pharmaceuticals, paint pigments and chocolate. MIM decided to work with Netzsch, which was a pioneer in the fine grinding field, and still a leader. Test work was undertaken using one of Netzsch's horizontal bead mills. It showed that such a mill could achieve the required grind size. However,

6734-489: The ore so that 80% of the ground particles were less than 7 μm (0.007 mm) if a saleable concentrate of mixed lead and zinc minerals (referred to as a "bulk concentrate") were to be produced. At the same time, the mineral grain size of the lead–zinc ore mined and processed at Mount Isa was decreasing, making it harder to separate the lead and zinc minerals. The liberation of sphalerite (zinc sulfide) grains dropped from over 70% to just over 50% between 1984 and 1991. As

6825-400: The other hand, amorphous silica can be found in nature as opal and diatomaceous earth . Quartz glass is a form of intermediate state between these structures. All of these distinct crystalline forms always have the same local structure around Si and O. In α-quartz the Si–O bond length is 161 pm, whereas in α-tridymite it is in the range 154–171 pm. The Si–O–Si angle also varies between

6916-504: The particles smaller than 53 μm). Anglo Platinum attributed an increase in recovery at its Rustenburg concentrator of over three percentage points to the installation of the IsaMills there. The M10000 IsaMill has proven very popular and sales of the technology have been strong since it launched onto the global stage. IsaMills are now used in lead–zinc, copper, platinum group metal, gold, nickel, molybdenum and magnetite iron ore applications. Xstrata Technology has recently been developing

7007-481: The payment received by producers of bulk concentrate is lower than that received for separate lead and zinc concentrates. The zinc in the Mount Isa bulk concentrate was eventually worth less than half that of the zinc in the zinc concentrate. These issues provided a great incentive for MIM to grind its ores finer. MIM metallurgists had undertaken fine grinding test work on samples from both deposits using conventional grinding technologies between 1975 and 1985. However, it

7098-491: The platinum group metals to concentrate and increasing quantities of chromite, which adversely affects smelter performance. These problems drove the industry to investigate the potential of new developments in stirred-medium grinding. The first mover in the area was Lonmin, which purchased an M3000 IsaMill in 2002. Anglo Platinum, which had at the time 20 operating concentrators around the Bushveld complex, followed in 2003 with

7189-469: The purchase of a smaller M250 IsaMill for testing in its Rustenburg pilot plant. After doing the test work, Anglo Platinum decided to use a scaled-up version of the IsaMill in its Western Limb Tailings Retreatment ("WLTR") project. It worked with Xstrata Technology, by then the holders of the marketing rights, and Netzsch to develop the M10000 IsaMill, which has a volume of 10,000 L and, at that time,

7280-401: The silicon atoms with an Si–O–Si angle of 94° and bond length of 164.6 pm and the terminal Si–O bond length is 150.2 pm. The Si–O bond length is 148.3 pm, which compares with the length of 161 pm in α-quartz. The bond energy is estimated at 621.7 kJ/mol. SiO 2 is most commonly encountered in nature as quartz , which comprises more than 10% by mass of the Earth's crust. Quartz

7371-418: The silicon, store charge, block current, and even act as a controlled pathway to limit current flow. Many routes to silicon dioxide start with an organosilicon compound, e.g., HMDSO, TEOS. Synthesis of silica is illustrated below using tetraethyl orthosilicate (TEOS). Simply heating TEOS at 680–730 °C results in the oxide: Similarly TEOS combusts around 400 °C: TEOS undergoes hydrolysis via

7462-684: The site is estimated to cost up to $ 1 billion. In 2015, the Northern Territory Government threatened to close McArthur River Mine unless it improved its environmental practices and agreed to increase the size of the financial bond for the site's final remediation. Local Indigenous people and environmental groups continue to call for the mine's immediate closure and rehabilitation of the site. The mine closed temporarily in March 2024 after flooding due to record levels of rain, reaching 274 millimetres in just 24 hours due to Tropical Cyclone Megan . Traditional owners then raised concerns over resulting erosion to acidic waste rock piles, however Glencore stated that

7553-492: The so-called sol-gel process . The course of the reaction and nature of the product are affected by catalysts, but the idealized equation is: Being highly stable, silicon dioxide arises from many methods. Conceptually simple, but of little practical value, combustion of silane gives silicon dioxide. This reaction is analogous to the combustion of methane: However the chemical vapor deposition of silicon dioxide onto crystal surface from silane had been used using nitrogen as

7644-401: The surface properties of the minerals and reduce the effectiveness of the separation. The IsaMill avoids these contamination-related performance issues through the use of an inert grinding medium. First used in the Mount Isa lead – zinc concentrator in 1994, by May 2013 there were 121 IsaMill installations listed in 20 countries, where they were used by 40 different companies. The IsaMill is

7735-446: The transformation is accompanied by a significant change in volume, it can easily induce fracturing of ceramics or rocks passing through this temperature limit. The high-pressure minerals, seifertite , stishovite, and coesite, though, have higher densities and indices of refraction than quartz. Stishovite has a rutile -like structure where silicon is 6-coordinate. The density of stishovite is 4.287 g/cm , which compares to α-quartz,

7826-547: The workforce to 735 by 2020. It will extend the mine's life until 2038 and is projected to contribute $ 8.4 billion to the Northern Territory economy and $ 9.3 billion nationally. The HYC deposit covers around and area of about two square kilometres and is 55 m in depth. Approximately 2.5 million tonnes of ore containing 383 kt of zinc, 93 kt of lead and 110 t of silver are currently mined per year, supplying markets in Europe , Japan and China . Bulk concentrate

7917-458: Was a newly available and low-cost zirconia-toughened alumina ceramic material, which was developed by Magotteaux International. The results justified an aggressive roll-out of more IsaMills at Anglo Platinum's concentrators, and by 2011, Anglo Platinum had purchased 22 IsaMills for its concentrators. The majority of the installations are in mainstream inert-grinding applications, producing relatively coarse product particles sizes (for example, 80% of

8008-474: Was acquired by Xstrata in the same year, wholly owning the mine by September 2005. Plans to expand the mine were announced in 2005. As the main ore body lies directly beneath the river, the expansion required the diversion of 5.5 km of the McArthur River . The mine's expansion was quickly approved, with the support of Prime Minister John Howard . The approval was later revoked by action taken by

8099-422: Was available for McArthur River to be developed. This unusual mineralogy combined with the ore's relatively high lead levels makes the lead and zinc virtually inseparable prior to smelting, and there are very few smelters which can process concentrate which is high in lead. These issues led Mount Isa Mines (later Xstrata) to develop a new lead-zinc leaching process in partnership with Highlands Pacific, known as

8190-452: Was found that conventional grinding had a very high power consumption and that contamination of the mineral surface by iron from the steel grinding media adversely affected flotation performance. It was concluded in 1990 that there was no suitable existing technology for grinding to the fine sizes in the base metals industry. Consequently, Mount Isa's head of mineral processing research, Dr Bill Johnson, began looking at grinding practices outside

8281-486: Was left to Peter Garrett , the Federal Environmental Minister at the time. Xstrata had threatened to sack all 170 staff unless Garrett made a quick decision. On 22 January 2009 he approved the expansion, "subject to a further 10 days of evaluation by Indigenous groups and others", promising also to protect local species such as the sawfish and migratory birds. Later in 2009, a report found that

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