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By F. M. Doyle, K. Osseo-Asare, E. Peters

With the aid of molecular orbital theory, a discussion is presented of the relationship between the electronic structures of ions and molecules, and the elementary steps involved in homogeneous electron transfer reactions. An electronic theory of the reactivity of oxidants and the mechanism of action of oxidation catalysts is then presented, with emphasis on the oxidative decomposition of metal sulfides. For model oxidants, two molecular reagents: O2 and Cl2, and two ionic reagents: Fe3+ and CU2+ were selected; silver (1) was chosen as the model catalyst. The reactivities of these reagents are rationalized in terms of constraints on orbital overlap, the availability of unoccupied d orbitals, and the rearrangement of electronic configurations.

Jan 1, 1993

By J. C. Franklin

The U.S. Department of the Interior, Bureau of Mines, has developed a data acquisition system to continuously monitor radon, working level, absolute pressure, temperature, relative humidity, and air velocity. Data have been taken in intake and exhaust drifts, working stopes, and sealed-off areas of positive and negative ventilated uranium mines. Radon emanation rates, ranging from 1.7- to 12.2 x 2 10-l4 Ci/cm /sec were determined in four mines. The ratios of short duration, primary fan shutdown time to radon normalization time were 1 to 2 and 1 to 4, respectively, for-negatively and positively ventilated mines. Blasting and slushing caused radon increases of 160 and 67 percent, respectively.

Jan 1, 1980

By A. Singh, C. Da Corte

"South Africa possess the biggest fluorspar reserves in the world followed closely by China. In light of the current commodity downturn this paper explores the use of Dense Media Separation (DMS) as a coarse pre-concentration method for two fluorspar deposits located in South Africa in which the dominant gangue is carbonate present in the form of dolomite and calcite. Heavy Liquid Separation indicated that conventional pre-concentration of the drill core samples from both deposits would result in unacceptably high fluorite CaF2 losses. At a maximum CaF2 loss to floats of 5% the benefit of DMS would be economically marginal and difficult to justify as a conventional pre-concentrator. In light of cashflow constraints, a twin flowsheet was proposed for the sole purposes of upfront cash generation in which the majority (67-77%) of the CaF2 would report to a high grade flotation plant in 38-41% of the mass whilst the rejects would be stockpiled for flotation at a later stage. Considering the proposed twin flowsheet approach the high grade product split was achieved using DMS and this paper documents the challenges encountered and results achieved. INTRODUCTION Fluorspar is the commercial term for the mineral fluorite (calcium fluoride, CaF2). Worldwide production of fluorspar is dominated by four countries namely China, Mexico, Mongolia and South Africa. Although South Africa is the fourth largest producer, it has the largest fluorspar reserves closely followed by China (U.S. Geological Survey, 2017a). Fluorspar is broadly categorized into two grades namely acid grade also referred to as acidspar (>97% CaF2); and sub-acid grade (ceramic and metallurgical grade) commonly referred to as metspar (=97% CaF2). Acid grade fluorspar is used for the production of hydrofluoric acid (HF) which in turn is used for the manufacture of fluorocarbons and semi-conductors in the electronics industry; metal processing; the production of insecticides, herbicides and cleaning detergents, and the manufacture of uranium tetrafluoride used to concentrate the uranium isotope 235 for use as a nuclear fuel (British Geological Survey 2010; Miller 2001). Ceramic grade fluorspar (85-95% CaF2) is used in the ceramic industry as a flux and opacifier in the production of glass and enamels. Ceramic grade fluorspar is also used to make coatings for welding rods and as a flux in the steel industry. Metallurgical grade fluorspar (60-85% CaF2) is primarily used in the steel industry as flux to reduce the melting temperature and remove impurities in steel making. Similarly metallurgical grade fluorspar is also used as flux in cement production to reduce energy consumption (British Geological Survey 2010; Miller 2001)."

Jan 1, 2018

By Zefang ChenLi, Laijun Ma, Lei Mao, Fang Lian

"In our work, the preparation technique of high pure manganese sulfate directly from low-grade rhodochrosite ore (MnCO3) was studied and improved intensively, including the effective leaching process and the short purifying process. Based on the same ion effect, the repeated leaching of rhodochrosite with sulfuric acid is proposed to improve the solubility of Mn2+ and inhibit the dissolution of the impurities Ca2+ and Mg2+. Moreover, the repeated leaching process could make full use of rhodochrosite and lower the dosage of sulfuric acidas raw material. With the aid of theoretical calculation, Ba(OH)2 was chose to adjust the pH value of manganese sulfate solution, and BaF2 to remove Ca2+ and Mg2+completely in the process of purifying. The results demonstrate that the extraction ratio and the recovery ratio of manganese reached 94.3% and 92.7%, respectively, which shows the prospect of industrial application. In manganese sulfate production, the heavy metal impurities have been decreased to less than 1ppm. Moreover, the content of calcium, magnesium and sodium has been decreased to less than 20ppm, which meets the standards of high pure reagent for energy and electronic materials. Our study enlightens an approach to the sustainable application of low-grade rhodochrosite.Introduction Low-grade manganese carbonate ores (=14%) becomes gradually the main resources for exploitation and applications in China according to national mineral resources survey (Tan et al 2004 and Singh et al 2017). Therefore, the electrolytic deposition technique of rhodochrosite faces great challenges including low electrolysis efficiency, high-resource input and high-pollution discharge (Fu et al 2010, Michelis et al 2009, Zhang et al 2013). Recently, more and more amount of manganese series with high or super high purity such as MnSO4, MnO2, Mn3O4 and MnO is demanded with the development of energy and electronic materials. Due to low-grade ores containing multiple elements such as iron, silicon, calcium and magnesium, conventional preparation of manganese sulphate with high purity from electrolytic product is characterized by long production-cycle and high-energy consumption (Subrat et al 2011, Mpho et al 2013). By contrast, hydrometallurgical method combined with thermal decomposition, hydrothermal synthesis and sol-gel processes has been widely studied because of its high efficiency, low consumption and low cost (Chen et al 2008). But the key problem in direct preparation of manganese series form low-grade rhodochrosite is to remove completely the multiple impurities such as iron, silicon, calcium and magnesium (Liu et al 2014). So it is urgent to develop a sustainable alternative approach with character of short process, high efficiency and environmental friendly."

Jan 1, 2017

By L. Evrard, M. Van Camp, J. Y. Yen, R. G. Reddy, D. Mantha

Viscosities of two industrial lead blast furnace slags have been experimentally determined as functions of composition and temperature. A Brookfield viscometer with alumina rods and crucibles were used. Experiments were carried out between 1200 and 1573 K in an argon atmosphere with up to 5% addition of FeO, MgO, and SiO2 to the slags. Results showed that 1) the viscosities of two slags decreased with increase in temperature; 2) addition of FeO decreased the slag viscosities; and 3) addition of MgO and SiO2 increased the slag viscosities. Use of the above slag compositions with the addition of FeO is recommended for successful lead smelter operation.

Jan 1, 2005

By S. N. Groudev

A process for the combined chemico-biological removal of iron present as oxide minerals in different mineral raw materials (quartz sands, kaolins, clays, etc.) was developed. In the process, mineral raw materials are leached at about 90 °C with lixiviant containing microbially produced oxalic and hydrochloric acids. The leaching is carried out in mechanically stirred acid-resistant reactors for periods of from 1 to 6 hours, depending on the iron content and the forms of iron in the raw materials being leached. The iron contents of some sands treated by this method were lowered from levels that were in the range of 0.035% to 0.088% Fe2O3 to less than 0.012% Fe2O3, making them suitable for the preparation of high-quality glass. The iron contents of different kaolins were lowered from levels that were in the range of 0.65% to 1.49% Fe2O3 to levels in the range of 0.44% to 0.75% Fe2O3. As a result, the whiteness was increased from values of 55% to 87% to values of 86% to 92%. The iron content of clay was lowered from 6.25% Fe2O3 to 1.85% Fe2O3, and this increased the “fireproofness" of the clay from 1,670°C to 1,750°C. A similar process was used for the leaching of aluminum from aluminosilicates, mainly clays and kaolins. However, in this case, the microbial fermentation fluid containing citric acid was acidified by means of sulfuric or hydrochloric acid or by means of different mixtures of mineral acids. For enhancing aluminum solubilization, the aluminosilicates were heated before leaching at 600° to 650°C for 1 to 2 hours. Over 90% of the aluminum present in different clays and kaolins were leached within 3 to 6 hours. "Silicate " bacteria related to the species Bacillus circulans were used to leach silicon from low-grade bauxite ores containing aluminosilicates as impurities. The bacterial action was connected with the degradation of the mineral structures (by means of microbial metabolites such as organic acids and exopolysaccharides), as well as with the selective separation of the rich-in-aluminum fine fractions, which were retained by the mucilaginous capsules of the bacteria. The solid residues after treatment were characterized by higher values of alumina and silicon module (A1203: SiO2 ratio), and they were suitable for processing by means of the Bayer process for recovering aluminum. The bending strength and other ceramic properties of kaolins were improved by contact with well-developed cultures of "silicate" bacteria. The improvement was caused mainly by bacterial metabolites (exopolysaccharides) that acted as resins during drying.

Jan 1, 2000

By Anna Sieminska-Lewandowska, Monika Mitew-Czajewska

"The construction of 6.3 km long central part of 2nd metro line in Warsaw was completed in September 2014 (7 stations - out of which three 25m deep stations - built using cut and cover method; two single-track tunnels constructed using four EPB TBMs as well as a short NATM section with soil freezing below the existing road tunnel). Central section of the 2nd metro line was opened to public after verification and testing in March 2015. Design and build tender for the extension of this line in East (three stations) and West direction (three stations) was announced with total length of running tunnels – approx. 5 km. Detailed description of a very complex geotechnical context, different construction methods, challenges encountered and solved during construction and finally lessons learnt on this interesting project are presented in the paper. DESCRITPTION OF THE PROJECT Introduction The very first concept plan of the metro system in Warsaw was designed several years after regaining independence by Poland in 1918. In 1929, following the geotechnical survey, design works begun, but the economic crisis of the 1930s stopped it. After a few years of break, in 1938 a coherent concept of the metro network was proposed to be implemented in phases over the next 35 years. In total, construction of 46 kilometers of metro, including 31 km of tunnels and 15 km on surface, was planned. Unfortunately, World War 2 made the implementation of those plans impossible. In the post-war period several metro designs were elaborated, but none except one was scheduled for implementation. Construction of the 1st, 23.1 km long, North-South line commenced in 1983 and finished in 2008 (Sieminska-Lewandowska et all. 2009). Nowadays, Warsaw covers the area of 517 km2 and, according to year 2014 statistical data, the city has much more than 1.7 million inhabitants. Only one operating metro line is not sufficient for such a populated city. Up-to-date metro plan, shown on Figure 1, includes also 30.5 km long 2nd metro line. It’s route is divided into four sections: Western Section with the length of approx. 9.2 km and 9 stations, Central Section with the length of 6.3 km and 7 stations, North-East Section with the length of 7.7 km and 6 stations, South-East Section with the length of 7.1 km and 6 stations. The construction of the central part of the 2nd metro line in Warsaw was completed in September 2014 and its operation started in March 2015. The paper focuses on challenges encountered and solved and lessons learnt during construction of the central part of the 2nd metro line in Warsaw."

Jan 1, 2016

By Fikret Suner

Two rare evaporite minerals, nahcolite (NaHC03) and trona (Na2C03?NaHC03?2H20), are both widely used in the production of sodium carbonate (Na2CO3) The largest natural carbonate deposits (trona) are in Wyoming, USA, the second largest deposits are in Turkey, in a lacustrine basin (Beypazari) where nahcolite and trona are located within the Miocene Hirka Formation. The Hirka Formation is mainly composed of bituminous shale, claystone, marlstone, tuffltuffite, and dolomitic limestones. Although numerous trona beds are interbedded within the above mentioned sedimentary units, there are only two beds of trona that are of economic interest. The lower part of the lower trona bed is rich in double carbonates such as pirrsonite (NA2C03? CaC03?2H20) and gaylussite (Na2C03?CaC03?5H20), indicating a change in Ca/Na ratio in the solutions which are responsible for the formation of soda occurrences. In contrast, the upper part of the upper trona bed is rich in nahcolite. This minerological pattern has been found in every drill- hole in the basin. While both trona beds average up to 10 m (33 ft) thick, the average thickness of nahcolite is approximately 0.5 m (1.6 ft). Also, thin section studies show that many fibrous and lath-like trona crystals contain small radial nahcolite crystals; all of them are euhedral and equi-dimensional. Geochemical studies of major, minor, and trace element contents also support this coexistence. Macroscopic and microscopic observations reveal that the nahcolites principally were formed as a result of an incongruent dissolution process of trona. In conclusion, the presence of nahcolite in the Beypazari basin is due to the dissolution process of trona, particularly during the last stage of evaporation, as a result of fresh water entering the basin. During that time, an increase in the HC03/ C03 ratio resulted in nahcolite-trona phase transitions.

Jan 1, 2001

By Gordon Clark, Basar Arioglu, Nasri Munfah, Sanja Zlatanic, Tolga Togan

"The 13.2 m (43 ft) external diameter, double deck Istanbul Strait Road Tube Crossing is one of the most challenging underwater tunnel projects in the world. Subjected to 11 bars of hydrostatic pressure, variable geology, and being in a very active seismic area, the execution of the project required innovative solutions, sophisticated construction techniques and prudent risk management approach. The 5 km (3.1 mile) tunnel consists of a 3.4-km (2.2-mile) tunnel boring machine- (TBM) bored tunnel, 1 km (0.62 mile) twin NATM tunnels and cut-and-cover sections. The project is being delivered in a build-operate-transfer (BOT) contract in a public-private partnership. The technical challenges, coupled with financial and commercial risks required the implementation of sophisticated risk management tactics including the provision of independent design verification. The project was opened to traffic on December 20, 2016, four months ahead of schedule.. This article presents the technical challenges of the project from the design, construction, and risk management aspects..Project backgroundThe $1.245 billion Istanbul Strait Road Tunnel Crossing project, dubbed the Eurasia Tunnel, is one of several major infrastructure projects being implemented in the Republic of Turkey in a public-private partnership approach. The project provides a direct and easy connection between the Anatolian (Asian) side of Istanbul and the heart of its historical district on the European side across the Bosphorus Strait which connects the Black Sea with the Sea of Marmara. The project improves connections to a wide network of motorways on both sides, increase capacity across the Bosphorus by 100,000 vehicles a day, reduces congestion and saves motorists an average of 45 minutes of commuting time in each direction bringing significant economic benefits to the city and the region. It eases traffic across the strait, reduces congestion, decreases pollutants and emission while maintaining Bosphorus. It is the most complex part of the project with the greatest challenges and risks. Part 2 is 5.4 km (3.6 miles) long consisting of 3.4 km (2.2 miles) of 13.2 m ( 43.3 ft) external diameter TBM bored tunnel under the Bosphorus Strait, 1-km (0.62-miles) of twin NATM tunnels on the Asian side, cut-and-cover transition boxes in the Asian and the European sides and depressed approaches on both sides. In addition, this segment includes the toll plazas, ventilation buildings, and the tunnel control and maintenance facilities."

Mar 1, 2017

By Bruce Clements

The Bagdad mill, located near Bagdad, AZ, was built in 1977 with a designed mill capacity of 36.3 kt/d (40,000 stpd). An autogenous mill-ball mill crusher (ABC) grinding circuit was chosen. The original mill contained three independent grinding circuits. Each contained one 9.75m-diam x 4-m-long (32-ft-diam x 13-ft-long) fixed-speed autogenous mill, a4.7-m-diam x 6.7-m- long (15.5ft-diam x 22-ft-long) ball mill and one 2. 1-m-diam (7-ft-diam) short head cone crusher. Total installed power per grinding circuit was about 8.4 MW (11,350 hp), with 5.9 MW (8000 hp) in the autogenous mill, 2.2 MW (3000 hp) in the ball mill and 261 kW (350 hp) in the crusher (Fig. 1). The autogenous mills were designed to be able to operate semi-autogenously. However, they were never converted to semiautogenous grinding (SAG) mills. As a result of this design, only about 4.1 MW (5450 hp) of the designed power is used in the autogenous mills. The grinding circuits are closed, with 2.4 x 6 m (8 x 20 ft) double-deck vibrating screens. A series of conveyors re- turn screen oversize underneath the mill coarse ore stockpile to feed the crushers. Variable speed belts feed the crushers and control power draw. Crusher product reports directly to the tail end of the autogenous mill feed belt (Fig. 2). A magnetic sensor detects tramp iron in the autogenous mill-crusher circuit.

Jan 1, 1992

By K. L. Purdy

Electron spectroscopy for chemical analysis (ESCA) was used to determine the-surface characteristics of products from operating Pb-Zn-Cu concentrators on the New Lead Belt of southeast Missouri and pure galena and sphalerite samples treated-with flotation reagents in concentrations similar to those used in the mills. The emphasis was on the action of surface modifiers such as Na2Cr207, starch, SO2, CuSO4 and NaCN in sphalerite flotation and in the galena-chalcopyrite separation. The objective of the investigation was to monitor the relative oxidation states of the mineral and reagent constituents and correlate these surface concentrations and oxidation states with flotation theory and practice. ESCA was able to follow the action of all the modifiers except NaCN. The existence of PbCrO4 on the surface of galena conditioned with Na2Cr207 was verified. The Pb in the bulk PbS-CuFeS2 scavenger concentrate was found to be significantly more oxidized than the Pb in the bulk PbS-CuFeS2 rougher concentrate. ESCA was found to be most useful for investigating the actions of modifiers rather than collectors due to the large amounts of sulfur and background carbon already present on the mineral surfaces. After calibration for the particular chemical system of interest, ESCA can yield semi-quantitative analyses of the oxidation states of many elements (except hydrogen, and helium) present in the outer 10 to 25 A of a sulfide mineral surface.

Jan 1, 1975

By E. A. Sondreal

Requirements of flue gas desulfurization (FGD) for Eastern and Western U.S. coals will not be the same because of differences in coal sulfur content, ash analysis, and beating value. The effects of these differences and of limited availability of water in the West are the subjects of this paper. Eastern and Central bituminous coals are generally high in sulfur and require removal efficiencies in the range of 70 to 90 percent to meet the Federal emission standard of 1.2 lb SO2/MMBtu. Ash in Eastern coals is low in alkali content and is relatively insoluble in scrubber solutions. High sulfur content and market availability make salable product methods more attractive in the fast and Central United States than in the West. Western subbituminous coals and lignites are generally low in sulfur content, however, only a few deposits could reliably meet the Federal emission standard without FGD, Required removal efficiencies generally fall in the range of 0 to 60 percent to meet the 1.2 lb SO2/MMBtu limit. If the standard were raised to 2 lb S02/MMBtu, approximately two-thirds of Western coals could be burned without FGD. Some Western coals contain ash high in alkali, some of which is soluble in scrubber solutions. This complicates scrubber chemistry, but it also provides the meant for displacing some or all of the limestone requirements when only moderate S02 removal is required. Dry areas in the West would benefit from full commercial developement of dry processes of FGD.

Jan 1, 1974

By Zhe Wang, Tichang Sun, Yongqiang Zhao, Zhengyao Li

Coal-based reduction followed by magnetic separation is a promising technology for processing refractory iron ores. Analysis of the size distribution of metallic iron particles is an effective approach for exploring the mechanisms of coal-based reduction. As metallic iron particles exhibit very complex shapes compared with nature ores, approaches for measuring and characterising metallic iron particles still remain unclear. In this study, the size of metallic iron particles was measured and characterised using manual point-counting by optical microscopy technics and image analysis. The effects of CaF2 as an additive on behaviour of the particle size distribution (i.e. mean size and cumulative frequency distribution) were also determined. Results indicate that CaF2 had a significant effect on the growth of metallic iron particles. When the CaF2 dosage increased from 0 to 8%, the mean size according to the area method increased from 9.03 to 16.28 μm, while the promotion effect gradually weakened and generated many fine metallic iron particles when the CaF2 dosage exceeded 8%. An increase in CaF2 dosage also led to cumulative distribution curves gradually shifting to the right mainly because F− can break the crystal structure of each phase during the carbothermic reduction of titanomagnetite and reduce the stability of the lattice structure, thus reducing the melting point and accelerating the growth of metallic iron grains. Compared to different measuring methods, the area method is a more suitable approach for measuring and characterising the size of metallic iron particles.

Sep 18, 2020

By C. B. Manula

This paper presents the results of an application of the PSU/USBM Open Pit Materials Handling Simulator (1) to a large stripping mine in the Southwestern Coalfield. The specific objective of the study was to demonstrate the application of the simulator to a complex multi-pit operation, with emphasis on simulating short term and long term production plans recommended for the mine by Theodore Barry Associates (2). Mine Description The mine is located in the Southwestern Coalfield, which encompasses parts of the states of Utah, Arizona and New Mexico. The lease area presently covers 121500 x 103 m2 (30000 acres) in a strip 37.007 x 103 m (23 miles) from north to south and up to 1609 m (1 mile) in width, located at an elevation above 1525 m (5000 ft). Three gently dipping coal seams are present, of which the upper seam (#3) averages 0-5.5 m (0-18 ft); the intermediate seam (#2) averages 0-1.2 m (0-4 ft); and the lower seam (#1) averages 0-2.4 m (0-8 ft). Overburden is mixed sand, gravel, calcareous clay, caliche and sandstone, with calcareous shale and sandstone burden between seams. Where the seams are covered by less than 6.1 m (20 ft) of overburden, they are generally weathered and oxidized and are not extracted. Stripping ratios have ranged from 3.5 to 6.0 with an average of 5.4. All future plans were based on a stripping ratio of 5.3.

Jan 1, 1979

By R. E. Moore

Refractories are unique ceramic materials, which are used in large quantities in steel making furnaces, metal smelting vessels, and glass melting tanks. They are required to possess high thermal shock properties and good slag corrosion resistance as well as creep resistance at high temperatures. Therefore, they are made from very refractory minerals such as lime, periclase, corundum, spinel, and zirconia. Slags are vitreous materials produced as a residue in steel refining processes. They cover a wide range of compositions and may contain pure oxides, silicates, and sulfides as well as fluoride phases depending on the melting and smelting processes. These minerals exhibit spectacular cathodoluminescence color under electron bombardment; therefore, cathodoluminescence (CL) microscopy is found to be a superior technique for the characterization of refractory corrosion by slags. Examples included in this study are (1) reaction of fluorine containing mold slags with ZrO2-C nozzle refractories promoting crystallization of the Cuspidine, Ca4Si2O7(F,OH)2, (2) corrosion of fusion cast refractories in TV panel glassmaking furnaces and formation of glass defects, and (3) reaction of spinel based castable refractories with copper smelting slags.

Jan 1, 2001

By Larissa Koroznikova, Steve Durkin, Bradley Drake, Michael Tuck

This paper presents the results from the investigation of the application of thermal fragmentation in Australian hard rock underground narrow-vein mining. Two geologically similar samples from an underground narrow-vein hard rock gold mine were collected to obtain a measure of the technology’s ability to recover ore by the creation of large thermal openings to assess the applicability of the thermal method. Particle size distribution showed a higher generation of fine product, − 2 mm, by thermal fragmentation compared with selective blasting by 31%. The Bond work index for thermal ore (12.62 kWh/t) is half to that of the blasted ore value (25.32 kWh/t). The average grindability obtained for the thermal ore sample was greater than the blasted sample by a factor of 2.44, a higher value indicating a decrease in the energy required to grind. The thermal fragmentation method generates product with higher dissolution of gold in cyanide, by 14% for the − 9.5 + 2 mm size fraction samples. Additionally, the thermal fragmentation results in higher production of − 9.5 + 2 mm material by 15 % compared with selective blasting.

By Larissa Koroznikova, Steve Durkin, Bradley Drake, Michael Tuck

This paper presents the results from the investigation of the application of thermal fragmentation in Australian hard rock underground narrow-vein mining. Two geologically similar samples from an underground narrow-vein hard rock gold mine were collected to obtain a measure of the technology’s ability to recover ore by the creation of large thermal openings to assess the applicability of the thermal method. Particle size distribution showed a higher generation of fine product, − 2 mm, by thermal fragmentation compared with selective blasting by 31%. The Bond work index for thermal ore (12.62 kWh/t) is half to that of the blasted ore value (25.32 kWh/t). The average grindability obtained for the thermal ore sample was greater than the blasted sample by a factor of 2.44, a higher value indicating a decrease in the energy required to grind. The thermal fragmentation method generates product with higher dissolution of gold in cyanide, by 14% for the − 9.5 + 2 mm size fraction samples. Additionally, the thermal fragmentation results in higher production of − 9.5 + 2 mm material by 15 % compared with selective blasting.

By Felicity Lloyd, Stuart Kearns, Roger McLimans

The metamorphic terrane of southwestern India is a geological environment containing ilmenite source-rocks, transport drainage systems, and resultant beach sand deposits that contain altered ilmenites greater than 60wt% TiO2. As such, this environment provides a geological laboratory, from source to deposit, for the investigation of ilmenite origin, alteration, and geochemical character. Ilmenite samples from potential source rocks, river sands, and beach sands all show degrees of alteration and a variety of alteration textures (iron leaching) producing leucoxene (here defined as >70 <90wt% TiO2) and progressing to rutile (here defined as >90wt% TiO2). Distinct alteration textures are specific to different source rocks and are used together with trace element geochemistry as provenance criteria. Ilmenites are classified on the basis of their trace element content. In India, the ilmenites are classified principally according to the Mg, Nb, and Mn content and this signature defines potential source rocks, even where the ilmenite is altered to a TiO2 content of 70wt%. The trace element data may fingerprint source rocks whose ilmenite is more prone to iron leaching and that criterion has application in exploration for higher-grade ilmenites.

Jan 1, 2005

By Tim Q. Haldane

The ability to efficiently process lowgrade ores has allowed the Gold Fields Mesquite Mine in Imperial County, CA to expand from a 2.1 Mt/a (2.3 million stpy) rate in 1986 to its present 7.3 Mt/ a (8 million stpy) processing rate. Increased tonnage demands led to the 1989 construction and startup of a dump leach pad to supplement the existing heap leach operation. This resulted in an excellent opportunity to compare the two processes at the same operation. Additional operating costs associated with the crushed ore heaps are justified through enhanced recoveries, even at very low ore grades. Gold Fields&apos; Mesquite Mine is a gold heap leach facility located about 55 km (35 miles) east of Brawley in southeastern California. Five open-pit mines will be developed over the projected life of the property, covering a total area extending to a maximum of 5.5 km (3.4 miles) to the east and west, and 2.4 kin (1.5 miles) to the north and south. Mesquite will process 7.3 Mt (8 million st) of ore and produce more than 6.2 t (200 000 oz) of gold in 1990.

Jan 1, 1990

By David L. Giles

The Lime Creek* ore body in northwestern British Columbia is one of the few commercial primary stockwork-type molybdenite deposits in North America. Others include the Climax, Urad-Henderson, Questa, and Endako ore bodies. They are mined on a low grade-high tonnage basis, and are open pit operations except for Climax and Urad-Henderson. Much recent geochemical research on both porphyry copper and stockwork MoS2 deposits has been concerned with dating of micas related to the mineralization and associated igneous rocks. The results appear to show that mineralization and the predominant magmatic events of the deposit are indistinguishable in age (1-5), except where dating has been in sufficient detail to resolve the analytical overlap (6). At Lime Creek, geologic information shows that the Main granodiorite, the major intrusive and dominant host rock for MoS2 mineralization, was emplaced and had solidified sometime prior to the introduction of MoS2. The first MoS2 episode is intimately related to localized bodies of kalialaskite which clearly intrude the older stock. K-Ar dating was undertaken to clarify the age relations between Lime Creek plutonism and the apparently younger hydrothermal event that began with kalialaskite.

Jan 1, 1975