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At long last, mining is on the rebound in Minnesota?s Iron Range and the excitement is starting to show. The SME Minnesota Section?s annual meeting was once again held in the heart of Iron Range country, at the Duluth Entertainment and Conference Center on the Duluth waterfront. The conference boasted a record attendance of 475 people and its largest-ever trade show. Appearances by Governor Mark Dayton?s new Iron Range Resources & Rehabilitation Board (IRRRB) appointee, Tony Sertich, as well as a local Fox news crew (see clip on SME website [link: http://fox21online.com/news/duluth-mining-conference-breeds-optimism-tech-innovation]) made clear that a lot of eyes [ ] are on the industry as it dusts itself off from the 2008-2009 recession. While the early years of the 21st century were very good to the Iron Range, the global drop in commodities prices and production left many companies reeling and brought back bad memories of the collapse of the industry in the 1980s. However, two years of solid growth and a rebound to above pre-2008 production levels have let the Minnesota mining industry to relax a little and talk seriously about long-term growth and stability.

Jan 1, 2011

By John O. Marsden

Technology development has played a crucial role in the minerals industry throughout history. The development of new technology allows mankind to produce metals and minerals at progressively lower cost of production in real terms, and therefore at progressively lower prices, improving their availability, accessibility and utilization worldwide. However, the developers of such technology are not guaranteed to reap the benefits from this effort: There is an expectation that technology developers will gain an advantage over their competitors. Is this a short-term benefit that results from a temporary cost or efficiency improvement, or is it a sustainable longer term "edge" that prevails even after metal or mineral price has been eroded by the implementation of a major step change technology? This issue is examined by reference to several case study examples in the copper industry. BACKGROUND The development and adoption of new technology has played a crucial role in the commodity minerals industry throughout history. As new, cost-efficient technologies are commercialized, the cost of production decreases, and this enables lower grade ore to be processed profitably. This in turn increases the availability and supply of the metal or mineral of interest, and ultimately (in a free market environment where the supply- demand balance determines price) inevitably decreases the metal or mineral price. This leads to the question: Why should mining companies invest in (new) technology development if the result is a decrease in the product price? The answer is to achieve competitive advantage, where the application of new technology enables one or more

Jan 1, 2004

By L. G. Hendrickson

Direct-reduction processes for converting iron ores to metallic iron in the solid state have been available for some time; and whenever scrap becomes expensive, there is a new wave of interest in these processes. It is well established that direct reduction, coupled with electric-furnace steelmaking, is a technically viable method for making steel and in some circumstances is economically competitive with the conventional blast-furnace--basic-oxygen-process (BOP) route to steel. This raises a number of interesting questions, several of which could be of great interest to the coal and ore mining industries. For example, what are the quality requirements of the raw materials for direct-reduction--electric-furnace steelmaking? Would they be different from the present requirements for blast-furnace--BOP steelmaking? Other questions relate to how much steel will be made by the direct-reduction route in the future. The quality questions can be discussed with a fair degree of certainty, but a prediction of the amount of steel that will be produced by the direct-reduction--electric-furnace route is beyond the scope of this paper. However, an attempt will be made to identify some of the factors that will influence whether there is a swing to direct reduction and the rate at which it may occur.

Jan 1, 1978

By M. Fig, J. Brune, C. Strebinger, G. Bogin

"A fundamental understanding of flame propagation characteristics through and around obstacles is needed to accurately model methane driven longwall coal mine explosions originating or propagating in the gob. Experimental investigations of methane flames in horizontal cylindrical reactors with simulated gob (i.e. rock piles) were carried out alongside coupled Computational Fluid Dynamics (CFD) and combustion simulations. Stoichiometric methane-air mixtures were ignited in semi-open reactor vessels of 5cm, 9.5cm and 71cm diameter, all with a fixed length to diameter (L/D) ratio of 8.6. This was done both with empty reactors and also with a rock pile placed at the open end of the reactor. The rock pile length to reactor length ratio was fixed at 0.3, and the rock pile height to reactor diameter ratio was fixed at 0.33 for all reactors. The smaller two reactor experiments were modeled with ANSYS Fluent in 2D. Experimental results indicate that for this geometry a similar acceleration mode occurs across scales: that the flame speeds up an average of 40% as it passes over a rock pile with this profile. The model is able to capture several important features of the experimental results, including the significant increase in velocity, the speedup ahead of the rock pile, and the leveling off of the empty tube flame front propagation velocity. INTRODUCTION Explosions in underground coal mines are among the largest industrial explosions, known to result in the rapid combustion of 20m3 of fuel gas or more [1,2] Coal beds hold methane gas under pressure, and when the pressure is relieved through mining activity some of this methane is released. The methane then mixes with ventilation air and, if not sufficiently diluted, may form a combustible mixture, which may result in an explosion. Several large coal mine explosions have occurred around the world recently. These include the 2014 Soma Mine disaster in Turkey that killed 301 people [3], and the 2009 Heilongjiang Mine explosion in China that killed 108 [4]. Other recent mine explosions, including the 2010 disaster at the Upper Big Branch mine that caused 29 fatalities [5], have demonstrated that explosive gases can accumulate and ignite within and around the gob area of a longwall coal mine and then expand into the active mining face and nearby areas, endangering workers and equipment. If enough combustible gas is involved, the initial flame can accelerate, eventually transitioning from deflagration to detonation [6]. Researchers are developing a fundamental understanding of the evolution of the explosion process from the laminar kernel to the fully turbulent regime, and its propagation through obstacles such as those found in the gob. Researchers also studied the initial development of methane flames and the potential for the development of a detonation."

Jan 1, 2018

By Kenneth Deaton

"A packaged cooling system is being developed for refuge alternatives (RAs) that will meet U.S. Mine Safety and Health Administration (MSHA) qualification guidelines for deployment in coal mines. This system will allow full occupancy ratings of deployed refuge alternatives to be maintained by keeping the apparent temperature inside the RA from exceeding 35° C (95° F).Research investigations sponsored by the National Institute for Occupational Safety and Health (NIOSH) have shown that heat buildup caused by occupants in mobile RAs will result in apparent temperatures that exceed the 35° C (95°F) limit established in 30 CFR 7.504.Figure 1 shows the temperature rise in an inflatable RA having an occupancy rating of 23 people at an 27° C (81°F) mine air temperature. This plot shows the need for either heat mitigation or occupancy derating in warmer mines.The Refuge Alternative Environmental Control System (RAECS) will be designed to provide enough heat mitigation to eliminate occupancy derating due to heat buildup over the 96-hour refuge period.This article describes testing of a prototype cooling system that uses proven vapor compression technology powered by batteries to keep the RA interior below the 35° C (95° F) limit for a minimum of 96 hours. Testing of this prototype cooling system was conducted in December of 2015 and January of 2016 at the NIOSH test mine in Bruceton, PA. December testing was conducted at the prevailing mine ambient temperature — approximately 15.5° C (60° F). The January testing was done with the mine ambient temperature in the immediate vicinity of the RA artificially elevated to 29° C (85° F). Realistic heat gain from RA occupants was provided by human simulators developed by NIOSH. These simulators add sensible heat corresponding to human metabolic processes and latent heat generated by respiration and perspiration. Heat generated by CO2 scrubbers was also added. Results of cooling system performance using these simulated loads at the two ambient conditions are described. A comparison of the apparent temperature in the RA using two different control techniques is also presented. This work documents the ability of the cooling system to meet the established apparent temperature limit at the full occupancy rating of a six person RA. A new cooling system intended for use with existing RA deployments and having greater cooling capacity is currently in development and will be described.Expendable desiccant modules were also used to provide supplemental water vapor removal and their role in mitigating cooling load is addressed."

Dec 1, 2016

By John S. Brock

During 1964 and 1965 a mineral exploration program was carried out over an area of approximately 250 square miles, located in the Anvil-Vangorda Creek area of east central Yukon, 125 miles northwest of Whitehorse. The Vangorda deposit, a massive lead-zinc sulphide body discovered in 1953, was centred in the area proposed for exploration, a northwest trending belt located between the southwestern flank of the Anvil Range and Pelly River. Exploration for base metals in the remote Anvil area had previously been restricted by poor metal markets in the late 1950's. Regional geologic information was also limited except for publication of a scale 1 inch to 4 mile map by the Geological Survey of Canada in 1961. To effectively explore this area, a combination of geophysical and geochemical methods were essential due to extensive overburden cover varying in depth from a few feet to over 300 feet. (Figure (i) Key Map) Dynasty Explorations initiated the first comprehensive regional exploration program in the Anvil area, utilizing saturation prospecting methods employing geologic, geochemical and geophysical methods. The program involved an approach demanding continual modification of technical and physical logistics. After a total of 12 months of field work involving an expenditure of approximately $450,00, massive sulphides were discovered which subsequently proved to be an economic orebody. Thirteen properties had been acquired and explored. Ten separate geophysical anomalies had been outlined by a combination of magnetic, electric and gravimetric survey techniques of which five were tested by rotary drilling and two by diamond core drilling. The discovery of the Faro deposit was a direct result of this program.

Jan 1, 1971

By S. Gaillard, E. Cauda

"Diesel particulate matter (DPM) is an occupational health hazard in underground mines. It generally occurs in the submicrometer size range and is often present in the mine atmosphere with significant concentrations of dust particles that tend to occur in the supramicrometer size range. As dust can interfere with analytical methods to measure DPM, it is often removed from a sample stream using an impactor-type size selector such as the DPM impactor (DPMI). Because the DPMI physically removes oversized particles from the stream, its performance may be gradually reduced with aging. Sharp-cut cyclones (SCCs) are an alternative size selector for DPM sampling applications, with a major advantage that, by design, they should not be susceptible to rapid aging. This paper presents the results of a field study designed to compare the performance of aged versus new/clean DPMIs and SCCs in an underground mine. DPMI aging resulted in clogging of the device and, eventually, a reduction of its effective particle cut size, but when sample flow rate was maintained, DPM sample mass collection was not affected until significant aging had occurred. Under the conditions of this study, the effects of SCC aging were observed to be minimal at the end of the study period. IntroductionSubmicrometer-sized particles are increasingly recognized as significant respiratory health hazards (Cantrell and Watts, 1997; Kenny, Gussman and Meyer, 2000; Ristovski et al., 2012). Diesel particulate matter (DPM) represents a major source of submicrometer particles in both public and occupational environments (Kittelson, 1998; Abdul-Khalek et al., 1998). Relative to other occupational groups, underground miners can have some of the highest DPM exposures due to their work in confined spaces where large diesel equipment is used (U.S. Environmental Protection Agency, 2002; Grau et al., 2004). DPM largely consists of solid elemental carbon (EC), commonly known as soot, and organic carbon (OC) that may be sorbed to EC particles (Kittleson, 1998; Abdul-Khalek et al., 1998). EC and OC can be measured by thermal-optical methods such as the U.S. National Institute for Occupational Safety and Health (NIOSH) 5040 standard method (Birch, 2016), and their sum is referred to as total carbon (TC). While the complex nature of DPM does not allow for its direct measurement, both TC and EC have been accepted as suitable surrogates for monitoring occupational exposures to DPM (Noll et al., 2007; Birch, 2016)."

Jan 8, 2018

By Dennis S. Kostick

Soda ash is the common name for sodium carbonate (Na2CO3), an alkali compound that is the 11th largest inorganic chemical in terms of production of all domestic inorganic and organic chemicals, excluding petrochemical feedstocks. Despite that most people have never heard of soda ash, it is an important industrial compound used to manufacture glass, chemicals, soaps and detergents, pulp and paper, and many other familiar consumer products. Natural alkalis have been used by mankind for thousands of years; however, their industrial manufacture dates back to only the latter half of the 18th century. Natural deposits of sodium carbonate have been known as early as about 3500 BC, when the Egyptians used natural soda ash in making glass. They also mixed lime and soda ash to make sodium hydroxide (caustic soda) that was combined with silicate minerals found in the Sinai desert. This made a soluble silica, which when added to aluminum-rich silt from the Nile River, produced a silica- aluminate cement mortar with excellent bonding properties for construction. The Romans in the first century AD also used natural soda ash in glass manufacture but expanded its use medically for the treatment of colic pains and skin eruptions, and in the making of bread. Elsewhere, people used the ashes of wood to obtain their source of alkali. People learned over time that different types of wood yielded various ashes with different properties; therefore, various plants were burned specifically for their ashes. Ash from plants grown in salt-bearing soils (such as saltwort) and from kelp and other seaweeds, especially Spanish barilla, were so different from ashes obtained from other vegetation that it became known as soda ash (due to its sodium content) versus pot ash, a potassium-based alkali ash. About 13 t of barilla ashes produced 1 t of sodium carbonate and 14 kg of iodine as a byproduct. The difference between these two ashes was relatively obscure until Duhamel Dumonceau made the distinction clear in 1736. The word soda ash developed from common usage and is perhaps more well known today than its synonym sodium carbonate. One of the primary ores of soda ash is trona, a sodium carbonate-bearing mineral that's name is traced back to Arabic origin. Trona also is known internationally by other names such as urao (Venezuela), kaum (Nigeria), natron (from Greek nitron and Latin natrium), and szekso (Hungary). The beginning of the Industrial Revolution in Western Europe in the late 18th century soon put a strain on the availability of raw materials to meet consumer demands. One of these scarce materials was soda ash. Because of the Seven Years War with England and the Napoleonic wars with other parts of Europe, France could not obtain sufficient quantities of Spanish barilla or other supplies of vegetable alkali to meet the growing demand. Efforts were needed to synthesize soda ash. In 1775, the French Academy of Sciences offered a large prize of 2,400 livres to someone who could find an inexpensive method to make soda ash. In September 1791 at St. Denis, Nicolas Leblanc (1742- 1806), a French chemist, developed such a technique using salt, sulfuric acid, coal, and limestone. The French Revolution interfered with its development, and his patent and factory were confiscated with Leblanc receiving only token compensation. Napoleon returned his factory to him; however, Leblanc was not able to raise enough capital to reopen it, and he committed suicide in 1806. A small, but not particularly successful, Leblanc plant was established in England in 1814. It was not until 1823 when the process first became commercially successful in Liverpool, England. The process was introduced in Germany in 1843 and in Austria in 1851 (Harness and Coons, 1942). Soda ash production by the Leblanc process reached its peak of about 599 500 t in 1880, after which it began to decline as the Solvay process became more popular. The Leblanc process was used to a limited extent in Europe during World War I but had disappeared by World War II. The Solvay process, also known as the ammonia-soda process, was developed by Alfred and Ernest (1 838-1922) Solvay in 1861 based on a concept by Fresnel that had been known since 1811. For the next 50 years, the implementation of the idea evaded industrial chemists because no large-scale and economic means could be found to commercialize the concept. Although Ernest Solvay was unaware of the existance of an ammonia-soda concept, he solved the problems by utilizing carbonating towers. The Solvay process produced soda ash from salt, limestone, and coke, with ammonia as a catalyst. With a capital of 136,000 francs, the first plant was built by the Solvay brothers at Couillet, Belgium, in 1863 with production commencing in 1865. Synthetic soda ash production amounted to 1.5 tpd in 1866, but reached 10 tpd by 1872. They patented their use of carbonating towers in 1872 that had made ammonia-soda manufacturing a successful continuous process. Their second plant was built in 1872 at Dombasle, France. In 1874, the first Solvay plant in England was built at Northwich by Ludwig Mond, the namesake of Brunner Mond and Co. (formerly Imperial Chemical Industries), the company that currently operates the two English Solvay plants. In the United States, William B. Cogswell in February 1879 heard a presentation on the Solvay process and sailed to Europe to meet with the Solvay brothers to seek their support for using their process in New York. At first, the brothers were not interested; however, Mr. Cogswell was persistent and ultimately gained their support. The Solvay Rocess Co. was formed Sep. 2 1, 1881, and construction began immediately on the first Solvay plant at Geddes, near Syracuse, NY. The plant came onstream Jan. 10, 1884, and produced 11 180 t in its first year of operation. In 1910, rotary calciners were installed that increased capacity to 1 000 tpd. By 1930, plant capacity was up to 2 400 tpd. The facility remained in continuous operation for more than 100 years. By 1939. 10 Solvay soda ash plants were in operation in 6 States throughout the nation. The Syracuse plant was officially closed Jan. 6, 1986, with total shutdown completed by Feb. 1986. Ironically, this facility was the first Solvay plant as well as the last. Other than the first Solvay plant beginning in 1884, the majority of US soda ash supplies during the 19th century came from imports. The remainder of the US supply

Jan 1, 1994

By Franziska Wolf, Rainer Ellmies, Helmut Mischo

"Mining is an important part of the economy of Namibia. In 2016, 11.1 percent of the GDP was the result of mining activities with 22 active mines (The Chamber of Mines of Namibia, 2016). Only one of them consists of an underground mining operation.The global annual production of fluorspar is approximately 5.4 to 6.3 Mt (6 to 7 million st) (U.S. Geological Survey National Minerals Information Center, 2017). Okorusu has produced on average about 45 kt/a (50,000 stpy) in recent years (U.S. Geological Survey National Minerals Information Center, 2015).The Okorusu Mine is Namibia’s only fluorspar mine. Fluorspar was mined in an openpit mine with four individual pits (A-D) since 1980. In 2014, the mine closed due to the increased stripping ratio and beneficiation problems. The mine assets were bought by Gecko Namibia. Currently, Gecko uses parts of the processing plant for beneficiation of graphite from a neighboring mine. Figure 1 shows a panoramic view with the four pits and the mine village.The intent is to develop a concept for the further underground development of the mine. There are still about 6.3 Mt (7 million st) of measured resources left in the deposit, with an average grade of 27.5 percent CaF2. This study focuses on the underground mine design. The above-ground plant and facilities are considered as remaining unchanged.For solving the task to design the mine, a site visit for data collecting was conducted. Resource estimations were calculated based on existing drill data, and consequently, block models were created. The development of the mine design included the selection of the most suitable mining method, mining technology and mine organization. Moreover, some economic considerations are pointed out, followed by a profitability assessment."

Jan 2, 2018

By A. Redfern, B. G. D. Smart

The ultimate objective of the development work presented in the paper is to devise an appropriate method for relating powered support specification to geological conditions and mining practice, thus enabling the longwall method of coalmining to be successfully implemented throughout the varied coalfields of the world. The paper begins with a review of various methods previously used to determine support rating, each method being analysed with regard to its source, the logic and theory which constitute the method, and subsequent recommendations. An alternative approach is then proposed, the Powered supports being considered to be one of three foundations, sharing load with coal ahead of the faceline which acts as another foundation, and the waste behind the supports which acts as the remaining foundation. The load/deflection characteristics of the coal and waste, which in turn are related to geological conditions and mining practice, are shown to affect the load transfer on to and hence the specification of the powered support. In particular the characteristic of the waste foundation is shown to be affected by the caving mechanism, an alternative form to that mechanism accepted for British conditions being proposed and designated "parting-plane-controlled" caving. A finite element solution for a beam on elastic foundations was used to translate the above concepts into numerical results, these results being compared with data from Indian and Chinese operating conditions. The Indian case study examines the effect of using a conventional chock type of support in a one-web back mode when mining towards a roof break generated ahead of the face, while the Chinese case study compares measured subsidence over a longwall with "blocky" roof conditions with the model results. The comparisons are encouraging, suggesting that the approach used is worthy of further development.

Jan 1, 1986

By Leonardo Rosas Sánchez, Darío Ángel Bulla

"The two track road sector between Cisneros-Loboguerrero (having a length of 14 km and 11 short unidirectional tunnels) is a new highway still on construction located along the existing Highway Buga – Buenaventura (Colombia). Due to the steep topography, difficult geological/geotechnical conditions, the traditional portal construction approach was impossible to be implemented in eleven (11) of the twenty two (22) portals. In this specific project, the skewed portal approach was developed as the optimal and more effective solution. The construction time and costs of portals were reduced in 21 months and 75%, respectively. At the same time, the natural equilibrium of the slopes was maintained, thus, facilitating adequate safety factors along the useful life of the project. This document pretends to show a detailed design experience (and the construction of the entry portal of tunnel 11 (left)). INTRODUCTION The Cisneros-Loboguerrero project is a 14 km length dual lane highway, connecting productive zones with the Pacific Ocean along the current Bogota-Buenaventura highway as shown in Figure 1. The project is located at the northern side of the Dagua River Valley. The preliminary design suggested constructing portals under challenging topographical conditions, i.e., slope cuts having heights between 50 to 100 m (some having slopes > 100%) requiring complex developments and having very high risks.The entry portal of tunnel 11 (left) was the first portal successfully built by implementing the skewed portal approach. Later, this approach was used as a model for the construction of the other ten (10) portal having similar topographic and geotechnical conditions. The development of this new alternative provided a considerable reduction on the construction time of portals, thus relieving a critical path in this project."

Jan 1, 2016

By R. Stefanko

Rock bolting as a method of support continues to increase with applications in many other industries in addition to mining. Nevertheless, with nearly 55,000,000 roof bolts installed in coal mines alone last year, this remains as the single greatest use. While bolts have frequently supported ground where conventional timbering could not, there are relatively few design criteria; and trial-and-error procedures prevail. Furthermore, development of suitable instrumentation that is simple to install and readout, sensitive, durable, reliable, safe and economical in evaluating the effectiveness of a bolt over long periods of time lags behind. Therefore, the pull test continues to be the most popular method of evaluating the applicability of a certain type of roof bolt under specific installation conditions. At Penn State in the Department of Mining, research has been conducted for a number of years to measure bleedoff in carefully controlled laboratory experiments as well as in underground investigations.1,2,3,4 Unfortunately, most of the instrumentation developed has been primarily suitable only for research purposes, not possessing all of the aforementioned characteristics desirable for routine underground use. Other groups also have met with restricted success. Therefore, while relatively crude, the torque wrench continues to remain as the most widely used load measuring device. While both field and laboratory tests continue to be conducted, analytical analyses are attempted to discover the more important design parameters in order that more efficient anchorage might be devised.

Jan 1, 1969

By S. R. Dindarloo

"Truck-shovel systems are the dominant material loading and haulage machinery in open pit mining operations. Optimal selection, sizing, and allocation of this capital intensive equipment is highly desirable for both achieving production targets and improving the mine’s economics. In this study, discrete event simulation technique was applied for modeling material transportation in Golegohar open pit iron ore mine in Iran. Direct observation of the material loading and haulage for duration of three months resulted in statistical modeling of the operation in the form of probability distribution functions. These probability models were used as the inputs of a stochastic simulation model constructed in GPSS/H simulation language. The model was validated through comparison with the actual operation and was used to test different what-if scenarios and sensitivity analysis of the current system. Some modifications in the number of trucks, shovels, and dispatching strategies were proposed. Simulation resulted in considerable improvements in the mine’s production and economics.INTRODUCTION There are three different mechanisms of discrete, continues, and hybrid material transportation in open mines, including but not limited to: i) in-pit crusher and conveyor belts (hybrid), ii) slurry piping (continues) and iii) truck-shovel system (discrete). Although, each mechanism has its advantages, the truck-shovel system is the dominant method of material loading and handling in open pit mines owing to its high production rate, excellent flexibility, relatively low operating and capital costs, and good maintainability. General objectives of optimal equipment selection include: i) meeting the long and short term requirements of production rates, ii) human & equipment safety, iii) environmental protection, and iv) economic operations (Figure 1).The two most important decision factors on a truck-shovel system selection and sizing are the equipment geometry and size. Geometry (equipment width, weight, turning radius, swing angle, etc.) is mostly controlled by mine’s designs and layouts, as well, as operational constraints. After selection of a favorable geometry based on the constraints; the next step is to select the equipment manufacturer. Once the geometry and manufacturers are selected; the next step is to decide on models (e.g. Bucket size) and required number of each unit"

Jan 1, 2015

By M. C. Roberts

The consumption of industrial minerals, like most other commodities produced from the earth, depends on the demand for the goods and services that use these materials. Minerals are not generally used directly by final consumers (table salt is a notable exception) but instead are used to either make products that are then purchased by customers, or the minerals are used to make industrial products that eventually contribute towards producing other goods and services. Therefore the demand for industrial minerals in most uses is derived from the ultimate demand for goods and services by consumers. The problem for producers of industrial minerals is that the demand for their mineral product fluctuates greatly in response to the changes in the production of goods and services over the course of the business cycle. In this respect, the producers of industrial mineral are innocent victims, subject to market fluctuations outside of their control. Because the demand for most minerals depends on the demand for the product and because minerals typically make up a minor portion of the costs of producing the product, changes in the price of the mineral often do not influence demand for it to a significant degree in the short run. This is described as a very low price elasticity of demand, as shown by the steep slope of the hypothetical demand curve in Figure 1. This demand curve shows that changing the price of the mineral does not alter the quantity demanded very much, but shifts in the demand curve will be the important determinant of the quantity of the mine.ra1 that is sold. The shifts are caused by the changing demand for the products using the mineral over the course of the business cycle.

Jan 1, 1994

By N. Bat, N. Sarantsatsral

Blasthole sampling practices were investigated at the Erdenet copper and molybdenum mine in Mongolia to address grade reconciliation issues. The goal of the study was to determine if the particle size distribution (PSD) of blasthole cuttings was accurately reflected in the samples. The study additionally examined if the measured grade was related to the particle size of samples. Using a sector sampler specifically designed to collect samples for the study, six large samples were collected from three blocks following a specialized protocol. Each sample was split into nine size fractions, ranging from larger than 12 mm to smaller than 63 µm. Copper and molybdenum grades were determined for each of the size fractions. For comparison, nine samples were collected from the same blocks following the standard mine sampling protocol. These samples were also split into the same nine size fractions. As with the other samples, grades were determined for each of the size fractions. The results showed that the PSD in the samples collected following the standard operating procedure varied significantly from sample to sample. This variation was much lower for the samples collected following the specialized protocol. Loss of fines was also indicated in the standard mine sampling process. These observations suggest that the standard sampling protocol did not consistently capture the PSD. The copper and molybdenum grades increased as particle size decreased, regardless of the sampling protocol used. This observation underscores the importance of the PSD of a sample being representative of the true PSD. Given the low number of samples in the study, it is not a strong conclusion that the standard sampling protocol captures the PSD inconsistently. However, it could be taken as a caution. On the other hand, the grade versus PSD relationship is more certain, given that it was observed regardless of the sampling method used.

Feb 1, 2017

By C. I. Wilmot

FMC's Paradise Peak Mine was discovered in July 1983. The deposit at discovery contained 11,340 ,000 tonnes (12,500,000 tons) of ore grading 3.71 glt (0.108 oz/ton) Au and 120 glt (3.5 oz/ton) Ag. A feasibility study was completed by Davy McKee in May 1984, with detailed engineering starting in June 1984. Construction of the facility started on January 2, 1985 with plant start-up taking place on April 14, 1986, two and one half months ahead of schedule and more than 10% under budget. This paper describes the status of the operation approximately 1-1/2 years after start-up including revisions and additions to equipment and process.

Jan 1, 1988

By Stacey Leichliter

The Cripple Creek and Victor (CC&V) Gold Mine (Cresson Project) (Fig. 1) is undergoing an expansion to extend production to the year 2025. This expansion involves building a high-grade ore mill, another valley leach facility (VLF) for heap leach operations and expanding the overburden storage areas. The current operating pits are progressing downward from the oxide ore into a more sulfide and telluride-rich orebody. There is still oxide ore present in the current pits and planned pits not yet mined. There is an increased need for two recovery processes for these two different types of ore. The key component to this expansion is the high-grade ore mill, which has gravity, flotation and carbon-in-pulp (CIP) circuits. The mill will be the main recovery process for the higher grade, more sulfide/telluride-rich ore. This ore type does not recover well on the heap leach pad due to its refractory nature. Geometallurgy is vital for ore characterization for the two recovery methods. Geometallurgy helps develop indices that are used to predict parameters that influence overall recovery and production, such as hardness, crushability, grindability, pH fluctuations, gravity (coarse) gold, flotability and cyanidability. Using geology and mineralogy along with other analytical data, geometallurgical models are constructed and applied to the resource block model for proper planning and extraction of the gold. Geometallurgy aims to analyze the variability in the different responses to the parameters to help reduce risk (costs) and optimize recovery (profit).

Jan 1, 2013

By William Gleason

"There are signs that the commodity downturn that has battered the mining industry for the past five years is beginning to ease up. As the dust begins to settle and mining companies begin to take stock of the battle, Newmont Mining Corp. will be one that is standing strong with just a few scrapes and bruises thanks in large part to the leadership of president and chief executive officer Gary Goldberg and his right hand man and chief operating officer, Chris Robison.As he closes in on retirement (for a second time) Robison, a third-generation miner from Nevada, took time to speak with Mining Engineering about a 33-year career in which, among other things, he is credited with not just helping Newmont survive the turbulent times but with steering the company to a safer, more productive and more profitable heading.“I think we did it better than anyone else,” Robison said when asked how the company fared during the past five years. “We didn’t talk about it a lot, we just put together a strategy and we delivered.”What Newmont, the world’s second-largest gold mining company by production, delivered since Robison took the position of chief operating officer in 2013 are improvements in costs, porduction, projects and safety.Operating under the mantra of “live within your means,” Robison was pulled out of retirement from Rio Tinto and into a challenging situation at Newmont. The price of gold was in a nose dive from a high of nearly $58/g ($1,800/oz) and heading to levels closer to $38.60/g ($1,200 oz).“Newmont is a big ship that can’t be turned, but has to be steered,” said Robison. “We recognized that we had to set a new course. The direction the ship was going was great for $1,600 to $1,800/oz gold but we were chasing ounces.”Like the rest of the gold mining sector before the falling gold prices, Newmont was focused on volume and was looking for gold wherever it could be found. The slogan at Newmont in 2011 was “7 million ounces a year by 2017.”When Robison came on board it was a different reality.“We had to begin focusing on value over volume as the cornerstone of Newmont going forward,” he said."

Aug 1, 2016

By Theodore H. Eyde

In 1971, the Minerals Division of The Superior Oil Company acquired exploration rights to an unpatented claim group in the Superior (Pioneer), Arizona mining district, lying west of the Concentrator fault. This major post-mineral fault displaces the Magma vein-fault, which is mined in the Magma Mine at Superior, Arizona. The Magma vein-fault and the enclosing section of pre-mineral rocks consisting of Paleozoic and younger Precambrian sediments and diabase, is overlain by a thick section of post-mineral rocks, consisting of the Gila conglomerate, the Apache Leap dacite, and the Whitetail conglomerate. Geologic information on the thickness and attitudes of the rocks obtained from previous diamond drilling indicated that the section of post-mineral rocks might be from 3,000 to over 4,010 feet thick in the target area. (Figure 1) The Magma vein-fault is a steeply dipping vein which has produced nearly a billion dollars of copper, zinc, silver, and gold. It has been mined continuously for nearly 10,000 feet along the strike and nearly 5,000, feet vertically down the dip. It ranges from less than a foot to over 50 feet wide and contains sulfide mineralization con¬sisting of pyrite, chalcopyrite, bornite, and chalcocite.

Jan 1, 1973

By J. B. Malcolm

The discovery of tungsten-bearing quartz outcroppings in Vance County, N. C., by the Hamme brothers in 1942, made international news in the mining industry and was, in fact, one of the major ore discoveries made in the U.S. during the last 25 years. Operations began at the Hamme mine in 1942, but after 16 years of successful operation, the mine was closed down in 1958 under adverse market conditions. By that time, it had produced nearly 20 million lbs of metallic tungsten. Because of the square-set timber mining method then in use, mine operating expenses were high, actually representing 78% of the total operating expenses at the property. In timber work alone, 160 men were employed. Approximately 500,000 bd ft of timber were placed monthly at a direct supply cost of $1.00 per ton of ore mined. Late in 1959, following a slightly improved position in the tungsten market, company management decided that, by changing the mining method, the operation could be economically feasible. The major premise in this decision was that a reduction of from 25 to 30% of the mining costs could be achieved by the conversion of the mining method from square-sets to horizontal cut and fill. Reopening of the mine began in February 1960, Full production has now been reached and overall mine productivity has been doubled.

Jan 1, 1962