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By Gary F. Rajala, Bruce R. Greenwood

INTRODUCTION The Empire Mine is an iron ore mining, concentrating and pelletizing facility operated by The Cleveland-Cliffs Iron Company in the Upper Peninsula of Michigan. Owners of the mine are Inland Steel, LTV Steel, Wheeling-Pittsburgh Steel and Cleveland-Cliff s. The orebody is a fine-grained, low grade iron formation with magnetite as the primary constituent. Also present are iron carbonates, iron silicates, chert, hematite, goethite and quartz. The original six concentrating lines were started in late 1963. Successive expansions of ten lines in 1967, five lines in 1974 and 3 lines in 1979 have resulted in Empire reaching a present annual capacity of 8.0 million long tons of pellets. The Empire flowsheet was developed over several years of laboratory bench testing, pilot plant testing and testing of a full-scale primary autogenous grinding circuit. Since the original flowsheet was established, modifications have been made based on pilot plant and full-scale plant tests. The present flowsheet for three sections of the concentrator consists of one stage of crushing, two stages of closed circuit autogenous grinding, two stages of magnetic separation, one stage of hydraulic concentration and two stages of flotation (rougher and scavenger). The flowsheet for the fourth section of the concentrator (Empire 4) is the same as the first three sections, except a crusher has been added to crush excess pebbles. The Empire 4 flowsheet appears in the at- tached figure. PRIMARY GRINDING CIRCUIT FLOWSHEET Empire has a total of 24 individual grinding lines. However, at the present time, Line 1 is not being used for processing crude ore. The primary mill on Line 1 is now grinding flux stone for fluxed pellet production and the secondary mill is being used as a ball mill to grind rougher flotation tailings prior to a scavenger flotation circuit.

Jan 1, 1992

By M. K. Mohanty

Due to inefficiencies of the flotation process, significant effort has been recently provided to develop gravity separators for treating ultrafine particles. As a result, several enhanced gravity concentrators have been developed and commercialized. The Altair Centrifugal Jig is an enhanced gravity separator that provides relatively efficient separations on +25 µm size fractions. An experimental program conducted on -600 µm coal found that the Altair Jig reduced the ash content of the 600 x 44 µm from about 30% to 10% with an 86% combustible recovery value. The pulse water pressure, feed volumetric rate and ragging volume were found to be the key operating parameters affecting the separation performances obtained from the process. An extremely low density cut point of 1.54 and an Ep value of 0.08 were indicative of the high process efficiency values achievable by the Altair jig.

Jan 1, 1998

By W. L. Wilson

This article could be entitled "The Rediscovery of the Windfall Mine," since it was originally discovered early in this century. The "Rediscovery" was made by personnel of Idaho Mining Corp. during the course of an investigation of the Windfall mine beginning in 1967. There had been historic production from the Windfall mine sporadically from 1908 until 1951 and there was present during much of this time a mill that vat leached crushed ore. Mining was underground to a depth of 91 m (300 ft). Prior to Idaho's activities, the mine had been inactive since the early 1950s. Idaho Mining Corp. was an "exploration company," privately owned and based in Reno, NV. The writer was at that time manager of exploration for Idaho Mining. The company held interests in the Cortez Gold mine, then being readied for production, and had conducted exploration for various mineral commodities in Nevada for several years. Idaho's attention was first directed to the Windfall mine in the Eureka District, Eureka County, Nevada (see Fig. 1, Nevada map) by a search of published geologic literature of the state of Nevada. An attempt was made to acquire a library consisting of all of the published geo-data for the state of Nevada as well as to obtain as much of the unpublished material as could be acquired. A study of these data, and in particular Tom Nolan's Professional Paper 406 (1962), indicated that the Windfall mine was anomalous for the Eureka District in that it contained deposits of disseminated gold. This source and other sources indicated that the Windfall had produced from underground operations approximately 59 kt (65,000 tons) grading 12.6 g/t (0.368 oz per ton) gold ore that was processed in a vat leaching operation and that the gold was "invisible" to the naked eye and could not be panned. It was ascertained that there were no active operations near the mine and a geologic reconnaissance was made and a few samples were taken to attempt to determine if the mineralization was indeed disseminated. The initial group of samples around the mine area averaged 1.25 ppm [11.5 g/t gold (0.036 oz per ton)] and the mineralization did appear to disseminate into the wallrock. The next step involved researching the ownership of property in the immediate area of the mine, and [ ] a property map was constructed that showed six or seven different ownerships of patented and unpatented claims, as well as some open ground, in the target area. Negotiations were commenced with the claim owners, ultimately resulting in the acquisition of all of the desired property, although some of

Jan 1, 1990

By R. M. G. Machunter

Computer models of metallurgical circuits are extensively utilised in design, and prediction of overall plant separation performance. As always, in the final optimised flowsheet design there is a compromise between the recovery of values and grade of the circuit output. This paper mathematically examines various circuit options for the generation of a heavy mineral concentrate from a generic mineral sands wet concentrator plant. Based on data derived from testwork, any particular mineral sand has a unique release curve describing the separation performance of the heavy mineral suite. Models are constructed that combine particular stage output streams as feed to other stages in various configurations. The ramifications of each option are discussed and reasons why one particular option is selected over the others examined.

Jan 1, 2005

By Alvaro Lucio

The continuous increase of the fuel oil price compelled CV3D to look for an alternative fuel. Charcoal was selected as the alternative energy source. This paper justifies its selection, describes charcoal properties, the methods for using charcoal in the pelletizing and shows the results of the in-plant tests.

Jan 1, 1982

By J. H. Wilhelm

Continuous thickeners can be sized either from previous experience, continuous pilot-scale test results, or from batch settling tests. Although it is a relatively simple process to size full-scale thickeners when previous experience or pilot-scale operating data are available, batch testing is often the only realistic method for sizing thickeners due to time restrictions, budget limitations and availability of sample material. Many authors have, therefore, suggested means of running batch tests and analyzing the resulting data. Fundamental thickening theory had its beginning with the work o£ Coe and Clevenger(1). In order to determine the size of the thickener settling area, they proposed that a series of batch settling tests be run at various initial concentrations. The solids handling capacity at each concentration can then be determined and the lowest capacity (maximum area requirements) used to size the thickener. Kynch(2) developed a mathematical analysis in which the relationship between solids concentration and settling rate can be obtained from a single batch settling curve. Talmage and Fitch(3), Yoshioka(4)(5) and Dick(6), have enlarged upon these works to give a basis for methods of sizing thickeners.

Jan 1, 1979

Mill #4 processes mildly refractory ore from Carlin Trend deposits. Diagnostic analysis of plant operating data was used to generate a mathematical model containing the key parameters influencing the gold recovery. The model was used to direct modifications to plant operating practice. The cyanide dosing strategy was changed to reduce preg-rob gold masses and cut reagent consumption A finer grind was achieved without capital investment. The density in CIL was lowered, and tighter control was exercised over plant throughput. These changes resulted in a recovery increase of at least 2%, worth $111,000/month at $300/oz, and concomitant reagent cost savings of $55,000/month.

Jan 1, 1999

By M. Schreiner, J. Brune, D. Theisen, C. S. -J. Tsai

This study reports that routine mining activities could produce a high number of nanometer sized particles which have not been well characterized and may represent an unacknowledged exposure present in the mining environment. A preliminary survey of the particle emission from the feed-leg drilling activity was conducted in the excavations of an experimental mine. The level of particulate exposure was monitored by real time direct reading instruments include a NanoScan scanning mobility particle sizer (measurement range 10-420 nm) and an optical particle sizer (measurement range 0.3-10 μm). Particulate morphological and structural examination was conducted through transmission and scanning electron microscopy and x-ray dispersive analysis of samples collected by a thermophoretic sampler, and a novel nanoparticle sampler. The real time instrument data revealed high concentrations (> 3.5 x 106 particles/cm3) of ultrafine/nanoparticles generated from the drilling activity. Analysis of particle sampler specimens with energy-dispersive x-ray spectroscopy showed a large amount of submicron silica, spherical primary particles and agglomerated soot particles rich in carbon. Exposure to particles in the nanometer size from various sources within the mining environment may be associated with the poorly understood rise in respiratory and systemic disease among miners. INTRODUCTION Exposures to mine dust have been measured and evaluated for decades. Exposures to aerosolized dust such as coal or silica particles can cause lung and other diseases (1-7). One way that The Mine Safety and Health Administration (MSHA) characterizes inhalation exposures within the mining environment is through measuring the respirable dust mass concentration within the breathing zone of workers (8). Respirable particulate matter (RPM) is of great concern due to its ability to deposit in the alveolar region of the lungs (9-10) where it can affect respiratory function. Interventions championed by MSHA have greatly reduced the prevalence of coal workers pneumoconiosis (CWP) and progressive massive fibrosis (PMF). Although great progress has been made, the prevalence of CWP and PMF appears to be trending upwards and the measured increase in prevalence is not elucidated in RPM measurements (11-12). Though the presence and risk associated with ultrafine particles such as emission from diesel engine within the mining environment has been previously established (13-14). There is suspicion within the mining industry that this resurgence of lung disease may be due to very fine particulate matter from various source that is not properly characterized by current sampling methods. Nanometer sized particles, in the range of ultrafine particles, fall within the RPM size range and have been found to deposit in all regions of the respiratory tract (15). Nanoparticles are commonly accepted as particles that are greater than 1 nm in two or three dimensions but smaller than 100 nm (16). Once in the lungs, nanoparticles can enter the blood stream (17) and selectively affect other target organs such as the heart, liver, bone marrow, lymph nodes, spleen, and brain (15,18-19). The size of nanoparticles has been shown to correlate with their translocation behavior on secondary target organs (20-21). There is strong evidence that the clearance mechanisms used to rid the lungs of particulate matter are not as effective on nanometer sized particles, leading to a greater fraction of never-cleared particles which may enhance disease development (20). Research has demonstrated that nanometer sized particles have unique properties (22) whose adverse health impact is greater than what has been found with micrometer sized particles of the same type (23-26). The large ratio of surface area to mass compared to larger particles is believed to make nanoparticles a greater hazard. Utilizing mass to measure these types of exposure will be very difficult to accurately characterize the quantity of

Jan 1, 2019

By M. Spangler

FirstMiss Gold installed a supervisory control system based on Pavilion Technology's Process Insights neural network software and Oil System's PI data historian. The primary goal of the system was to control the acid preconditioning circuit. However, our first successful control loop was on the limestone feed rate to the neutralization circuit. The information gained by modeling these circuits and the better control provided by the system has resulted in reagent savings of over $80,000 per month.

Jan 1, 1995

By Jerry W. Owens

Current steel consumption for grinding media, mill liners and rods in North America runs in excess of 400,000 tpy in the mineral processing industries. Steel consumption ranks as one of the major consumables along with energy in most operations with total annual industry expenditures in excess of $275 million. It is generally agreed that there are 3 main categories of wear responsible for this metal loss. These three main types can be loosely defined as follows; 1) Abrasion. The cutting, rubbing, scrapping and gouging of the metal surface by the ore with which it is in contact; 2) Impact. Spalling on both micro and macro scale, breakage, and deformation due to metal to metal contact; 3) Corrosion. The oxidation losses of the metal due to electrochemical interaction between the grinding media and the slurry

Jan 1, 1984

By Richard J. Stoehr

Man has mined in all his time on earth about 3 billion ounces of gold. About one-half of this has been mined in the past 35 years. This gold is roughly in 3 large holdings: one-third held as reserves in Central Banks; one-third held as personal reserves; and one-third is in jewelry or other fabricated products. The world per capita availability of mined gold is increasing and there are many factors and forces shaping gold's future. Currently, gold has a favorable exchange ratio and this is encouraging many new gold-mining developments. Production is increasing and new techniques are surfacing. The use of gold in the financial markets is increasing in some unique ways and gold is again fulfilling its role as a universal money, making gold's future predictable. Currently, man is mining gold at the rate of approximately 44 million ounces annually and is therefore adding to the total supply of gold approximately 1.5% of newly mined gold each year. This current production plays a small role in the pricing mechanisms since a very large part of the 3 billion ounces mined in all of history is available to the market in one form or another.

Jan 1, 1984

By LUIS ALBERTO TORRES-CRUZ

The assessment of liquefaction vulnerability is crucial to understanding the potential consequences of a tailings dam failure. The “Plewes method” is a relatively well-known and simple screening method to assess liquefaction potential based on results of cone penetration testing (CPT) which may be complemented with laboratory testing. The objective of the current work is to emphasise the screening nature of the method and its uncertainties when applied in tailings deposits. Specifically, the paper highlights the difficulties in assessing the intrinsic uncertainty of the method and the additional uncertainty that results from variations of the slope of the critical state line (λ10) along the depth of the CPT sounding. The results of the method are too uncertain for detailed characterisation of tailings even when a relatively low intrinsic uncertainty is assumed. However, the method characterises weaker soils with lower uncertainty (although still too high for detailed characterisation) than stronger soils. The uncertainty of the method is negatively affected by the relatively low λ10 values that are typical of nonplastic tailings. It is suggested that the results of the method should be presented in scatter plots in which the spread of the data is consistent with the uncertainty of the method.

Jan 28, 2021

By R. E. Blair

The mining and minerals industry has been, and continues to be, at the cutting edge of high technology. Iron and steel built the Industrial Revolution/copper electrified the world/coal tars and petroleum and gas feedstocks developed the organic chemical industry. Industrial minerals now carry forward this tradition. Two, of hundreds of examples of hi-tech industrial minerals are quartz crystal and rare earths. Both demonstrate the international market aspects of mining, processing and finished product trade.

Jan 1, 1988

By A. Datta

An appropriate scale-up methodology is very useful for ball mill design and optimization of the grinding circuit. To date, the scale-up is based on the selection and breakage function model using lab mill data. However, a major drawback of that approach is that the charge motion in a lab mill is vastly different from that in a large industrial mill. Therefore, in the methodology proposed here, first the energy of individual collision in the mill is computed employing the discrete element method (DEM). Then the breakage of particles as a function of collision energy is studied in a separate experiment. Together, this information constitutes what is known as collision energy based population balance model. The appropriateness of this model is shown for different batch grinding mills.

Jan 1, 1999

By D. B. Spears

The sillimanite group includes the aluminosilicate minerals sillimanite, kyanite and and alusite, all of which have the same chemical composition (Al2SiO5). This discussion also includes the closely related mineral, mullite(about Al6Si3O15), which, although rare in nature, is produced artificially for industrial use. All of the minerals in this group have a low coefficient of thermal expansion and high corrosion resistance. This makes them desirable for refractory applications, especially in the steel and foundry industries. Other uses include electrical insulators, abrasives and household ceramic products. The minerals in the sillimanite group decompose with an irreversible expansion at temperatures between 1,300° C and 1,600° C (2,372° F and 2,912° F). Sillimanite and and alusite have relatively small expansion on decomposition (4 percent to 6 percent) and, therefore, can be used as aggregates in refractory products. Kyanite’s expansion on decomposition is large (18 percent). So it is sometimes used to balance shrinkage of other materials such as clays in refractory mixtures. For applications requiring high-temperature volume stability, mullite is more desirable. As an additive, mullite improves resistance to creep and corrosion, and imparts thermal and electrical insulating properties.

Jan 1, 2005

By K. P. Chong

Fracture toughness of oil shale is an essential property in fragmentation to optimize particle sizes and permeability distributions in in-situ processes. Fracture mechanics of oil shale has been based on conventional fracture mechanics using notched samples and assuming the material to be isotropic and elastic. Oil shale is a layered material more accurately characterized as transversely isotropic. The senior author proposes to use a semi- circular core specimen with a center crack subjected to three point bending. Singular crack tip elements with isoparametric elements are used. The precracked semi-circular disk is modeled under displacement loading. The effect of crack length on the non-dimensionalized stress intensity factor is investigated by strain energy method, ellipse method, and stress method. Very close agreements are found. The fracture toughness is obtained by compressing the specimen in to failure. Parameters such as oil yield are investigated.

Jan 1, 1984

By G. Gaidajis

In this paper, a semi-qualitative methodology is presented and then applied to an aluminium extrusion industrial facility in order to perform an initial environmental assessment. The results of the assessment enable an improved understanding of the environmental performance of the facility and more importantly identify the areas of significant environmental concern. Following, the application of case-specific sustainability indicators related with the areas of significant environmental concern, leads to a more comprehensive sustainability assessment. The applied two-step approach offers a quick and reliable environmental assessment and help focusing on the most environmentally problematic areas. Moreover, the follow-up of the specific indicators seems to be appropriate for the improvement of the environmental performance of the examined industrial facility.

Jan 1, 2008

By John C. Edwards, Robert C. Bates

Results are given of a mathematical study by Bureau of Mines personnel of overpressurization ventilation effects in underground uranium mines. The mathematics and computer codes make it possible to analyze many facets of transient and steady-state radon diffusion with Darcy flow. Rapid changes in radon flux occur after imposing a pressure differential across the model. Flux into the model mine drops to near zero and then increases to the steady-state level, while the sink flux increases rapidly and then drops slightly to the steady-state level. Magnitudes of mine flux decreases and sink flux increases are dependent upon the distance from the mine to sink, permeability, and amount of overpressure. Current work on more complex models is also described.

Jan 1, 1981

By Sandeep Kumar Jeripotula, Govinda Raj Mandela, Aruna Manglapady

Dumper operators are frequently exposed to whole body vibration (WBV) in surface mines. Surface mining activities involve the amalgamation of comparatively high intensity of vibration and extended exposure durations. Efficient risk reduction mandates knowing of important phases of a task that poses a threat to health of dumper operators. So far in India very limited studies have been reported on WBV exposure with regard to surface mines. This paper evaluates WBV of dumper operators based on ISO 2631-1:1997 Standards and European Union (EU) Directive 2002 for different phases of job cycle. Six dumpers were considered for this study and the vibration measurements were made for all the four phases of the job cycle by placing the triaxial accelerometer on the operator’s seat-surface and at the seat-back, independently. The findings of the study revealed that the haulage task (loaded travel and empty travel) remains the chief contributor to vibration exposure according to seat-surface and seat-back measurements. Maximum frequency weighted root mean square (RMS) of 1.12 m/s2 and 1.09 m/s2 were reported for empty travel task for seat-surface and seat-back measurements, respectively. For seat-surface measurements based on RMS, Z axis remains as the dominant axis of vibration for all the dumpers during haulage task, whereas for seat-back measurements, the dominant axis varies between X and Y. Exposure action value (EAV) based on RMS has exceeded the threshold value of 0.5 m/s2 for all the dumpers during loaded travel and empty travel for seat-surface as well as for seat-back measurements.

By Tania Schmid, Marco Portal Valdivia, Sandra Nowosad

Today’s mining industry faces rapid transformation driven by automation, climate responsibility, and ESG demands, requiring more than technical expertise. Future mining engineers must blend engineering excellence with key human skills such as communication, leadership, resilience, empathy, adaptation to change, curiosity and lifelong learning. Based on two recent surveys, one to senior leaders with over ten years of experience in the mining industry and a second, focused on understanding the perceptions of young professionals, this paper explores which skills become core competencies by 2030 for navigating complexity, leading responsibly, and enabling sustainable transformation. Furthermore, it also examines how educational institutions can adopt strategies to foster the development of these critical skills, preparing future mining talent for evolving challenges.

Feb 22, 2026