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By J. J. Crowhurst

The modem open pit-heap leach operation by Pegasus Gold Ltd. at Zortman and Landusky in Phillips County, Montana, is a new chapter in the mining of gold in these districts. The discovery of bulk tonnage ore bodies and their development and ultimate production was based on a long history of mining and exploration in that part of Montana. Gold was originally discovered in the Little Rocky Mountains as placer deposits by Pike Landusky and Lou Myers. This discovery in the 1880s was not significant, but Pike Landusky continued prospecting for lode deposits, and he eventually located the Gold Bug and Little Ben, two of the larger Au-Ag producers in the district. Eventually two camps, Landusky and Zortman, grew in the LittleRocky Mountains. By the time Landusky was killed in 1894 by Kid Curry, the district was still a discontinuous small producer. Steady production commenced in 1907 with the organization of the August Gold Mining Co. Eventually high grade ores on specific veins were exhausted by selective underground mining and the district was idle by May 1942. After World War II in the early 1950s. E.A. Scholz tried to continue selective underground mining, but he realized the stockworks surrounding the larger veins constituted bulk tonnage targets. Ultimately in the 1976- 1979 period he organized two exploration efforts, one each for the Landusky and Zortman areas, and brought these into production as the Argo and Pegasus gold mines. By the time of his death, Apr. 8, 1980, both operations were producing gold. Later the two companies were merged as Pegasus Gold Ltd. Upon the death of Scholz, V.F. Hollister continued as the geological consultant, Ed Roper was engaged as general manager, and J. J. Crowhurst was given the responsibility of executive vice president. The discovery of open pittable ores and the application of heap leach technology was important in the development of mining. Both contributed to the low cost operation that continues to this day. The attached article by L.M. Rogers, then chief geologist, and M.S. Enders, his assistant, describes the geology of the deposit. It was presented at the Northwest Mining Association meeting in 1982.

Jan 1, 1990

By John E. Edkins

Metal sulfides, chiefly pyrite and mFnor sphalerlte zssociated with che Herrin (No. 6) coal member of the Pennsylvania Carbondale Formation, have been concentrated in a coal refuse deposit in southern Illinois. Oxidation of pyrite has produced highly acid waters with high concentrations of iron, zinc (up to 200 parts per million) and toxic trace elements that have leached downward to a water system perched on glacial drift. Chemical, petrographic, low-temperature ashing and x-ray diffraction were performed on cores. The data show that economic recovery of zinc and other trace metals is unlikely at this site. Energy (coal) recovery at the Superior Washer site is possible if resultant environmental problems are considered in the planning.

Jan 1, 1981

By C. Clark, R. Pakalnis, B. Seymour, L. Martin, M. Stepan, M. Roworth, C. Caceres

The National Institute for Occupational Safety and Health (NIOSH), Office of Mine Safety and Health, Ground Control Engineering Branch is investigating the use of shotcrete in weak rock mass mines with the objective of reducing fatalities and injuries resulting from rock fall accidents. When shotcrete is used as part of a multielement ground support system, there is a need to know the support characteristics that the shotcrete contributes to the overall system. To quantify the support provided by the shotcrete, flexural strength tests were conducted with two common, commercially available fiber-reinforced shotcrete (FRS) mixes using the round determinant panel (RDP) test method, ASTM C 1550. A portable RDP test machine developed by NIOSH researchers was used to determine the peak flexural load and residual load capacity for a steel FRS and a synthetic poly FRS that were sprayed using dry mix procedures and equipment. Besides the flexural strength and loading behavior determined from these tests, a method was also developed for measuring the width of cracks exposed on the underside of a shotcrete panel during a RDP test and relating these measurements to residual load values. Quantifying the peak flexural load and residual loads of a shotcrete mix through on site testing at a mine and visually assessing the loading cycle and load-carrying capability of the shotcrete applied to underground workings will improve mine safety by providing a better assessment of the stability of shotcrete supported entries.

Jan 1, 2010

By K. A. Natarajan, K. S. N. Murthy

Growth of Thiobacillus ferrooxidans on pyrite mineral surfaces and in 9K leach media was studied through estimation of bacterial protein in the different phases. Bacterial attachment was found to be governed by particle size of the mineral, period of incubation and by stationary or agitation conditions used during incubation. Increased bacterial growth in the liquid as well as on the solid phase was observed with decreasing particle size and increasing incubation periods. Increased bacterial attachment to pyrite mineral surfaces was observed to promote iron dissolution.

Jan 1, 1993

By Tsuneyoshi Funazaki, Takayoshi Nakamura, Keizo Miki, Takashi Imaishi

The underground portion (about 10 km) of Tokyo Wan Aqua-Line consists of eight shield tunnels connected with Kawasaki Man-Made Island in between, at four underground locations. The connection work had to fulfill strict precision and safety requirements in the ground about 60 m below soft seabed, but was completed successfully in May 1997. This report describes the connection work in detail, featuring the method of investigating shield machines’ relative positions, ground freezing method and connection mechanism and procedures. It also mentions the present state of Tokyo Wan Aqua-Line that was put in service on December 18, 1997.

Jan 1, 1999

Load transfer capacity and failure mechanism of a fully grouted bolt installed across joints in shear is evaluated both experimentally and numerically in five types of bolts (low strength steel, rebar bolt and high strength steel). The strength of the concrete, bolt profile configuration, bolt mechanical properties and bolt pretension load play significant influence on the shear resistance, shear displacement and failure mechanism of the reinforced medium. Failure location moves towards the bolt joint intersection due to the increasing shear load, shear displacement and axial load developed along the bolt. Finally bolt failure occurs as a result of the induced axial and shear stresses acting between hinge points on either sides of the shear joint plane.

Jan 1, 2006

By C. Clark, J. Johnson, M. Stepan

"Shotcrete and mesh are often installed to control ground deformation, falls and ejection between bolts. The combination of mesh and shotcrete forms a panel or plate that is typically bent by ground extruding between restraining rockbolts. The ground pressure applied (that is, the resistance of these panels to bending) over large ground deformations is important for maintaining ground support safety. This paper describes a new test device that measures this resistance and its evolution over large deformations. Mixes of shotcrete, mesh and other components that can maintain significant support pressure are desired, a characteristic described as the “toughness” of support. Results show toughness depends largely on how shotcrete is integrated with other components. Shotcrete strength is less important. INTRODUCTION Ground control safety often depends on supporting, or at least containing, the ground between the rockbolts. Shotcrete and mesh, in various combinations and with other components, are often called upon to do this (Figure 1). Applications are especially common in mines with squeezing ground or seismic loading. The support pressure maintained during ground deformation is key to the performance of these systems, and to protecting miner safety. However, the toughness of a design is difficult to estimate. Researchers at the Office of Mine Safety and Health Research (OMSHR) responded to this deficiency or “gap” by designing a full scale test device, described in this paper, and beginning a testing program. Some initial results from this program are reported to demonstrate test capabilities.BACKGROUND - TOUGHNESS Mining in ground that fails from the combination of in situ and mining induced stress is commonplace. Ground support elements are installed to reinforce such ground and preserve mine safety. Typically, the strength of support is considered key, and is used to prevent or halt yielding. However, ground movements driven by creep of weak ground or seismic loading may be impossible to halt altogether. In these cases, it is essential that support is able to yield with the ground in a safe manner while maintaining confining pressure that mobilizes the strength of rock in the immediate perimeter of the opening. In addition, it’s usually desirable to contain ground between rockbolts to protect miners from loose rock that might fall or be ejected. Shotcrete and screen are often employed, sometimes together and in combination with other support elements, to accomplish this function. A key characteristic of such a system is its ability to maintain support pressure through large ground deformations, a characteristic often called “toughness” – especially in support systems incorporating shotcrete. Toughness can be quantified as the work done during deformation (e.g. force x displacement)."

Jan 1, 2015

Improvements in cost efficiency, noise control, environmental design and ergonomics ? the mining and construction industries are facing demands on many fronts. The international manufacturers of construction machinery are responding to these challenges, and they will be presenting their innovations in all these fields at bauma 2013. bauma, the international trade fair for mining and construction machinery, mining vehicles, and building material machines, takes place from April 15 to 21, 2013 at the Messe Munchen exhibition center in Munich, Germany. The last bauma, in 2010, attracted 3,256 exhibitors from 53 countries, and more than 420,000 visitors from more than 200 nations. Covering a total of 555,000 m2 (5.97 million sq ft) of exhibition space, bauma is one of the largest trade shows in the world. This year?s fair is expected to surpass the 2010 figures. Here are some examples of the new developments visitors can expect to see at the show.

Jan 1, 2013

By Alan T. Nelson, Ronald D. Mariani

The Tilden concentrator was originally constructed in 1974 for the processing of low grade hematite. Flotation is a key concentrating process in the operation, and therefore flotation optimization has been a major concern since the plant startup. This paper will discuss some of the modifications made in the process to achieve optimization. The conversion that now enables the plant to process magnetite as well as hematite also will be discussed. INTRODUCTION The Tilden Mine, located in Ishpeming, Michigan, is managed by Cleveland-Cliffs Iron Company and is owned by Cleveland-Cliffs and two Canadian steel makers. It was constructed and started production in 1974 and expanded in 1979 for processing a low grade, fine-grained hematite iron formation for which there was previously no technology available. Several papers have been written describing the unique character of the concentrating operation. The hematite plant consists of 12 grinding and concentrating lines, which utilize two stages of autogenous grinding with crushing of an intermediate sized product. The ground product is deslimed in a highly dispersed alkaline environment to reject silica. Corn starch, the flocculant, has a high affinity for iron at the operating pH range of 10.5 to 11.0. The ore is upgraded from 35% to 45% iron in the desliming step. The deslime thickener underflow is the feed to flotation. Each flotation line consists of a bank of 10 rougher cells, followed by four scavenging banks incorporating 5, 4, 3, and 3 cells each. The Wemco flotation cells are each 14.1 cubic meters (500 cubic feet) in volume. A total of 12 flotation lines are available. [ ] A reverse flotation process is employed, using a straight-chain, 8 to 10 carbon primary ether amine silica collector. At the levels used in the circuit, the amine also serves as a frother. A final concentrate is produced in the rougher cells. The concentrates from the four scavenging steps are combined and recirculated to the feed end of the roughers, with the fourth scavenger froth being discarded as a final tailing. Upgrading to about 65% iron is achieved, with control of the circuit based on final concentrate silica grade. Starch is again used, this time as a depressant for iron. During the years of operation, several key areas of the flotation process have been targeted for optimization. The most significant improvements have been realized in the following areas: *Grade Control Automation *Control of Water System Chemistry *Flotation Spray Water This paper will focus on these areas, but other minor improvements also will be briefly discussed.

Jan 1, 1993

By D. Hulse

Mineral resource classification is described in both the SME and CIM Standards for Mineral Resource Reporting. The CIM Standard states “… sampling … is sufficient to assume geological and grade or quality continuity between points of observation”, thus is a function of continuity and sample spacing. Continuity can be measured by use of a variogram model, but average sample spacing in three dimensions is more difficult to measure. The declustering algorithms provided with Geostatistics software, are commonly used to weight data for statistical analysis due to the sometimes-irregular spacing between drill holes during exploration. The weights are lower when data is closer, reflecting shared influence between samples, and higher for isolated samples reflecting independence. This paper will discuss the potential to use estimates of the declustering weight as an inverse relative measure for average sample spacing to gauge the confidence of the estimate independent of the single nearest sample. PROBLEM The classification of mineral resources and reserves has long been a combination of science, past experience of the estimator, judgment, and feeling. All of the definitions as presented in the standards of the various countries that participate in CRIRSCO are similar and deal with “sample points sufficiently closely spaced to support confidence in the continuity of …” This has been interpreted as the distance between the block estimated and the nearest sample (or samples). Geostatistics gave us the calculation of the estimation variance of the block, an implicit part of the calculation of weights in Kriging, to account for the confidence in the estimate. More recently, “Kriging Efficiency” has been used, however it is still dependent on the estimation error and responds in a similar fashion to the distance to the closest sample. It is also sensitive to the variogram nugget. Many of these methods result in very low distance/high confidence measures for blocks adjacent to a sample point with confidence decreasing (sometimes rapidly) as the distance to one nearest sample increases. This results in the “spotted dog” phenomenon where individual samples are surrounded by a higher classification near each sample decaying into pattern of decreasing confidence halos. In addition to the visual image of the spots, this raises the more practical problem of mine design when the classification changes between measured, indicated and inferred. This has led to ad hoc methods to classify material within the mining block so all of the stope receives that classification. These manual methods re both labor intensive and subjective. A popular technique is a multiple search method, where the estimator defines a minimum of number of samples from a minimum number of holes within a nested set of search distance that are used to classify estimates. These specified set of increasing distances are usually proportional to the variogram range. While this is generally a good technique and overcomes the spottiness of the closest sample or kriging error, it has certain issues including:

Jan 1, 2019

By Joel L. Morrison

Wet bituminous coal fines from active and abandoned slurry impoundments are currently being examined as a recoverable feedstock for the production of coal water slurry fuel (CWSF). Preliminary analysis indicates that these coal fines can be converted into low solids, low viscosity CWSF with acceptable stability without the use of viscosity modifiers (dispersants) or stabilizers. Efforts are now underway to determine if the impounded coal fines can be economically cleaned by froth flotation to an ash level of < 12 wt. % and a total sulfur content of 1.2 wt. %.

Jan 1, 1995

By Richard B. Muter

In determining the layout or combination of unit operations to be utilized in a modem preparation plant, several factors must be taken into account. Among these are the washability data, size consist data, the particular market or markets for the coal, the mining method used, the degree to which the coal must be prepared, expected fluctuations in raw coal and markets, and the overall economics of the process. In addition, there are the health and safety aspects of coal utilization and preparation. Chapter 1 of this book discusses the characteristics of coal and coal markets, while Chapter 2 deals with the design of preparation plants. Once the unit operations for a particular plant have been decided upon, these arrangement may be depicted by using a flowsheet. A coal preparation plant flowsheet is a two-dimensional graphical representation of the sequence of operations, the arrangement of machinery, and the flow of materials for a particular coal cleaning operation. The flowsheet is usually qualitative in nature, becoming more quantitative as material balances, water balances, numbers and sizes of various pieces of equipment, etc. are added. The usual convention in preparing a flowsheet is to show the feed flowing from left to right, starting at the top left and working down as in an all-gravity process. Various symbols are used for each unit operation as depicted on a flowsheet, and Fig. 14-37 is a compilation of the commonly accepted international standard symbols for each unit operation. Fig. 14-38 through Fig. 14-40 are flowsheets of various coal cleaning processes as published in the January 1976 issue of Coal Age. Each process has its own unique features which, among others, depend upon the coal being cleaned, the coal market, and the mining operation. Fig. 14-38, for example, is a flow diagram for a jig plant preparing steam coal from two strip mines located a few miles apart. In addition to the jig washer, cyclones are used to treat the finer size coal. Fig. 14-39 is a flowsheet of a heavy media plant using a heavy media washer for + %-in. (+6.3-mm) coal, froth flotation for -28 Tyler mesh (-0.6 mm) material, and dewatering phase units (dwp) for Y, in. x 28 Tyler mesh (6.3 x 0.6-mm) cleaning of steam coal. In addition, thermal drying, centrifuge drying, and the use of vacuum disk filters and thickeners for dewatering are depicted. Fig. 14-40 is a flowsheet of a plant producing metallurgical coal. In addition to the heavy media and froth flotation circuits, a tabling circuit is also employed. These flowsheets are intended to give the reader an example of how the various unit operations for coal cleaning may be linked together. Figs. 14-41 and 14-42 illustrate the conversion of block diagrams into an IS0 prescribed set of symbols.

Jan 1, 1991

By J. Ainsworth, W. Trudel, L. Schutz, C. L. Bolin

Newmont mine geologists have added substantial economic value developing over 1,150 tonnes into quality surface and underground gold reserves since 1986. However, the recent 5-year gold price slump from $387 to $262 per ounce has shifted mine geologists focus to optimizing open pit profitability and developing high-grade, high cash flow and low capital development underground reserves. More than $65 million projected revenue has been added to the Gold Quarry south layback following multi-departmental model reconciliation investigations. Kriged mine polygon construction, controlled blast heave and high-quality geologic advice in selective mining will have multi-million dollar beneficial impacts.

Jan 1, 2002

By E. A. Devuyst, G. H. Robbins

The Inco process can be retrofitted into a typical heap operation with minimum capital. Capital cost for a mid to large size heap would be less than 1 cent/ton. Operating costs are typically in the order of 8 cents/ton. Ammonium bisulphite is the preferred reagent. The process provides the equivalent of fresh water r?1s­ing and thus minimizes the time of the _nnse program. A typical heap (the Snow Caps Mine, California) was rinsed completely

Jan 1, 1996

By James G. Donovan, Mario G. Karfakis

A large percentage of Southern Appalachian coal reserves are located in seams less than 36" thick. As thicker and currently more mineable deposits are exhausted, methods of underground thin-seam extraction must be developed. Past experience with highwall mining of thin-seam coal has indicated that recovery rates tend to be lower than in conventional operations. It is suspected that this will also apply to underground thin-seam mining, regardless of proposed technology or mining method. Backfilling is one alternative for thin-seam coal mining; although backfill has been used extensively in hard rock mining its use in coal mining has been limited. The ability of backfill to provide additional ground support may enhance coal recovery by allowing for the design of undersized pillars. Backfill is capable of providing additional ground support by restricting lateral deformation of surrounding coal pillars and roof. This additional support can result in significant increases in recovery from thin-seam coal deposits. However, the overall feasibility of backfill is dependent on the in situ behavior of the fill material, the properties of the fill, the effects of the filling method on the total mining operation, and the cost of filling per extra ton of coal recovered.

Jan 1, 2001

By Chapman Young, Donald E. McCarthy

Many hard rock tunneling projects, where the majority of excavation can be accomplished with TBMs, will still require considerable specialized excavation which can not be done with a TBM. This secondary excavation, involving cross cuts, galleries, flattening of the invert, increases in bore diameter, et cetera, may be accomplished with conventional drill and blast, applied on a small scale and usually with fracture control techniques, or with mechanical splitters. The problems of using explosives in many of these cases and the high cost of mechanical splitting excavation make the consideration of other approaches attractive. The PCF rock excavation method, which has recently been reduced to commercial practice for mine-development excavation, offers an attractive alternative to drill and blast and mechanical splitters. With the PCF method the rock is excavated utilizing a small-charge, propellant-driven, controlled, penetrating-cone fracture process. Excavation is carried out continuously by combining the PCF hardware with integrated mucking capabilities on a carrier which remains at the excavation point. In addition to the benefit of providing for complicated excavation geometry, the PCF method also causes minimal damage to the remaining rock which will significantly reduce ground support requirements. In very bad ground, the continuous nature of PCF excavation allows ground support to be applied as limited sections are exposed thus reducing both the duration and extent that the ground would be free to move. Data on PCF excavation parameters, as measured in actual mining operations, indicate that crosscuts, galleries and the like could be excavated at considerable cost savings compared to drill and blast or mechanical splitters.

Jan 1, 1995

By Regina N. Tempel, Mae S. Gustin, Mark A. Engle

This study characterizes the hydrogeochemistry of groundwaters near opalite-hosted epithermal hot-spring type mercury deposits in the Ivanhoe mining district, Elko County, Nevada. Local groundwaters generally range from Ca-HCO3 to Ca-Mg-Na-SO4 type waters with background mercury concentrations ranging from 0.014 to 0.32 ug/l. Leaching experiments conducted on mineralized rocks, using typical water chemistries to represent local groundwaters, yield total mercury concentrations ranging from 6.3 ug/l to 27.4 ug/l after one year of reaction. Geochemical modeling indicates dissolved mercury is dominated by HgO(,) and that precipitation of quicksilver controls mercury concentrations to an upper limit of 63 ug/l.

Jan 1, 2000

By L. Donovan Clark

The term "powder factor" is almost universally accepted as the measure of the efficiency of a blasting program. It represents the economics of blasting since it designates quantity of explosive (thereby providing quality control in rock fragmentation) in terms of the associated volume broken. It is the wide use of this concept that explains the interest shown in an approach to rock blasting preferred by A. W. and Z. W. Daw* in a treatise on 3 blasting (1) substantiating its use in the form, Q = CVW3 for single shot hole, where Q = quantity of explosive lb Cv = blasting coefficient W3 = unit volume of rock It is obvious that the term Cv could also be called the apparent powder factor should the equation be written in the form, Cv = Q/W3 (lb per cubic unit). However, while the approach was ingenious** and the practical applications straightforward, their original, rather limited experimental work, along with certain assumptions, was questioned.

Jan 1, 1970

By Rami Abousleiman, Gabriel Walton, Sankhaneel Sinha

"Although conventional coal mine designs are conservative regarding pillar strength, local failures such as roof-falls and pillar bursts still affect mine safety and operations. Previous studies have identified that discontinuous, layered roof materials have some self-supporting capacity. This research is a preliminary step towards understanding these mechanics in coal-measure rocks. Although others have considered broad conceptual models and simplified analogs for mine roof behavior, this study presents a unique numerical model that more completely represents in-situ roof conditions. The discrete element method (DEM) is utilized to conduct a parametric analysis considering a range of in-situ stress ratios, material properties, and joint networks to determine the parameters controlling the stability of single-entries modeled in two-dimensions. Model results are compared to empirical observations of roof-support effectiveness (ARBS) in the context of the coal mine roof rating (CMRR) system. Results such as immediate roof displacement, overall stability, and statistical relationships between model parameters and outcomes are presented herein. Potential practical applications of this line of research include: (1) roof-support optimization for a range of coal-measure rocks, (2) establishment of a relationship between roof stability and pillar stress, and (3) determination of which parameters are most critical to roof stability and therefore require concentrated evaluation.INTRODUCTIONRecent studies on pillar design have suggested that the assumptions utilized in traditional methods such as tributary area theory (TAT) (i.e. overburden has no self-supporting capacity, infinite pillar array, and CHILE material properties) are invalid in many geo-mining conditions (Esterhuizen, Mark, and Murphy, 2010; Frith and Reed, 2017). Although TAT is conservative with respect to pillar loading, and mine fatalities have steadily decreased since 1990, roof-falls and pillar bursts still occur and injure hundreds of miners per year (Mark, Pappas, and Barczak, 2011). Even though large-scale global mine failure has not occurred in a US coal mine since 2007, the mechanics of global and local stability as governed by the relationship between geologic parameters, mine geometry, and engineering design are still not well-constrained.Numerical methods are a highly effective tool that can be used to gain further insight into these relationships. When using such an approach, calibration to existing empirical relationships is imperative to ensure that numerical model results are realistic. In this study, we utilize the discrete element method (DEM) approach in Itasca’s Universal Distinct Element Code (UDEC v. 6.0) (Itasca, 2010).DEM accounts for explicit separation and contact of individual deformable blocks (Jing, 2003) and captures how discontinuities can affect system behavior. Discontinuous and anisotropic rockmass properties are typical features in coal-measure rock which contain various horizontal (bedding) and sub-vertical (joints) fractures depending on their depositional environment, diagenesis, and historic and current stress states."

Jan 1, 2019

By Ralph E. Weeks

Utilization of true in situ technologies for mining copper in Arizona will involve a complex environmental permitting process. This process is a key factor in determining the feasibility, costs, and implementing time frames required for development of this innovative mining method. The regulatory structure in Arizona is presently changing due to enactment of the Environmental Quality Act (EQA) of 1986 and development of new aquifer protection rules and regulations. The Bureau of Mines has reviewed the comprehensive hydrogeologic characterization, ground water monitoring, mechanical integrity testing, well construction, contingency planning, and other regulatory elements that will serve as mechanisms to assure protection of ground water resources. The purpose of this paper is to inform the domestic copper industry of the significance of the new Arizona regulatory structure and its implications for prospective in situ operators.

Jan 1, 1988