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By Jeffrey A. Pontius

The Cresson gold deposit is in the southcentral portion of the Cripple Creek mining district in central Colorado (Fig. 1). The deposit is hosted by a series of 32 Ma (Kelley, 1995) felsic to mafic, alkaline volcanic rocks that were deposited in a diatremal environment. Mineralization in the Cresson deposit is structurally con-trolled. It occurs as disseminated and vein type. Gold deposition is closely associated with potassium-pyrite metasomatism and quartz-telluride vein development(Pontius, 1992). The Cresson deposit is owned by the Cripple Creek and Victor Gold Mining Co. (CC&V), a joint venture between Pikes Peak Mining (67%) and Golden CycleGold (33%).

Jan 1, 1996

By E. A. Gyawu, L. L. Eng, M. Fikru, K. Awuah-Offei

Investors and other stakeholders are increasingly concerned about the quality and quantity of sustainability disclosures as well as the extent to which such disclosures correlate with sustainability practices of mining firms. This is because disclosure policies vary widely across firms in terms of extensiveness, materiality, and disclosed topic. In this paper, we conduct a preliminary examination of the relationship between sustainability performance and disclosure. We use sustainability performance indicators such as water and energy use and the Sustainability Accounting Standards Board’s (SASB’s) standards to evaluate disclosures. Our preliminary results show that some measures of sustainability performance (energy use) are negatively correlated to the amount and quality of disclosures while others (water use) are not. Thus, investors should not judge sustainability performance based solely on the amount and quality of sustainability disclosures. In addition, our results suggest that firm size and ownership as well as institutional membership could impact the strength of correlations between disclosure policy and sustainability performance

Mar 2, 2022

By Steve Chorley

Open-type, or main beam, tunnel boring machines (TBMs) can achieve impressive rates of production. This type of TBM typically outperforms other types of TBMs currently in use around the world. In good ground conditions, main beam machines have achieved production rates of more than 1 km/month (0.6 miles/month). However, installing effective ground support in poorer rock conditions on main beam machines can be a major cause of concern. The design of main beam machines is such that installation of ground support equipment, particularly at the front of the machine in what is commonly known as the L1 support zone, has traditionally been limited to rock drills and basic working platforms. Personnel working in the L1 zone have, until recently, been protected by roof supports and extended fingers, often with restricted access to working areas.

Jan 1, 2011

By Paul Lynch

"Since being reported to the 2012 UMI in Shanghai, the Cook Islands has been steadily developing for the commencement of it Seabed Minerals sector in its large Exclusive Economic Zone which contain a vast and unique Manganese Nodule resource, estimated at 10 billion tonnes1. At the 2013 UMI in Brazil, it was reported that the Seabed Minerals Act had commenced and all the necessary complex Technical aspects of this developmental work was being undertaken. At the 2014 UMI in Portugal, full details of the final developments leading to the opening of the Tender of Exploration Blocks in the Cook Islands EEZ will be presented in a brief but comprehensive method, using Poster displays, Powerpoint and active Website interaction. This will show the drafted Regulations, prepared on best international standards, to address both Licencing and Environmental requirements, to give clarity and security to the Resources Owner, industry and stakeholders. This work in being coordinated by the Cook Islands Seabed Minerals Authority, with the valuable collaboration of many international, regional and national stakeholders, including the Cook Islands NGOs, Marine Resources, Marine Park and National Environment Service."

Sep 1, 2014

By J. R. Patts, A. B. Cecala, E. J. Haas

Exposure to respirable crystalline silica (RCS) remains a serious health hazard to the US mining workforce who are potentially exposed as various ore bodies are drilled, blasted, hauled by truck, crushed, screened, and transported to their destinations. The current Mine Safety and Health Administration (MSHA) permissible exposure limit (PEL) for RCS remains at approximately 100 μg/m3 , but it is noteworthy that the Occupational Safety and Health Administration (OSHA) has lowered its PEL to 50 μg/ m3 (with enforcement dates staggered through 2022 for various sectors), and the National Institute for Occupational Safety and Health (NIOSH) has held a 50 μg/m3 recommended standard since 1976. To examine a method for reducing RCS exposure using a NIOSH-developed video exposure monitoring (VEM) technology (referred to as Helmet-CAM), video and respirable dust concentration data were collected on eighty miners across seven unique mining sites. The data was then collated and partitioned using a thresholding scheme to determine exposures that were in excess of ten times the mean exposure for that worker. Focusing on these short duration, high magnitude exposures can provide insight to implement controls and interventions that can dramatically lower the employee’s overall average exposure. In 19 of the 80 cases analyzed, it was found that exposure could be significantly lowered by 20% or more by reducing exposures that occur during just 10 min of work per 8-hour shift. This approach provides a method to quickly analyze and determine which activities are creating the greatest health concerns. In most cases, once identified, focused control technologies or behavioral modifications can be applied to those tasks.

By John F. M. Sims

Political issues and a glaring infrastructure deficiency have retarded the emergence of a strong mining component to the Alaskan economy in recent years. Barriers to orderly mineral development are slowly being removed attendant upon changing political circumstances. Infrastructure development, as an investment avenue as well as a responsibility of the State, is receiving much greater attention than in the past. Alaska of course has a rich and varied mining history going back to the 19th Century. This paper, however, focuses on the mining potential, not the mining heritage of the 49th State. The mining industry is emerging from a nadir in the economic cycle - times during which it was buffeted by unsympathetic administrations and confused and confounded by the protracted land status- conflicts prior to enactment; of the Alaska National Interest Lands Conservation Act (ANILCA) and other milestone legislation. Today Alaska's mining industry looks toward a bright and healthy future and, in the process, will become a very important and vital component of the State and national economy.

Jan 1, 1982

By J. R. Patts, A. B. Cecala, E. J. Haas

Exposure to respirable crystalline silica (RCS) remains a serious health hazard to the US mining workforce who are potentially exposed as various ore bodies are drilled, blasted, hauled by truck, crushed, screened, and transported to their destinations. The current Mine Safety and Health Administration (MSHA) permissible exposure limit (PEL) for RCS remains at approximately 100 μg/m3 , but it is noteworthy that the Occupational Safety and Health Administration (OSHA) has lowered its PEL to 50 μg/ m3 (with enforcement dates staggered through 2022 for various sectors), and the National Institute for Occupational Safety and Health (NIOSH) has held a 50 μg/m3 recommended standard since 1976. To examine a method for reducing RCS exposure using a NIOSH-developed video exposure monitoring (VEM) technology (referred to as Helmet-CAM), video and respirable dust concentration data were collected on eighty miners across seven unique mining sites. The data was then collated and partitioned using a thresholding scheme to determine exposures that were in excess of ten times the mean exposure for that worker. Focusing on these short duration, high magnitude exposures can provide insight to implement controls and interventions that can dramatically lower the employee’s overall average exposure. In 19 of the 80 cases analyzed, it was found that exposure could be significantly lowered by 20% or more by reducing exposures that occur during just 10 min of work per 8-hour shift. This approach provides a method to quickly analyze and determine which activities are creating the greatest health concerns. In most cases, once identified, focused control technologies or behavioral modifications can be applied to those tasks.

By Andy Mille

The paper highlights development of tunneling methodology in the UK during the years 1990-2000 using the example of two major tunneling contracts where there solution of difficult tunneling problems during construction has benefited the industry as a whole. The paper deals with specific difficulties on two Contracts. The London Water Ring Main 80 kms (50 miles) long tunnel average internal diameter 2.54 m (9 ft4 in) and the Brighton Stormwater Tunnel 5.2 km (3.2 miles) long tunnel with an internal diameter of 6 m (19 ft 8 in). The results of human endeavour and technological innovations will demonstrate the giant strides made in tunneling methodology in the last decade of the 20th Century.

Jan 1, 2001

By R. Merkl

Since the 1940s, decanter centrifuges have become more important for increasingly complex solid-liquid or solid-liquid-liquid separation processes. Sometimes processed industrial or metalliferous minerals are abrasive or are treated with corrosive chemical agents. Traditional mining applications include the processing of coal, gravel and other products, where low-speed decanters, as well as screen bowl decanters and filters, dominate. These have been increasingly replaced by high-speed decanters during the last decade. Decanter centrifuges also started to play a key role in applications such as drilling muds, processing carbonates and separating SX crud in copper platinum ore concentrations of nickel and gold. Communication between machine producers and mineral processing engineers is vital for the right choice of materials and the design of the right decanter centrifuge for the individual process.

Feb 1, 2012

By Christian F. Baiz

A new agenda has risen. Born out of governments' policies and world economies, the years ahead will carry with them reduced growth. For inflation dependent and capital intensive industries, such as metals and mining, as well as most other natural resource industries, a period of long-term contraction in outmoded and costly capacity will evolve. This will be supplanted by new, lower cost capacity in some cases, but only if the total cost of production, including cash operating and debt service costs comes in at or below current market conditions. The industrial outlook can be characterized as bearish. As one major U.S. bank economist put it, mining companies planning their five-year forecast from 1984 out, should take the current market conditions and straight-line them to the end of the decade. With low growth and low inflation, the real price of metals will remain flat or slightly declining. As a result, capital funding will be problematic. The low cost producer, that is one with low cash costs and low principal and interest costs per unit of production, will succeed.

Jan 1, 1984

Mine design and selection of ore processing capacity depend upon a correct estimate of the grade-tonnage distribution. The estimate must reflect what can be recovered and processed. The McCoy/Cove operation in central Nevada, USA, is a gold and silver mine. Case studies of recoverable reserve estimation for gold and silver were made using multiple indicator kriging and the log-affine variance correction. From this model, the grade-tonnage distribution was constructed. Optimal pits were generated by utilizing the distribution, and the results were compared with the pit generated by ordinary kriging. Studies indicate that the proposed method for multi-metal recoverable reserve estimation is more accurate than ordinary kriging in terms of both tons and the grade. Using recoverable reserves for mine design will maximize global recovery of mineral resources.

Jan 1, 1997

By Richard W. Patton

With the advent of the Clean Air Act and the installation of flue gas desulfurization (FGD) equipment (scrubbers) on coal fired power plants, the management of solid wastes has taken on added importance. Aside from the large amounts of fly ash and bottom ash usually generated, large quantities of liquids in the form of scrubber sludge are also produced. These wastes must be disposed of within the constraints of land and water quality regulations. This paper describes the practices adopted by the electric utility industry in denting with this problem, including methods of generation and treatment, quantities and characteristics of the materials, and transportation and disposal practices. The paper also briefly describes final product characteristics and several applications for commercial utilization and land reclamation.

Jan 1, 1983

By Bill Kendall

"In coal mines, handheld air, electric and hydraulic powered drills are used along belt conveyors, in single entry development, in entries where there are obstructions, and in longwall recovering bolting. In hard rock mines, pneumatically powered jackleg drills are typically used in narrow vein mining. Drilling and bolting in narrow confines has traditionally been performed with pneumatically or hydraulically powered hand-held drills or newer electrically powered hand- held hammer drills due to their low cost, simplicity of operation, and extreme flexibility due to their small size. Mechanized equipment has typically been too large, too expensive, inefficient due to the confined space, and too restrictive due to lack of flexibility for use in narrow confines.Although the handheld equipment is effective, it requires operator exposure to certain inherent hazardous conditions in use. These include falling rock from the roof, rib and face; tripping hazards; bending twisting lifting hazards; high noise levels and chemical fumes from the pneumatic exhaust. The operation of the hand held equipment can adversely affect the long-term health of the operator - continual jackleg operation frequently results in longterm damage to hearing, shoulders, arms and wrist joints and back injuries. This results in a reduction in life style for the operator and higher personnel turnover rates for the mining company.Hand-held drills also typically have limited thrust and torque capability that limits their ability to push long resin bolts, inadequate torque to properly install resin bolts or to properly torque mechanical or tensioned rebar bolts. Hand-held drills do not offer any type of protection for the operator from roof or rib falls. They do not offer any means for handling roof or rib mesh. Since the operator stands on the ground the maximum safe drilling height without use of a ladder or "riding the drill" is limited to 2.44 m (8 ft)."

Jan 1, 2014

By Ashish Ranjan Kumar, Steven Schafrik, Oscar Velasquez

Flooded-bed dust scrubbers installed on continuous miners use fibrous type multi-layered filters to capture dust from the airstream. Prolonged operations of the scrubber could lead to filter clogging due to dust accumulation. This results in reduced flow through the scrubber and elevated dust levels in the mine environment. This paper compares the performance of a conventional fibrous screen filter and a novel impingement type dust filter. The impingement filter is a self-cleaning system and was designed to have a resistance similar to the fibrous filter. The cleaning efficiencies for these filters were computed using iso-kinetic sampling and optical counting of coal dust particles in a clean unclogged state. The cleaning efficiency of the impingement filter also increased with an increase in particle size and was comparable with the conventional fibrous filter. The cleaning efficiency of the fibrous filter improved significantly with an increase in water flow. The non-clogging nature of the impingement filter and minimal maintenance requirement makes it an attractive alternative to the conventional fibrous type filter in mining applications. The research also proposes a term called ‘filter performance factor’ to compare the performance of different filters under similar operating conditions.

Sep 19, 2020

By T. W. Camm

Some of the defining characteristics of narcissists include a grandiose sense of self-importance, preoccupation with success and power, a sense of infallibility, and a supreme confidence in their ability and intelligence. Ironically, many of these characteristics are rewarded in business organizations, which may explain why there seems to be so many narcissists in management positions. Assuming we will be dealing with narcissists throughout our career, it makes sense for us to understand what makes them tick, and more importantly what we can do to work with them in a constructive manner.

Feb 23, 2014

By P. Zhang

The use of phosphate depressants in the cationic flotation of silica from francolite in the Florida phosphate industry is rarely practiced. The occasional use of gelatinized starch derivatives and pH adjustments to assure a slightly alkaline flotation feed slurry pH have been used in some processing plants to improve selectivity. This paper presents a preliminary laboratory comparison of several potential phosphate depressants for use with the flotation of siliceous phosphates. It was found that starch is ideal for floating fine (-35 mesh) silica from phosphate, while sodium tripolyphosphate may be the best for coarser (+35 mesh) feeds.

Jan 1, 2009

After several years of laboratory and field evaluations, it has been established that each frother has its own unique relationship among bubble size reduction, gas hold-up increase, froth stabilization and frother concentration. It has been shown that a frother?s hydrodynamic properties can be characterized using the relationship between the froth zone property froth height and the pulp zone property gas hold-up. The relationship is established in a bubble column run at a given air rate over a range of frother concentration. The use of relationships in frother selection and plant diagnostics is illustrated in a series of plant case studies.

Jan 1, 2009

By William G. Freeman

As with most industrial minerals, barite is freight sensitive. This paper is given so that others might gain from the experience of barite companies in reducing their transportation costs. Some of the approaches used were unusual and others standard, but by perseverance considerable savings were realized.

Jan 1, 1973

By R. C. Warner, L. Mills, S. D. Botts, M. Marticorena

The Antamina Mine is located in the mountainous region of the Ancash Department of Peru at an elevation of approximately 4200m.The 120 km main access road crosses the headwaters of numerous high-value trout streams and is adjacent to pristine lakes, some of very high ecological and scenic value. In addition, the mine discharges mine water and tailings supernatant to the Antamina and Ayash watersheds. These streams provide the primary water supply for irrigation by local residents and provide excellent fishery habitat. The rock walls and earthen diversions constructed by historic and current indigenous residents of Peru are world-renowned and local residents continue this tradition, passed down from the Inca Civilization, for both agricultural purposes and water distribution. The key elements of sustainable development – economic, environmental and social development have been incorporated into Antamina’s sustainable development program through integration of indigenous knowledge and capabilities into enhanced storm water, erosion reduction and sediment control systems. Examples of incorporating indigenous technologies and knowledge into cost-effective and environmentally sound environmental controls are:(1) placement of rock walls on steep terrain to reduce slope length and erosion, (2) installation of rock walls (porous rock check dams) within elongated sediment ponds to increase detention time, (3) construction of rock-lined ditches to convey clean water (4)use of rock walls, with or without geotextile, to function as a seep berm, and (5) appropriate selection and usage of native Andean species for protection of canals and sediment ponds, and steep slopes.

Jan 1, 2004

By Christopher J. Bise

INTRODUCTION Perhaps no other area reflects the art as well as the science of mining-engineering design quite as obviously as strata control. This is due to the fact that the design of mining structures is difficult because rock rarely behaves as a homogeneous medium. Further, the original state of stress and the mechanical proper- ties of the in situ rock are somewhat difficult to deter- mine. However, those aspects that are hard to treat mathematically can and have been successfully approached by model studies and in situ measurements. This chapter will review the fundamentals of strata- control design and will provide examples of applications to typical problems. STRESSES AROUND MINE OPENINGS A close examination of Fig. 1 reveals that, prior to mining, stresses exerted in the overburden can be in both the horizontal and vertical directions. In the example problems of Chapter 1, it was shown that the maximum compressive stress (uv) at any depth (D) below the surface can be approximated as follows: [ ] Further, the lateral stress (oh) is related to the maxi- mum compressive stress by utilizing Poisson's ratio (µ): [ ] As soon as a heading is driven, such as the one in the coal seam shown in Fig. 2, the stresses shift to the sides, or abutments, of the opening. Clearly, these compressive stresses around the opening exceed the pre-mining conditions. The problem of designing an underground opening, therefore, is to determine the maximum stresses and to note if they exceed the ultimate strength of the rock. Table 1 lists several rocks with their corresponding strengths. Figs. 3 to 5 depict the boundary stress concentrations around circular, ovaloidal, and rectangular openings. M is the ratio of the horizontal stress to the vertical stress, or as defined above, p/(l-p). This text will concentrate on the state of stress represented by M = 0.33, which corresponds to the condition of no lateral deformation in a rock having a Poisson's ratio of 0.25. For an ovaloid with an opening width-to-height ratio of 2.0 (Fig. 4), the boundary stress concentrations are at their maximum values at the comers of the opening, with values in excess of 3.0. If the depth of overburden is 500 ft, then the maximum boundary tangential stress ([ ] ) of the ovaloid is: [ ]

Jan 1, 1986