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By Arland R. Krueger

You have asked me today to tell you how quarried stone is meeting the challenges of contemporary architecture. The new position of stone, the oldest building material, in contemporary architecture, was described to me very concisely the other day by a very distinguished avant garde architect. He said rather wryly, "Do you know, if quarried stone had only just been discovered, we would all be calling it the most miraculous of all the modern miracle building materials." His prognosis was, I believe, much more than a witty quote. It echoes the surprise and. enthusiasm with which a considerable segment of the architectural profession is rediscovering stone as a most modern building material that offers unsurpassed values in beauty and practicality - well deserving of the term "miracle".

Jan 1, 1960

By A. Vilinska

The adhesion of Leptospirillum ferrooxidans bacterial cells onto the sulfide minerals pyrite and chalcopyrite was evaluated using two different physical-chemical approaches; thermodynamic and extended DLVO theory. For the parameters incorporated into calculations, the zeta potentials and contact angles of powdered solids and bacterial cells were acquired experimentally. The Hamaker constants essential for Lifshitz-van der Waals inter-action calculations were calculated following two different methods: macroscopic and microscopic. Adsorption tests were carried out at physiologic conditions to estimate the amount of cells adsorbed onto a mineral surface and the extent of alteration of that mineral surface in biobeneficiation. The free energy of adhesion was found to be negative for both minerals, indicating that the adhesion is energetically favored and preferred. The interaction energy diagrams of the total interacting force was also negative for the cases where the particles were charged oppositely; in the remaining cases, the total force was attractive after overcoming an energetic barrier caused by the repulsive electrostatic forces. Under the conditions of the adsorption test, the experimental results are in agreement with the theoretical; this suggests that the physical-chemical forces are crucial for bacterial adhesion.

Jan 1, 2011

By E. Steel

The asbestifom habit is most commonly developed in certain amphiboles and chrysotile, but other minerals may also crystallize with this unususual habit, The habit may be characterized by 1) a fibril structure, single or twinned crystals of very small widths (generally less than 0.5 inn) which have gram with a common fiber axis direction but which are disoriented in the other crystallographic directions, 2) anomalous optical properties, primarily parallel extinction, 3) unusual tensile strength, 4) high aspect ratio, and 5) flexibility. In addition, there is evidence to indicate that some amphibole asbestos may have unusual surface properties.

Jan 1, 1979

By Yun Bai, Sarah Wilson, Michael Salcher, Mark Trim

Over the last decade more than 62 miles (100 km) of civil transport tunnels were constructed in Sydney, Australia, using the sequential excavation method (SEM). The WestConnex motorway tunnels, each stage of which used over 20 roadheaders to excavate up to 40 tunnel headings, had numerous caverns up to 100 feet (30 m) wide and 82 feet (25 m) high. SEM tunnels in North America typically have far fewer active headings. This paper examines the differences in scope and risk allocation for construction phase services, including comparison of the Permit to Tunnel (PTT) process in Australia and the Required Excavation and Support process in North America.

Jun 23, 2024

By L. Hagenbuch

Off-highway truck purchasers know the amount of tonnes, pounds, kilograms, etc, a truck will carry. However just because a truck is rated at 240 tons may in no way correlate to what that truck will actually carry. Two numbers define the carrying capacity of an off-highway truck: 1. The weight carrying capacity of the truck; 2. The volume carrying capacity of the truck. These two numbers must be in sync or the amount of payload carried will vary from the carrying capacity of the truck. Currently the Society of Automotive Engineers (SAE) standard J1363 January 1985 defines the volumetric carrying capacity of an off-highway truck. However as is well known in several South American countries, the SAE standard overrates the truck’s effective volumetric carrying capacity 15% to 20%. This paper presents a method for measuring “effective” body volumetric carrying capacity, resulting in a truck body for carrying the targeted load, matched to the loading equipment that interacts positively with the truck chassis.

Jan 1, 2002

By Terry Owen

Business development process. Throughout Cyprus Amax's early months in Russia, the company stayed focused on what was needed from a deposit for economic success. Cyprus Amax's reason for success in Russia is that all involved - its Russian partners, the workforce and expatriates - provided a focused effort that served the project as it worked through the tender process and the Russian regulations. The company developed an understanding of the regulatory process by working with solid, ethical partners. Infused into the Kubaka management structure were Russians with the knowledge to facilitate the process and a professional group of expatriates. Developing credibility and a solid rapport with the Russian mining authority was critical to the success of this venture. Identifying and gaining the trust of key Russian individuals was also critical during the early stages. Gaining their trust and building credibility was part of the process. These key Russians were brought to the United States to visit existing Cyprus Amax mines. These efforts proved valuable in building an understanding with the Russians about the kind of company Cyprus Amax is and the kind of efficient operations that it can run. This was a learning process for all parties. Fortunately, the company was dealing with intelligent and educated people.

Jan 1, 1997

By J. A. M. Cano

Since the beginning of operations at the pellet plant at Ponta Ubu ES, Samarco Mineração SA has produced pellets for direct reduction and blast furnace processes. Of the total amount of pellets produced from 1977 through 1993, 55% are used in the blast furnace, about 45 Mt (49.6 million st). The principal components of pellet gangue are calcium oxide, magnesium oxide, silica and alumina. They should be added in adequate quantities to guarantee the mechanical resistance of the fired pellets under blast furnace conditions. Over the years, the pellets produced by Samarco had a silica content between 2.5% and 2.8% and varying binary basicity preferably between 0.8 and 0.85. On the other hand, the increasing amount of industrial waste in siderurgical plants caused by the increase of steel production has caused some countries to put into practice methods to reduce the volume of slag produced in the blast furnace. This paper’s goal is to find an alternative for decreasing the amount of slag produced in the blast furnace. It is possible to decrease pellet gangue by decreasing the silica content to about 2%, leaving the metallurgical properties and quality of pellets unaltered. For this work, Samarco pellets were used with SiO2between 2.5% and 2.8%, pellets with high silica and pellets with SiO2 between 2.0% and 2.3% low silica. Both were partially fluxed by the range of varying basicity CaO/SiO2from 0.8 to 0.95 during production.

Jan 1, 1995

By Jeff W. Butwell

Mill flotation tailings impounded at the Gooseberry Mine site between 1976 and 1984 were determined to be an economic source of gold and silver. The tailings would be recoverable by standard heap leach technology in conjunction with feed agglomeration. Metal recovery at 85% gold and 75% silver is attained on properly agglomerated (pelletized) tailings that average 85% -75 µm (-200 mesh). The impounded tailings averaged more than 18% moisture (32% moisture maximum at depth) in place behind the storage dam. Therefore, the mining method, mixing and agglomeration technique, and materials handling practice were major considerations in making this operation a financial success. The Gooseberry Tailings Project is located about 35 km (22 miles) east of Sparks, NV. The project is owned by Asamera Minerals (US) Inc. The company's Western Nevada Gold prop¬erty surrounds the Gooseberry Mine by several miles on all sides. Gold and silver mineralization at the Gooseberry Mine is restricted to a narrow calcite-quartz vein. Calcite makes up more than 80% of the vein throughout the mine. The host rock consists of porphyritic andesites and dacites constituting volcanic flows. The rocks are propylitized or silicified to a varying degree. This ore mineralogy, then, also describes the tailings processed by heap leaching. The Gooseberry tailings were auger sampled in 1983 and again in 1987 after a final lift of 109 kt (120,000 st) was deposited in 1983 and 1984. The total volume behind the dam was calculated from planimeter measurements from tailings surface to original area topography.

Jan 1, 1990

By John H. Raymer

Groundwater inflow into hard rock tunnels is strongly affected by recharge and drawdown of the water table. Previous analytical and empirical methods for estimating inflow have generally not accounted for these factors in an accurate or systematic way, resulting is wrong conclusions about inflow and the effects of the tunnel on the surrounding environment. This paper discusses these issues and provides some simple analytical equations to estimate inflow and water table drawdown around the tunnel. Examples from tunnels in the Atlanta area are provided.

Jan 1, 2005

By V. Galla

Waste rock facilities (WRF) generally have a large footprint depending on the strip ratio the mine plan provides. Considerable planning is involved during the initial phase of the mine plan regarding the location of the WRF. As the mining operations are commenced the locations of the WRF change accordingly with the variations in the mine plan involving feedback and support from local communities and stakeholders. Waste rock facilities management becomes challenging when the area available for placement is limited due to terrain topography, environmental and permitting constraints. Risks associated in the design of waste rock facilities constitute particle size of rock, chemistry associated with the rock for reactivity and stability of the over all facility. This paper will provide some insights on designing, scheduling and managing a WRF. Emphasis on geotechnical, geophysics and geochemistry aspects of waste rock with reference to design, construction process and scheduling of WRF are also presented. Design improvements in the reclamation slope of WRF for erosion control will be discussed. Continuous improvement (CI) methodology will be introduced in the process of WRF operations. Current practices and future recommendations towards sustainability and consistency in operating WRF will be discussed in conclusion.

Jan 1, 2011

By Víctor Vázquez, Guillermo Tiburcio, Martin Encinas, Jesús L. Valenzuela, Erick Montaño, Alejandro Valenzuela, José Parga

Merrill-Crowe is the primary process used for the concentration and purification of silver in a cyanide solution. The Langmuir Adsorption model for silver recovery in a cyanide solution was used for the study. The maximum adsorption capacity was 6.19 mmol/g for silver. This model properly adjusts the experimental results of the adsorption equilibrium with high correlation coefficients, which also favors the formation of a single layer of molecules adsorbed for the silver in the electrocoagulation- generated species. The thermodynamic parameters ΔG, ΔH, and ΔS were estimated, and it was found that the adsorption process is exothermic and spontaneous. For the kinetic study, the Lagergren second-order equation was used to study the adsorption speed. To characterize the solids coming from the electrocoagulation, X-ray diffraction (XRD), and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) were used; the results of this study suggest that silver is present in aluminite, hydroniumjarosite, and alunogen.

Oct 30, 2021

By D. Royston

SAG mill liner development draws primarily on practical experience from SAG milling operations supported by computer-based modeling of charge motion in SAG mills and on established good design practice. Liner design needs to respond to the process aspects of mill liner action that are critical to good SAG mill performance, i.e., the impact of shell liners on the grinding action and of grates and pulp lifters on pulp discharge. In recent years, the trend in large SAG mills has been to use wide-spaced shell lifters with large lifter face angles, primarily to reduce packing and ball/liner damage, and to use larger, hence fewer, mill liner parts to reduce downtime at liner change-outs.

Jan 1, 2007

By Milton E. Wadsworth, Jeffrey S. Thompson

The effect of an activator on gold dissolution in clear solution is examined using a rotating disk gold electrode. Steady state polarization curves for anodic dissolution of gold and cathodic reduction of oxygen indicate that the dissolution rate increases in the presence of the activator. The activator enhances gold disso­lution under standard cyanidation conditions; however, optimum activator concentration at the maximum dissolution rate is a function of the cyanide level. In the presence of an activator, the gold dissolution mechanism is controlled by surface kinetics and may be explained by a metal dissolution over-potential model. The dissolution rate with activator is higher than the dissolution rate at a higher cyanide concentration but without activator. The dissolution rate measurements indicate that 3 PPM of activator in a 500 PPM NaCN solution provides a higher dissolution rate than 1000 PPM NaCN alone. Activator technology may be a cost-effective means to reduce cyanide concentration.

Jan 1, 1998

By N. L. Dorset, K. L. Heasley

Unfortunately, mining and mining accidents have gone hand-in-hand since man first started to extract ore from the ground. In the first published treatise on mining, De Re Metallica, Georgius Agricola (1556) stated that cold, water, dust, stagnant and foul air, roof falls, falls from ladders and demons all caused injury and death in the mines of his day. Although demons are no longer considered a cause of accidents in modern mining, the other factors remain with us still. The United States government started keeping track of fatalities with the establishment of the federal Bureau of Mines in 1910. Successor agencies, such as the U.S. Mine Safety and Health Administration (MSHA) continue to track fatalities today. Looking at the records, it can be seen that coal mine fatalities dropped from 2821 in 1910 to only 27 in 2004. The reduction in fatalities and injuries didn’t “just happen.” It took concentrated effort from the entire mining industry: miners, supervisors, safety officials, mining inspectors and mining researchers. But first, specific hazards must be identified before they can be corrected. In past, coal mining accidents have been analyzed by: type (roof fall, electrical, etc), mine attribute (location, seam height, etc.), and aspects of the mineworker (work experience, job classification, etc). Much of this research helped to direct the industry’s attention to where additional vigilance and safety training was needed. No doubt this directed effort has led, at least in part, to the decrease in coal mining fatalities. This paper takes a novel look at coal mining fatalities: it examines the risk of fatalities based on how long the mine has been open.

Jan 1, 2006

By Jean-Michel M. Rendu

According to statistical theory, the geostatistical methods of ore reserves estimation are greatly superior to any other method. However acceptance of geostatistics by the mining industry has been slow and not as wide spread as one would expect. One of the reasons for this cautious approach is that it is often questioned whether the geo- statistical assumptions are satisfied in real world situations. When blocks of ore are estimated in a mineral deposit, geostatistical theory can be used to determine which method of estimation should give the best results. Using this theory, the relationship between estimated value and true block value can be quantified. There is a need to verify that this theoretical relationship is actually observed in practice, and that the block estimates ' obtained using the theoretical ly best method of estimation, are actually most similar to the true block values. In this paper the results expected according to the theory are compared with the results actually obtained. Sample values from a large bedded gold deposit have been used. Blocks of ore have been estimated by a number of methods, including the polygone, inverse power of the distance, kriging, logarithmic kriging and other geostatistical methods. The block estimates have been calculated from samples on a large grid, and compared with the true block values obtained from additional samples on a much smaller grid. The results of this comparison show extremely good agreement between theory and actual results.

Jan 1, 1979

By Roland F. Beers

At East Union, Knox County, Maine, near the shore of Crawford Pond, an outcrop of basic rock has been known for more than a century. The occurrence has been regarded as an unusual type of peridotite-pyroxenite, containing disseminated and massive pyrrhotite with nickel, copper and cobalt in recoverable amounts. From the outcrop, the sulfide body had been mapped more or less continuously for a distance of two miles through geophysical methods of several kinds. This paper describes the methods in sufficient detail to evaluate their significance. A core drilling program has con- firmed the location of the conductor and offers a positive means of correlating the geophysical measurements with the physical properties of the ore body. The history of the exploration offers a unique opportunity to evaluate the method of multiple geophysical methods.

Jan 1, 1962

By Dean Brox, Jason Morrison, Peter Procter

The Galore Creek Mine project is one of the newest major mining projects underdevelopment in Canada. The project is located in a very remote area of northwester British Columbia and is being developed by Nova Gold Resources of Vancouver. The mine project comprises one of the largest and highest grade undeveloped porphyry-related gold-silver-copper deposits in North America. In order to access the mine site anew 120 km road is planned to be constructed including a 4.4 km mine access road tunnel. Glaciers with heavy snow pack cover approximately two-thirds of the tunnel alignment with a maximum cover of 1,200 m. The size of the access road tunnel is about 50 m2 and has been designed as a large single lane road tunnel to accommodate the transport of large size mining equipment for mine start up and ongoing operations. The rock conditions along the tunnel alignment comprise very strong volcanic rocks. Key services for mining operations will be incorporated into the tunnel comprising diesel and power as well as the concentrate pipeline. Structural portal canopies have been incorporated into the tunnel design due to the risk of rockfalls and avalanches in the portal areas. The mine access road tunnel is a significant and critical-path component to the overall project to provide vehicular access to allow construction of the mine site. In order to meet the expected mine start up date the construction of the tunnel works are to commence prior to any other works at the mine site and will be constructed entirely by helicopter support. Geotechnical investigations commenced in the summer of 2006 with the removal of the overburden materials at the portals to assess bedrock conditions. Tunnel construction from both portals is expected to commence in the spring of 2007. The construction of the mine project is subject to and awaiting environmental approval in the spring of 2007. The mine access road tunnel will be the longest private road tunnel in North America. The key design and constructability issues for the mine access road tunnel project are presented and discussed.

Jan 1, 2007

By A. S. Atkins

The interest in the use of micro- organisms in the leaching of sulphide minerals has been traditionally exploited as a scavenger process for the recovery of valuable metal by- products from waste ore dumps. Environmental concern on sulphur emission from conventional pyrometallurgical plants together with the cost of stack cleaning systems to comply with legislative control also indicate baccerial leaching to offer a low cost treatment for the processing of sulphide minerals. The paper describes the effect and limits of relatively coarse particles on the complete leaching of pyrite and its importance to the practical application in dump leaching operations of sulphide minerals. It has also been demonstrated that static leaching techniques have encouraging economic potential for process plant operations compared with agitated leaching systems.

Jan 1, 1984

By Kot F. v. Unrug

In spite of extensive research and accumulated experience from mining operations, appropriate coal strength values for pillar design remain debatable. Coal strengths determined in the laboratory on standardized samples vary widely among various coal seams with poor repeatability. Penetrometric in situ strength testing obtains multiple measurements at multiple horizons within the coal seam to provide a strength profile. Alliance Coal has used that method in many of its mines for pillar design. Pillars in these mines perform well. This paper presents a series of case studies and discussion of issues related to coal pillar design. The analysis demonstrates that the proposed default in situ strength of 900 psi is appropriate when no other data exist. However, in the case of appropriate strength measurements combined with analysis of pillar structural composition, differing values can be used successfully. In areas where the penetrometric derived in situ strength is greater than the standard 900 psi in situ strength, reserve recovery has been optimized as required by law without compromising safety.

Jan 1, 2009

By W. Randall, Robert M. Leary

Twin 1250 m (4100 ft.) long highway tunnels through Cumberland Mountain near Middlesboro, Kentucky are planned to be completed in the early 1990's. The tunnels will be excavated in sandstones, limestones, and shales, dipping at 35 to 50 degrees and striking nearly perpendicular to the tunnel alignment. In 1985-86 a pilot tunnel was excavated as a crown drift along the alignment of the southbound tunnel. The benefits of the pilot tunnel in reducing uncertainties for main tunnel construction are discussed. The cost-benefits of the pilot tunnel are examined in view of estimated main tunnel costs.

Jan 1, 1987