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By M. Javier

Management is a major part of sustainability research. Many different aspects of sustainability have already received significant research attention, but the management processes in mining from the perspective of their impact on society are less understood and integrated as a holistic frame. It is evident that mining technology has received major blame in past ecological disasters and major mining-induced environmental hazards, but the management-mining process has escaped unscathed. This should not have happened. Instead, the management processes should share equal blame with obsolete technology for the failure to identify and monitor potential environmental hazards before their inception of mining. We will present an emergent style of management for the future of mining. It challenges the actual ?mind-set? of mining management. It describes balance and equilibrium: physical, chemical, and biological in nature as an understanding of nature?s language, which is Geomimic along side ?the bottom line?. The goal is to minimize loss instead of maximize profits (waste design) at the design stage of mining and to develop clean technologies (nature's values) to achieve non-social environmental impacts that provide a prosperous legacy to future generations.

Jan 1, 2010

By K. S. Gritton

The implementation of advance control systems brings with it the expectation of improvements in process performance and controllability. Specifically, expectations include a shift in the mean value of the gross measure of process performance, and/or a decrease in process variability. When determining statistically-defensible measures of these benefits care must be taken to preclude process parameters from biasing the determination. Specifically, the effects of ore type, shift personnel, water availability, etc., must all be separated from the effect on performance of the advanced control system. Methods are presented for separating the effects of process control from other process parameters. Examples of the required data analyses are also presented.

Jan 1, 2001

By G. T. Austin

Every year the United States consumes millions of dollars worth of abrasive materials as blasting media. Entrained in either a gas or liquid stream or propelled by paddles or wheels, they are directed onto the surface of another material to modify that surface. The modifications to impacted surfaces include cleaning, cutting, deburring, etching, finishing, and peening. Blasting media can be either organic or mineral abrasive materials. Information and data presented are for only a portion of the mineral abrasives, they are; fused aluminum oxide, coal slag, copper slag, garnet, metallic shot and grit, nickel slag, olivine, silica sand, silicon carbide, and staurolite.

Jan 1, 1994

By E. A. Metz

It has been approximately four years since IARC reclassified crystalline silica as a “Group One” substance. Since that time, crystalline silica has been considered a human carcinogen. Silicosis is a preventable disease and several aggressive campaigns have been developed to increase awareness of silica dust related problems in the industrial environment. New analytical techniques are being developed to determine quantitatively the amount of crystalline silica in materials. Yet, still much is to be learned about the surface properties of silica and the way in which the disease progresses into full-blown silicosis. This paper will discuss the interaction of free radicals generated by the mineral particles and lung tissue. It is the cell injury and DNA damage that progresses to fibrogenesis. Freshly fractured surfaces of silica contain free radicals. These free radicals play an important role in the stimulation of the alveolar macrophage and the development of the inflammatory reactions leading to the fibrotic response caused by silica. Engineers, scientists, and physicians need to discuss the mineralogy of silica and the technical issues concerning the development of silicosis.

Jan 1, 2000

By M. J. van der Meulen

"The Netherlands has major resources of sand, gravel and clay, exploited mainly for construction works and the building materials industry. As in most western countries, mineral extraction meets with considerable societal resistance. To this end, Dutch minerals policy aims to prevent extraction by promoting economical use of materials, and the use of alternative (secondary or renewable) materials. Up till recently, it also included a system of production planning to sustain supplies of regionally scarce materials. Dutch policy development is reviewed and discussed in terms of pitfalls and possibilities for mineral planning in general. Promoting secondary substitution has been quite successful, and presents an example. In contrast, the production planning system has been controversial from the start and ineffective as a result, mainly because it attempted to solve supply problems without properly addressing the underlying resistance. For this reason the system is in the process of being abandoned. The full paper will be published in: Petterson, M., McEvoy F, & Marker, B.R. (Eds) 2005, Sustainable minerals operations in the developing world, Geol. Soc. Lond. Special report series, in press. This abstract is reprinted with kind permission of the publisher."

Jan 1, 2005

By B. K. Belle

The use of diesel engine locomotives in South African mines can be traced to Van Dyk Consolidated Mines Ltd on the Witwatersrand gold mines in 1928 as a replacement for battery locomotives. The advantages and disadvantages were recognized in those days, and surprisingly, there are no significant additions to this list, but only refinements. In the absence of any Occupational Exposure Limit (OEL) for Diesel Particulate Matter (DPM) in SA, the Mine Safety and Health Administration (USA) rule is currently being used as a benchmark for the ventilation engineering designs. This paper discusses the ongoing SA journey of measurement and limitations of exposure data for ventilation planning and regulatory purposes. The currently accepted DPM limits are based upon the belief that they are economically and technically feasible for the mines to reach and are not necessarily health based. For SA underground platinum mines, a median TC/EC ratio of 1.8 with a range of 1.2 to 5.8 was observed. For SA coal mines, a median TC/EC ratio of 1.44 with a range of 1.25 to 2.13 was observed. While it is common practice in the USA to use the ratio of TC/EC for metal mines to be 1.3, the ratio found in local platinum mines is 2.2 and for coal mines, the ratio was 1.53 which is lower than Australian studies, i.e., 1.96. It has been shown that a need for critical analysis of TC/EC ratios exists, and possible reasons for variance must be understood before stringent adoption of overseas recommended limits for DPM. It is hoped that the findings from this paper would provide input to scientific approaches in developing appropriate conversion factors, limits for DPM and also in ensuring appropriate error factors (currently 1.14 for TC and 1.2 for EC) for compliance determination.

Jan 1, 2009

By R. J. Sheets

"What is the primary responsibility of geo-engineers in mining? Early in my career, I was asked this question by an experienced engineer. After explaining some various tasks, I was informed that the main responsibility was to monitor. Although this proved true for many cases, I came to understand that monitoring is merely one means to achieve the primary responsibility of a geo-engineer — ensure the safety of all personnel. The potential for groundwater to impact stability allows this responsibility to be shared with hydrogeologists as well. Inherently, we monitor to identify risks; we analyze designs and develop models to mitigate risks; and we are provided opportunities to explain to supervisors the geo-risks to personnel and mine plans that will result from particular courses of action. A couple years ago, I took an opportunity to share experiences from the first several years of my career as a geotechnical engineer with junior geoengineering staff within my company. The intent was to share situations that were a part of my development, so they could learn and understand their responsibility to the safety of all personnel. Similarly, the purpose of this article will be to share these thoughts with new geo-engineers in the industry in order to help prepare them for the challenges they will face.What is our purpose?A senior hydrogeologist shared an experience that occurred in their career. The experienced hydrogeologist had spent some time with the hydrogeology staff, most of them relatively new to the mining industry, to understand how they viewed, and carried out, what they perceived as their responsibility at an active mining operation. After a couple months of observing and mentoring, the senior hydrogeologist met with everyone and posed the question “What is our purpose?” I am sure that most junior geo-engineers would start explaining different tasks or projects that they must complete. The list would include monitor ground water levels, track slope movement, evaluate designs, build models, oversee drilling programs, etc. These individuals did as well their supervisor. After going around the room allowing each individual to answer, the experienced hydrogeologist provided them the real answer to the question: Safety. If you examine the root intent of nearly every responsibility geotechnical engineers and hydrogeologists have, it is to apply our professional skills to ensure the safety of our workforce. When the objective of safety from the geotechnical and hydrogeology disciplines is achieved, inherently accomplishing the mine plan should follow suit, or it should significantly minimize the impact by gravity or ground water."

Jan 9, 2018

By I. Loomis, D. Rachmad, I. Duckworth

During the past two years the Underground Mine Ventilation Group at PT Freeport Indonesia has undertaken to upgrade their Hygiene Laboratory. This process has included upgrading equipment for dust sampling and gas monitoring, as well as procurement of an OCEC analyzer for Diesel Particulate Matter analysis. While the laboratory equipment represents one factor, these changes have also required re-evaluation of the sampling protocols and the burden of ventilation monitoring personnel. This paper provides a review of these experiences.

Jan 1, 2006

By John D. Morton, J. H. LaVerne Palmer, Douglas J. Belshaw

An extensive programme of ground instrumentation and observation was carried out for the West Duff in Outfall Sewer tunnel project prior to and during construction, to establish the performance characteristics of the rock through which the tunnel and appurtenant openings were dug and to examine the nature of the lining-to-ground interaction. The existence of high horizontal residual ground stresses was confirmed, and values established by overcoring. Rock deformations and stress changes were monitored during tunnelling. Permanent stress and strain monitoring devices were set into the final lining and these are continuing to operate. INTRODUCTION The site is located on the north shore of Lake Ontario at Pickering, some 20 miles (32 kilometres) east of Toronto, Canada where a variable thickness of glacial or interglacial sediments overlies bituminous shale bedrock of. the Collingwood Formation which is lower Ordovician age. Approximately 50 feet (15 metres) of glacial cover exists at the shaft, though this thins abruptly at the regressing cliffed shoreline such that several small areas of exposed bedrock exist in the lakebed. The general location, overall geological section and detailed site plan and profile are illustrated in Figs.1,2 and 3 respectively. General properties of the rock as established during an extensive test drilling and site investigation programme are listed in Table 1, while stress determination by USER overcoring stress meter device are given in Table ll. These data formed the basis of analyses which were done to examine the intended outfall design, and to detail the construction procedure and the observational instrumentation programme.

Jan 1, 1979

By L. Mukka

The existing main mine ventilation system for the production areas to the Kiruna mine was constructed during the period 1994-1996 and extended with 4 more shafts, including fan stations, for the sea ore body from 1997-1998. Two papers have been presented from this project at the 7th US Mine Ventilation Symposium in 1995 and at The 6th International Mine Ventilation Congress in 1997. In 2005, pre-studies for a new main haulage level were started. Different haulage methods were presented including ventilation systems. The pre-studies showed that the existing ventilation system, including fan stations for the new main haulage system in the production area, could be extended. However, a new system for the central area, which was not in the initial investment program, would be needed. In the beginning of 2006, a decision was made to design a new ventilation system for the central area to make it possible to get air to the development work for the new main haulage system, independent of the haulage method. This system was operational by the beginning of 2007. The new main haulage system, which was decided to be located on level 1365 m, only requires that the existing shafts be extended - the capacity of the fans seems to be enough. However, the problem is that the existing level 1045 m and the new level 1365 m have to be in operation in parallel for approximately 7-8 years. The challenge for the moment is determining how to ventilate the production areas for both levels at the same time, while simultaneously constructing the extended system. This paper will describe the problems associated with the extension of the main ventilation system and some potential solutions for these problems. The new main haulage level 1365 m must be in operation by 2012.

Jan 1, 2009

By J. Wesley Atkins

In considering the importance of lease management and administration, I have decided to approach the topic, Lease Default and Eviction: Action or Reaction, as a three phase presentation dealing with mineral lease administration and management, past, present and future. Though the title may border on the dramatic, it illustrates the real consequences of alternative approaches to property management viewed from my experience in the evaluation, development and implementation of a number of such systems and services in my current position as president of Talco Group Corporation. First, though, let's take a moment and set the stage by giving a few actual examples of why a pragmatic approach is needed in this particular area.

Jan 1, 1983

By Bruce Clements

The Bagdad mill, located near Bagdad, AZ, was built in 1977 with a designed mill capacity of 36.3 kt/d (40,000 stpd). An autogenous mill-ball mill crusher (ABC) grinding circuit was chosen. The original mill contained three independent grinding circuits. Each contained one 9.75m-diam x 4-m-long (32-ft-diam x 13-ft-long) fixed-speed autogenous mill, a4.7-m-diam x 6.7-m- long (15.5ft-diam x 22-ft-long) ball mill and one 2. 1-m-diam (7-ft-diam) short head cone crusher. Total installed power per grinding circuit was about 8.4 MW (11,350 hp), with 5.9 MW (8000 hp) in the autogenous mill, 2.2 MW (3000 hp) in the ball mill and 261 kW (350 hp) in the crusher (Fig. 1). The autogenous mills were designed to be able to operate semi-autogenously. However, they were never converted to semiautogenous grinding (SAG) mills. As a result of this design, only about 4.1 MW (5450 hp) of the designed power is used in the autogenous mills. The grinding circuits are closed, with 2.4 x 6 m (8 x 20 ft) double-deck vibrating screens. A series of conveyors re- turn screen oversize underneath the mill coarse ore stockpile to feed the crushers. Variable speed belts feed the crushers and control power draw. Crusher product reports directly to the tail end of the autogenous mill feed belt (Fig. 2). A magnetic sensor detects tramp iron in the autogenous mill-crusher circuit.

Jan 1, 1992

By William H. Dresher

Introduction A subject long debated but rarely resolved involves the interaction between the academic community and industry in the sponsorship and conduct of research. The subject is, unfortunately, too often treated as a controversy involving ethics and the profit motive. But, in fact, the two branches of society - industry and academia - are necessarily part of the same system. In the last 25 years, the realization has developed that research alone is not sufficient to bring about use of those results to benefit society through productivity gains and economic growth. The flow of events shown in Fig. 1 was generally believed to be the steps required for reaping the benefits of research. Today, research still has the very important role of creating new information or new ideas. However, it is recognized to be but one of many steps in a process that we now refer to as technological innovation. Charpie (1967) said, "Technological innovation is the driving force behind economic growth in the US. In this context, innovation means the process by which a new idea is successfully translated into economic impact within our own society, by providing better products, and simultaneously creating new jobs in the manufacturing of those products. Only after an investigation is put into sufficient use to have an economic effect, is it termed an innovation." One of the best depictions of the technological innovation process is shown in Figs. 2 and 3. These are adapted from Haeffner (1975), and modified by the Committee on Mineral Technology of the National Research Council (1981). Figure 2 identifies the many steps involved in the process. It designates a generalized form for interaction between the academic community and industry. Figure 3 identifies the steps in the "innovation activity" box of Fig. 2. Academia is generally responsible for developing of new knowledge and ideas, as well as maintaining and enlarging the collected body of scientific knowledge. Industry is responsible for developing new products, methods, and processes. Both institutions operate for the benefit of society, but under different driving forces. In academia, the driving force is the achievement of academic excellence. In industry, the driving

Jan 10, 1984

By R. C. Bratton, R. Q. Honaker

Hindered-bed separators are recognized as low-cost, high-capacity devices for both classification and density separation; however, since their inception, there have been few significant advances in the fundamental technology. Recently, Eriez has shown through modeling and pilot-scale testing that the innovative approach to feed presentation offered in the CrossFlow teeter-bed separator provides improved metallurgy when compared to traditional hindered-bed classifiers or single-stage coal spirals. This design feature prevents excess water from entering the separation chamber and disrupting the overall fluidization flow rate within the teeter zone. Most recently, a side-by-side industrial scale evaluation has verified that this technology improves overall efficiency and simultaneously reduces the separation cut-point. With regards to coal processing, data from full-scale units indicate that the CrossFlow offers good separation efficiency, high unit capacity, and metallurgical results consistent with laboratory- and pilot-scale separators.

Jan 1, 2006

By Walter R. Curtner

Many, if not most, of today's pollution liability claims are related to events ("occurrences") that happened in the past. This fact creates an opportunity to obtain a large amount of insurance coverage at essentially no cost. Furthermore, in many cases, this insurance coverage is readily available. Scenario #1 For some 15 years, an underground gas tank has had a slow leak. The leak has now been discovered because the gas has contaminated nearby wells. As a result, an expensive $1 million cleanup is required. In addition, a liability suit has been filed for damages due to the contamination of nearby wells. Consequently, legal expenses are being incurred. Are all of these actual and potential costs insured? Obviously, if you have a pollution liability policy in place, the above costs will probably be insured. I say probably because business liability policies are not uniform. But, what if you don't have a pollution liability policy and what if your current general liability policy excludes all pollution liability (as most of them do today)? Under these circumstances, it first appears there is no insurance for this $1 million cleanup and liability suit. But this is probably not the case. You may well have insurance coverage, and you may well have much more insurance coverage than you ever expected. And, the insurance that I'm referring to is already in place. You simply need to find it and learn how to use this insurance - I'm referring to your old policies. In many cases, old liability insurance policies provide coverage for claims made today, because these policies were written on an "occurrence" basis of coverage. In fact, most still are written this way. This means that the insurance policy covers bodily injury or property damage liabilities (as defined in the policy) arising out of' "occurrences" or accidents that happen during the policy period regardless of' when the claim for damages is made. Therefore, for insurance purposes, the key question is: when did the "occurrence" take place? If someone falls and breaks a leg, that is clearly an "occurrence." The broken leg occurrence is, therefore, insured by the liability policy that was in existence at the time of the fall - regardless of when the claim or suit is filed, if ever. However, the answer to this question is seldom an easy one when you are looking at a pollution claim. In our scenario, the tank had a slow leak over 15 years, but property damage was not discovered until now. The question of when the "occurrence" (as defined in the insurance policy) took place has been litigated and continues to be litigated in many courts across the country. But, most often the answer has been that, for insurance purposes, the "occurrence" is the entire period that the tank was leaking (15 years), even though the contamination to the water was not discovered until 1987. This means that the person or company that is insured can potentially use all of its general liability policies (if they are "occurrence" policies, and most were), which were purchased during the 15 years from 1972 until 1987. And, these policies will potentially insure all of the claims and related exposures that arise out of this leaky underground gas tank. Scenario #2 In our first scenario, the claims and expenses were insured by past general liability policies because the claims arose out of events in the past, which, in turn, caused damage. Let's look at another example. In this scenario, Company XYZ has received a request to help clean up a landfill site because 10 years ago, XYZ dumped some toxic substances at the site, which was totally legal at the time. XYZ has not dumped anything at the site since this time. Nevertheless, XYZ is now being required to contribute $2 million to the cleanup of this site. In this scenario, if you had purchased "occurrence" general liability policies 10 years ago, these 1977 policies would (potentially) apply to the current $2 million cleanup claim. And, the reason is that the "occurrence" leading to the 1987 claim took place in 1977.

Jan 10, 1987

By K. Sasaki

Diffusion phenomena in mine airways are important to trace gas and dust introduced into mine ventilation flows. Authors have carried out tracer gas measurements to check mine ventilation using concentration-time curves measured in mine airways, however dispersion mechanism to enhance effective diffusion have not been cleared. A numerical model using discrete tracer points dosed into tube flow has been presented to simulate their movements in consideration of turbulent velocity profile and fluctuation. Numerical simulations have been carried out to predict distributions of dosed points in tube flows with turbulent velocity profile, turbulent intensity profile and Reynolds stress. The numerical simulation results show that a combination of turbulent velocity profile and fluctuation creates extremely large dispersion of points in longitudinal direction and concentration curve with long tail was observed. This dispersion by velocity profile and fluctuation contributes large effective diffusion coefficient compared with original diffusion coefficient dominating in uniform velocity fields. Furthermore, the effect of Reynolds stress on the concentration-time curves is discussed.

Jan 1, 2009

By B. J. Vorster

Introduction The South African Iron and Steel Co. Ltd., in Sishen, operates a large iron ore mine in the Cape Province of the Republic of South Africa. The mine is about 600 km (370 miles) west of Johannesburg. Its annual capacity is 100 Mt (110 million st) of ore and waste. Present production is 60 Mt/a (66 million stpy). The mine operates continuously six days a week. Primary equipment includes 55 154 t (170 st) Wabco and Unit Rig trucks and 14 P&H shovels. During 1979, a feasibility study into the application of a trolley assist system was launched. This was due to the escalation in diesel fuel costs and the appeal by the South African government to reduce the use of fossil fuels. Tests and economic evaluations proved the system technically feasible. The estimated discounted cash flow return exceeded 50%. Diesel fuel consumption would be reduced by 120 ML (31.7 million gal) in the next 10 years. The construction of 7.7 km (4.8 miles) of line and the conversion of 66 154 t (170 st) trucks were completed in March 1982. System description The conventional 154 t (170 st) diesel electric rear-dump haul-truck is equipped with two direct current wheelmotors in the rear axle. They drive the rear wheels through planetary gearboxes. A 1.2-MV (1600-hp) diesel engine and an alternator is used to power the wheelmotors. The trolley assist system consists of an overhead power line, a current collector mounted on the truck, and add-on control equipment where external electric power is routed by way of the current collector to the motorized wheels. The diesel engine is used to propel the truck on level sections. On inclines, the wheel-motors of the truck are coupled by way of a current collector to the externally generated electrical power supply for propulsion. The diesel engine, having lower output than the wheelmotors, limits the truck performance. Previously, maximum output was required from an engine on inclines. By supplying the wheelmotors from a virtually unlimited outside electric energy source, the truck performance is enhanced to the extent that speed is increased by 46% and fuel consumption reduced by 75%. System design The unique operational requirements of this mine rendered the already proven trolley pole system useless. Minimum loss in truck mobility and flexibility was required. Overhead lines and substations were required to be relatively light and portable. This enables fast repositioning of a line with no loss in material. These unique specifications set the base for the design of the Sishen system. Steel I-beams, 203 x 203 mm x 52 kg/m (8 x 8 in. x 35 lb per ft) with lengths varying from 8.3 to 11.3 m (27 to 37 ft), mounted on base plates about 4 x 2.6 m (13 x 8.6 ft) were used as masts. The masts were erected at about 50 m (165 ft) and the base plates covered with about 12 t (13 st) of iron ore to keep them absolutely stable. Results from the pilot installations indicated that using single cantilever cross arms for insulator and overhead conductor suspension was not practical. The tension in the overhead varied too much with temperature changes, causing too much sag in the lines. There had to be a positive and negative conductor. It was decided to suspend each polarity on an independent cantilever and keep the conductors under constant tension by weights acting through a two-to-one pulley tensioning arrangement. For each overhead conductor, a standard 160-mm (6.5-sq in.) grooved copper railway conductor was used. To obtain the necessary current carrying capacity, two of these conductors are used in parallel per pole. Insulators are rated at 4 kV and are of the composite type. An 11-kV three-phase line, supported by the pantograph line masts on the opposite side of the dc line, feeds the rectifier stations. The rectifier stations consist of an 11-kV to 860-V, three-phase 1.46 MVA transformer and a three-phase diode bridge rectifier. The output voltage is 1200 V do earthed through a current limiting resistance network so that the line po-

Jan 4, 1986

By Eung Ha Cho, Wendi Li

Wet desulfurization of Pittsburgh No. 8 coal and Illinois No. 6 coal were conducted with sodium hypochlorite in the laboratory. Pittsburgh No. 8 coal was leached by hypochlorite at high pHs in one step only. The hypochlorite concentration varied from 0.2 to 0.6 molar; sodium hydroxide concentration, from 0.2 to 0.8 molar; and temperature was at the levels of 80 and 90°C. The desulfurization of Illinois No. 6 coal was conducted in three consecutive steps of pretreatment in concentrated ammonia at room temperature, leaching with hypochlorite at room temperature and hydrolysis in sodium hydroxide solution at 90°C. In the leaching step, hypochlorite concentration varied from 0.2 to 0.8 molar. The desulfurization method of Pittsburgh No. 8 coal was found to reduce mainly pyritic sulfur. More than 70% of pyritic sulfur removal was achieved at the optimum conditions of 0.4 molar hypochlorite, 0.4 molar sodium hydroxide and 90°C. The desulfurization method for Illinois No. 6 coal was capable of reducing significant amounts of organic sulfur. The removal of organic sulfur achieved a 37.8% reduction at the optimum operation of leaching at 0.4 molar hypochlorite and room temperature followed by hydrolysis at 0.3 molar sodium hydroxide and 90°C. The chlorine content in the coal produced by the chlorination during leaching was kept below the threshold value of 0.3% at the optimum conditions of the desulfurization method for each coal.

Jan 1, 2005

By D. Rutledge

Discrete (digital) signal processing techniques are proving to be very valuable tools for miners using the block cave method. Waveform analysis of different measured signals associated with active mining provides valuable information on production dynamics and safe operation of the mine. For example, correlation of the 3D surface displacement velocity waveform and the production output waveform reveals a remarkably predictable time-varying physical process. Studying the geometrical and temporal relationship between these two signals opens a broad window through which new management techniques become apparent. In this paper we discuss the signal processing techniques used to study these relationships, as well as the related implications for mining. This research was carried out in association with the Chevron Mining underground molybdenum mine in Questa, New Mexico. Some of these new techniques will be integrated into the decision management process at the mine and will provide insight on ore production, draw control, and safe reclamation. The science of signal processing involves the analysis and interpretation of physical processes that vary with time. Two general categories of signals1 are recognized. A continuous signal is a waveform of varying amplitude that is continuous in time (such as a sine wave). A discrete signal is a sequence of quantized values. The independent time variable and amplitude are sampled periodically such that we only know the value and shape of the waveform at the sampling frequency. Displacements measured by a Global Positioning System (GPS) receiver are an example of this. Discrete signals may be studied in the time, frequency, autocorrelation, or wavelet domains. In this paper the amount of ore extracted from the mine and the measured surface displacements are analyzed in the time domain.

Jan 1, 2008

By I. S. Parrish

One of the most common errors uncovered while performing a reserve, or resource, audit is not in the geological modeling or grade problems due to poor sampling, prepartion or assaying. The error most commonly found is in tonnage or, more specifically, in the tonnage factor - that factor applied to volume to derive tonnage. Tonnage factors In the metric system, the tonnage factor is the density, or specific gravity. Specific gravity (Sp.g.) is defined by Dana (1947): • "The specific gravity of a mineral is the ratio of its density to that of water at 4° C (39.2° F). • "Density is the mass of the unit volume or weight of the body divided by the weight of an equal volume of water." When Sp.g. is multiplied by the metric volume it yields metric tonnes. In the English system, the tonnage factor is usually expressed in cubic feet per short ton (cu ft/st). When the volume in cubic feet is divided by cu ft/st, the resulting figure is in English short tons. Table 1 gives the cu ft/st factors equivalent to specific gravities from 1.6 Sp.g. to 5.8 Sp.g. The table is based on the following equation: cu ft/st = 0.9072 divided by Sp.g. times 0.02832 The blase attitude that most geologists have toward tonnage factors is echoed in the prevailing definitions of Reserves and Ore, as provided by the US Securities and Exchange Commission (S.C Form S-18), Canadian National Policy 2A and the SME Proposal for Reporting Terminology (SME February 1991). In each case, it is stated that "quantity" (SEC, SME), or "tonnage" (Can.2A), "is computed from dimensions revealed in...." etc. Unfortunately, "dimensions" do not directly yield tonnage. Dimensions must be factored by density to derive tonnage.

Jan 1, 1993