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By H Mischo, G Barakos, J Gutzmer

The continuously growing demand for rare earth elements (REEs), in combination with the crisis of 2009 and the price spike of 2011, has initiated a treasure hunt for rare earth deposits all over the world in recent years. Since then, commodity prices have declined and are now quite stable, yet the world is still dependent on China’s dominance of the market and its export policies. Exploration is unremitting and numerous resources of potential interest have already been revealed in many countries; however, proceeding to mining operations is not that simple, especially when it comes to the exploitation of rare earth deposits. Evaluating the feasibility of a mining project is always a unique, sensitive and rather complex process that depends on multiple criteria.This paper focuses on clarifying the present and future global situation in the development of respective deposits and on identifying rare earth-specific criteria that influence the overall feasibility assessments of any potential (especially underground) mining projects. Environmental impacts, legislation issues and the presence of radioactive pollutants are some of the notable boundary conditions that govern rare earth mining operations and need to be taken into consideration. Furthermore, the balance problem between the supply and demand of the different REEs can determine decisively whether a deposit of specific REEs is economically exploitable. For this reason, evaluations are made regarding the future strategies to be enacted in order for the rest of the world to detach itself from this situation. The ultimate goal of these evaluations is for them to be incorporated in an overall assessment tool for rare earth underground mining procedures that will be implemented in real case studies to determine their sustainability.CITATION:Barakos, G, Mischo, H and Gutzmer, J, 2015. Status quo and future evaluations of global rare earth mining (with respect to special rare earth element-industry criteria), in Proceedings Third International Future Mining Conference, pp 21–30 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

By Edward D. Thimons

Because of the high number of accidental methane gas ignitions in metal and nonmetal mines, the Bureau of Mines searched for a simple guideline that would allow mine personnel to evaluate the methane hazard in a given mine. Air samples were collected by the Bureau in 53 metal and nonmetal mines and analyzed for trace evidence of methane gas. Samples were collected in the returns and at the working faces. Those mines classified as gassy by the Mine Safety and Health Administration had a significantly higher average methane concentration than those classified as nongassy. Of the 9 gassy mines sampled, 7 had methane concentrations above 100 ppm, whereas only 1 of the 44 nongassy mines had a concentration above 100 ppm. The 100-ppm concentration may be used as a simple and convenient guideline for forecasting the methane hazard in a mine, whether or not the mine is classified as gassy. There was no consistent correlation between commodity mined and methane concentration, nor was there a correlation between mine depth and methane concentration. Neither of these factors can be considered a guideline for predicting methane hazards.

Jan 1, 1979

By T Clemens, D Trumm

Adopting environmentally acceptable practices in New Zealand is a crucial requirement for mineral wealth development. Recent planned expansions in the coal industry have increasingly placed mining in the media spotlight. A lack of appropriate national environmental guidelines has resulted in inconsistent responses and assessments of current and prospective mine sites. Such inconsistencies have lead to delays in decisions on developing economic mineral deposits that may have only minor short-term impacts, and have also allowed unacceptable environmental management practices to continue elsewhere.   A research collaboration between CRL Energy, Landcare Research, University of Canterbury and University of Otago aims to provide regulator groups and the mining industry with a unified approach to the requirements of the Resource Management Act 1991, which is the legislation that predominantly drives the nationÆs environmental policies and guidelines. The tangible outcome of this research programme will be guidelines for an integrated decision-making framework based upon robust multidisciplinary science. The result of this unified process will facilitate the development of viable mineral deposits and prevent excessive environmental impacts.   The framework will be derived from a synthesis of four objectives. Objective 1 identifies potential water quality impact. This objective is based on a targeted geochemical study of the lithology and waterways of the West Coast and Southland. Objective 2 categorises the degree of impacts on the ecology of receiving aquatic ecosystems and determines the processes that drive aquatic ecosystem recovery. Objective 3 identifies best strategies to sufficiently manage impacted ecosystems, and to prevent future unacceptable impacts. Objective 4 combines the findings of Objectives 1 - 3 into a standard decision-making framework. The development of this framework development will include wide consultation with representatives of the mining industry and regulator groups. It is anticipated that this multidisciplinary approach will provide a robust and coherent, standardised system that will assist in achieving industry and environmental targets.

Jan 1, 2004

By D. H. Baker

THIS REPORT presents the technique and equipment used in determining the hardness of titanium sponge. Detailed descriptions are given of the methods used in preparing test samples for chemical analysis and hardness testing, the method of melting and surfacing test ingots, and the technique of reading Brinell-hardness impressions. The arc-melting furnace described, for which engineering drawings are included, will produce from 70 to 90 double-melted buttons each 8 hours of operation. Experimental data are also presented depicting the effect on hardness of the methods of surfacing specimens, temperature of test specimens, and the effect of time at test load. These data show that surfacing of the specimen involves no critical machining operations but that the test surface must be paralleled by a relatively flat surface for contact with the anvil of the Brinell tester. The heating of a specimen to 150° C. during surfacing does not materially affect the results if the ingot is cooled to room temperature before the hardness impressions are made. The optimum time at load appears to be approximately 30 seconds, but load times of as much as 1/ ½ minutes will not cause major errors.

Jan 1, 1959

By Jerry W. Ramsey

The Bureau of Mines examined a low-, a medium-, and a high-volatile Pennsylvania anthracite by densimetric methods using four mesh si.s of each anthracite. Using high-pressure mercury the macropore volumes and distributions of these pore volumes determined, densities in mercury were calculated, and specific pore vo1.r. ware obtained from these mercury densities in conjunction with helium densities. The helium densities were also used with the ultimate analyses of these anthracites in calculating structural parameters by statistical densimetric methods. The effect of 106 or 108 rads of gamma irradiation in the presence of air and in vacuum upon the properties studied with two mesh sizes of each anthracite. Results of the statistical densimetric method seem to show some breakdown of condensed ring structural units at the lower irradiation level, with subsequent polymerization at the longer period of gamma irradiation. The structural parameters obtained also indicated that in going from high- to low-volatile anthracite, either the number of condensed rings per structural unit increased, or the degree of polymerization increased.

Jan 1, 1965

By J. Bakos

Solar Hydrogen Energy Corporation (SHEC Labs) recently constructed a pilot-plant to demonstrate a Dry Fuel Hydrogen Generation System that is powered primarily by sunlight focusing-mirrors. The pilot-plant consists of: A Solar Mirror Array and Advanced Solar Concentrator and Shutter System; and two thermo-catalytic reactors to convert Methane, Carbon Dioxide, and Water into Hydrogen. Results from the pilot study show that Solar Hydrogen generation is feasible and cost-competitive with traditional Hydrogen production. More than 95% of Hydrogen commercially produced today is by the Steam Methane Reformation (SMR) of natural gas, a process that liberates Carbon Dioxide to the atmosphere. The SMR process provides a net energy loss of 30 to 35% when converting from Methane to Hydrogen. Solar Hydrogen production provides a 14% net energy gain when converting Methane into Hydrogen since the energy used to drive the process is from the sun. The environmental benefits of generating Hydrogen using renewable energy include significant greenhouse gas and criteria air contaminant reductions.

Jan 1, 2005

By D. A. McIsaac

In these days, when mass production seems to be the watchword of all industrial companies, nothing is left undone to attain this end. Transportation, where necessary, becomes a question of very great importance. For this reason every mechanical contrivance known to man is employed, with its resultant advantages. So successful has man's ingenuity been that, offhand, we are inclined to say that practically all transportation on a large scale is done mechanically, that is, where speed and economy are desiderata. Granting this, one would think that to read a paper on the horse before your honourable and highly technical Society would surely be a waste of time, and that any Company employing old-fashioned 'horse' power would certainly be very much behind the time, to say the least. However, the fact remains that the biggest industry in our country today-coal mining-must use horse power to a great extent, being compelled -both by considerations of economy and by necessity. For this reason,' in the production of coal under present conditions, the pit horse is of great importance to this industry and is to be considered seriously as one of the units that help to make coal mining a success or a failure. Hence, in employing horses as a power for transportation, care must be exercised in selecting the animals, and the care of this power must be considered as seriously as any other department of such an organization. In selecting a pit horse, several things must be borne in mind, that is, one must get as much horse power as possible in as compact a form as is practicable. This determines the type of horse we must use, which is of very great importance under our present conditions of coal mining. With low roof, steep grades, and forced production, a distinct type of animal must be selected.

Jan 1, 1930

By D. A. McIsaac

In these days, when mass production seems to be the watchword of all industrial companies, nothing is left undone to attain this end. Transportation, where necessary, becomes a question of very great importance. For this reason every mechanical contrivance known to man is employed, with its resultant advantages. So successful has man's ingenuity been that, offhand, we are inclined to say that practically all transportation ?On a large scale is done mechanically, that is, where speed and economy are desiderata. Granting this, one would think that to read a paper on the horse before your honourable and highly technical Society would surely be a waste of time, and that any Company employing old-fashioned 'horse' power would certainly be very much behind the time, to say the least. However, the fact remains that the biggest industry in our country today-coal mining-must use horse power to a great extent, being compelled both by considerations of economy and by necessity. For this reason,' in the production of coal under present conditions, the pit horse is of great importance to this industry and is to be considered seriously as one of the units that help to make coal mining a success or a failure. Hence, in employing horses as a power for transportation, care must be exercised in selecting the animals, and the care of this power must be considered as seriously as any other department of such an organization. In selecting a pit horse, several things must be borne in mind, that is, one must get as much horse power as possible in as compact a form is practicable. This determines the type of horse we must use, which is of very great importance under our present conditions of coal mining. With low roof, steep grades, and forced production, a distinct type of animal must be selected.

Jan 1, 1930

By Nicholas Kyriazi, John P. Shubilla

A joint effort by the U.S. Bureau of Mines (USBM) and the US. Mine Safety and Health Administration (MSHA) was undertaken to determine how well self-contained self-rescuers (SCSR's), deployed in accordance with Federal regulations (30 CFR 75.1714), held up in the underground environment with regard to both physical damage and aging. This report presents findings regarding laboratory-tested SCSR's in the fourth phase of testing from 1989 to 1993. The SCSRYs were tested on human subjects and on a breathing and metabolic simulator (BMS). These results indicate that most of the apparatus, if they pass their inspection criteria, perform as expected except units with manufacturing defects. However, when the apparatus are carried in and out of the mine daily and stored at the working section, they may suffer abuse. Physical signs of abuse, unless extremely obvious, are frequently not detected by the miners or mine operators. In addition, some apparatus collected for this study had not been returned to the manufacturer in a recall effort for correction of a manufacturing defect. In both cases, the apparatus would have presented problems in emergency use. Recommendations include improved training in inspection procedures and better enforcement of recall notices.

Jan 1, 1994

By Thomas A. Wheeler

The reagents commercially used in coal flotation and their roles are reviewed and discussed According to their function the reagents are divided into often overlapping groups: 1. Collectors 2. Frothers 3. Conditioning Reagents Frothers have by far the largest effect on the amount of coal recovered They act not only in their traditionally accepted function of “bubble makers”, but in coal flotation they serve in a seldom acknowledged role of collectors. A lab flotation study on four samples of different coal ranks shows how these react to various frother families and proves that no froher is the optimum reagent for all types of coal. The advent of new technology in flotation equipment in the past decade has resulted in various novel designs of column cells, Jameson and Centrifloat™ cells, air-sped hydrocylones, etc. All should require special frothers or blends of frothers to meet their specific needs.

Jan 1, 1994

By Winmill T. F.

(Paper presented at the Institution of Mining Engineers' general meeting held in London on 8th June 1916.) The conclusions reached in this paper may be summarized briefly as follows: (1) The method of estimating moisture in coal by determining the loss in weight of a sample heated to 105°-110° Cent, in an air-bath for an hour is untrustworthy, the results so obtained being too low. (2) Dried coal has a very considerable power of absorbing moisture, and a sample, after being dried, must be protected instantly if it is to remain free from moisture. (3) A fairly accurate estimation may be made by heating the coal in a current of dry air at 105° to 110° Cent., and collecting the moisture evolved. (4) In cases in which it is proposed to use the dried coal for any further experiments, the drying must be done in the absence of oxygen, and this can be done simply and quickly by the vacuum method now described

Dec 1, 1916

By Carl Belser

Approximately 30 million pounds of tungsten trioxide in the form of ferberite concentrates have been shipped from Boulder County. Since 1940, the production has varied considerably, being affected by the emergency needs of World War II and the Korean conflict. During World War II, attempts to stimulate production were made by the Metals Reserve Company by stabilizing the price for a specified period, the Reconstruction Finance Corporation by small mining development loans, and the Bureau of Mines and the Geological Survey, who cooperatively explored some of the district by surface and underground core drilling. During the Korean conflict and continuing through the first half of 1954) tungsten production was being stimulated by a Government-gauranteed price and by financial assistance loans under the Defense Production Act of 1950 to qualified operators of properties that have merited exploration. This combined program has increased production in Boulder County from about 1,900 pounds in 1949 to an estimated 383,000 pounds of tungsten trioxide in 1953. The 1953 production came from 67 properties. One of the problems confronting producers is the need for improved beneficiaton methods. Ores from the area have not been amenable to flotation concentration and gravity methods have resulted in poor recovery, often less than 70 percent.

Jan 1, 1955

By J. Szekely, S. Rhee

"A mathematical formulation has been presented to describe heat and fluid flow phenomena in CVD operations. In the statement of the problem, which included consideration of plasma enhanced CVD systems, emphasis was placed on identifying the parameters which play a key role in determining the rate and the spatial uniformity of the deposition process. This was done both through the appropriate dimensionless groups and by presenting an extensive set of computed results. The main conclusions that may be drawn from this work are that the deposition rate will be inherently non-uniform for atmospheric CVD systems; this may be somewhat ameliorated by inclining the susceptor or changing the vessel contours. Operation at greatly redeced pressures and for PECVD systems will give a much more spatially uniform deposition rate.1. INTRODUCTIONIn recent years, there has been a growing interest in chemical vapor deposition techniques for the preparation of thin films for semiconductor, photovoltaic applications and for coatings in general, as evidenced by numerous journal articles and symposium proceedings devoted to this topic (1-6). An interesting variant of this technique is to perform the deposition in a plasma or glow discharge at low pressures because this technology obviates the need for the thermal decomposition of the precursor at the substrate surface and permits operation at greatly reduced temperatures (7-10).By far, the largest portion of the reported work dealing with both these aspects of the technology has been concerned with the characterization of the deposit, quite properly so. However, in more recent times it has been realized that the transport aspects of these processes are also deserving of attention because the understanding of heat flow, fluid flow and diffusional phenomena may provide the key to the solution of problems associated with obtaining uniform deposits and the proper scaling of laboratory measurements in order to design industrial CVD systems."

Jan 1, 1986

By Steve Davidow, Ashely E. Evans, Peter M. Kandaris

"Annually thousands of deep foundations are constructed across North America supporting high voltage transmission line structures. However, a recent state of the practice survey by the Deep Foundation Institutes’ Electric Power Systems Foundation Working Group discovered that the electric power utility industry lacks consistent foundation design guidelines. The survey identified a wide variability in design assumptions, a minimal understanding of risk based analysis, and a need to standardize design methodologies. This paper summarizes the state of practice in electric system foundation design and proposes a framework for risk-based foundation design by accounting for uncertainty from both loads and resistances. Loads derived from electric system codes do not necessarily provide a compatible level of reliability for the design of foundations, as they are a mixture of probabilistic and deterministic values. Load uncertainty is derived from variability in weather conditions, structural models and material properties, typically accounted for by code derived overload factors. Resistance uncertainty arises from variability in natural soil properties, resistance models, subsurface construction techniques, material sampling methods, and limited observations. A consistent methodology is offered relating nominal resistance capacity (strength) to structure loads and service state criteria. Discussion also includes the need for risk-based assessments to account for non-structure load influences (fluvial loads, scour ground loss, liquefaction, etc.).INTRODUCTIONNearly 40 years ago the Electric Power Research Institute (EPRI) embarked on a major research effort to optimize reliability and economics of transmission line foundation design. Strategies focused on improvements in design models, site characterization, exploration strategies and testing to reduce uncertainty and variance in analysis. Transmission line engineers realized that safety and reliability advancements in design based on probabilistic approaches, with a focus on the unique nature of transmission line, could better control risk and cost.Some transmission line professionals took full advantage of these advancements, particularly where research led to improved software and models. Yet, even after two decades of extensive research, by 1995 the industry still had made little progress in changing design habits. The majority of designers were still characterizing sites via deterministic methods, using loads that may or may not relate to a consistent probability of occurrence, and applying a traditional global factor of safety approach (Phoon, et al. 1995). The following two decades have seen even greater developments in software and reliability-based analysis methods, but old habits seem to die hard as recent surveys show less than half of design professional quantitatively assess risk in their design process."

Jan 1, 2017

By S. L. Ducummon

Inactive underground mines now provide essential habitat for more than half of North America's 44 bat species, including some of the largest remaining populations. Thousands of abandoned mines have already been closed or are slated for safety closures, and many are destroyed during renewed mining in historic districts. The available evidence suggests that millions of bats have already been lost due to these closures. Bats are primary predators of night-flying insects that cost American farmers and foresters billions of dollars annually, therefore, threats to bat survival are cause for serious concern. Fortunately, mine closure methods exist that protect both bats and humans. Bat Conservation International (BCI) and the USDI-Bureau of Land Management founded the North American Bats and Mines Project to provide national leadership and coordination to minimize the loss of mine-roosting bats. This partnership has involved federal and state mine-land and wildlife managers and the mining industry. BCI has trained hundreds of mine-land and wildlife managers nationwide in mine assessment techniques for bats and bat-compatible closure methods, published technical information on bats and mine-land management, presented papers on bats and mines at national mining and wildlife conferences, and collaborated with numerous federal, state, and private partners to protect some of the most important mine-roosting bat populations. Our new mining industry initiative, Mining for Habitat, is designed to develop bat habitat conservation and enhancement plans for active mining operations. It includes the creation of cost-effective artificial underground bat roosts using surplus mining materials such as old mine-truck tires and culverts buried beneath waste rock.

Jan 1, 1997

By R. T. Artz

Disposal of sewage is an important part of mine sanitation. Improper... handling and.disposing of sewagerare conducive to the spread of disease and often add foul and nauseating odors to the mine air. The diseases spread by unsafe methods of disposing of waste in mines are typhoid fever, cholera, amebic dysentery, hookworm, and other intestinal diseases due to parasites. Sanitary toilet facilities, with a good sewage-disposal system, each maintained in good order at all times, should help to prevent the spread of diseases transmitted by intestinal body wastos. The metal and nonmetal-mining industries have recognized the impor-dma tance and need for disposing sewage properly; accordingly, facilities of some sort are installed and need today in most large mines. The coal-mining industry has given little thought to the disposal of sewage underground; however, in most mines of the anthracite industry, the inflow of large vol- unes of highly acid mine water and the extensive drainage system required to remove this water provide a natural means for disposing of sewage.

Dec 1, 1946

By J Hadjigeorgiou

Narrow vein mining, as most types of mining, faces important geotechnical challenges. The specificity of geotechnical challenges in narrow vein mines stems from the nature of the deposits, which are often inclined, discordant and found within fractured rock or faults or in shear zones within country rock. This complicates the construction of representative geomechanical models and limits the applicability of several engineering design tools. Furthermore, in certain cases, the severity of encountered geotechnical problems is considerably greater in narrow vein than in wider orebodies. This paper provides an overview of geotechnical and other challenges in narrow vein mines with a focus on how these are currently addressed. Of particular concern is the use of manual labour working close to the mining face where there is greater exposure to geomechanical hazards. This review concludes with a particular emphasis on understanding the limitations of commonly used engineering tools and techniques to address geotechnical problems in narrow vein mines.CITATION:Hadjigeorgiou, J, 2012. Geotechnical challenges in narrow vein mining, in Proceedings Narrow Vein Mining 2012 , pp 15-22 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 26, 2012

By Agne Rustan

INTRODUCTION This work is a continuation of the preparatory study by Rustan and Stöckel 1979 (3) and (4) of the possibilities to introduce automatic mine ventilation in Swedish mines and construction works. The preparatory study has been financed by the Swedish Board of Technical Development. In the study it was recommended that an automatic step by step control of the fans near the working place due to diesel exhaust emission would be the best solution. A more advanced alternative would be to regulate the fresh air continuously in proportion to the contamination. The latter alternative has been studied by Boliden Mineral Co in the Udden mine. In this study it was found that the air supply could be regulated continuously but it was very important where the sensors feeling the contamination were placed. An intense study of the environment underground is now being planned by our division together with specialists from the National Board of Health and Safety, The Swedish Work Environment Fund, LKAB and the local Governmental Inspection of the Workers Safety. Different gases, radon, dust, airspeed, moisture temperature and pressure is planned to be measured continuously and correlation between the parameters is going to be established to decide the best measurement parameters for regulating the system. The best situation of sensors is also going to be studied. Despite this work hasn't been done yet this paper covers some of the problems which could be encounted with continuous regulation. In this report the environment has been studied during the test with step by step regulation of fans by radio. Diesel vehicles are the largest polluters under ground in Swedish mines and we have therefore suggested that the large diesel vehicles should regulate the fans. The goal of this study has therefore been to find how active diesel vehicles should be able to start and stop gallery fans at both intake and return air. In this paper different methods for activating fans are discussed. Then the best methods are chosen and tested in the mine. In this study we have found that changes of temperature is a cheap and effective method to start and stop cross cut fans in sublevel caving and radio signals seem to be an attractive system for start and stop of gallery fans. This work has been done in close collaboration between LKAB in Kiruna and the University of Luleå - Division of Electronics and Division of Mining and Rock Excavation. A reference group for the project has been established with ventilation experts from the mines, representatives for the local mine worker's unions and authorities from the local Governmental Inspection of the Workers Safety. VENTILATION SYSTEM STUDIED In the project the ventilation system at LKAB in Kiruna has been studied. The mining method used is sublevel caving with 9-13 m slice height. The air is heated winter time over ground by hot water heat exchanger. The main fans are pushing air down to a main distribution level along the 4000 m long and about 100 m wide orebody. From the distribution level, air is taken through shafts down to the sublevels, where it is pushed through the levels by local gallery fans on both intake and return side, see fig 1. The air ( ~ 8 m3/s) is moving freely through the gallery head. The cross cuts are ventilated with smaller fans, diameter 500 mm, and flexible duct, see fig 2. The aim of this study has been to study how to start and stop gallery- and cross fans and examine the environment when the fans are stopped . In Sweden there are no regulations telling that a minimum of air amount must be supplied. Instead the hygienic limits must be fullfilled.

Jan 1, 1981

By David Runnels

The Mount Wright iron are mine and upgrading plant were brought on line in the fall of 1975. The mine is located near the Quebec - Labrador border some six hundred miles northeast of Montreal. This paper describes the crushing, grinding and concentrating facilities at Mount Wright, and some design: criteria used in equipment selection and flow sheet design. Also mentioned are some "asbuilt" modifications. A brief description of the over-all flowsheet is also included. Introduction IN SEPTEMBER 1970, the Quebec Cartier Mining Company started development of the Mount Wright iron ore mine. The estimated are reserve is in excess of 1,000,000 ,000 long tons of concentrates, with an average crude are grade of 31.5% Fe. The run-of-mine ore is crushed, ground and concentrated to a product having 66% Fe and 5% silica at an annual concentrate production r ate of 18.4 million long tons. The daily production rate of over 50,000 long tons of concentrate necessitates a daily mine output of approximately 250,000 long tons of material, of which 50% is waste.

Jan 1, 1977

By W Valery, A Jankovic

A growing demand within the minerals industry for sustainable development and the introduction of carbon taxes have resulted in a significant focus on improving the energy efficiency of comminution circuits. However, in this drive for improved energy efficiency the role of classification has been overlooked. Inefficient classification and large recirculating loads reduce circuit capacity, result in over-grinding and higher specific energy consumption.It is well understood that classification increases mill capacity; therefore, closed ball mill-cyclone circuits have become an industry standard. However, due to limitations in cyclone classification efficiency, the optimum recirculating load is limited to about 250 per cent. A simple relationship quantifying the effect of classification efficiency and recirculating load on grinding circuit capacity is presented in this paper. The possibility of improving the capacity of ball mill circuits by improving classification efficiency is discussed, considering the current practical limitations of classification equipment. Simulation tools were used to evaluate circuits with cyclones and with high frequency screens to identify opportunities to improve energy efficiency. The investigation also identified potential benefits to flotation recovery due to a reduction in over-grinding.CITATION:Jankovic, A and Valery, W, 2012. The impact of classification on the energy efficiency of grinding circuits - The hidden opportunity, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 65-70 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012