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By YUSONG MIAO, DI WU, XIANRONG YAN, YIPING ZHANG, JIE LIN, KEBIN LI

Rock fragmentation has been a concern in hard-rock mining for the mining industry. Rock fragmentation distribution is an important index to measure the blasting effect. It not only affects the cost of drilling and blasting, but also affects the efficiency of subsequent operations, such as loading, transportation and secondary crushing.

By David G. Chedgy

It is probably safe to assume that most operating personnel working in coal preparation plants are exposed to noise levels in excess of the MESA Noise Regulations unless they are wearing ear protection. The excessive in-plant noise levels have received little attention until recently. Noise control has not been an important design consideration in existing coal preparation plants. This situation is rapidly changing as plant owners and plant operators are requiring that new coal preparation plants be designed to provide a safe noise environment for operating personnel and also meet MESA Noise Regulations. This paper discusses the noise exposure hazards, noise generating mechanisms, and some possible noise control solutions for typical coal preparation plants.

Jan 1, 1975

By Ross W. Smith

Many studies have been made of the microflotation of quartz (1,2,3,4,5,6) and alumina (3,5,6, 7,8) using various anionic and cationic hetero- polar hydrocarbon surfactants as collectors. A few studies have been made on these minerals using amphoteric hydrocarbon collectors ( 9,10, 11,12) and only a few studies have been made on the use of fluorocarbon surfactants as flotation collectors (13,14). The present investigation compares microflotation response of the two minerals in hydocarbon and fluorocarbon collector systems of the anionic, cationic and amphoteric types. An attempt is made to relate flotation response of the minerals to their electrokinetic behavior and the pKa values of the collectors.

Jan 1, 1979

By SAHENDRA SINGH, SANJIT KUMAR PAL, DHARMITA HORO

This study was carried out in Ichadih to map the sulfide/gold mineralization using combined electrical resistivity tomography (ERT) and self-potential (SP) methods. No geophysical analysis has been carried out to delineate such ore deposits in the area. Thus, the study provides a different approach for approximate location and extension of the quartz reef associated with sulfide/gold mineralization. It also provides the elementary idea for further detailed subsurface investigation in terms of geological and geophysical approach. 

By E. G. dos Santos, M. M. Veras, C. H. Sampaio, A. S. Young, R. S. Paranhos, C. O. Petter, A. C. Bastos

"The major challenges of the current mining are the energetic optimization, the lowest water consumption and minimizing environmental impact. One technique that eliminates much of the waste avoiding milling sterile, operating without water and to decrease the generation of waste at the end of the process, must be considered a major innovation. One of the most important developments in these past 10 years in the mining industry was expanding the use of high-tech sensors aimed at pre-concentration of ore. Among the mining areas where this type of technology is booming is the industrial minerals. The most common sensors are color sensors with Charge – Coupled Devices (CCD cameras) allowing through the RGB colorimetric system, the separation of minerals with different hues, and in many cases, a difference in brightness. More recently, the development of the use of dual energy X-ray transmission (DE-XRT) Dual Zone allowed the separation by atomic density of the mineral constituents of the rock. This paper presents a review of these two techniques (CCD and DE – XRT) as well some results showing the use of these two techniques for Earth Rare and Limestone. INTRODUCTION The mining industry is going through one of its biggest technological changes since the industrial revolution by the implementation of new technologies, according to Australian Mining Magazine (2015), whose theme emphasized one of the 10 greatest challenges that mining will face in the coming years. Optimization of the energy matrix in mining is focused on reducing water consumption and minimizing environmental impacts. The implementation of sensor technologies (Sensor-Based Sorting - SBS) allows elimination of mill tailings and permits the mill to operate with reduced use of water or totally eliminate this consumption (Young et al, 2016). According to Jönsson (2014) mining has undergone striking changes with the expansion of sensors of high technologies applied in the pre-concentration of mining ores. These techniques have contributed over the past 10 years in the recapture of mining areas with emphasis on the environment and/or operational optimizations. In line with the requirements of technological innovation, the mining industry is forced to make improvements in gravimetric processes ensuring better levels of Run of Mine ore feed in beneficiation plants. The implementation of automatic sorting, assisted by dual energy x-ray transmission (DE-XRT) sensor technology, or charged coupled device (CCD) image capture camera technology in the feed plant, allows for the selective sorting of individual particles into pre-concentrations (Veras et al, 2016)."

Jan 1, 2017

By W. Haupt, M. Thormé, H. J. Ertle, K. Reim

Though Germany has a very old mining history, her experience in uranium mining only started in the late sixties. Today in the Federal Republic of Germany (FRG) there are only 5 small mines in the exploration stage, namely Menzenschwand and Müllenbach in the Black Forest and Mähring, Popenreuth and GroBschloppen in northern Bavaria. In all these exploration mines much development is required to define shape and size of ore bodies. Mining engineers, government authorities and environmentalists alike are very much concerned about environmental safeguards and protection of mine workers against radon and its daughter products. Miners are affected by internal and external radioactive exposure. In general the external [f3]- and [µ] -exposures can be considered as small in comparison to the internal exposure and are therefore not discussed in this paper. The internal exposure is caused by the inhalation of radon and its daughter products and is relevant to the lung as the critical organ. The nobelgas radon is inert and does not from compounds with other elements easily. Contrary to the physical half-life of 3,8 days the biological half-life of radon is only 10 to 20 minutes. During the rentention time in the body only approximately 1 % of the long-lived decay products are retained in the system (SCHOGER, 1976). In this connection is it important that the radon resorption as well as the radon secretion varies individually and depends to a large extent on the age of the person (SCHOGER, 1960). RENOUX et al. (1978) have determined that the greatest part of the a(-activity in the air is attached to aerosoles with a diameter of 0,4/14. The radiation exposure of the lung by radon is negligible if compared with the exposure by short-lived decay products. For this reason one has introduced the concept of the potential [o](-energy (P) of the short-lived radon decay products, which means the total [ct]-energy, which is produced when an atom decays in the decay-series down to the long-lived lead-210. [ ] The unity of the potential [o]-energy concentration in the SI-system is 1 j/m3 air. In radiation protection however a specific unit is used namely the working level (WL): [ ] The WL-unit, though internationally recognised has not been introduced officially in Germany. Because of the large amount of tunneling still to be done in the FRG, the various mines departments responsible for safety and health in mining ask searching questions such as: - What are the laws governing radon emanation in tunneling? - Can workers be adeguately protected against radiation hazards? - How should one drive through high grade uranium ore? - What happens if the ventilation system breaks down?

Jan 1, 1981

By Paul Richardson

This paper discusses the drilling techniques and equipment used by Loffland Brothers Company to drill the AEC's UC-3 large diameter shaft in Nevada. Included are pictures and illustrations of the drilling-mud circulating system, the surface and downhole drill-string and the special heavy-duty mast and hoisting equipment required to do the job. The purpose and method of lining the large diameter holes along with the technique and materials used to backfill the lining to hole annulus are discussed briefly. Areas requiring improvement in both equipment design and technology for large diameter shaft drilling are discussed briefly. Shafts as large as 140 inches in diameter to depths of 5,000 feet can be drilled with existing equipment and technology.

Jan 1, 1969

By C. Garcia, A. Potulska, J. J. Opazo, T. Comi

"The Sierra Gorda SCM sulfide ore processing plant began commissioning in the third quarter of 2014. Located in the Atacama Desert in northern Chile, the project is an open pit mine and Copper-Molybdenum processing plant is one of the most highly-instrumented operations in the world. It is the first hard rock operation in Chile and the second in South America to utilize HPGR technology. It is a significant Molybdenum resource especially in the first five years and the Molybdenum separation plant is complex. Designed to process up to 60 million lbs. of fine Molybdenum per year, it uses the latest technology and equipment to ensure superior recovery and product quality. It also has gas handling and alarm systems to fulfil the Company’s vision of “Zero Harm”. This paper discusses the overall operation and issues relating to the concentrator start-up. These include a review of the mineral processing design, the unified process control center and management information systems, and the correlation of geological and metallurgical performance data (mine-to-mill) for use in anticipating and preparing for treatment of diverse ore deliveries. INTRODUCTION Sierra Gorda SCM is a joint venture partnership with KGHM International (owned by KGHM SA, Poland), Sumitomo Metal Mining, and Sumitomo Corporation (Japan) operating in northern Chile. The Sierra Gorda open pit mine and Copper-Molybdenum processing plant will become one of the largest mines in the world. The need for optimum production efficiency and sustainability has driven the creation of the most modern, well-instrumented mine in Chile. This paper contains a general review of the project including geology and history. This was a very fast-track project going from greenfield site acquisition to mill start-up in 10 years. Highly-experienced and motivated engineers and technical staff have overcome many significant challenges resulting in a rapid ramp-up of production capacity. A potential expansion to double the production rate in the fourth year of operation has also been intensely studied. The Sierra Gorda property is located in the Atacama Desert of northern Chile, in the District of Sierra Gorda, Region II of Antofagasta, Chile (see Figure 1). There is almost no precipitation in this area. The mine site is generally flat with some rolling hills. The project is located about 5 km from the village of Sierra Gorda at an elevation of approximately 1,700 m above mean sea level. The village is near a highway and railway line. The city of Calama, home of the famous Chuquicamata Mine, is located about 60 km northeast of Sierra Gorda. In addition, the SG mine is in the midst of numerous other mines including Spence, Esperanza, Mantos Blancos, El Tesoro, Lomas Bayas, Gabriela Mistral, El Abra, Radomiro Tomic, and Escondida, to name a few."

Jan 1, 2015

By BHAMIDIPATI S. SASTRY, KATTAMURI PAVAN KUMAR, ADITYA PANDEY

Several laboratory methods are available to determine the thermal conductivity of rocks, but most of them are complex and cumbersome. The present study explains the working principle of Lee’s apparatus, which is relatively simple, easy to fabricate and use, and provides consistent results. In the present study, thermal conductivities of sandstone cores obtained from an Indian coal mine are determined using Lee’s apparatus. An approach is discussed to determine the temperature gradient of sandstone specimens while cooling and is used to calculate thermal conductivity. The thermal conductivities of different sandstone specimens have values between 2.37 and 2.59 Wm−1°C−1. For different sandstone cores obtained from the field, properties including specific gravity, specific heat capacity, thermal diffusivity and porosity, along with thermal conductivity, were determined and highlighted in this study.

By James R. Tompkins

This paper details the successful progression of a promising exploration property into a producing gold mine in only 35 weeks on schedule and on budget. While under construction, an extensive exploration program continued to add to the mine life through the increase in reserves, resulting in a decision to increase the mill capacity from 500 tonnes per day to 1000 tons per day while maintaining the original construction schedule. Details are provided on the unique geology at the Puffy Lake Gold Mine, development from the exploration stage through construction and ultimately to production, with a detailed flow sheet. In addition, of note is the successful change over from contract mining to the hiring of Pioneer personnel who are successfully carrying on both stope mining and development. Operating costs per ounce of gold production are projected at $185 U.S. and alternate methods of mining are currently being examined which could further reduce operating costs.

Jan 1, 1988

By A. W. Randall

Geological Aspects of Ore Reserve Estimates of Pine Point District Zinc- Lead Deposits, N.W.T. Zinc-lead ores of the Pine Point District, Northwest Territories, Canada are hosted in paleokarst cavities within a Middle Devonian carbonate barrier complex. Of the nearly 100 deposits found, most are irregularly distributed along two main regional stratigraphically controlled trends. The ores, which occur predominantly as open space filling, form deposits most of which average one million tonnes in size with an average grade of 10% combined zinc plus lead. Geological features related to karsting control not only distribution of deposits but also their shape, size and grade. The higher grade ore in these deposits generally occurs in a relatively small core area. Consequently, accuracy of reserve estimation is dependent on drill hole density and understanding of karst geometry. Several case examples will be reviewed to demonstrate the relationship between shape, size and grade of deposit, geological reserves and drill hole density, along with a discussion of geological ore reserve estimation methods.

Jan 1, 1985

By Inoka E. Perera, Michael J. Sapko, Marcia L. Harris

Experiments conducted with limestone dusts and dolomitic marble dusts have indicated that when rock dust is wetted and subsequently dried, it becomes a solid, non-dispersible cake. However, in order to be effectively inert a coal dust explosion, rock dust must be able to disperse as individual particles to air. To counteract this, rock dust manufacturers created treated rock dusts that will resist caking after moisture exposure. National Institute for Occupational Safety and Health (NIOSH) researchers conducted a series of laboratory-scale experiments on four base rock dusts and their treated counterparts to assess the effectiveness of various anticaking additives after being exposed tomoisture and then dried. The dusts were exposed tomoisture using humidity cabinets having a high relative humidity (99% RH) and by also exposing the rock dust bed to water through bottom wicking. The dusts were then evaluated for dispersibility after drying using the NIOSH-designed dust dispersion chamber. The anti-caking additives were different concentrations of stearic acid, oleic acid, and xylene-based surfactants. All results were compared to a reference rock dust used to conduct large-scale experiments in the Lake Lynn Experimental Mine (LLEM), Fairchance, PA. When the untreated dusts were dried after exposure to moisture for 1 day, no dispersion was measured. However, rock dusts treated with anti-caking agents were readily dispersible even after exposure to moisture for 6 months. This report details the analysis and characterization of anticaking additives using the NIOSH-designed dispersion chamber and the 20-L explosion test chamber.

Apr 12, 2021

By C. J. Bise

In August, 1977, the Federal Surface Mining Control and Reclamation Act was signed into law [I]. It stated that: "The Congress finds and declares that because of the diversity in terrain ... and other physical conditions in areas subject to min ing operations, the primary governmental res- ponsibility for developing, authorizing, issuing, and enforcing regulations for-surface mining and reclamation operations subject to the Act should rest with the States." Section 516 of Title V (Control of the Environ mental Impacts of Surface Coal Mining) of the Act deals with the surface effects of underground coal mining operations. "Each permit issued under any approved State or Federal program pursuant to this Act and relating to underground coal mining shall re quire tfieoperator to adopt izeasures consist ent with known technology in order to prevent subsidence, causing material damage, to the extent technologically and economically feasible, maximize mine stability, and main tain the value and reasonable foreseeable use of such surface lands, except in those instances vhere the mining technology used requires planned subsidence in a predictable and controlled manner: Provided, that nothing in this subsection shall be construed to prohibit the standard method of room and pillar mining. "

Jan 1, 1980

By John C. Edwards, Robert C. Bates

Results are given of a mathematical study by Bureau of Mines personnel of overpressurization ventilation effects in underground uranium mines. The mathematics and computer codes make it possible to analyze many facets of transient and steady-state radon diffusion with Darcy flow. Rapid changes in radon flux occur after imposing a pressure differential across the model. Flux into the model mine drops to near zero and then increases to the steady-state level, while the sink flux increases rapidly and then drops slightly to the steady-state level. Magnitudes of mine flux decreases and sink flux increases are dependent upon the distance from the mine to sink, permeability, and amount of overpressure. Current work on more complex models is also described.

Jan 1, 1981

By S. G. Zahony

The Moris gold deposit resides in a massive ridge-forming sulfide-poor epithermal quartz and calcite vein system and consists of a mineable reserve of four million tons of 2.1gm Au/ton. Post-mineral normal faulting along the hanging wall of the main fissure has caused a hogback-like exposure of the vein, allowing for inexpensive opencut mining. The vein formed between pre-Cretaceous(?) phyllitic clastic sedimentary units in the footwall and Tertiary andesitic volcanic rocks in the hanging wall. Part of the ore reserve is hosted in a Tertiary conglomerate that rests unconformably atop the phyllitic footwall sequence. The original unoxidized vein material contained substantially less than 1 gram Au/ton. A four-fold upgrading of gold occurred by enrichment when gold recrystallization took place in the electric fields of oxidizing pyrite cubes.

Jan 1, 1993

By E. Sabina Brady

Over the next two decades there will be significant trade and development opportunities in China for mining, engineering, equipment, and construction companies interested in becoming part of the development of China's chemical and fertilizer industries. At last count, China's phosphate ore reserves of 11.8 Gt (13 billion st), ranked fourth in the world behind the US, the USSR, and Sahara-Morocco. However, a recent statement by the head of the Ministry of Geology and Minerals, Sun Daguang, claims that with increased prospecting in the last few years, China's phosphate reserves now rank first in the world. Whatever the actual size of its known and potential reserves, China's present phosphate processing capabilities fall far short of demand, while the substantial progress that has been made in this area points out the severity of the problems that still remain. Since 1949 China has developed 181 mines and increased its phosphate concentrate production from 10 kt (11,000 st) to 10.86 Mt (11.97 million st). By the 1980s, China was the third largest chemical fertilizer producer in the world-although this claim is slightly misleading as China's nitrogen/phosphate potassium ratios are far from average world ratios and even further from US standards. According to the Sixth Five Year Plan promulgated in 1982, the country's development plans emphasize the expansion and upgrading of key energy and industrial sectors, including that of fertilizer production-specifically phosphate and potash. Within the framework of the plan, the Ministry of Chemical Industry's development priorities are to: • Increase potash production by 150% to 50 kt (55,115 st). • Raise phosphate fertilizer production 21.2% to 2.8 Mt (3.1 million st), 46 kt (50,705 st) of which will come from new projects constructed and completed within the Sixth Five Year Plan, with projected new production of phosphate concentrate and complex fertilizer in the next decades totaling 500 kt (551,146 st). • Commence work to increase phosphate ore production by 8.33 Mt (9.18 million st). Facilities for 2.43 Mt (2.68 million st) will be completed and come on stream by 1985. • Commence work to increase iron pyrite ore production by 3.69 Mt (4.07 million st), facilities for 2.9 Mt (3.2 million st) will be completed and come on stream by 1985. • Verify 600 Mt (661 million st) of new phosphate ore reserves. Since the promulgation of the Sixth Five Year Plan, Chinese authorities have announced that 70 key construction projects will receive top priority in the implementation of the plan. These projects include five in the chemical industry area, including the construction of four fertilizer plants in Urumqi (Xinjiang), Zhenhai (Zhejiang), Beijing, and Lucheng (Shanxi), and a pyrite mine in Yunfu (Guangdong). In addition, by 1985 the state will expand or construct three major phosphate mines: Wangji in Hubei, Kaiyang in Guizhou, and Kunyang in Yunnan. Fertilizer Ratios In 1982, China's fertilizer production was slightly higher than 12 Mt (13.2 million st) and consisted of 80% nitrogen, 19% phosphate, and 0.19% potassium. By 1985, state officials project that fertilizer production will reach 13.4 Mt (14.8 million st) and consist of 78.4% nitrogen (10.5 Mt or 11.6 million st), 21.2% phosphate (2.8 Mt or 3 million st), and 0.39% potassium (52.3 kt or 57,605 st). To attain the world average using the country's 1985 projected production level for nitrogen, China will have to double its 1985 phosphate production to 5.76 Mt (6.35 million st) and increase its 1985 potassium production almost 80 times to 4.1 Mt (4.5 million st). These numbers demonstrate the seriousness of the fertilizer production problem in China today and the long-term nature of the problem's solution. Development Examples Yunnan is the third largest phosphate-rich province in China with verified deposits of 1.9 Gt (2.1 billion st). Despite this abundance, the province only mines around 3 Mt (3.3 million st) of phosphate rock annually. In June of this year, Yunnan announced its intention to initiate 39 development projects within the next two and a half years, requiring an estimated $200 million worth of foreign investment. The three areas receiving the most emphasis will be:

Jan 9, 1983

By Omar A. Muhtadi

8.1 INTRODUCTION Several methods currently exist by which gold may be recovered from a pregnant leach liquor. Two of these methods are discussed in this chapter, the Merrill-Crowe (zinc cementation) process and the carbon adsorption process. These two methods represent the most frequently used techniques for gold extraction and are, -in fact, used almost exclusively in U.S. heap leaching operations. Because of the efficiency and ease of use of these two methods, it is extremely likely they will continue to be quite prevalent within the gold mining industry in years to come. The remainder of this chapter includes information on the history of the two processes, descriptions of the actual processes, criteria to consider in selecting a recovery process, and commercial design and construction considerations for both of the gold recovery methods. As with other chapters in this book, some fairly technical information is presented for the benefit of those readers needing a greater level of detail. However, the overall intent of the chapter is to provide an overview of the processes likely to be used in gold extraction, thus giving the reader a firm basis for more technical research into the topic, should this be needed. 8.1.1 History of Zinc Cementation During the late 18901s, zinc cementation was introduced for the precipitation of gold and silver from cyanide solutions. This occurred at about the same time as the introduction of the cyanidation process, the history of which is recapped in Chapter 1. The initial cementation process involved introduction of a gold-bearing cyanide solution onto a bed of zinc shavings. It proved to be quite inefficient because the reaction rate was very slow. The zinc quickly became "passive", inhibiting further gold deposition. Shortly after this first introduction, zinc precipitation was improved by adding a lead salt (usually lead nitrate) to the zinc. This allowed a zinc-lead couple to form on the surface of the shavings, eliminating passivation of zinc surfaces and thereby allowing continued deposition of gold. Further improvements were shortly forthcoming. The first of these involved the use of zinc dust rather than zinc shavings. This provided a much

Jan 1, 1988

By M. A. Trevits, G. Frampton

"Mine safety training materials have long included pictures of mine conditions, equipment, hazards, etc. These images are invaluable to both the trainee and the trainer to convey many important concepts. The human eye takes in a tremendous amount of information, while the field-of-view from a consumer grade camera is, generally, 40 degrees to 90-degrees. This difference in field-of-view is a primary reason that pictures, especially of dark and dusty areas, don’t adequately describe the scene. For conveying information to a trainee, these images lack context. Today, 360-degree cameras are available with consumer-grade cameras costing a few hundred dollars. Also, the display technology is already owned by most trainees and trainers and is widely available. The resulting 360-degree videos and pictures can be readily viewed on smart phones and inserted into Microsoft PowerPoint slideshows. These images and videos can easily be included in existing training modules, disseminated using the internet, and used by trainees easily. We propose a methodology for utilization of 360-degree video and images with simple display technology for miner training. INTRODUCTION AND BACKGROUND In mining, as in other production-related industries, the safety of workers is dependent upon many interrelated factors. One of the more important safety factors is a miner's ability to recognize hazards in their workplace. The ability to perceive and identify hazards is perhaps more difficult to master in underground mining than in general industry because the work environment is confined, noisy, dark, and inherently dangerous because of the hidden unknowns created by the geological setting and the conditions created by the mine opening. Further complicating the situation is a setting that is continuously changing as mining advances (Barrett 1995) [1]. Hours of excellent mine safety training have been developed and utilized over the years. Pictures of mines, activities, hazards, etc., are included in many of these training courses. These photographs, especially those taken underground, often lack context because of the limitations of the cameras and lenses. Notable research by the US Bureau of Mines and then later by NIOSH showed that the use of stereoscopic three-dimensional slides in training exercises was an effective aid for improving the ability of miners to recognize hazardous ground control conditions (Barrett 1988) [2]. An example of type of three-dimensional slides and slide viewer is shown in figure 1."

Jan 1, 2018

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 Sidney A. Hiscock

INTRODUCTION Lead and zinc are today rightly regarded as sister metals. Historically, however, they differ markedly with lead being known and in general use as the metal since 3000 BC in several countries which at that time might have been described as mature economies. Zinc was not isolated and recognised as an industrial metal with distinct and valuable properties until about 1700-1800 AD (although it had, of course, been utilised as a constituent of brass for some 2000 years previously). c were well established as industrial metals by the beginning of the 20th century. The present paper briefly reviews the overall growth in world consumption* and changes in the three main areas which today represent the mature economies or industrialised areas, i. e. ,Europe, the United States and Japan. Trends in overall consumption are determined by the demands for the individual uses for lead and zinc. The changes in patterns of use in the industrialised areas - individually and collectively - and reasons for the changes are also considered. LONG TERM TRENDS - 1900-1984 The World Picture Since the beginning of the 20th century the world consumption of lead (3.9 million tonnes in 1984) has grown almost fourfold and that of zinc (4.7 million tonnes in 1984) is almost eleven times greater than it was in 1900. The long-term trend has been one of continuing expansion for both. metals although the pattern has been severely disturbed at certain periods, for example in the years immediately following the two world wars and at times of marked recessions in industrialised areas. Apart from such major setbacks, new levels of consumption have been established regularly every few years. Recently, however, consumption has not really grown and with only a slow and partial recovery in world industrial activity at present, there is no indication that the peak consumptions of 4.2 million tonnes of lead, set in 1979, and 4.8 million tonnes of zinc (1973) will be exceeded in the near future. The growth in world lead and zinc consumption since 1900 is shown in Figure 1 (which includes changes in copper and aluminium for comparison). Overall growth over the period 1900-1984 has been about two percent a year for lead and about three percent for zinc (annual growth for copper has also been about three percent). Increases in tonnage consumption and growth rates by decade for lead and zinc are summarised in Table I. However, the growth rates by decade sometimes conceal very large individual annual increases and decreases. For example, in 1975 lead consumption fell by 13 percent and zinc consumption by 22 percent compared to 1974. In 1976 consumption of lead and zinc rose by 12 percent and 18 percent respectively. The years when consumption 'landmarks' (ie one, two, three and four million tonnes) were first reached are shown on Table 2. Clearly, the pattern of shorter periods being required to attain each extra million tonnes of consumption was broken in the 1970's. The consumption of zinc overtook that of lead for the first time in 1940, and since 1946 has always been at a higher level. Trends in industrialised areas The two key industrialised areas at the beginning of the 20th century were Europe and the United States which between them accounted for some 95 percent of world lead consumption and 98 percent of zinc consumption. Figures 2 and 3 show the growth in lead and zinc consumption, and Figures 4 and 5 the percentage shares for each area since 1900. Europe has usually been the major user of lead except for some years in the 1920fs, most of the 40's and early 50's when consumption in the United States was larger. In 1900, Europe accounted for about 64 percent of world lead consumption and the United States just over 30 percent. Currently, Europe takes about 40 percent of world consumption and the

Jan 1, 1986