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By E. Emelyanenko, P. Solozhenkin, J. Yagudina, O. Ibragimova

To recover tetrahedrite-tennantite series minerals from porphyry copper-pyrite ores by the froth flotation method, further research on thiol collectors is launched to promote the utilization efficiency of copper ores. In the present paper the adsorption mechanism of the collectors on tennantite surface has been investigated by computational modeling and FTIR-spectroscopic analysis, which have revealed that the decrease in prognosis of collector activity evaluation (PCAE) for tennantite is in the following order: BX (-0.34318), AEROPHINE 3418A (- 0.61756), AERO 5100 (-14.18857). The lower PCAE the stronger the ability of the collector to interact with the mineral surface of tennantite and form the stable complex. More kinetic reliable conditions to form suitable adsorption layer and rupture of the liquid interlayer with AERO 5100 have been observed by FTIR spectra due to decrease of the intensity and stretching and bending vibrations of water (less than 20 and 65%, respectively). In order to verify the feasibility of AERO 5100 as a collector the industrial flotation tests have been conducted. Flotation performance has improved significantly with the stadially grinding and preflotation of tennantite in intercycle copper flotation that allows to avoid desliming of the fragile mineral and minimize loss of Cu and As in tailings. The recovery of copper in copper concentrate increases by 3.9% with the grade maintained.

Jan 1, 2018

By Kevin G. Stricklin

Introduction Continuous monitoring techniques have been used in the US and abroad for many years. A continuous miner has a monitor that measures methane and automatically gives a warning if the methane exceeds 1%. It deenergizes the continuous mining machine automatically at a maximum concentration of 2%. Main fans are also continually monitored to ensure operation. Alarms may also be given at a remote location should a fan slow or stop. The systems being developed can continuously monitor various gases and equipment throughout the mine and transmit pertinent data to a surface monitoring station. At this station, conditions throughout the mine can be monitored and, in some instances, controlled. These are known as Mine Wide Monitoring Systems (MWMS). History The use of environmental monitoring systems began in 1976 when a federal court approved the petition of modification to use belt air at the face. The first mine to receive a modification did install a system to supplement existing safeguards. Later, the Mine Safety and Health Administration (MSHA) and the US Bureau of Mines (USBM) conducted tests dealing with the use of belt air. Findings from these tests are being used to set guidelines as requirements of a petition. These requirements include: • Velocity of air has to be 0.25 to 1.5 m/sec (50 to 300 fpm); • Monitors will be installed at each belt drive and tailpiece and at intervals not to exceed 610 m (2000 ft); and • An alarm level of 10 ppm, above the ambient level is appropriate. The early uses of environmental monitoring could only be used outby the last open crosscut. That may be a reason for an initial slow growth of these systems. In June 1982, MSHA began evaluating systems that could be used in returns to ensure that monitoring systems being used in areas where permissible equipment is required does not of itself pose an explosion hazard. This is known as the Mine Wide Monitoring Systems Evaluations and Sensor Classification program. The evaluations and classifications granted are based on electric currents and voltages. Use of mine wide monitoring systems The environmental aspect of MWMS in today's coal industry deals with carbon monoxide (CO), methane (CH4), and air velocity. Just as all mines are different and encounter different problems, the MWMS are diverse and can be used to provide necessary data in all areas of coal mines. Mine operators in an ultragassy seam, for example, may be concerned with monitoring methane, while a mine that used diesel equipment may want to continuously monitor for diesel contaminants. In a mine with roof fall problems, airflow monitors may be helpful as an indication of whether the air is flowing in its normal course and at its normal volume. Today's MWMS can monitor any or all of these parameters. Most systems can be expanded as mining needs require. For example, a mine is now being monitored for methane and five years from now CO monitoring would help increase safety. It may be possible to use the same system by adding additional equipment. In the US, 30 environmental monitoring systems were installed from May 1985 through May 1986. In 1984 and 1985, there were 38 and 44 environmental monitoring systems in operation, respectively. Due to mine closings, 11 of these are no longer in use. However, the number of mines using environmental monitoring systems increased to 63. Use of these systems are not limited to any geographic area or

Jan 9, 1987

By Jetson Lemos Ferreira

O presente estudo teve por objetivo verificar a independência tanto da Curva Limite de Tensão (CLT), quanto da Curva Limite de Deformação Plástica Efetiva (CLDPE) em relação à trajetória de deformação. Para tal, foram utilizadas Curvas Limite de Conformação (CLC) de aço livre de intersticiais (Interstitial Free - IF), determinadas, primeiramente, por meio de trajetórias lineares e, posteriormente, por trajetórias bi-lineares estabelecidas por níveis de pré-deformação nos modos de tração uniaxial e estiramento biaxial simétrico. As previsões da CLT e da CLDPE, calculadas a partir das deformações limites da CLC convencional em trajetórias lineares e bi-lineares, mostraram-se independentes em relação à trajetória de deformação. Entretanto, verificou-se que o critério de escoamento adotado tem grande influência na forma e posição destas curvas limites.

Aug 17, 2017

By T. T. Wang, T. H. Huang, S. S. Zhan

"Fractures with diverse features dominate the hydraulic behavior of fractured rocks and are one of the major subjects for hydrogeological characterization of a site. This study investigates curve patterns obtained by packed tests, and as well the influence of fracture features based on 59 sets of in situ packer tests with different fracture combinations and fracture features. The result shows that, in the example of Heshe site, neat and tidy fractures usually provide stable channel for water flow during testing, and the hydraulic properties of fractures infilled with breccia and mud may change during testing because of leaching and/or washed out of infilling breccia and mud. Different combinations of fractures with diverse features in packed test sections lead to different curve patterns for in situ hydrogeological tests. For groundwater flowing predominately through neat and tidy fractures, the pressure-discharge curve of modified Lugeon tests are usually linear curve pattern, and the pressure decrease while the discharge increase in pressure-discharge-time curves of single-hole double packer tests, which benefit statistically determining the transmissivity of dominant fracture sets. INTRODUCTIONFractures interlaced in rock masses are major channels for groundwater flow and generally account for the anisotropic and heterogeneous characteristics of permeability for fracture rocks. To describe reasonably the permeability of a fracture rock, the Discrete Fracture Network (DFN) approach and others with similar ideals have been developed. Many methodologies and associate equipment, for instance, the televiewer and the in situ hydrogeological test, have been proposed to investigate the spatial distribution and the transmissivity for different fracture sets, which are two main parameters necessary for the DFN or similar model simulation (Pearson & Money, 1977; Barker & Black, 1983; Hsieh et al., 1985; Bernard et al., 2006; Quinn et al., 2012). However, diverse outlooks for the pressure-discharge curves and the temporal pressure and associate temporal discharge curves often confuse the investigation results by significant deviations on derived permeability (Houlsby, 1976; Zlotnik, 1994; Royle, 2009; Camilo, 2010).Aiming on technical development for in situ hydrogeological tests and fracture investigation, an experimental well site with 10 wells has been established in Heshe in central Taiwan since 2011 (Wang et al., 2011; Song, 2012; Zhan et al., 2013). Extensive geological survey and well-hole scanning by a televiewer provide spatial distributions and outlooks of fractures in detail. Additionally, a series of Lugeon tests, double packer injection tests and pumping tests have been performed to investigate the permeability of fracture rocks, and dominate fracture sets as well. Based on the results obtained from the Heshe site, this study classifies the curve patterns of hydraulic packer tests. The features of fractures involved in packed sections for packer tests are then inspected in detail. Relationship between the curve patterns of hydraulic packer tests and associated features of corresponding fractures in rock are discussed and addressed accordingly."

Jan 1, 2015

By Allan Rocas, Aswathy Sivaram, Daniel Cressman, Tatiana Chiesa

The City of Toronto plans to construct a 1,350 mm consolidation sewer along the East Don Roadway (EDR). The project includes installation of approximately 260 meter of 1,350 mm diameter concrete pressure pipe through microtunneling methods. The sewer alignment crosses underneath a busy 5-lane arterial road and then follows the very narrow East Don Roadway road allowance. This paper discusses the significant challenges overcome to design the Don Roadway sewer using slurry microtunneling methods through mixed face conditions below the groundwater table in a congested road allowance. A curved microtunnel was ultimately required to avoid conflicts with existing utilities, condominium tiebacks and a bridge structure.

Jun 13, 2023

By R J. Soriano, S Ciutina

The Masbate gold deposits are situated on the island of Masbate, 350 km south of Manila. A new plant was commissioned in April 2009. The grinding circuit consists of one semi-autogenous (SAG) mill Ø9.75 m × 4.27 m, two ball mills Ø5.6 m × 7.1 m and a pebble crushing circuit, which is usually called a SAG-ball mill-crusher configuration. The SAG mill was originally equipped with radial pulp lifters. The mill runs at fixed speed of 10.9 rev/min, which is approximately 80 per cent of critical speed (per cent CS). Due to the high speed of the mill the original radial design pulp lifters presented a high volume of recirculating load inside the chamber and consequently heavy wear on the outer circle (bottom pan).In order to address the high wear on the pulp lifters a number of avenues were considered in early 2011. The chosen solution was to change the geometry of pulp lifters from radial to curved design. The pre-existing drilling pattern on the discharge end of the mill was a major constraint. A number of designs were considered. The selection of the most suitable option was to be made based on 3D discrete element modelling (DEM) and smoothed particle hydrodynamic (SPH) simulations.The original radial design and two potential solutions for curved pulp lifters were simulated with 3D DEM and SPH software. The main three objectives were predicting the charge dynamics, the expected wear patterns and discharge efficiency. One of the solutions was chosen and implemented during 2012.Observations carried on after installation of the curved pulp lifters have confirmed, as expected, a reduction in wear intensity on the outer pulp lifters. In addition to this, at early stages of operation with curved pulp lifters, the mill operator noticed a reduction in energy consumed by the mill with no detrimental effect on mill performance.This paper is intended to further study the effect of curved pulp lifters on mill energy consumption.CITATION:Ciutina, S and Soriano, R J, 2014. Curved pulp lifters – can they save energy?, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 109–116 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By C. R. Kuzell

INTRODUCTION KNOWLEDGE of the thermal capacity of gases is of great importance in making metallurgical calculations. The metallurgist is, frequently called upon to investigate and determine furnace efficiencies in which the heat carried into or out of the furnace by gases is a large item in the heat balance. Not only do such problems present themselves in the determination of furnace efficiency, but also in the study of the application of heat is accessory apparatus, such as stoves, regenerators, waste-heat boilers, driers,.etc. The thermal effect of the use of excess air in the combustion of fuel, the theoretical temperatures of combustion, the quantity of heat in hot blast at various temperatures, the effect of hot blast on furnace temperatures, are a few more examples of frequently occurring calorific problems involving gases. So many are the applications of the data on the heat capacity of gases that the subject merits careful study. The heat in a gas maybe due to its heat of combustion, if it is a combustible gas, and to its temperature. The latter is called its sensible heat and is the heat absorbed or evolved by a gas as its temperature is raised or lowered. The heat of combustion of gases is well established and is commonly known. The values can be found in almost any mcdern treatise on metallurgy. The sensible heat of gases has not been so well established because it is in most cases a function of the temperature, and the values of specific heats of gases over a wide range of temperatures have only recently been determined. It is the purpose of this paper to deal with the sensible heat of gases.

Jan 8, 1914

By C. S. Parsons

Custom milling-plants have been operated successfully for a great many years on this continent. One of the outstanding examples in the United States is the Golden Cycle mill at Colorado Springs, which mills the gold-telluride ores from the Cripple Creek district. In eastern Canada, the Northern Custom Concentrators, Limited, at Cobalt, successfully treated the cobalt-silver ores of that area for a number of years. Flotation plants have entered the custom field in the past few years. The building of flotation concentrators to treat ores on a custom basis indicates the advance which has been made in flotation. In fact, three years ago it was considered almost impossible to treat successfully a mixture of miscellaneous ores by flotation. The methods used at that time were considered so delicate that any change, even in a single ore, would usually result in decreasing the effectiveness of the separation. Today we find four large custom flotation plants in the United States and one in Canada for treating complex lead-zinc ores from many different localities. The advent of these mills was brought about by the serious problem confronting the lead-smelting plants due to increasing amounts of zinc in the ores presented for treatment. It was necessary to penalize the mines shipping high-zinc ores. The penalty is justified, because high zinc in the lead blast-furnace charge not only decreases the tonnage of the furnace but increases the amount of flux necessary, as well as increasing the metal loss in the slag. It has been estimated that in the Salt Lake valley alone, 75,000,000 pounds of zinc was lost in the slag-dumps from the operations of three large lead blast-furnace plants. It has also been estimated that $150,000 worth of additional flux was required to slag this zinc. It was to avoid at least a part of this wste and to help maintain an ore supply that custom flotation concentrators were built by the smelters.

Jan 1, 1928

By Michael T. McCaffrey

The wide range of potential feed materials, process steps, and products in metallurgical facilities means that standard equipment might not be available to adequately meet the project technical and economic needs. Custom designed equipment should be considered only after rigorous research precludes purchasing standard equipment. However, the decision to use custom equipment introduces a new element of risk into the project. To manage the risk, custom equipment design should be developed through the same front end loading (FEL) phases as project development. If more than incremental development of custom equipment is required, appropriate test work or pilot trials are required to test key uncertainties. Important activities during custom equipment design include maintaining clearly defined performance objectives, conducting appropriate reviews, carefully crafting commercial and intellectual property agreements with design and fabrication partners, and assembling a multidisciplinary team with sufficient development expertise.

Jan 1, 2015

By J. David Chapman

There are a variety of choices of materials for mineral extraction processing. Traditionally, end users have used metallic piping for fluid handling and little is known about the advantages (or limitations) of non-metallic piping systems. This presentation will review custom FRP pipe systems and their use in severe corrosive and erosive process streams. These systems can be designed to various pressure and temperature ratings and different components (such as resin and glass type) can be varied to suit the process conditions

By Franz Kolmbauer

At Primetals Technologies Brazil Ltda. Rio de Janeiro Santa Cruz Workshop we electroplate mold coppers for continuous casting by tank plating. Tank plating submerges the copper in the bath of the plating solution. This is the most common method of plating and is applicable for both broadface and narrowface copper plates. Mold copper plates have a decisive impact on the product quality as well as the cost for maintenance and production. A perfect understanding of the operational influences on the plates and performance variables are the first step for the right selection of a copper plating method. Variable Hiper Coat keeps the Copper Plates 50% up to 100% longer in operation because of applying hardness on the Copper Plate where it is needed. Primetals Technologies Brazil provides the solution which meets and exceeds the requirements for todays and future demands.

Aug 16, 2017

By Daniel Hack

A few progressive mining software companies have recognized the benefit of broadening their capabilities to the sand and gravel (aggregate) industry. The most promising new developments have been designed for use with Surpac Vision, one of the world’s leading geological modeling, mine design, and production management systems. Surpac’s broad user-base, who have always had a propensity for customization, are now focusing on development of solutions in the Tool Command Language (Tcl), an interpreted scripting language. Surpac Software International made changes to TCL to add Surpac specific extensions, thus creating the Surpac Command Language (Scl). The Tcl interpreter, including Scl extensions, is bound into the Vision executable to provide a seamless interface to the data objects used internally by Vision, the GUI, and the 3D rendering system. Custom solutions can be incorporated as Vision extensions, or as stand alone-modules used in correlation with modeling, design, and planning functions.

Aug 25, 2002

To suppress the natural bacterial action in acid mine drainage (AMD), the major contributor to acid formation. Approach Recycle partially-treated affluent back to the source of AMD within a mine, or to the coal or coal-waste stockpile. This effectively eliminates any further biologically-promoted AMD by inhibiting catalyzed weathering or oxidation by acid-forming bacteria. How it Works AMO-type effluents can be largely reduced by "recycling" the acidic outflow back to the source of AMD within a mine or to the Input side of a waste pile to percolate through the reactive pyrite and bacteria mixture. The bacteria in the cell thrive on the oxidation of ferrous to ferric iron through the electron transfer, Fe2 +[=]Fe3 + + e. Its reaction product [s, therefore, essentially ferric iron. While small quantities of Fe3 + will not interfere with the exponential multiplication of the bacteria

Jan 1, 1982

Narrow vein mining, with enough challenge and also where the cutting edge technology can be applied, is still a very important and exciting portion of the mining industry. Based on the deposit characteristics, the most flexible mining method, cut and fill, has been being tested mining this high grade Northern Nevada property, Hollister, since the year of 2008. In the last three years, 254,000 tons of ore were hauled out of the portal and 23,000 feet of development were excavated underground with the winning of several safety and environmental awards. Together with mine geology, the essential segments include mining cycle, ground control, ventilation, grade control and backfill method in cut and fill stopes were covered in this paper.

Jan 1, 2012

By John G. Hall

The unstable metal market during 1949, with resulting lower metal prices, has focused every mine operator's attention on the problem of reducing operating costs. Improvement in mining methods, use of modern mechanical mining equipment, and increasing the efficiency of the labor force are the tools with which we will have to work. Careful planning is necessary to coordinate all phases so that no one phase is overdone. A mine may become over-mechanized if, for instance, capital charges against new equipment exceed the savings in labor costs, or where a large enough tonnage is not produced. The cooperation of labor is essential to any mechanization program. There have been too many instances where mechanization and improvements have done nothing more than make up for a decrease in labor efficiency, thus bringing the production of labor back to its old standard. The operator has gained little and labor has gained only a "softer job." In any mechanization program there are gains to be had by both the operator and labor. By the efficient application of modern equipment and improved mining methods the operator should gain by decreased costs, and labor may profit by receiving a share of these decreased costs.

Jan 8, 1950

By Sebastián H. Troncoso

Open pit mine planning is normally based on the selection of an economic envelope that has been generated by the Lerchs & Grossman algorithm, which requires individual economic valuation of each block of a geological block model. The selected envelope, usually called Final Pit, is later discretized in pushbacks and benches, which correspond finally to the fractions that the production schedule will allocate in time. This planning methodology has been widely used by the mining industry in countless projects to exploit open-pit mines, however, in many of the deposits can be found some undesirable elements such as arsenic, phosphates, ash among others that tend to reduce the value of elements of economic interest, either by disrupting the processes of concentration or as deemed impurities that affect the quality of the final product. Thus, a fair amount of blending would be required to capture the real value of the ore body. The traditional approach under estimates a block value by penalizing the block value by the amount of contaminant even when at the mine a set of blocks is amine at a time. This paper proposes a methodology for computing cut off grades over time that would maximize net present value allowing blending that should fulfill a set of metallurgical constraints. Preliminary results show significant increases in value and reserves quantity, questioning the use of fixed cut-off grades in generating a production schedule when blending applies to fulfill a set of geometallurgical constraints. Finally, the model allows the authors to show the importance of having adequate planning tools that will lead to the ability to look at the potential economic value of a mineral deposit.

Oct 1, 2009

By Seib W

In cut-and-break rock excavation use is made of the fact that breaking rock in tension towards a free face requires a specific energy of excavation which is small in comparison with that required for rock excavation using conventional tools operating by a process of indentation of the rock.The process of cut-and-break excavation comprises firstly a cutting step in which a groove is cut into the rock surface, followed by a breaking phase in which a tool is inserted into the cut in order to break the rock adjacent to the cut.

Jan 1, 1992

By Joel K. Waterland

GENERAL DESCRIPTION Homestake Mining Co.'s operations are at Lead, SD. Production from the various methods used are: 1 155 753 t/a (1,274,000 stpy) by open cut-and-fill, 68 039 t/a (75,000 stpy) by square set cut-and-fill, 144242 t/a (159,000 stpy) by shrinkage stoping, 107 048 t/ a (118,000 stpy) by blasthole stoping, and 67 132 t/a (74,000 stpy) in development work for a total of 1 542 214 t/a (1,700,000 stpy). Mining takes place from the 616-m (2000-ft) level to the 2073-m (6800 ft) level (Fig. 1). The average travel time to the stope is 45 min. GENERAL ORE BODY REQUIREMENTS AND LIMITATIONS Size, Shape, and Dip of Ore Body Six major ledges varying from 914 m (3000 ft) long by 228.6 m (750 ft) wide to 305 m (1000 ft) long by 122 m (400 ft) wide are mined. Within these ledges are irregular-shaped areas of varying sizes. These ledges dip at approximately 1.2 rad (70°) to the east and plunge to the south from 0.26 to 1.57 rad (15° to 90°). Ground Conditions The ore is cummingtonite (chlorite schist) which is very competent except for major bedding planes and fracture patterns. The footwall is a slate but because of the dip presents very few problems. The hanging wall is also a slate which because of the dip and bedding is very weak and requires considerable rockbolting. No problem has been encountered with rock bursts to a depth of 2438 m (8000 ft). Ore Value The ore values vary somewhat from ledge to ledge, but the average ore delivered to the mill is approxi¬mately 6.2 g (0.2 oz) of gold per ton. A small amount of silver is the only byproduct of this operation. Annual production of gold is approximately 10 575 183 g (340,000 troy oz). Production Requirements The mine has a mill capacity of approximately 1 723 651 t (1,900,000 st) but because of several fac¬tors (manpower, depth, etc.) this mill capacity has not been attainable for the past several years.

Jan 1, 1982

By B. Hornsby

At the Mount Isa mine, Mount Isa, Qld., Australia, sublevel open-stope mining is used for copper ore while both sublevel open-stope and cut-and-fill methods are used for the silver-lead-zinc ores. Production in 1979¬80 was 4 730 000 t (5,200,000 st) copper ore and 2 590 000 t (2,850,000 st) of lead ore. The deepest mine level currently is 960 m below the surface. GENERAL ORE BODY REQUIREMENTS AND LIMITATIONS Size, Shape, and Dip The mine is located in the valley of the Leichhardt River in Lower Proterozoic sediments of the Mount Isa group. The regional strike of the sediments is north¬south and they have a persistent westerly dip of about 1.1 rad (65°). In the mine area, the Mount Isa group comprises a sequence of alternating bands of dolomitic shales and siltstones some 3.2 km (2 miles) in width. It is bounded on the east by greenstones and quartzose sediments of the Eastern Creek volcanics, and on the west by the Mount Isa fault, west of which occur schists and other metamorphic rocks. The ore bodies as currently known at Mount Isa are restricted to the Urquhart shale, a formation of thinly bedded pyritic, dolomitic, and volcanic shales some 1070 m (3500 ft) thick. Towards the top of the Mount Isa group sediments, copper and silver-lead-zinc ore bod¬ies occur as contiguous but discrete entities and are mined and treated separately (see Figs. I and 2). Argentiferous galena, sphalerite, pyrite, and minor associated sulfides occur in distinct concordant bands throughout the Urquhart shales. Wherever these bands are grouped together in sufficient density they constitute silver-lead-zinc ore bodies with widths varying up to 36.6 m (120 ft). Other mineralized bands are common in intervening beds. Individual ore bodies persist for many hundreds of meters concordant with the strike and dip of the enclosing shales. Intersections of these beds with fold axes provide local zones of enrichment but otherwise the mineral content of the ore bodies varies only slightly throughout the extent of the dip and strike. Chalcopyrite is the only important primary copper mineral. It occurs in association with pyrite and pyrrhotite as disseminated flocks and as vein fillings throughout irregularly shaped zones of folded, brecciated, and re¬crystallized Urquhart shale. These zones, which are lo¬cally termed "silica-dolomite" bodies, are broadly transgressive to the shale bedding and confine all significant copper mineralization to the virtual exclusion of silver¬lead-zinc mineralization. In some areas, the downward percolation of acidic water through faults and shears has caused extensive leaching of the coarse-grained carbon¬ates to depths in excess of 610 m (2000 ft), but most of the silica-dolomite remains unleached and the ground is competent. The majority of lead ore being mined is north of the main shaft pillar (R62, U62) area. The major lead¬producing areas for many years have been the Black Star ore bodies (2 and 5 ore bodies) and the Racecourse ore

Jan 1, 1982

By Raimo Matikainen, Pekka Särkkä

HISTORY The history of mining in the Outokumpu Co. shows continuous development of small and medium-sized mines, coupled with a permanent improvement in min¬ing methods and mechanization. Tables 1 and 2 provide a brief outline of the major events over the years of operation. Some of the mines have had relatively short lives as in the case of Nivala, Korsnas, Kylmäkoski, the surface pits of the Kotalahti, Vuonos, and Hammaslahti mines, and some very small pits. The sequence in which the mines started opera¬tions is shown in Table 1 and production increases in Table 2. GEOLOGICAL FRAMEWORK Most of the ore deposits in Finland (see Fig. 1) are situated in middle Precambrian (1500 to 2300 m.y.) formations corresponding to the Baltic shield. The ores and country rocks are generally firm, with a minimum compressive strength of 60 MPa (8700 psi). The sulfide ores, of importance to the national econ¬omy, can be divided into copper-nickel deposits, asso¬ciated with basic and ultrabasic rocks (1900 m.y.), and the sulfide ores found in well-preserved Svecokarelidic crystalline schists (1800 to 2300 m.y.) which contain varying amounts of copper, zinc, cobalt, nickel, and lead. Over 90% of the sulfide ore mined to date in Fin¬land and existing in the known ore reserves belongs to deposits situated in the main sulfide ore belt. This belt extends diagonally across the country over a breadth of Table 1. Sequence in Which Mines Began Operations 1913 Mining started at the Outokumpu mine (now called Keretti) 1928 Large scale systematic exploitation started in the Outokumpu mine Opening of mines: 1942 Nivala mine (1942-54) 1943 Yiojärvi mine (1943-66) 1947 Orijärvi mine (1947-54) (Mining started in 1757) 1948 Aijala mine (1949-58) 1952 Metsämonttu mine (1952-58 and 1964-74) 1954 Keretti's new mine plant 1954 Vihanti mine 1959 Kotalahti mine 1961 Korsnäs mine (1961-1972) 1962 Pyhäsalmi mine 1966 Virtasalmi mine 1967 Kemi mine 1970 Hitura mine 1971 Kylmäkoski mine (1971-74) 1972 Vuonos mine 1973 Hammaslahti mine 1978 Vammala mine Table 2. Ore Production of the Outokumpu Oy Mines Year 1000 t of Ore 1913-1928 252 1929-1954 13 075 1955 1 105 1960 1 784 1965 2 627 1970 3 269 1975 5 825 1976 5445 1977 4 939 1978 5 766 1979 5905 40 to 150 km, from Lake Ladoga to the coast of the Gulf of Bothnia. The main sulfide ore belt includes the Outokumpu copper-zinc, the Kotalahti nickel-copper, the Pyhäsalmi copper-zinc, and the Vihanti zinc ore zones. The Outokumpu ore district occurs in a mica schist area about 60 x 100 km, in association with belts of metamorphic Svecokarelidic quartzites, black schists, dolomites, skarn rocks, and serpentinites. The main ore minerals are chalcopyrite, pyrrhotite, pyrite, and sphalerite. In addition there are nickel and cobalt minerals such as cubanite and cobalt-pentlandite, which have been of economic importance. In this area, Outokumpu Oy exploits the deposits at Keretti and Vuonos. The latter was discovered as an extension of the Keretti ore field about 6 km to the northeast. The Kotalahti geological formation extends across nearly 400 km. The host rock of these mostly pipelike deposits is generally serpentinite, pyroxenite, or norite. The main ore minerals are pyrrhotite, pentlandite, and chalcopyrite. In this zone, the deposits of Kotalahti, Hitura, and Virtasalmi are at present under exploitation by Outokumpu Oy. The Vihanti geological formation is located in west¬ern Finland and is about 40 km wide and some 200 km long. The rock associations are crystalline schists including dolomites, mica schists, mica gneisses, gray¬wacke, and acidic or basic volcanic rocks, which change generally, in connection with the mineralization, into skarn and cordierite-anthophyllite rocks. The host rocks are dolomite, skarn, graywacke, and quartzitic rock and the principal minerals are sphalerite, chalcopyrite, galena, pyrite, and pyrrhotite. The accessory minerals are mainly cubanite, arsenopyrite, molybdenite, and native gold and silver. The two largest ore bodies being exploited at pres¬ent by Outokumpu Oy are the Vihanti mine, which pro¬duces zinc, lead, and copper, and Pyhäsalmi, which con¬tains copper and zinc. Deviating from the sulfide ore types described earlier is the Hammaslahti copper ore located in the southeast-

Jan 1, 1982