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By J J. Cilliers, K Hadler

The potential of air rate profiling to significantly improve the flotation performance of a bank of cells has been shown by numerous studies. To date many profiles have been evaluated; balanced, increasing, decreasing and combinations of these. An increasing air rate profile, where the air rates are increased proportionally to each cell down the bank, has been typically found to yield improved flotation performance compared to other profiles. Air rate profiling has two distinct components; determining the correct total air rate for the bank, and determining the correct distribution of that air. This can be done simultaneously by finding the optimal air rate to each cell in the bank in turn through air recovery optimisation. Air recovery is the fraction of the inlet air which overflows the weir of a cell as unburst bubbles. The peak in air recovery (PAR) is a robust measurement of optimal performance for the operating conditions in the cell, and sets the PAR air rate. In this study, plant trials of different air rate profiles and profiling based on PAR, were evaluated. The total air rates to the bank for all profiles tested were approximately equal, allowing direct comparison. The highest cumulative mineral recovery was achieved by operating at the PAR air rates for each cell down the bank. Different distributions of the same total air rate to the bank gave the same cumulative upgrade ratio, but lower cumulative recoveries. In this work the upgrade ratio is defined as the ratio of the concentrate grade to the feed grade. The increase in cumulative mineral recovery, at the same upgrade ratio, in this study was greater than 33 per cent. Air recovery based optimisation of air rates to banks of cells significantly improves flotation performance as it simultaneously determines the optimal air rate to the bank, and the optimal distribution of that air.

Jan 1, 2009

The reduction of titanium tetrachloride to trichloride can be achieved by employing hydrogen and electric arcs. It is possible to produce melts containing up to 50% TiCk in the eutectic mixture of LiCl/KCl by striking a D.C. arc at the surface in the presence of hydrogen and TiCl. vapour. If the electrode IS made to just penetrate the surface of the salt mixture, a hot zone results from the' high resistance contact with both lower chlorides and sintered titanium may be produced. The sintered metal forms just below the melt surface while the trichloride forms at the gaslIiquid junction.The "hotspot cathode" appears to offer a solution to the problem of producing coherent deposits as the spong'e metal can 'be continuously withdrawn in a similar manner to the "calcium process".INTRODUCTIONConsiderable interest has been shown for some years in the possible development of a cheap electrolytic process for the extraction of titanium metal, since a method using simple materials and cheap electric power would materially reduce the cost of production. Even when cheap starting materials are used, however, there exist several general difficulties in the operation of plant which both limit the speed of production and increase the cost of the product. It happens that most of the techniques so far tried produce a powder as cathodic deposit, and when this is the case the following difficulties arise:1. The whole contents of the bath must be treated with solvent in order to extract the 'metal powder which may itself tend to oxidise, and thus become contaminated.2. Fine metal powders, which often contain residual entrained salts, are less easy to consolidate by arcmelting than metal sponge.

Jan 1, 1956

By Y Peng, D J. Bradshaw, X Chen

At NewcrestÆs Telfer gold mine, a strategy of regrinding pyrite rougher flotation concentrates has been proposed to increase gold recovery and reduce cyanide consumption in the CIL circuit. The regrinding will be followed by an additional copper/gold flotation stage, where copper minerals need to be separated from pyrite. However, although the minerals are well liberated, the separation of chalcopyrite from pyrite in the cleaner stage is not always straightforward. The surfaces of the fine particles, produced during regrinding, are more easily oxidised and contaminated than coarse particles, directly influencing the particle floatability. The depression of pyrite is difficult in the cleaner stage as well due to copper activation, a process which is also highly dependent on the grinding environment. In this study, different grinding media, including mild steel and stainless steel, was used in the regrinding to produce different regrinding chemistry, such as, pH, Eh, and iron hydroxide contamination. The effects of regrinding conditions on chalcopyrite flotation and its separation from pyrite were studied. It was found that the stainless steel grinding media, which produced an oxidising environment, was more beneficial for the separation of chalcopyrite from pyrite after regrinding. The mild steel grinding media had a detrimental effect on both chalcopyrite and pyrite flotation. This study addresses the importance of choosing suitable regrinding conditions in the pyrite and copper flotation circuit.CITATION:Chen, X, Peng, Y and Bradshaw, D J, 2012. Effect of regrinding conditions on the flotation of chalcopyrite and its separation from pyrite in the cleaner stage, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 279-286 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

In recent decades the awareness of environmental issues by the general public has developed at an accelerat- ing rate. This is the result of a number of factors including more scientific knowledge of environments and of the impacts of modern society upon them, higher levels of education, the opportunity for people to travel more, and the success of the various communication media in bringing in- formation to the communities of the world about such environmental crises or threats as the smogs of Los Angeles and London, the Torrey Canyon and Santa Barbara oilspills, Minamata disease in Japan, the spread of the Crown of Thorns starfish, the disposal of toxic industrial wastes into the Upper Rhine, the discovery of high mercury and zinc contents in marine foods in southern Australian waters, and the proposal to mine limestone at Precipitous Bluff in Tasmania.

Jan 1, 1975

The earth is a planet limited in size and limited in total resources. For the forseeable future, it is the only available habitat for mankind. Therefore, it follows that the more we know about our planet the better we can utilize its space and its resources for our well-being now and in the future. But, to accomplish this, we need reliable basic information. Geosciences provide such information. Recently, Dr. M. King Hubbert took note of the important effect of the geosciences on society, on how we think, and how we live. In the first century of modern geology, 1780- 1880, the influence of geology was primarily on how we think, i.e. changing our concept of the earth from one with a short catastrophic history to one that developed gradually over enormous spans of time. In the second century, 1880-1980, the emphasis was on how we live, on expanding the knowledge base so that we could more easily find and utilize the earth's resources. Now, in the third century, i.e. from 1980 towards the year 2000 and beyond, we should concentrate on both how we think and how we live; i.e. how we can better estimate potential global' resources and how we can manage these resources for maximum benefit to mankind. Like other sciences, the geosciences build upon what has already been done. Progress is achieved by using the thoughts, measurements, and observations of past workers, adding to these the insights from new experiments and from new concepts. Geology has its own methodology and approaches; but more than most sciences, it calls also upon the tools of physics, chemistry, mathematics, engineering, and biology to help solve its problems. Today's increasing population, increasing industrialization, and increasing complexity of modern society demand more detailed geoscience information so as to better use the land, reduce geological hazards, provide an inventory of resources, facilitate waste disposal, and prepare for long-term effects such as changes in climate and sea level.

Jan 1, 1986

Although this is a symposium on "The Occurrence, Preparation and Use of Australian Black Coal", I do not think that, in these days, any of the main energy resources can be considered only in terms of country of origin or only by itself in isolation from other energy resources. Accordingly, I propose to comment on solid fuels generally in the world energy scene, and make some brief references to Australian solid fuels, and to some other matters in the latter part of this paper. In this address I am drawing heavily on the 1974 survey of energy resources published just recently by the World Energy Conference. I do this for a number of reasons. Firstly, the survey is the latest and most comprehensive publication of its kind; secondly, it is the result of several years' work by a panel of eminent people, from all the energy industries and from some 16 widely spread countries; thirdly, substantial assistance was given by the U.S. Atomic Energy Commission in its compilation; and, finally, to let all know of the existence of the book, as I believe it to be a source document for all those interested in world energy resources. The United Nations "J" series of statistical papers provide important information on the annual production and consumption of and trade in the various forms of energy. In their respective areas, these two publications are primary information sources. Our present sources of energy throughout the world are fossil fuel deposits (coal, oil, gas), nuclear materials, water, geothermal, solar and tidal - but we are at present heavily dependent upon the natural stores of non-renewable fossil energy resources. Fig. 1 shows the changing use of energy resources in the present century. A comparison between 1900 and 1973 shows clearly the shift which has taken place.

Jan 1, 1975

THE MORWELL BROWN COAL DEPOSITSTHIS deposits of brown coal in the neighbourhood of Morwell, are of tertiary age, and are represented on several horizons, but, owing to lack of evidence, the exact age cannot be fixed definitely. It is chiefly by reference to the basalt flows of the Older Volcanic series that the brown coal beds have been classified as of Pre-Volcanic and of Post-Volcanic age. The Pre-Volcanic brown coals are less widely distributed, and the seams generally are thin, though near Thorpdale a thickness of 40 tt. has been recorded, and from 10 ft. to 12 ft. in the vicinity of Narracan. Both of these localities lie to the south-west of Yallourn, and it has not been proven as yet whether these older coals and accompanying basaltic flows pass under the Morwell beds.The brown coal deposits have accumulated in an area where extensive faulting in early tertiary times has taken place with oscillations of elevation and depression of the land surface. In the vicinity of Yallourn, Paheozoic strata (probably Silurian) are exposed on either bank of the Latrobe River about a mile above the powerhouse weir, where the river flows through steep banks rising a couple of hundred feet on either side. The Silurian strata are highly inclined, and consist mostly of slates and Illudstones. Resting unconformably on the upturned edges of the Silurian is a conglomerate bed of Mesozoic age, above which occur beds clipping to the south-east of felspathic sandstones, with alternating mudstones at times carbonaceous, and containing thin seams of black coal.The brown coal seams and associated lignitic Clays, sands, gravels, etc, rest on the Mesozoic strata (as proved in the vicinity of the power-house and by boring north of the Latrobe River, near the old open cut), but do not appear on the surface of the Mesozoic, where these beds attain an altitude of more than 50 ft. above the present level of the Latrobe River.Half a mile upstream from the power-house a layer of basalt of the Older Volcanic series, almost resting upon the Silurian strata, is...

Jan 1, 1924

Equity finance provides the most suitable and frequently the only access to capital during the exploration and evaluation stages of resource projects when project risk is at its highest. Investors are prepared to provide equity funds in the knowledge that they are compensated for the higher risk they take on with higher potential returns or sufficient upside potential to justify the higher risk. The context of resource projects which determines the role of equity finance has changed considerably. Prior to the resurgence of the gold price and the development of new mining technology many resource projects were selectively mining orebodies by underground methods frequently with limited reserves proved up in advance of mining. The limited proved ore reserves base and the volatility of the gold price all contributed to a higher risk and higher return investment environment in which the use of equity finance was more appropriate and frequently the only option for capital raising. The financial risk of a resources project can be transferred to an underwriter who makes the commitment to distribute the financial risk between a number of investors. There is also the opportunity for financiers to use a mix of equity and debt finance to allow a company to proceed with the development stage where without such a mix the resource project would not proceed. By using a level of equity finance the project becomes robust enough in its ability to service the debt finance facility and the project proceeds with the equity participants receiving a suitable risk reward return. The liquidity from the establishment of a market for the company's securities enhances further capital raising and generally enables the company to satisfy its financial requirements on more favourable terms particularly during bull markets. The role of equity finance in the management of the financial risk during the exploration, evaluation, development and mining stages of resource projects is summarised in Table 1. In more detail the principal roles of equity finance and the ways in which equity finance impact on the risk management of resource projects will be considered in turn.

Jan 1, 1994

Pasminco is actively addressing the optimal utilisation of the known orebody at the Broken Hill mine, in addition to actively exploring for economic mineralisation in the region. As part of the policy of better utilising the known mineralisation a major upgrade of geological systems at the mine was initiated. The software chosen for this change was Maptek's Vulcan, mainly because of the ease of use of this package. Rather than having numerous data sources in varying software packages the mine aimed to limit interfaces and packages. The decision to upgrade the mine's software was not taken lightly, especially in view of the inature stage of Broken Hill mining operations. However, the current mine life of Pasminco Broken Hill mine is I I years, which is longer than many new mines setting up in Australia today. Also, a more sophisticated system brings with it a better understanding of the economic mineralisation, possibly extending the mine life further. The process of moving the Broken Hill databases into Vulcan was a huge task which included, database transfer, digitising, wire framing, modelling and eventually ore resource calculation. To ensure the validity of the new ore resource accounting system, the existing system was run as a duplicate for the introductory year, providing a comparison and if necessary a safety net. The benefits of such a change, however, became apparent almost immediately. Area geologists realised the opportunity to revise geological interpretations in their areas of responsibility, enabling them to obtain a better understanding of orebody morphology. Three- diniensional analysis provides an excellent method by which review of ore targets both in the underground and mine lease exploration areas can he made. As each new find of mineralisation enters the system and hopefully extends the mine life, the opportunities for further mineral exploration in Broken Hill area by Pasminco are enhanced.

Jan 1, 1997

The patented "Epytensic" pump of Minnovation Ltd, a multiple piston pump, is used widely on shearer loaders and by partial high pressure watcr jet cutting strategically in relation to cutter picks not only improves cutting rates, but saves power and increases the life of gearboxes and picks, as well as improving dust suppression. The "Face Side Pump", also a piston pump, located on the ranging arm gearhead has advantages over gateroad pumps and shearer body pumps. The "Extraction Drum", hydraulic air mover system, linked with the above innovations and high pressure water, have further advantages in methane and dust removal. Some modifications providing these systems need workshop applications but most are possible underground with minimal changes to shearer profiles and advantages of minimising hosing, along with the other advantages stated.

Jan 1, 1991

Interest in mineral sand mining in the south west corner of Western Australia began in the late 1940's and significant production commenced in 1956. Early land use conflicts arose because of conservation implications (Ludlow tuart forest), expanded to include post-mining rehabilitation requirements (the Wonnerup mine near Busselton) and today include some agricultural/mining disputes. These latter conflicts are largely caused by the need for mining companies to secure longer-term reserves. To date, deposits containing mineral valued at A$440 million have been sterilized and are unlikely to become available in the future. There is additional pressure being placed on presently available reserves and a pessimistic picture could be drawn, whereby the southwest mineral sands industry ceases to exist by the year 2010. However, sensible land use planning, the support of policticians and the community, and responsible attitudes towards compensation and rehabilitation could, in combination, see the industry maintain significant mineral output until the middle of the 21st century. Examples of deposits sterilized by adverse land use will be given.

Jan 1, 1986

By E Ferrow, R Herbert, M E. Malmstr, M Fuchs

The study of microbial sulfide oxidation and oxidation rates of tailings requires the use of sterile control samples in laboratory experiments for comparison purposes. The need for sterile tailings sand is also apparent in the study of microbial communities and processes. This study compares six different methods with regard to sterilisation efficiency and investigates chemical and mineralogical changes in the samples as the result of sample treatment. In addition, the effect of sterilisation on mineral weathering rates is also studied. The efficiency of the different methods with regard to sterility is estimated by most probable numbers (MPN) of both sulfur and iron oxidising bacteria. The sterilisation methods that were compared are: washing with sterile water, washing with ethanol, applying antibiotics, repeated heating to 70¦C, autoclaving, and γ-irradiation. There are several possible drawbacks with the different methods, including the risk of an applied chemical acting as a substrate for micro-organisms in the system, and the risk of altering the tailings. The results show a substantial difference in sterilisation efficiency between the treatments. For example, autoclaving, repeated heating, ethanol and irradiation efficiently kill micro-organisms, rendering an undetectable amount of bacteria after one month of incubation, whilst washing with water exhibits virtually no microbiological effect, with a bacterial content comparable to the control. The use of antibiotics for sterilisation ranks intermediate: the lag-phase was twice as long in the antibiotics treatment compared with the controls. X-ray diffraction, optical and electron microscopy, M÷ssbauer spectroscopy, and mineral magnetism indicate no significant change in the bulk mineralogical composition. However, X-ray photoelectron spectroscopy analyses show that with some of the treatments, sulfides are partially oxidised, as indicated by the formation of sulfate and partially û oxidised sulfur species at the tailings surfaces. Aerated batch weathering experiments performed on sterilised tailings samples and untreated controls indicated that while the initial rates of element (S, Fe, Cu, Zn, Mg, Na, K, Ca) release may differ between the samples, over the course of ~100 days of experiment at pH 2 and room temperature, the rates declined toward a similar value for all samples. To conclude, there does not appear to be one perfect method for tailings sterilisation. Autoclaving and heating damage the mineral grain structure and oxidise the sulfide surfaces. Ethanol, antibiotics and rinsing greatly alter the pore water chemistry through the washing procedure. In addition, ethanol and denatured antibiotics might serve as a substrate and also, in the case of antibiotics, adhere to mineral surfaces thus obstructing chemical reactions. Irradiation seems to be the preferable method on an overall basis, although the formation of surface Fe3+ was suggested by M÷ssbauer spectroscopy.

Jan 1, 2003

There are countless petroleum and mineral fiscal systems throughout the world. This is because many petroleum and mineral producing countries have developed their own methods of calculating government take through fiscal evolution or individual negotiation. Those countries fortunate enough to have petroleum and mineral reserves within their national boundaries are naturally reluctant to yield this resource without a reasonable return for their population. As resource companies are perceived to be enormous conglomerates with endless amounts of cash and resources, governments and the general public demand reasonable division of production while these finite resources last. On the other hand, because companies engaged in the exploration for, and production of, minerals, oil and gas have to be large or lucky (preferably both) to sustain the great physical and commercial risks involved, the income and profit figures look so large that the general public sees them as an acceptable target for taxation. Taxation of the resource industry has been one of the industry's greatest cash flow problems through the years. Allen and Seba (1993) attribute this to the fact that the most equitable tax systems are those that affect the widest possible total of the population.

Jan 1, 1996

By N Madani, N Battalgazy

Geostatistical simulation has been widely used in mineral resource classification of metalliferous deposits based on international standards such as JORC code which is one of the most extensively used around the world for reporting the mineral resources and ore reserves alongside with objectives of the companies (Sadeghi, Madani and Carranza, 2015). However, the modeling process becomes challenging whenever the relationship between the variables of interest is complicated and cumbersome to model. This characteristic sometimes manifests itself in complex spatial and global cross-correlation measures, deeply depending on the formation and genesis of the deposit. The objective then is to generate the models that not only reproduces these significant characteristics, but also, it leads to a better understanding of a mineral resource estimation and successive decision-makings. In this respect, there are different approaches taking into account the spatial correlation structures, for which can be classified as independent simulation, co-simulation, and factor-based methodologies. In this paper, three techniques: Turning Bands Independent Simulation (TBSIM), Turning Bands Co-Simulation (TBCOSIM) and Projection Pursuit Multivariate Transform (PPMT); from those aforementioned approaches are selected to model two cross-correlated variables (Iron and Aluminum Oxide) belonging to an Iron ore deposit located in Brazil, in order to examine which methodology better reproduces the corresponding complexity in terms of local correlation measure. CITATION: Battalgazy, N and Madani, N, 2018. Mineral resource assessment in complex ore deposits based on international standards, in Proceedings Complex Orebodies Conference 2018, pp 79–81 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 21, 2018

The occurrence of metallic minerals in Australia to the time of the proclamation of South Australia as a Colony in 1836 was unknown. It is, therefore, perhaps, surprising that British settlers arriving in the Coromandel included among their number a German scientist Johannes Menge who had been appointed by the South Australian Company to the post of Mine and Quarry Agent and Geologist on 1 July 1836. His instructions were to `explore the natural productions of the Colony above and below ground and to superintend the working of quarries of stone and slate, the boring for water, metal, lead, coal and other mines at a salary of ú150 per annum for one year and for as much longer as the Company require your services not however exceeding five years'. In the event, he was to have little influence on those matter.

Jan 1, 1993

By Westcott PC

The development of a coal project must pass through a number of phases, taking it from a preliminary evaluation through to detailed mine planning. For each phase the cost of data acquisition and associated mining studies increases exponentially for linear improvement in confidence levels. Within each mine planning phase there are four main activities. These are the economic ordering of reserves, the development of optimum mining strategies, mine design and scheduling and finally the estimation and analysis of costs. The development of the optimum mining strategy is one of the most critical aspects of a mining evaluation and the application of economic criteria at this stage of the project is vital to the successful generation of an optimised mine design. A recommended method is the concept of Economic Ratio (ER) which expresses the likely cost of mining from a given location in a deposit in terms of the value of the product likely to be recovered. The most economic mining strategy will be to mine areas from low economic ratio to high economic ratio within the constraints of reasonable equipment application. When selecting equipment a particular machine should not be selected solely on comparison with other machines in isolation, but the total application must be analysed. In the final selection the decision should be based on whether or not it has a beneficial effect on overall project economics. The economic assessment must take into account the time value of money, so the real cost can be determined with adequate provision for capital and operating costs over different time spans.

Jan 1, 1983

By E McLean, J Fleay, M Davis

Performance testing is often used by project owners and financiers to provide protection from, or assessment of, technical aspects of project design, procurement, construction and commissioning. The performance tests can range from comprehensive performance warranties relating to process performance and production in the case of lump sum turn key (LSTK) projects to less onerous demonstration tests for cost reimbursable contracts. This paper will discuss performance testing from both the contractorÆs and ownerÆs perspectives and focuses on: when performance tests are required, what type of performance test/warranty is optimum for each type of project, and how project performance should be evaluated. The requirement for performance testing can be driven by the project financiers, particularly in the case of smaller resource development companies. In such cases, differentiation between ownerÆs risk and contractorÆs risk can become contentious. At the other end of the spectrum, larger mining houses may choose to heavily influence the engineering and design process with the contractor supplying services on a reimbursable basis. In that case, the performance testing process is often limited to demonstration tests that validate performance for the ownerÆs corporate governance requirements. This paper was prepared due to the lack of published benchmarking of performance testing and the resultant differences in expectations between a contractor and a project owner that often surface late in the contract negotiation process. The paper provides a checklist of requirements for both the owner and the contractor that may be used to provide æcommon purposeÆ early in the contract negotiation process.

Jan 1, 2007

By D Laurence

Significant developments in future mining systems, technology and best practices are emerging that are driven by issues relating to human resources, competitiveness, environmental and social responsibility, within the dynamics of globalisation. It is proposed that the definition of the role and attributes of the mining engineer in the mine life cycle needs to be viewed more holistically in the face of increasingly more diverse and complex responsibilities. These developments are motivating the need to consider a fresh approach to mining education and training at all levels for industry. A growing diversity and complexity of professional responsibilities is extending the mining engineerÆs broadly based skill set and reinforcing the need to play a central role within increasingly interdisciplinary teams. On the other hand, the imminent new technologies that will transform the mining process are prompting the assumption that more focused and specialised skill sets will be needed. A way forward is suggested that would first define a blueprint for the future mine, as an attempt to characterise the systems architecture, processes and organisation of the next generation mine. This can be the basis for assessing the nature of the workforce and distribution of responsibilities, from which can be inferred the skills and training requirements. In the context of the mining engineer, the paper explores how understanding such future requirements will enable more proactive development of a strategy for educational development. The paper then concludes by considering issues and lessons learned from some recent mining educational development initiatives underway in Australia and Canada that are shaping significant change.

Jan 1, 2008

Accidents in open pit mining have a high cost in lost time of person- nel, damage to equipment and installations, and lost production. The realities of export competition require that Mine Management sig- nificantly reduce the costs associated with accidents and workplace ill-health. Newer management approaches are proving effective in reducing the Total Cost of Risk through a strucured Occupational Health and Safety Programme exhibiting the following features: ò Formal Company Policy ò Accountability for OH&S performance clearly designated to each level of management and supervision ò Effective utilisation of a Mine Occupational Health and Safety Co- Ordinator and a Mine Occupational Health and Safety Adviser ò Development of realistic OH&S Objectives ò Training of Management, Supervision and Workforce in Occupa- tional Health and Safety ò Development and adoption of Safe Work Practices and Procedures ò Effective employee selection procedures, control of Contractors ò Monitoring of the health of the workforce ò Collection, recording and distributing information on all Mine inci- dents, accidents, injuries and damage ò Ensuring that the Mine environment is healthy and safe ò Effective Emergency Procedures to deal with injury, fire, rescue and other situations of risk ò Controlling those Mine hazards which cannot be removed ò Adopting a high standard of Occupational Rehabilitation ò On-going visible Management participation in the programme to ensure that momentum is developed and maintained. This approach requires that Occupational Health and Safety be given equal status with product quality, maintenance of plant and output per- formance; its implementation is rewarded with improved morale and major cost reductions.

Jan 1, 1989

By A D. Farmer

Power ultrasound may be used in a number of ways to enhance the processing of minerals. It is both technically and commercially feasible to apply ultrasound to leaching processes in order to enhance the removal of contaminating minerals, or the rate and ultimate recovery of valuable mineral. When applied to the production of synthetic rutile from reduced ilmenite produced by the Becher process, its use proved beneficial to both the aeration and the final acid leach process. The enhanced performance is achieved through the very localised high energy release at the mineral surface from the collapse of cavitation bubbles produced by power ultrasound. This gives rise to two effects: initially, the rapid cleaning of mineral surfaces û of oxidation products and coatings of fine adhering gangue minerals û and the attenuation of the boundary layer at the mineral surface during leaching, which allows fresh leachant to contact the surface more readily.

Jan 1, 2000