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By P. Latostenmaa, T. Veneranta, J. Järvi, E. J. Peuraniemi

Boliden Harjavalta has operated a copper flash smelter since 1949 thus the smelter celebrates 70th anniversary of flash smelting in 2019. This paper shortly describes the historical perspective of the smelter and gives an update of the current operational issues and process modifications made during the recent years. The plant has carried out several major investments lately providing a firm view on the future. A new landfill area for the final slag was commissioned in 2018. A modernization of the concentrate storage area, a new acid plant and a debottlenecking project of the smelting line have been recently commissioned. At the same time, the tankhouse capacity will be expanded. This paper focuses on smelter modernizations. INTRODUCTION Boliden is a metal company operating mainly in northern Europe with core competencies in the fields of exploration, mining, smelting and metal recycling. Boliden Harjavalta, located in Finland, is part of the Smelters Business area of the Boliden Group and operates a copper and nickel smelter with related sulphuric acid plant in Harjavalta, and a copper refinery in Pori. As a short historical review, Harjavalta’s history may be dated back to the year 1910 when the Outokumpu ore body in eastern Finland was discovered. By the end of 1913, a copper mine was in operation and a copper plant based on Hybinette process was ready for commissioning. Due to difficulties in metal recoveries and throughput the Hybinette process was permanently shut down in 1929, and 100% of the mining production was sold as concentrate abroad. As the mine production increased steadily, a decision of a new smelter was made in early 30’s. In 1936 Outokumpu’s copper smelter based on electric smelting was commissioned in Imatra. The smelter was dismantled and transferred to Harjavalta during the final stages of the Second World War. The copper refinery started in Pori already in 1941 and the first copper anodes were cast in Harjavalta in 1945. First sulphuric acid plant started operation in 1947. Due to the post-war shortage of electrical energy, the plant metallurgists initiated a major development work to start exploiting the latent heat of concentrates. Thus, the flash smelting method was developed in Harjavalta and commissioned in 1949. Ten years later, flash smelting was also applied for nickel concentrates. Table 1 summarizes major historical and technical milestones of Harjavalta. The history of flash smelting is described in details in another paper of this conference (Jåfs et al., 2019).

Jan 1, 2019

By Xuanxue Mo, Zengqian Hou

"Yidun Island Arc in Sanjiang Region is one of the important Kuroko-type volcanogenic massive sulfide deposits (VMS) districts in southwestern China. Tectonically, the region is situated in the eastern portion of the Tethys orogenic belt, and is a late Triassic extensional island-arc. The island-arc underwent earlier arc construction, intra-arc rifting, later arc construction and backarc spreading during its evolution and formed a complete trench-are-basin system, i.e., the Ganzilitang suture zone, forearc basin, outer are, intra-arc rifting zone, inner arc and back-arc basin from east to west across the island-arc.Kuroko-type VMS deposits and occurrences discovered so far are limited to within the intra-arc rifting zone of the Yidun Island Arc and tend to occur in groups or clusters distributed in separate faultbound basins; e.g., Zengke, Gacun and Xiangcheng basins, in which submarine volcanic rocks, especially bimodal volcanic suites, were extensively developed. The VMS deposits formed in the waning stages of volcanic eruption in the late Triassic and are hosted in the uppermost section of acidic volcanic rocks (rhyolitic-dacitic) within a bimodal suite. The orebodies are associated with these host rocks: rhyolitic-dacitic pyroclastic rocks and exhalites and chemical sedimentary rocks.All VMS deposits in Sanjiang are of the Zn-Pb-Cu type. The architecture of the deposits is twofold, consisting of concordant lenses and layers of massive sulfides and an underlying discordant stockwork. All deposits show metal zoning. The hydrothermal alteration related to mineralization is strong and asymmetrical, and is found dominantly within the stockwork zone and host rocks surrounding the ores. There are two alteration patterns: (1) chloritization - sericitization - silicification from outer sides to core of the alteration pipe; and (2) silicification + sericitization - silicification + carbonate from the lower to upper part of the alteration pipe.The mineralization temperatures of ore-forming fluids vary in the range 200°C to 335°C. Thermal evolution of the fluids displays temperature profiles that first increase and then decrease with progression of mineralization processes. The majority of black-ore minerals (Groups I and informed during intensifying stages of hydrothermal activity, and the majority of semi-yellow-ore minerals (Group III) formed during a thermal maximum. There followed the formation of fine-grained black-ore minerals (Group IV), which interacted with barite layers during decreasing temperature phases.Oxygen and hydrogen isotope studies show that the sources of ore-forming fluids for the Kurokotype VMS deposits are two-fold: seawater and magmatic hydrothermal solutions, represented by the Kuroko deposits in Japan and Kuroko-type VMS deposits in Sanjiang, respectively. In the latter case the hydrothermal solutions reacted with host rocks and mixed with cold seawater percolating downward, and circulated through volcanic rocks resulting in development of alteration zones and formation of ore minerals in Kuroko-type VMS deposits."

Jan 1, 1993

By M. Moghadami

Design and construction of underground openings are associated with many uncertainties with regard to input data. In the construction process of underground openings various levels of risks exist and these affect the safety and profitability of the project. The development of underground openings can be broadly categorized into three major phases of data collection, design, and construction. A significant level of uncertainty is associated with some of the key parameters involved in the aforementioned development phases. Moreover, it is very difficult to evaluate and quantify the effects of uncertainties on the underground project construction process. Additionally, the interactions between important risk elements are typically not well understood. The intention of this study is to develop a general risk model for underground opening projects located in soils and weak rock masses. The goal of the research is to identify and quantify important geotechnical risk elements. Moreover, a weighting procedure will be proposed for the identified risk elements. Finally, all important risk elements will be assembled into a general model with emphasis on geotechnical parameters. The final objective of this study is to apply the proposed model to a real underground project scenario and verify it for actual field conditions. The proposed model, once calibrated properly, will provide a useful support tool for the decision making process.

Aug 1, 2013

By Al Gagnon

Since start-up in 1972, many circuit problems have been encountered, most of which were related to the abundance of fines (-28 mesh), which the circuit had not been designed to treat. The major problems associated with the original circuit included excessive loss of magnetite, reduced throughput during periods of a high proportion of fine coal in the plant feed and low yield in the fine coal circuit. This paper outlines the coal processing circuit at Fording Coal Limited as it exists today, with emphasis on the changes to the original fine coal treatment circuit.

Jan 1, 1978

Concentrator Improvements -1990-1995Back to Basics ?pilot plant versus plant opportunities identified ?understand process fundamentals & baseline -1996-2000Point ?C?Projects ?strategy to improve global competitiveness ?structure implemented to generate & drive ideas ?capital investment for life of mine asset renewal - 2001-200?Six Sigma Methodologies ?emphasis on data, measurements & analyses ?dedicated, highly trained personnel on projects 1990-1995 Improvement Phase??Philosophy??back to basics?approach?understand what each piece equipment needed to do?understand reagents, control variables?confirm operating strategies ??probe, stabilize, institutionalize??test theories, confirm with lab and plant trials?process stability (equipment reliability, controls)?enhanced operator guidelines, operator training?focus on continuous improvement?optimize existing equipment capability?stop looking for ?magic?solutions 1990-1995 Improvement Phase??Technical?finer grind, same equipment?optimize media size/shape to grinding application?balanced available ball mill power to applications?lowered cyclone feed densities where possible?improved selectivity, same equipment?balanced available cells to applications?streamlined process (eliminate process steps)?added cleaning stages where required?understanding pulp/mineral surface chemistry?lowered flotation pulp densities 1990-1995 Improvement Phase??Effort?numerous studies to understand process?liberation and mineralogical characterization?pulp and mineral surface chemistry?flotation kinetics and entrainment?extensive internal and external manpower?Brunswick, Noranda Technology Centre?CanMet, AMTEL, MinnovEx, Lakefield Research, McGill University?small capital expenditure

May 1, 2002

By D. P. Wilkinson

There are significant global environmental and supply issues with existing energy paths today . Global emission and fuel regulations, global fuel and power structure, energy security, and cost are driving new technology and non-conventional approaches . Fuel cells will play a significant role in the strategy to effect positive global change, increase fuel efficiency and decrease dependency on traditional fossil fuels. Fuel cells do not require recharging, just refuelling and a wide range of fuels are possible with hydrogen being the most desirable. Technical progress as well as investments in fuel cells for transportation, stationary, portable, and micro fuel cell applications have been dramatic in recent years. The present view is very optimistic for fuel cell power generation and the status is presently at the field trial level, or early commercialization stage, moving into volume commercialization. A number of demonstration programs are in progress worldwide such as the California Fuel Cell Partnership which involves original equipment manufacturers (OEMs), fuel providers, transit authorities, state and government bodies. Fuel cells and a hydrogen infrastructure are key to a long-term solution to global energy issues. Fuel cells will need to be competitive on an economic basis with the established and highly developed internal combustion engine and other forms of power generation There has been significant technical progress in a number of fuel cell areas including power density, transient / dynamic response, multiple fuels, cost potential, reliability and durability. However, significant technology gaps still remain today. This presentation will focus on the status and progress of the fuel cell today, current fuel cell research and development, the challenges going forward, and the future view of the fuel cell and it's impact on global energy issues.

Jan 1, 2005

By Parsons. Robert B.

"Starting this year, corporations that conduct business in Ontario face a new tax a corporate minimum tax. This tax is in addition to the myriad of other taxes that make up a corporation's total tax burden including federal and provincial capital 1oXJ!S, payroll tax and sales taxes. Mining companies with gross revenues in excess of $10 million or total assets exceeding $5 million may be liable for this new tax. IntroductionOn December 8, 1993, the Ontario government introduced legislation to implement the corporate minimum tax (CMT promised in its May, 1993 budget. There are very few differences between the final legislation and the budget proposals.The CMT is effective for taxation years commencing after 1993. Subject to certain specific exemptions (detailed below), the tax applies to all corporations liable for Ontario Corporate Income Tax that have either gross revenues in excess of $10 million or total assets in excess of $5 million. These measurements apply to the aggregate gross revenues and total assets for all corporations in an associated group and a corporate partner's share of partnership assets and revenues must be included in the determination.In essence, the CMT is an income tax that is based on financial statement profit instead of an income amount that is determined separately under a statute. Accordingly mining companies (including so called ""junior"" exploration companies), which traditionally sheltered their taxable income by claiming generous exploration and development deductions, could find that they have a CMT liability."

Jan 1, 1994

By J. Bhattacharya, S. K. Mukhopadhyay, S. K. Pal

"While time and again many authors have categorically stressed the restoration of the environment, very little effort has been made in the mineral industry to develop the economy of environmental control. There are many abatement procedures that search a maze of variants. Among them pricing environmental damage seems to be more logical and easily implementable.IntroductionMining as an operation has a severe impact on the Earth's natural resources. While economical environment control is much sought after, solutions are often varied and complex, and can differ in the problems of single or multiple mine sites.Determination of Optimum use LevelsIn “mining environmental control"" it is required to strike a balance to find optimum use levels. The solution is to find where the welfare benefits equal the cost involved to curb the degree of environmental damage (Fig . I) . In the mining industries this can be done by modifying the production/extraction process itself. For most pollutants, the marginal costs of control will exceed the benefits from further reduction of damage long before the zero pollution damage point is reached (Fig. I). From an economic perspective the optimal alteration of environment by mining would occur at z; pollution continues to be caused by ""zy"" control units, but it would be inefficient to pursue the redemption efforts further because the marginal cost involved would exceed marginal welfare benefits."

Jan 1, 1992

The Cadia mine is shifting from the open pit operation to the Cadia East underground block cave. The resulting increase in milled tonnes and the decrease in fines production through shifting to block caving require an increase of over 25% in installed power. This expansion is being accomplished via the installation of up-front crushing and HPGR milling of the ore, with the SAG mill receiving a secondary crushed feed. This design, criteria and rationale for selection is presented. Over the coming years, the mine will further expand capacity. The target is to accomplish this with minimal addition of installed power or use of fresh water. This presents a challenge that epitomizes the future constraints on our resource dependent and intensive industry. The approach and proposed options to this longer-term expansion are also presented.

Jan 1, 2012

By Alexander Smith

Surf Point and Edye Pass mines are on the northwestern part of Porcher island; 25 miles southwest of Prince Rupert. During the 1930's they produced about $750; 000 in gold from ore averaging better than one-half ounce a ton. The deposits are quartz veins; containing auriferous pyrite; concentrates average about 8 oz. gold a ton. The veins occur in a quartz diorite; stock. Their distribution shows an apparent control by primary flow structures; for the principal deposits lie on the axis of an arch of flow layers. The technique used in mapping the structures in the intrusive is that known as the Cloos method and described by Balk.

Jan 1, 1954

By Christopher Boys

"Many water inflows in Saskatchewan potash mines are linked to salt anomalies. Potash ore and three anomalies in the PCS Cory potash mine in the Patience Lake Member of the Prairie Evaporite Formation were studied to understand the processes involved in their formation. Another goal was to find geological indicators of the proximity of anomalies. A geological model that relates the potash to the salt anomalies has been developed.Up to five post-burial facies may be recognized. These range from carbonate-mud collapse breccias to bedded sylvinite, and probably result from post-burial leaching. In this model, the same fluids that caused widespread recrystallization and possibly enrichment of the potash salts, started by dissolving huge cavities in the evaporites. The effects of the leaching were highly variable, indicated by selectively preserved delicate laminae and chevron textures, to deformed and totally dissolved salt beds. In at least two major events, Late Devonian and Cretaceous, collapse structures may have acted as conduits for overlying formation waters to cause pervasive leaching and recrystallization of the Prairie Evaporite Formation.Geological indicators of the proximity of an anomaly may include: a change in insoluble seam color from greenish-gray to mottled brown and greenish-gray, unusual local increases in ore grade, large patches (e.g., >200 cm2) of sylvite-poor potash crosscutting units near the top of the ore wne, and drops in topography > 10 m of the marker seams. Anhydrite was more common in an anomaly than in ore. The local abundance of anhydrite in ore may indicate the proximity of some salt anomalies. Once an anomaly has been encountered, indicators of a major collapse feature may include: stretched clay seams, folded beds, small collapse features (1 m to 20 m), numerous washouts, or split clay seams with injected salt. Any number, or none, of these indicators may be found close to a major collapse feature."

Jan 1, 1993

By George Carico

Research and related demonstration projects are being conducted in West Virginia on both existing and former coal surface mine lands to determine potential post-mine land re-use options that offer the greatest likelihood of future benefit and success. Examples of projects include renewable energy considerations that incorporate solar, wind, and/or biomass options, and contain components designed to educate business, government entities and the local community on renewable energy options and potential opportunities Multiple property re-use options are being researched and evaluated, based on site-specific conditions and characteristics, including infrastructure, local community needs and regional economic conditions. Re-use options being explored include innovative uses and needs, such as specialty housing, unique business and industrial needs, and an extensive variety of recreational and small business opportunities that best fit the specific needs of the local community and regional economic structure.

Aug 1, 2013

By A. Vasenev

The quality and durability of asphalted roads strongly depends on the final step in the road construction process; the profiling and compaction of the fresh spread asphalt. During compaction machine operators continuously make decisions on how to proceed with the compaction accounting for project specific aspects as: ambient conditions, road geometry, roller type, asphalt mixture characteristics and behavior of other machines. In discussions over quality improvement in road construction it is often suggested to robotize rollers. To operate such robots would of course require operational strategies and routines. The reality of this moment is that these operational strategies and routines are not documented. To identify the existing best working practices and, ultimately, to proceed with developing automated robotized compactors, the knowledge of machine operators should at first be explored and described in a formalized way. Unfortunately operators have difficulty verbalizing their expertise. Observation of behavior, as machine movement patterns, could be helpful to extract the operational strategies, but such observations are time and labor consuming. To overcome this burden we developed a Virtual Reality (VR) environment. In this VR environment operators perform compaction virtually, and their operational choices are traced and analysed. This paper describes this VR development and explains how it helps in following machine operators and extracting their (tacit) professional knowledge. The road geometry and the working conditions are visually represented; the operators show - rather than explain - how they would proceed with the compaction process in the given conditions. Movements of virtual machines are documented, analysed, visualised and discussed. This VR approach is expected to contribute to learning, to more formal description of operational strategies; stepping stones towards compaction algorithms for roller robotisation.

Aug 1, 2013

By L. Shasko, M. Hurlbert

As climate change is increasingly perceived as a problem, and fossil fuel based power production options are increasingly limited through regulatory restrictions and public distaste, future options become constricted. Reflexivity and social learning elicited through qualitative and mixed research methods offer important insight into what future power production pathways might be. Given factors of cost, baseload requirements, and energy density, options such as nuclear may be increasingly accepted. This paper explores this literature and possible methods of pursuing the reluctant acceptance of nuclear energy.

Jan 1, 2020

By J. H. Douglas, A. F. Matheson

"The Hard Rock is the most easterly producing mine in the Little Long Lac area. The Company was formed in 1934 to develop a surface showing of gold in quartz made by a prospector, W. W. Smith, in 1931. Although some ore was eventually produced from this discovery, the principal orebody, hidden below 10 feet of muskeg, was found about 1,000 feet to the north by exploratory diamond drilling early in 1938 from the No. 2 shaft workings at the 250-foot level.Production started in 1938 and to January 1, 1947, 201,000 oz. gold had been obtained from 1,165,282 tons of ore mined and 869,397 tons milled. Of this ore about 15 per cent came from the development and mining of the original orebodies discovered at the surface. The remainder came from the ore found by the underground diamond drilling done in 1938. Of the latter ore, the Company estimated, at January 1st, 1947, only 140,000 tons remained. The orebody, therefore, contained approximately 1,100,000 tons.OREBODIES AND GENERAL GEOLOGYThe orebodies of the Hard Rock mine are of two main types: the quartz ore of the south and No. 1 shaft zones, and the sulphide ore of the north zone. The quartz ore consists of white quartz veins mineralized with sparse, fine, light-coloured pyrite, or, less commonly, nests of coarse, crystalline, light pyrite. A little tourmaline, scheelite, pyrrhotite, chalcopyrite, arsenopyrite, and native gold are also present. Native gold occurs in a few places in quartz veins in exceedingly rich cemcentrations, apparently where there are large, light-coloured, pyrite crystals of imperfect form. The ore of the north zone is massive pyrite with arsenopyrite and in places pyrrhotite. Many short irregular quartz veins, from a few inches to 2 feet in width, are also present, but the quartz forms a very small percentage of the whole. The veins may be flat to vertical, and sulphides on one or both sides replace the host rocks. The gold is closely associated with the sulphides . The quartz is commonly barren except where it contains sulphides or along the borders of the sulphide ore zone where native gold is not uncommon in quartz stringers."

Jan 1, 1954

By Robert B. Parsons

"Finance Minister Paul Martin's first budget disappointed almost everyone. The business sector was disappointed at the some what feeble attempt to grapple with the country's deficit. The mining industry was disappointed by tax proposals regarding mine reclamation that fall short of the industry's needs. Has anybody been happy with a federal budget? Federal Budget DisappointsThe federal government's budget papers that were tabled on February 22, 1994, contained a rather bizarre mixture of unrelated tax proposals. The budget signals an unexpected attack on the tax treatment of debt settlements, on certain types of corporate reorgani2ations, and on income earned by foreign affiliates. This is an old style budget, which proposes a pot pourri of technical changes and policy initiatives. Mine ReclamationEffective February 23, 1994, a taxpayer's contributions to a prescribed mine reclamation trust fund will be deductible as a current expense. The budget papers do not provide a definition of what will constitute a ""prescribed"" trust: this definition will surface in due course. However, the budget papers indicate that:• income earned in such trusts will be subject to tax each year;• all withdrawals from the trust (including income already taxed) will be included in computing the income for tax purposes of the recipient;• reclamation costs will continue to be fully deductible at the time incurred; and • contributions, trust earnings, and withdrawals will not be taken into account for the purposes of determining a taxpayer's resource allowance."

Jan 1, 1994

By Daniel L. Cluff

The Canadian mining industry needs to find viable alternatives to the conventional cemented pastefill/hydraulic methods of backfilling open stopes for underground mines located within a permafrost zone. The harsh environment and the isolated location of a mine north of 60° impose additional challenges to standard backfill methods and opportunities to the technological and operational issues related to the use of frozen fill. Underground open stoping mining methods require the placement of fill material to enable the controlled recovery of ore from secondary and tertiary stopes. The typical design of the fill material requires the specification of inert material, water and binder. The permafrost conditions provide the additional parameter of subzero temperatures for backfill design and process control. The paper presents the results of an experimental field study, using large size samples, to determine the strength capacity of frozen backfill. The experimental work was performed utilizing rockfill and tailings material with moisture content consisting of water and ice crystals. Preliminary results indicate that the mixture of rockfill, tailings and moisture, develops strength that meet the demanded requirements for open stoping. A thermal equilibrium modelling analysis is presented in the paper.

May 1, 2008

By Walter Valery, Lauren Hafla, Megan Tibbals, Adrian Dance, Jeff Snyder

"Newmont Mining Corporation’s Carlin (“Carlin”) operation processes roaster feed through a double rotator, dry grinding mill following secondary crushing. Metso Process Technology & Innovation (“PTI”) was involved in a review of crushing and dry grinding circuit operations in August 2009. A number of opportunities for increased throughput were identified in the PTI study.Extended plant trials were conducted in July 2010 to provide justification for possible circuit modifications and if needed, additional equipment. The trials confirmed that a finer crusher product would reduce the build-up of material ahead of the coarse grinding chamber in the double-rotator. Also revealed were material transport and airflow restrictions in the dry grinding circuit that resulted in a high circulating load.The secondary crushing plant demonstrated it was capable of reducing the amount of +¾” material in the mill feed thus increasing dry grinding throughput. However, wet and sticky feed affected screening efficiency resulting in low utilisation of the existing crusher capacity. The open circuit configuration also made it difficult to control crushing circuit product size.For the dry grinding circuit, changes in grinding media size, transfer grate design and increased airflow were recommended to reduce circulating load issues and increase circuit capacity. This paper summarises the crushing and grinding circuit review, the extended site trials performed by PTI and the improvements in dry grinding operation that resulted from this study."

Jan 1, 2012

By Franc R. Joubin, Donald H. James

"THE PROPERTY of Rexspar Uranium and Metals Mining Co. Limited is situated within 3 miles of Birch Island, British Columbia, a village on the C.N.R. main line 80 miles north of Kamloops. The claims extend up the south slope of the North Thompson River valley.Prospecting in the area dates back many years. Fluorite was reported in 1918, lead showings in 1926, and bog manganese in 1929. Diamond drilling in 1942-43 indicated more than a million tons of material containing 20 per cent fluorite and 15 per cent celestite in what is known as the 'fluorite zone'. Marketing and beneficiation difficulties have delayed further development of this deposit.Systematic checking of specimens and drill core by the B.C. Department of Mines and the Geological Survey of Canada revealed low radio-activity in the fluorite zone material. Subsequent prospecting with Geiger counters revealed zones of higher radioactivity a few hundred feet distant from the fluorite zone. The property at this stage came under the development direction of Technical Mine Consultants Limited, who undertook a program of diamond drilling. Of the several radioactive zones located, two have so far rewarded development and appear to constitute low-grade uranium orebodies. These are referred to as the ""Black Diamond"" or ""BD"", and the ""A"" zones -see section. Open-pit mining of the thick, dip-slope orebodies appears possible.General GeologyWalker (1) describes the local rocks as metamorphosed sediments cut by granodioritic intrusives and by greens tone. At the property the sequence is:GreenstoneUnconformity or intrusive contact Trachytic member -tuffs, breccia, flows. Argillite -black, thin, not always present. Schist -thin-bedded sericitic quartzite and siltstone with some calcareous layers."

Jan 1, 1949

By Dale A. Sketchley

"Abstract - Large differences in gold content between rock fragments or small volumes of unbroken rock, commonly referred to as the nugget effect, are related to sample and subsample weights, crushing and pulverizing sizes, and density, shape and size distribution of gold grains. Gy’s sampling theory, which relates gold grain characteristics to sample weight, fragment size, and error, provides a method of estimating a sampling constant that quantifies deposit characteristics that contribute to the nugget effect.Sampling control tests provide methods for determining the sampling constant. Sampling control charts, comprising nomographs that relate sample weight, error and particle size, use the sampling constant to optimize sample weights and comminution sizes, and to minimize the variability introduced by incorrect or inadequate sampling and sub-sampling procedures. The sampling constant is useful in classifying ores into arbitrary categories according to expected sampling difficulties. Spatial variations in the sampling constant can be used to aid in defining ore types for modeling geological domains, which should have unique sampling protocols. Examples that illustrate the relationship between the sampling constant and expected sampling problems, and the spatial variation of the sampling constant, are given for various deposits. Case histories of sampling programs are presented.Quality control procedures consist of monitoring sample contamination amd accuracy and precision of analytical results. Accuracy, precision and contamination are monitored by including standards, duplicates and blanks into batches of samples being analyzed. Analytical results of standards and blanks are plotted on a batch-and-time basis with control lines at plus or minus two/three standard deviations as confidence limits of the accepted round-robin value. Examples are given that illustrate a laboratory system in statistical control and the various types of problems encountered when interpreting quality control data. These include sample transcription errors, degradation, contamination, sampling errors, detection limit problems, instrumental drift, lack of statistical control, laboratory bias, procedural problems and data tampering.Where bias is negligible, precision, as a function of concentration, can be obtained from duplicates using the Thompson-Howarth precision algorithm, which also allows calculation of the practical detection limit. Examples are given that illustrate variations in precision, with grain size, for different types of duplicates, as well as mineralogical changes and sampling errors."

Jan 1, 1998