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By Jan E. Nesset, Phillip J. Mackey, Joo Y. Kim, Giovanni Di Prisco, André R. Laplante

Understanding the appropriate gold recovery to associate with copper recovery when assessing laboratory testing on porphyry deposits is often complicated by several factors including variable and/or complex mineralogy, and the variability contributed by the low Au content of the various flotation products. As a result, gold recovery is often underestimated and the value contributed by the gold to project economics is less than it should be, a problem that could influence overall project viability. Typically, for these types of deposits, the gold recovery is found to be lower than the copper recovery. In this unique project, having the objective of seeking a better understanding of gold recovery relative to copper recovery, mill feed samples from a selection of six operating world-class Cu-Au low-grade deposits were collected along with the mill metallurgical results for the corresponding sample periods. The samples were subjected to laboratory flotation tests, as well as the Laplante gravity recoverable gold (GRG) test, mineralogical assessment and cyanidation leaching. The aim was to better understand the copper and gold recovery relationship, the links between laboratory and plant flotation performance, the influence of mineralogical differences, and the potential for enhancing gold recovery by gravity recovery techniques. A new correlation of copper and gold recoveries based on the results is presented in the paper. The results showed that the link between copper and gold recoveries established in the best laboratory tests were maintained in the plant results, and further, that the potential for improving Au recovery by gravity or flash flotation methods is directly proportional to the amount of gold greater than 75 microns.

Jan 1, 2005

By M. Fornaro, E. Lovera, I. Sacerdote

"The analysis of the mining laws of the different European States reveals big diversities and, often, remarkable complications. This is due, firstly, to the history and culture of different States and, secondly, to the assets of natural resources. It is therefore difficult to find a common line between the text of the various mining laws, but it can be observed that nearly all the States distinguish the mining resources in two categories: the materials whose importance is considered strategic belong to the first category; in the second category the materials whose importance (above all economic) is mainly local are comprised. The paper, analysing in detail the planning procedures in some important Countries, investigates the possible perspectives of arranging some guide-lines for a correct approach to the sustainable exploitation planning/programming of mineral resources (with particular reference to "quarry" materials, such as aggregates), considering both the environment protection and the production needs."

Jan 1, 2005

By H. S. Rathor

NTPC (National Thermal Power Corporation), a multi-unit organization, is generating 26% of India’s total power. This power is produced from its 14 coal based stations and 7 gas based stations. NTPC is entering into the business of power-distribution, power-trading, setting up of coal mines and diversification in non-conventional energy sector as well. For achieving the goal of the country “Power for All” NTPC has taken a giant stride by entering into Hydro Power generation which is also the cheapest and the cleanest renewable source of energy. In its pursuit for excellence, 800 MW Koldam Hydro Power Project is NTPC’s first venture in hydro sector. In Koldam, hydropower potential will be harnessed by constructing a 163m high earth and rock fill dam in a narrow gorge at upstream end of Bhakra reservoir. The river diversion is envisaged through two parallel, 14m finished diameter ‘horseshoe’ tunnels of length 901m and 934m at village Kian on the right bank, where the river forms a 180° loop. The diversion tunnels are designed to accommodate a flood of 6500m3/sec, taking into account the maximum probable discharge of 200 years return period. The tunnels pass through dolomite and limestone rock formations. The excavation of tunnels was done with drill and blast method. The excavation was attempted from both inlet and outlet faces. During geological investigation a rock fault was located at the outlet area. The location of the fault was such that it was passing through the edge of the Tunnel-1portal and around 30m away from the face of the Tunnel-2 portal. The quality of the rock at Inlet was also poor. To save the portals from slips, excavation of the tunnels was planned to start after the completion of the open excavation and its support system both at inlet and outlet. The tunnel excavation at inlet was envisaged by approaching the tunnels’ portal by constructing a road through 540EL bench and meeting the inlet portals on the upstream end, which would have been ready by mid2003, only after completion of the open excavation and its support system. To save time and cost, it was felt necessary to modify the planning by starting the tunnel excavation simultaneously along with open works both at inlet and outlet. The excavation at the inlet face of the tunnels started in December 2002 after rerouting the approach road to inlet portals through haulage road on the downstream and similarly Tunnel-1 at the outlet was started in the low cover area before completion of open area works. Thus the tunnel—heading excavation was started nearly 06 months early with the change of methodology.

Jan 1, 2005

By Terry M. Tilley, Gregory P. Sherry

Purpose This is a unique project because the mining and tunneling industries have become highly mechanized and cannot normally accommodate a project where surface disturbance must be minimized or eliminated when there is less than 10 feet of ground cover. More traditional less mechanized methods must be employed and the skills and techniques for accomplishing the work have become all but non-existent. Therefore, this article highlights those areas of specialized skills and techniques. Methods The article will describe the design approach, the method(s) of ground support selected, the method(s) of excavation selected, the planning, scheduling and materials selection process. In addition, the article will describe the actual production characteristics and the results of the project. This approach will concentrate on productivities, adaptations to actual conditions and the quality of the end product. The design approach basically was to insure that the temporary support methods were adequate for the excavation and shoring stage of the project. The final concrete liner was designed using conventional structural design methods with the goal of constructing a tunnel that will last 100 years. The methods of support were spiling and variations of spiling in order to provide advance temporary ground support. In this project spiling is steel channel cantilevered and driven into the ground ahead of the working tunnel face which supports the ground allowing the face muck to be removed with overhead protection’. Conclusion This will be a discussion of the applicability of the methods. The actual performance of the excavation and shoring methods will also be evaluated. The final concrete liner completion results, the actual production rates and the conformance with budget and schedule will be addressed.

Jan 1, 2005

By Omid Lashkari

Keywords: SEED, SSM materials, Microstructural evolution, Rheology, Swirling Speed SEED (Swirled Enthalpy Equilibration Device) is established itself as a new technology amongst the many Semi-Solid Metal (SSM) processes, where swirling of the mush plays an important role in modifying the dendritic structure of as-cast parts. A range of semi solid metal structures, dendritic, rosette and/or globular morphology of primary phase, can be prepared using SEED. The current article reports on the application of rheological tests in characterizing microstructural evolution during SSM processing of 356 Al-Si foundry alloy. A simple parallel plate test machine, designed and constructed at our labs, was used to determine viscosity values for each structure and identify the optimum structure with superior die filling characteristics. Such findings have important technological and economical implications during high pressure die casting of semi- solid metals. The strain-time graphs for 356 Al-Si foundry alloy indicated lower viscosity values for globular microstructure, i.e. improved die filling.

Jan 1, 2005

By A. Steinmüller

Introduction In the design and operation of gravity concentration circuits, the application of process models for spiral concentrators offers significant benefits. A substantial amount of work has been produced over the last 30 years in the field of modeling the metallurgical performance of spiral concentrators. It is not the aim of this contribution to add to the refinement of modeling technique but to share some of the experiences and potential improvements which can be achieved in a relatively simple way. The design of spiral circuits usually requires extensive testing. This is often conducted in batch operation only, either due to lack of suitable continuous testing facilities, the unavailability of sufficient quantities of sample, or other constraints. Typical problems arising during circuit development from batch testwork are the extrapolation of results to different feed conditions, and resolving of internal recycles. Model selection and development The classic approaches in spiral modeling technique range from fundamental fluid dynamics, based on the Navier-Stokes equations in combination with expressions for local slurry properties, to fully empirical and statistical models. With the initial objective of developing an in-house tool for gravity circuit optimization and development, mathematical model types from each category, available either commercially or in the published literature, were evaluated. Model selection For the desired purpose, an approach proposed by Holland-Batt (1990) was found suitable, which was adopted and modified. Holland-Batt reported that the shape of release curves in spiral applications could be described by a combination of a linear function in the initial recovery zone, and a power law function outside this zone. The proposed recovery function was formulated as

Jan 1, 2005

The market for titanium feedstocks (ilmenite, rutile,synthetic rutile and slag) is driven primarily by offtake from the titanium dioxide (TiO2) pigment industry. The pigment sector depends on the performance of the global economy. Titanium sponge is the first stage of titanium metal manufacture. It constitutes a minor component (3 percent) of overall demand for titanium feed-stocks. Production and consumption TiO2 pigment consumption in 2004 was estimated to be 4.63 Mt (5.1 million st), up 7.6 percent from 2003. It was driven by strong demand in most regions. In the United States, apparent TiO2 pigment consumption rebounded by 5.4 percent (highest growth rate since 1997) to an estimated 1.12 Mt (1.23 million st), following the decrease in demand during 2003. Chinese TiO2 pigment consumption continued its strong upward trend, increasing by 10 percent to 598 kt (659,000 st) in 2004.

Jan 1, 2005

By A. M. Clegg

In general, overall experience has shown that the approach to the appointment of a project manager is given much attention, but little specific attention is given first to the risk associated with the project conceptual design and its overall executability within either the new legislative framework or the sustainability of the outcome. The risk in project executability and sustainability within the ?new age? legislative framework of the Mining Charter, etc, is itself however, of far greater importance. The degree of importance being defined by the intended projects impact on the business going forward. This is particularly the case where the intention of the implementation is effectively to turn around or even enhance a loss-making strategic investment like a mine or process plant operation in an ?old-order rights? or Brownfield?s operation. This paper attempts to highlight the importance of a ?pre-project project? (PPP) to mitigate the risk in the ?new age?, with specific reference to operational due diligence (ODD) and project conceptual design.

Jan 1, 2005

The lignite resource in the southern part of the South Island is New ZealandÆs largest source of indigenous primary energy. The ten deposits evaluated by the Liquid Fuels Trust Board (LFTB) have a total recoverable reserve of 6.2 billion tones equivalent to 74 000 PJ of energy or 20 times the original energy content of the Maui gas field. Updating the economics of the original LFTB studies indicates that lignite could be mined for between NZ$1.0 and 3.0/GJ. Its conversion to synthesis gas for production of petroleum products, chemical methanol, ammonia/urea fertiliser or electricity would be in the national benefit and likely to be commercially economic at todayÆs product prices.

Jan 1, 2005

By Helmut Hass, Michael S. Shultz

For many tunneling, deep shaft and deep excavation projects ground freezing is one of the best if not the only technique available to create a watertight and load bearing temporary support system in soft ground conditions. When appropriate attention is given to the details of the ground freezing system design, ground freezing is a very safe method and is economically viable with competing techniques and combinations of techniques. Recent innovative uses of the technique in Europe are highlighted in this paper and compared with current uses in North America.

Jan 1, 2005

By Bruce Geller

The 2005 Prospectors and Developers Association of Canada (PDAC) convention continued the upbeat mood found in 2004. The global mining industry is booming due to higher commodity prices in nearly every sector. Other factors include low commodity inventories, China’s strong resource demands, the weak U.S. dollar, the very strong Euro, global uncertainties, an almost overripe investment climate for natural resources and the highest mining exploration budgets in seven years. Even unglamorous commodities, like iron, uranium and zinc, received copious attention in talks, the investors’ exchange, the core shack and in certain hospitality suites. The following impressions were gathered at the convention and enhanced by conference handouts and some abstracts that are available on the PDAC’s Web site, www.pdac.ca. At least 119 papers were presented, almost twice last year’s number.

Jan 1, 2005

"The Antamina orebody is a geologically complex, polymetallic skarn located in the Peruvian Andes. A range of copper and copperzinc ores are campaigned separately through the concentrator producing copper and zinc concentrates as well as lead and molybdenum by-products.Ore type classification at Antamina is based on chemical assays; geological or lithological variations are not considered. Consequently, each ore type demonstrates a wide range of concentrator performance.Antamina is currently implementing a system to track ore movements from the shovel face to the concentrator. Relatively sophisticated models of run-of-mine and coarse ore stockpiles ahead of the mill will be used to account for the variable delay between mining and milling.One of the numerous benefits of ore tracking is the ability to directly associate the measured concentrator performance with a physical location in the orebody. Using existing mine planning software, three-dimensional models can be created of such performance measures as metal recovery, concentrate quality, operating cost, and reagent consumption.Such a database of information allows the true value of different ore sources to be determined. The value of an ore source is conventionally measured as metal content (individual or combined ‘equivalent’) with a cut-off grade applied to indicate some base level operating cost. However, the true value of an ore source should include dynamic factors like haulage cost, reagent use, smelter penalties, and even prevailing metal prices. If an ore source is considered from all perspectives rather than simply its potential to deliver value, the concept of ore becomes more flexible. Any ore source that reveals itself to be unprofitable can be eliminated from the mine plan or possibly blended with others to improve its value. The ability to predict mill performance, and thereby profitability, is a powerful tool.In an operation such as Antamina, where managing ore sources, campaigns, and the delivery of a variety of concentrates in a narrow timeline to customers is a daily challenge, prediction is the key to success and improved efficiency."

Jan 1, 2005

By C. Sykes, E. Turner, M. Wyart-Remy

This paper follows that of the Milos Conf, 2002 and examines the collection and reporting of SDIs in the industrial minerals industry in Europe. It compares the characteristics of the GRI Reporting Guidelines, with its Metals and Mining Sector Supplement with those of the EU DG Enterprise Scheme, launched in 2001. The particular issue of SME's and companies which are not publicly traded is examined. The pros and cons of participating in such schemes is a central theme of the paper. The paper concludes that there and many business benefits for these companies in participating and submitting their data. The European Commission Scheme is strongly recommended for companies in the sector which are SME's and not-publicly traded as well as large firms who are listed on European Stock Exchanges.

Jan 1, 2005

By Michael S. Zhdanov

One of the major problems of mineral exploration is the ability to reliably distinguish between uneconomic mineral deposits and economic mineralization. While the mining industry uses many geophysical methods to locate the mineral deposits, until recently, there was no reliable technology for mineral resources identification and characterization. The main goal of this project is to develop a new geophysical technique for subsurface material characterization, mineral exploration and mineral discrimination, based on electromagnetic methods. The proposed new technique is based on examining the spectral induced polarization effects in electromagnetic data using the modern distributed acquisition systems and advanced methods of 3-D modeling and inversion. The recovered parameters of the relaxation model will be used for the discrimination of different rocks, and in this way will provide an ability to distinguish between uneconomic mineral deposits and zones of economic mineralization using geophysical remote sensing technology (Zonge, 1976). The proposed research and development is undertaken using multi-partner collaboration between the University of Utah, four major mining companies, Kennecott Exploration, BHP Billiton World Exploration Inc., Placer Dome Inc., Phelps Dodge Exploration, and Zonge Engineering Inc., which is equipment manufacturer and service provider to the mining industry. The multi-partner collaboration between the academic institution, the University of Utah, and mining industry helps to identify the appropriate mining target and conduct the field experiment for practical demonstration of the developed new technology, which is an important part of the this project.

Jan 1, 2005

By R. K. Wharton

The paper reviews the development of European harmonised standards for fireworks, recent major incidents involving the bulk storage of fireworks which led to research funded by the European Commission, progress with the forthcoming European Regulation on pyrotechnics and potential issues relating to the certification of products within the scope of the new Regulation.

Jan 1, 2005

By Shimi Tzobery, John E. Shamma, Samuel Swartz, Gary B. Hemphill

The trapezoidal tapered ring method has made significant progress in recent years for shielded-TBM projects, excavating tunnels with high overburden, strict water tightness criteria, and multiple curve alignments. The selection of compatible tapered rings is critical for successful advancement of the tunnel, assuring efficient installation of rings, as well as prevention of ring damage and excessive leakage. Using experience from the Arrowhead Tunnels Project, this paper describes guidelines for ring selection in tunnel curves, geometric analyses that comply with criteria principals, and provides techniques developed to determine the appropriate relative key position.

Jan 1, 2005

By Guangyi Sun

Wall rock classification method for coal mine support is the main factor affecting mine support. It is greatly affected by the combined effect of randomness, fuzziness and human being's incomplete knowledge. There are several coal rock classification methods. Using different rock classification methods the same engineering rock mass can be classified into different classification leading to different construction practices.

Jan 1, 2005

By Scott Chesman

Increased TBM performance is leading the way for resurgence in tunneling activity in NYC. Tunnels will be excavated in the same geologic formations as previously excavated D&B tunnels whose construction records are providing valuable insight into the prediction of rock mass behavior. This report compares an eight mile stretch of NYC Water Tunnel #2 with the recently excavated eleven mile stretch of the TBM driven Water Tunnel #3. Comparisons of the type and amount of rock support installed as well as water inflows and grout quantities are made. Rock mass characteristics specific to TBM performance are also evaluated.

Jan 1, 2005

By Paul Hewitt, Tim Smirnoff

Design and construction of the Epping to Chatswood Rail Line tunnels in Sydney, Australia required an innovative approach to define hydrogeological properties of the Sydney Hawkesbury Sandstone and provided an insight into the hydraulic behaviour of fractured sedimentary rocks. To meet restrictive water inflow and infiltration criteria both the pre-treatment of zones of fractured or highly jointed rock, and waterproofing using an interior spray on membrane for the finished drained tunnels and stations was required. Methods typically used to address the interaction of groundwater and tunnels in the Sydney Basin are demonstrated by case histories from major design-build tunnel projects.

Jan 1, 2005

This paper reviews ore pass practice in some Canadian mines in Quebec and Ontario. In particular it reviews ore pass configuration, flow control mechanisms and monitoring practice. A review of the type of problems encountered and the tools to restore flow is also presented.

Jan 1, 2005