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By H. Zniber El Mouhabbis

Ore dilution or stope overbreak increases the cost of production and ultimately reduces the profitability of a mining operation. The adverse economic impact of ore dilution is due to the added costs associated with the mucking, haulage, crushing, hoisting, milling, and treatment of waste rock or low grade ore in the hangingwall and footwall. One factor that could have a significant influence on stope overbreak is the undercutting of the stope into the walls. Undercutting stope walls is often necessary, in particular in narrow vein mines. Moreover, equipment size has a role in drift sizing where stope undercutting may become a must in order to fit the mobile equipment while respecting legal clearances.

May 1, 2009

By Adrian C. Dorenfeld, John T. Oleksy

Fuel problems of two lesser developed countries (LDC 's) are presented. In particular, the paper reviews cement technology and the fuel-intensive cement industries of the Philippines and South Korea. Based on current financial and cost data, analyses are presented of the proposed substitution of high-sulfur and slow-sulfur American coal in place of fuel oil. The analyses show that economic substitution of coal for oil is not only based on relative prices for coal and oil, as expected, but also to be an inverse function of degree of intensity of energy use, and a direct function of financial incentives such as accelerated depreciation, taxes on the savings made by the use of coal, and cost of capital.

Jan 4, 1979

By A. W. Hale

In a work published in 1838, De Morgan, the author of the article on " Probabilities," in the Encyclopedia Metropolltimn, says: " The method of least squares is not yet introduced intb the affairs of common life,.....that many things which are denlonstrable only by the higher branches of mathematics are looked upon as useless." And he mentions an instance in which "a method was suggested for estimating the relative importance of boroughs, by considering their population and ~wntributions to the revenue con)-

Jan 1, 1881

By Craig J. Nelsen, David A. Smith

In 1987, LAC Minerals (USA), Inc. conducted a high resolution helicopter electromagnetic (EM) and magnetic geophysical survey on the Ortiz Mine Grant, New Mexico. The primary purpose of this survey was to assist in geologic mapping of a major structural zone, the Tijeras-Canoncito Fault System (TCFS). This structure is a very important ore- controlling feature in the area. Geophysical signatures over known deposits was a secondary goal of the survey, but direct detection of mineralization was not anticipated. The TCFS was revealed to be a complex, branching and anastomosing system of faults which locally form the bounding structures of a graben. The geophysical survey guided subsequent geologic mapping by redirecting field investigations, and geophysically redefining some features which previously had been only partly defined.

Jan 1, 1989

By Fathi Habashi

Precipitation of a metal from an aqueous solution of its salts by another metal is known as cementation, because the precipitated metal is usually cemented on the added metal. This phenomena was once described by the alchemists as "transmutation," when they dipped a piece of iron in a solution of copper sulfate and the iron was coated with a layer of metallic copper. The process can be predicted in terms of electrode potentials. The metal with the more positive (oxidation) potential, as given in Table 13-1 of the electromotive series, will pass into solution and displace a metal with a less positive potential.

Jan 1, 1970

By R. V. Ramani, R. A. Jankowski, R. Bhaskar

The spatial distribution of airborne dusts, deposition of dust in the airway, as well as the effect of airflow velocity and particle density on dust behavior in mine airways were studied in a set of experiments performed in a mine airway under controlled conditions. Considerable deposition of dust near the source was indicated. Pronounced effects due to velocity were observed in ambient dust concentration and deposition along the mine airway, both in the respirable and the total size ranges. Cross-sectional concentration measurements indicate an increase in concentration from the roof to the floor. The average cross-sectional concentration is about 75% of the concentration in the center of the airway.

Jan 1, 1987

By Arpad E. Torma

The electrochemical behavior of a zinc sulfide concentrate during the microbiological leaching was investigated using ZnS-carbon paste electrodes and a cyclic voltametric technique. The effects of Zn2 [ ] , Fe2+, Fe3+ and Cu2+ on the cathodic and anodic currents associated with zinc sulfide leaching in presence and absence of microorganisms, were assessed. The semiconductor nature of zinc sulfide was discussed in terms of ability of microorganisms to obtain their metabolic energy (through removal of electrons) from this high energy gap substrate. The intermediate electrochemical reactions involved in the ZnS leaching were described.

Jan 1, 1989

By Johnston G, Revy T

Dominion Mining Ltd. and the JKMRC have conducted a detailed investigation of the performance of two of Dominion Mining's gold treatment plants (Haveluck and Paddy's Flat). In terms of design each plant is considerably different. The Paddy's Flat plant uses a single stage SAG mill with recycle crusher, followed by single stage ball milling. The Haveluck plant uses the more traditional approach of multi-stage crushing and ball milling. The performance of these two plant designs in terms of energy efficiency and cost of comminution equipment, developed at the JKMRC, to accurately predict both power draw and size reduction characteristics at these plants is evaluated.

Jan 1, 1991

By Jürgen Lotze

Previously (1981), it was shown that the fiscal policy practised by some IBA-member countries is mainly responsible for a significant shift of known bauxite resources into higher processing-cost categories. The possible impact of politically imposed fiscal costs on the competitiveness of relevant bauxite resources is investigated in detail by means of a model calculation procedure.

Jan 1, 1984

By Goran Cirkovic, Zvonimir Ester, Josip Krsnik

During the reconstruction of the motorway Zagreb-Krapina three reinforced concrete bridges were demolished, for their width was not adequate for the new motorway. Demolition of the three bridges was carried out by blasting as duration of the traffic cut on the motorway and the railway was limited to maximally 4 hours. During that period of time the demolished bridges had to be removed. Therefore, very tiny granulation was requested suitable for loading and not endangering the surrounding structures. Before each of three main blasting, trial blasting were carried out including the seismic measurements registering the seismic effects. The nearest residential building was at the distance of less than 30 m from the place of blasting. Additional difficulty was the fact that by each of the three bridges there is a new bridge, with minimal distance between the old and the new bridge being 30 cm. As each of the bridges is of different construction and of various thickness, particular blasting technique has been prepared for each one of the bridges.

Jan 1, 1997

By R. M. Board

This paper will focus on measurement and control of four main aspects of crushing, namely horsepower, bowl level, mantle position and feed rate, and will discuss related sensors and control techniques, some of them designed specifically for crusher control, that have proven successful and reliable in many installations.

Jan 1, 1982

By Richard H. Ross

A broad definition of' "Mill Design" might cover everything from the first tentative choice of general process to the final structural details for construction. The first phases are mainly concerned with metallurgy and economics and the final stages with the mechanics of putting the selected equipment together into an integrated plant. It is the purpose of this article to discuss only data, derived from laboratory testing, that contributes directly to design of the milling plant itself, and only the plant design phases that are influenced by laboratory testing. Most ore beneficiation testing is devoted to determining recoveries, grades of products, elimination of impurities, reagent and supply requirements, etc. having little to do with physical plant design although these factors are of prime importance in the evaluation of a mining project.

Jan 3, 1964

By T. J. DeMull

More than 1.81 mt (2 million tons) of low grade ore have been heap leached at the Alligator Ridge mine. Since inception of leaching in 1980, several modifications have been made to ore agglomeration, heap construction, and leach operation practice. These modifications have improved the percolation rate of the ore and the rate of gold extraction from the ore. Changes made in each of these areas are described and the effects of the changes are discussed.

Jan 1, 1984

By K. J. Stanaway

Syngenetic concentrations in clastic sediments of valuable mineral particles with specific gravities exceeding that of quartz constitute placer deposits. Two fundamentally different modes of concentration characterize "trap" and "bed" placer variants. Trap placers originate during sediment erosion or reworking. Bed placers form during episodes of sediment accumulation in a variety of depositional environments and lithofacies where mineral supply and fluid dynamics are favorable. Because trap placers are thin and generally limited in area, they rarely yield economic heavy-mineral deposits. They can become economically significant if they contain more valuable "heavies," such as gold, or if they occur within or very close to much larger but characteristically lower-grade bed placers.

Jan 1, 1993

By S Slusarczyk, Z Kozlowski

Vibration of surface caused by seismic quakes can make a risk to great mining costruction. We have to do with this risk in the Belchatow open cut mine where seismic quakes of various energy and range have occured since the end of 1970s. The seismic risk influence on the mine structure with the special attention to the slopes of an internal dump has been presented. Hydrogeological and geotechnical conditions of the lignite mining and internal dumping of overburden and ash from Belchatow power plant have been considered. Seismic activity in Belchatow open cut from 1979 to 2001 was described and the connection between mine working and seismicity of this area was investigated. The energy and approximate location of the quakes and seismological parameters of the strongest ones observed from 1995 to 2001 were presented. The mechanism of the quake focuses was determined by means of the primary-arriving wave method. Stability of the slopes was evaluated by means of the Fellenius method. It has been found that seismic events occured in Belchatow region may cause only local eboulements whereas there are not any safety risks to the stability of slopes of the internal dump in Belchatow open cut.

Jan 1, 2003

By Kenneth Medearis

The accurate prediction of possible damage to historic structures subjected to blasting-related ground motions is not infrequently the dominant factor in whether or not a mining or quarrying operation is allowed to proceed. A recent scenario involving an 1802 Pennsylvania Historic House was resolved satisfactorily, primarily because of the use of modern structural dynamics analysis techniques rather than simplistic peak particle velocity guidelines. One of the associated dominating factors was the truly significant agreement of the analysis results and the values obtained from actual on-site test shot blast motion recordings.

Jan 1, 1993

By C. M. Suhr

n order to validate the borehole analysis valuation procedure commonly used in the South African gold mining industry, a simulated orebody was used to create borehole values which would serve as data for the procedure. After confirming the distribution, calculating the variance size of area relationship, estimating the block variance, and calculating a profit measurement for each set, comparisons were made to the known population parameters. Results show only one overall bias (in the estimation of the lognormal third parameter), which is carried throughout the analysis. The remainder of the analysis is unbiased, validating the procedure.

Jan 1, 1987

Drilling is one of the most, significant cost components of any stoping or develop- ment operation. Two of the factors contri- buting to the drilling cost are the supply and servicing of consumable items such as drill rods and bits. The purchase cost of consumable items can be controlled to a large extent by using the correct balance of quality and price. However, the service cost is a less easily controlled factor and it is in this area where potential savings are significant. In June, 1976 a six month trial period was commenced at The Zinc Corporation, Limited and at New Broken Hill Consolidated Limited with two separate suppliers supplying and ser- vicing all longhole drilling parties (one supplier for each mine) at a guaranteed cost per metre. As a result of this six month trial period a new contract was commenced in December, 1976 with one supplier supplying and servicing all longhole drilling parties at both ZC and NBHC for a twelve month period. This concept has now been in operation for over twelve months and has proved to be a significant means of slowing down the increas- ing cost associated with drilling operations.

Jan 1, 1977

By S. C. Bouffard

Barrick's Zaldivar operation in Chile produces copper by heap leaching, solvent extraction, and electrowinning. The heap consists of a dynamic pad, and its stacking and operating conditions have changed over its 11 years of operation. These changes have included pad re-mining midway through the cycle, tightening of the irrigation drip lines, an increase of the coarseness of the particles, and an increase of the heap height. This paper reviews the heap operating data to understand the effects of these changes on the kinetics and recovery of copper minerals. Field tests demonstrated that neither re-mining nor tightening the irrigation grid added value for both low and high grade oxide and sulfide ores. The P80 of the feed ore was increased by 0.8 mm, which did not reduce the copper recovery of oxide and sulfide ores. The increase of the heap height above 8 m lowered moderately the copper recovery from sulfide minerals, and very slightly the recovery from oxide minerals. Despite the lower recovery, the higher tonnage stacked in the taller heap increased the copper output. Optimizing the chemistry of the agglomeration and feed solution holds more promise for increasing the copper recovery than the above physical changes.

Jan 1, 2007

By A. J. Lynch, N. W. Johnson, D. J. McKee

The behavior of nonsulfide gangue in chalcopyrite flotation circuits has been investigated. Plant and laboratory tests were conducted on five different ores. Linear relationships between the recovery rates of free nonsulfide gangue and water were observed. From pilot plant tests, there was evidence that the linear relationship was actually a linear approximation to a parabolic relationship. There was evidence that free nonsulfide gangue is transported from the pulp to the froth in the water and that the gangue is subjected to hydraulic classification in the froth column. A classification matrix has been proposed to define this behavior. This matrix is suitable for inclusion in a mathematical model of the process.

Jan 1, 1975