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By K B. Quast

Changes in feed size distribution can have significant effects in rod mill grinding. The product sizing resulting from wet batch milling of a tin ore showed little influence on fines production after truncating the feed at either the coarse or fine end. The addition of fine material caused a less amount of fines to be produced and a possible increase in grinding at coarse sizes, although this is complicated by the changing feed size distribution. The changes in feed size distribution caused no tendency for preferential grinding of the cassiterite.

Jan 1, 1998

By J. L. Thornton

Introduction The importance of coal in our economy is well established, but it may not .be so generally realized how important a part it plays in our daily life. Select a product - any product - and, if it is made in America, bituminous coal has touched it first. Everywhere we will find coal, derivatives of coal, or functions made possible by coal. Apart from the well known major uses of coal for domestic purposes, coking, utilities, railways, and manufacture of steel and cement, there are over 200,000 products derived from coal, from lipstick colours to nylon products and perfumes. An item of interest is the recent action of the Canadian Government in voting $90,000 for development of coal deposits in Yukon Territory to make coal available to the settlers in that area. The value of this move, in case of some emergency, is very evident. Coal in its several stages of formation as peat, lignite, sub-bituminous, bituminous, semi-bituminous, semi-anthracite, and anthracite, has been used for centuries. Coal, as such, was not very well known to the ancients. First reference to "magic stone', or coal, was in 371 BC by Theophrastus, a pupil of Aristotle. This substance was said to burn like wood coal or charcoal and was used by the smiths. The first record we have in modern times was in 852 AD, when sea coal was gathered by the cowled monks of Durham, in Britain, and even at that time a major problem was transportation. Our first record of coal in this continent was near Richmond, Virginia, in 1700. Commercial mining was not under way, however, until 1750. The anthracite fields (presumably in Pennsylvania) were opened in 1793. Even so, there was no extensive mining until about the year 1820. The famous Pocahontas coalfields were opened in 1883. The earliest record of coal mining in Canada is about 1746.

Jan 1, 1950

By B. J. Arnold, N. Terblanche

The features of the ‘Turbo’ froth flotation column will be discussed, including the double aeration system that improves flotation yield while not sacrificing grade, the internal launder system, and the unique feed/tailings sump that evens out flow to the flotation column preventing upset conditions. Results from various test programs and installations will be presented.

Jan 1, 2001

By J. R. Thoenen

In Progress Rerort 1,4/ a number of facto were demonstrated and conclusions drawn from experimental tests and records made during commercial blasting operations at a number of quarries. For example, the tests showed (1) that vibrations received on outcrops were of comparatively

Jan 1, 1938

Innovative and Resource-Preserving Washing Processes for Primary and Secondary Raw Materials

Sep 13, 2010

By M. Irish, M. Jahraus

Accurate prediction of gold (or other metal) production from a heap leach operation is essential to the economic vitality of any such operation. However, this is also one of the most challenging issues facing managers of these facilities. Three approaches to modeling gold production from the Valley Leach Facility (VLF) at Anglogold’s Cripple Creek & Victor Gold Mining Company are presented. Evolution of these modeling methods has been necessary as ore heights and volumes have increased. In addition, the complex geometry of the VLF presents additional complications to production modeling, Comparison of actual and predicted gold production are presented

Jan 1, 2001

By S. M. Rupprecht

"SynopsisOver the last decade in South Africa, there has been a significant increase in the number of mining operations, both open pit and underground, which use independent contractors to carry out mining activities. Often mine owners will choose the contractor option without fully understanding the consequences of undertaking this option. Traditionally, contract mining has come at a cost premium of about 15% to 20% compared to an owner mining scenario. However, due to the large number of junior mining companies entering the mining arena in South Africa contract mining rates have increased, with cost premiums as high as 50% being reported. This paper looks at the merits of owner mining versus contract mining and describes under what conditions it may be favourable to select the one option over the other. In addition, the methodology of entering into contract negotiations with the objective of establishing a fair and sustainable relationship is discussed.IntroductionOver the last decade in South Africa, there has been a significant increase in the number of mining operations, both open pit and underground, which use independent contractors to carry out mining activities. Surface mining, for example, may use contractors to conduct drilling and blasting operations or load and haul operations. Underground mining may contract out work such as shaft sinking, mining, support, construction work, cover drilling, sweeping and vampings. Common surface operations such as mineral beneficiation, waste disposal, security, and product transport may also be outsourced to contractors.Many companies have a business model that utilizes contractors for the entire mining cycle, maintaining a small head office to provide direction and control. The difficulty with this option is that often mining companies will choose the contractor option without fully understanding the implications."

Jan 1, 2015

This publication summarizes, for potential contractors and all other interested parties, the research and development of in-house and contract projects programmed by the Bureau of Mines for fiscal year 1983 (October 1, 1982-September 30, 1983) under its Health and Safety Technology program. The objective of these projects is to provide an ordered and sequenced series of advance toward the Bureau's overall goal of providing the systems technology required to create a more healthful and safer working environment for the Nation's mining and minerals processing workers.

Jan 1, 1982

By Yuanbo Zhang

Zinc leach residues produced by hydrometallurgical zinc plants contain many valuable elements (zinc, iron, lead, gallium, indium silver, etc), while they have not been utilized effectively hitherto. In this paper, a new process of flotation-reduction roasting-magnetic separation to recover these valuable elements from zinc leach residues is developed on a basis of mineralogy investigations of them. The results show that silver concentrate with grade of 4321.6 g/t and recovery of 80.69% have been obtained, using 1750 g/t Na2S as conditioner, 750 g/t ammonium dibutyl dithiophosphate and SN-9 (assistant collector) as combined collector and 100 g/t terpenic oil as frother, if zinc leach residues with 523 g/t silver are floated at pH = 5.0. When the flotation tailings are subjected to reduction roasting at 1100? for 2 h, the volatilizations of zinc, lead and indium are over 96%. After roasted products are treated by wet-grinding and magnetic separation, the grade of gallium and gallium in the concentrates achieved respectively reaches 1805 g/t and 1536g/t, and the recovery of them is high to 94.67% and 93.20%, respectively.

Jan 1, 2006

By F. W. Brackebusch, R. O. Sack

"A method for determining the fineness of Au in electrum from the composition of fahlore coexisting with pyrite and chalcopyrite is presented. This method is based on previously published experimental brackets and activitycomposition models for electrum and fahlore, and it is potentially useful for defining temperatures of hydrothermal mineralization and retrograde evolution of precious metals deposits. The authors demonstrate that it successfully predicts compositions of electrum reported for this assemblage in the literature and illustrate its application for three gold-quartz vein deposits from the Coeur d’Alene mining district, Idaho, that are prospects of the New Jersey Mining Company, the Coleman vein, High-Grade prospect, and Silver Strand mine. Temperatures calculated from average electrum compositions estimated from gravity concentrates (molar Au/(Au+Ag) = 0.76-0.39) and from microprobe analyses of the fahlores (molar Ag/(Ag+Cu) = 0.039 ± 0.004, Zn/(Zn+Fe) = 0.57 ± 0.03, As/(As+Sb) = 0.23 ± 0.02) from the Coleman vein indicate that the electrums underwent retrograde re-equilibration to temperatures between about 80°C and 240°C, roughly 80°C below the temperature of hydrothermal mineralization and 10°C to 40°C above the temperature inferred for retrograde equilibration of Fe and Zn between sphalerite and fahlore. Fahlores from the High-Grade prospect [molar Ag/(Ag+Cu) = 0.009 ± 0.004, Zn/(Zn+Fe) = 0.55 ± 0.11, and As/(As+Sb) = 0.04 ± 0.03] and Silver Strand mineralized zone [molar Ag/(Ag+Cu) = 0.10 ± 0.04, Zn/(Zn+Fe) = 0.63 ± 0.02, and As/(As+Sb) = 0.06 ± 0.02] exhibit strong core to rim depletions in Ag due to retrograde operation of the reaction1/10Cu10Fe2Sb4S13 + Ag + FeS2 =Cu-fahlore electrum pyriteCuFeS2 + 1/10Ag10Fe2Sb4S13chalcopyrite Ag-fahlorewhich proceeds to the left with decreasing temperature. Electrum inclusions in arsenopyrite from the High-Grade prospect [molar Au/(Au+Ag) = 0.90 ± 0.02] define a minimum bound on the temperature of hydrothermal mineralization of 273°C, and the temperatureelectrum composition curve constructed for the most Ag-rich fahlore in the Silver Strand mine indicates that the fineness of its electrum is significantly less than in the other deposits."

Jan 1, 2004

By Grant R. Brown

The report provides guidance for determining those environmental impacts associated with the surface mining of steeply pitching coal seams. In addition to the environmental impacts, four additional issues are addressed, namely (1) Time and motion studies of those coal mining systems employed in mining seams which pitch in excess of 25°, (2) Assessment of those mining techniques, (3) Development of rationale for the mining methods employed, (4) Identification of the reclamation practices and determine whether these practices were in compliance with appropriate Federal and State regulations. Five surface mines located in three geologically distinct basins of the United States were analyzed during the period of August through November 1979. The three basins include the Hanna Basin of Wyoming, the North Park Basin of Colorado and the Southern Anthracite Field of Pennsylvania.

Jan 1, 1980

By understanding the ore breakage characteristics and utilising comminution circuit modelling, the benefits of SAG mill feed size manipulation can be readily assessed. This paper looks at the benefits and problems of total secondary crushing of mill feed and advocates partial secondary crushing as a means of improving grinding efficiency for certain hard ores. Case studies are reviewed for new and existing SAG mill circuits.

Jan 1, 2007

By Edgar S. Rush

This study was conducted to make a limited evaluation of experimental and standard tractor dozer blades. A field test program was conducted in the southeastern part of Kansas on strip-mined areas where the spoil banks are parallel with rest-to-crest distances between 90 and 120 ft and maximum dozing distances usually less than 50 ft. This evaluation was a part of an overall joint Pittsburg and Midway Mining Company--U. S. Bureau of Mines (USBM) Specialized Reclamation Field Test Program primarily centered on the field t sting of experimental high-volume lateral relocation blades. The three blades evaluated were the 60-ft-wide angle (A) blade mounted on two 41B tractors. a 48-ft-wide A blade mounted on two D9H tractors, and a 13-ft-wide reclamation universal (Rec U) blade mounted on a D9H tractor. In addition to the experimental blades, three commercially available blades were tested: A 20-ft universal (U) blade mounted on two side-by-side (SxS) D9H tractors; a 20-ft U blade mounted on a 418 tractor; and a l2-ft straight (S) blade mounted on a D8H tractor. The dozer blade evaluations compared measured blade performance with soil and other site characteristics and with estimated earth-moving performance rates based on earthmoving methodology that accounts for the traction and speed of the tractor. The earthmoving methodology was also validated with data collected during this program.

Jan 1, 1978

By L. Obert, D. E. Stephenson

The objectives of this investigation were to develop a laboratory procedure in which core discing could be produced under known (and variable) stress conditions, and to study the discing characteristics of several fypes of rock. Discing of rock cores refers to the formation of discs or wafers of relatively uniform thickness which fracture or rupture on surfaces approximately *Fracture is a type of failure in which there is a complete loss of cohesion and fresh surfaces are created. Rupture is a type of failure in which there Is only a partial loss of cohesion. normal to the axis to the core (see Fig. 1). Usually the surfaces of the discs are concave-convex with the concave side toward the collar of the hole. The surface of the fractured discs are like those created by a tension failure (or possibly a shear failure with virtually no normal compressive stress). This phenomenon has been observed by a number of investigators1-5 in the course of diamond drilling in underground mines, especially in areas suspected of being under high stress. The state of stress in the core required to produce discing is not exactly known. Tranter and craggs6 theoretically investigated the stress distribution in an infinite cylinder, subjected to hydrostatic pressure, minus p, from z = 0 to z = 8 and unloaded from z = 0 to z = 8, Fig. 2. The exact solution to this problem shows that a tensile stress develops in the loaded region near z = 0 with the greatest tensile stress on the axis of the cylinder. A tensile stress also developed on the surface of the cylinder at a point just outside of the loaded zone. Jaeger and Cook3 experimentally investigated the discing mechanism by biaxially loading cores in a pressure jacket sealed at the ends by O-rings. According to the Tranter and Craggs theory it would be expected that failure should occur at the pressure discontinuity at the O-rings. The experimental results showed that if the specimen was unjacketed it broke at random points within the pressurized zone and at a pressure somewhat greater than the tensile strength of the specimen, presumably due to the development of a

Jan 1, 1965

By T. M. Ruff, W. G. McCoy, M. J. Beus, S. Iverson, W. Hasz

Technology to enhance safety during mine hoisting has been developed by researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health. Assessment of current hoisting technology suggests that monitoring conveyance position and load directly from the skip or cage top offers several significant safety advantages. Wireless data transmission schemes and a package consisting of sensors, batteries, and a charger mounted on the wire rope and skip have been developed. A state-of-the-art automated hoisting test facility was constructed to test the concept in a controlled laboratory setting. Field tests in a fill-size shaft are underway.

Miners and explorers in New Zealand are expected to consult with stakeholders, keep out of core conservation areas, and operate a high standard of environmental management and rehabilitation. These requirements are not difficult to meet, but many of the industry's own actions have brought it to a low level of general public esteem in New Zealand. Reasons for this are discussed, drawing examples from the Maruia Society's experiences with the industry since the mid-1980s. The boundary between core conservation areas and other land is not easily drawn, and the Maruia Society has sought to work with the mining industry to promote legislation for net conservation benefit trade-offs. However this initiative was not successful. Today the industry, unlike most other major industry sectors in New Zealand, has no accord with the country's conservation movement.

Jan 1, 1997

By Stephen L. Chryssoulis

"""Preg-robbing"" of gold by carbonaceous matter during the cyanidation of certain types of carbonaceous gold ores is well documented. Recent studies established that ""preg-robbing"" of gold is not limited to carbonaceous matter. Gold sorbed on the surface of pyrite grains was detected and quantified by TOF-LIMS (Time of Flight Laser Ionization Mass Spectrometry). Crystallites of pyrite from a number of ores from different geological environments have been shown to have gold on their surface apparently sorbed from the ore forming solutions. Surface gold accounts for significant fractions of the gold head assay. Preg-robbing of gold by pyrite from pregnant cyanide solutions was also documented, and accounts for significant losses to tailings. Preventative measures are discussed.1.0 IntroductionThe detection and subsequent quantification of gold sorbed on the surface of pyrite particulates came about during routine determinations of the deportment of gold employing the comprehensive mineralogical approach (Chryssoulis and Cabri, 1990). In some pyritic gold ores it was discovered that the sum of the various forms in which gold ""conventionally"" occurs, was short of the gold assay. The mineralogical procedure used involves the independent determination of each fraction of gold, in other words there is no form of gold which is calculated ""by difference"". The systematic shortfall after having added the forms of gold listed in Table 1 led to the inquiry for the 'missing' gold and its discovery on the surface of pyrite grains, such as crystal facets and fractured surfaces.Preg-robbing of gold by pyrite from pregnant solutions was first described by Lloyd. In his studies, preg-robbing was measured by changes in the solutions/solids gold assays. This paper describes the first application of a direct measurement method for surface gold on pyrite particles from untreated and processed samples, its impact on gold deportment and processing. The advantage of the direct measurement lies in the absence of interference from other forms of gold, leading to more accurate and precise determinations of this unconventional form of gold."

Jan 1, 1997

By T. J. McKeon

Partition curves are used to evaluate the separation performance of gravity-based concentrators. The partition curve is used to identify the nominal density cutpoint and relative sharpness of the separation. In addition, the graphical representation makes it possible to quickly identify the root cause of misplacement based on the characteristic shape of the partition curve. Partition curves have been traditionally constructed using data obtained from float-sink tests using heavy organic liquids. These toxic liquids are environmentally unfriendly and have been banned in several countries. Another method of establishing the partition curve is to introduce density tracers into the feed and plot the distribution to the lights and heavies. For heavy mineral separations, this approach is generally impractical due to the fine particle size. In addition, the partition data obtained using these existing techniques do not account for secondary factors such as particle shape that may influence the separation. In light of these problems, a methodology was developed for constructing partition curves using experimental data obtained from microscopic grain-counts. This technique, which essentially uses the different mineral species as density tracers, provides a powerful tool for evaluating heavy mineral separations. A case study is provided to demonstrate how this analytical approach can be used to assess and improve the separaton performance in an industrial upgrade plant.

Jan 1, 2005

During an eight month period, January to August 1978, nine bore holes were drilled in the Mikonui River gravels. On account of two rebores required from near bottom, the number of bores is in effect 11. Just on 1300 feet were drilled with an average depth of 120 feet. Depth varied from 102 feet to 133 feet. Penetration on average per hole value, varied from 7.4 to 16.4 feet per day. Gold values were even more erratic. Drill rig used was the Keystone churn drill manufactured locally by the Dispatch Foundary. It is skid mounted and requires a crew of two persons.

Jan 1, 1979

By Clay Haynes

While the Kansas River Tunnel is a relatively short, small diameter tunnel, the shaft excavation methods implemented were long and large on innovation and use of reverse circulation drilling equipment. ATS Drilling, L.P. used mechanical excavation techniques for both soil and rock segments of the 42.7 m (140 feet) and 38.1 m (125 feet) deep shafts that were 2.9 m (9.5 feet) and 4.1m (13.5 feet) diameter, respectively.