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By J. A. Eisele, G. E. McClelland, M. D. Wroblewski

The Bureau of Mines is conducting research at its Reno Research Center to develop a staged agglomeration-heap leaching system and to electrowin the dissolved precious metals from the pregnant leaching solution. For direct electro- winning to be successful, the pregnant solutions generated during the Initial stages of leaching must be higher grade than obtained by conventional heap leaching. The precious metal concentration of the pregnant solution can be Increased by agglomeration pretreatment with cyanide solution which starts the leaching process during the curing period, by leaching with small volumes of solution and by cycling the leaching solution through more than one heap in a staged manner. The resulting pregnant solution is passed directly through an electrowinning circuit. The barren solution from electrowinning is recycled to the leaching circuit. Bench-scale research on the development of the staged leaching system and on the development of an efficient electrowinning cell are described. The Bureau of Mines developed agglomeration- heap leaching technology. This technology was readily adopted by the mining Industry for heap leaching crushed ores and mine wastes. Current research involves the application of this technology to finely ground feed materials such as precious metal-bearing milled tailings. Tailings agglomeration-heap leaching has also been used commercially.

Jan 1, 1984

By Ross W. Smith, Xiapeng Zheng, Merrill P. Allen

The results of flotation of a primary desliming hydrosizer overflow material containing 14.6 wt.% P20, and 3.6 wt.% MgO are presented. The phosphate minerals were collophane and francolite and all minerals appeared to be liberated. The material had not been previously treated with flotation reagents. In the experimentation, various collectors were evaluated for effectiveness. The relative effectiveness of flotation in different flotation devices was determined. Finally a two-stage flotation scheme is proposed using column flotation of dolomite in the first stage and Denver cell flotation in the second.

Jan 1, 2002

By Levent Ozdemir, Robert J. Evans

An ongoing research program at the Colorado School of Mines is investigating the application of low to moderate pressure water jets to assist the cutting performance of drag type cutter bits commonly used on coal mine cutting machinery. The results to date indicate that a water jet directed to impinge the rock in the immediate vicinity of cutter tip can provide significant benefits in terms of reduced cutting forces, prolonged bit life and less airborne dust, as well as reduced tendency of sparking during cutting. This paper describes the findings of this research effort designed to fully evaluate and optimize the parameters affecting the performance of a combined water jet assisted drag bit cutting system for coal mine applications.

Jan 1, 1983

By Simon T. Johnson, Robert J. Fowell

The application of roadheading and drag tool equipped machines requires an assessment of both cutting performance and tool consumption. Neither parameter can be assessed purely from compressive strength and tool consumption is often neglected, at a cost to the project. Results from in-situ monitoring show that a measurement of relative abrasivity using the Cercharscratch abrasivity test provides a basis for the assessment of tool consumption. This can be modified by also considering the effects of the machine specification and the rock mass quality.

Jan 1, 1986

By W. J. Stone

In response to concerns over the impact of mining on the hydrologic balance at the Navajo Mine in northwestern New Mexico, a recharge study was conducted using a chloride mass- balance approach. Impact of mining on annual recharge volume was assessed by comparing pre- and post-mining recharge values. The mean regional recharge rate for reclaimed ground (weighted by acreage) is 1.02 mm/a (0.04 in. per year) or twice that for undisturbed ground, 05 mm/a (0.02 in. per year). Comparison of regional recharge volumes for identical areas shows mining increases recharge 92%. The increase is only 80% if no closed depressions are constructed during reclamation. However, the increased rates are so low that there should be no detrimental impact on regional water resources. The chloride method proved useful at Navajo Mine and should succeed at others surface coal mines as well.

Jan 1, 1991

By J. D. Miller

Reaction kinetics for gold dissolution in acid thiourea solutions were investigated using formamidine disulfide as an oxidant. For the conditions studied it appears that a surface reaction limits the rate of gold dissolution. The rate was found to be first order with respect to thiourea concentration and half order with respect to the concentration of formamidine disulfide; the apparent activation energy for the reaction was 10.40 kcal/mol (43.40 kJ/mol); and the reaction rate was independent of pH for the pH range 1.0 to 3.0.

Jan 1, 1999

By Jan W. Oberholzer, Jan J. L. Du Plessis, Gerard Appelman, Andrzej M. Wala

The use of on-board scrubbers on continuous miners is an important aspect in efforts to reduce the amount of dust that heading workers are exposed to. As part of the CSIR:Mining Technology's research programme to combat dust, a collaborative project with the University of Pretoria was conducted to evaluate scrubbers. Based on fundamental parameters that were identified to play a role in determining the efficiency of scrubbers, a protocol for testing scrubbers in the laboratory environment, as well as the working section, was established. Tests on various prototype scrubbers were conducted in the laboratory environment. These tests proved some of the fundamental premises according to which scrubbers were designed. By testing some of the newer scrubber types underground, insight into the effect of alternative design aspects on scrubber efficiencies was obtained. The importance of the factors which play a role in reducing the amount of dust in the air is illustrated, as well as the role which other non-design factors play in the reduction of dust levels.

Jan 1, 1995

By Heinz Distelmeier

Short Historical Review Tunnelling in Germany is as old as it is in other industrial countries. Until the middle of this century German contractors had no chance to work continuously in this business except if they were operating internationally. Since 1960, however, tunnelling has been a growing market domestically. The reasons for this growth have been both in the growing demand of traffic routes and also in an increasing environmental consciousness, which tries to transfer any cause of disturbance underground. Tunnelling engineers of course don't complain about this trend. As almost every German city is built upon water-bearing soft ground, shields have been used soon after they were first successfully utilized in Great Britain and the United States. Until the seventies lining systems for shield tunnels were predominantly either cast iron segments or concrete segments for primary support combined with different sealing systems and a secondary concrete lining cast-in-place. Steel ribs and timber lagging for primary support has not been utilized in Germany, since the owners don't accept timber to be left in the ground. In 1973, for the first time, permanent linings were constructed with watertight segment rings of precast concrete (Fig. 1). This lining was developed as an economical solution for use with slurry shields in noncohesive, water-bearing soils that required an immediately watertight lining. Extruded linings have a similar effect, although these still need a secondary lining

Jan 1, 1987

By Ronald K. Frobel, Christopher J. Wienecke

Geomembrane systems and associated geosynthetics such as geotextiles, geonets, geogrids and geocomposites have been used in precious metal heap leach and tailings facilities for many years. Geomembranes have been used in the heap leach process in pad design and solution recovery ponds as well as associated collection channels as the primary liquid barrier to contain and collect metal bearing leach solution. Geomembrane systems offer an effective, low cost alternative to other containment methods such as compacted low permeability soils, asphalt or concrete. In the 19BO's, rigid High Density Polyethylene (HOPE) liners were used to a great extent with a gradual transition to the use of the more flexible Very Low Density Polyethylene (VLDPE) and Polyvinyl Chloride (PVC). These three geomembrane systems have been used successfully in precious metal heap leach solution containment. Predominant material thicknesses have been 30 and 40 mil for PVC, 40 and 60 mil for HOPE and VLDPE. Variants in recent years have included roughened HDPE and VLDPE to provide higher surface friction characteristics, as well as newer polymer materials such as polypropylene. In addition to providing an economical method for providing enhanced solution recovery, geomernbranes are also providing the primary liquid barrier for prevention of groundwater contamination. Because heap leach solution chemical components and dissolved metal constituents are classified as toxic substances, they are subject to environmental regulation. Many regulatory agencies are still developing guidelines for heap leach pad design, however a geomernbrane liner system is often used as a single liner or in conjunction with other materials to form composite double or even triple lined systems. "Other" materials can include alternate layers of drainage aggregate, geotextiles, clay layers and other geomembrane or geocomposite layers.

Jan 1, 1993

By D. W. Dew, D. M. Miller, P. C. van Aswegen

The bacterial oxidation (BIOX®) process for pre-treatment of refractory ores for gold recovery is marketed by BIOMIN Technologies S.A. The process was originally developed by GENMIN who are still providing testwork, design and commissioning assistance to BIOMIN. This process offers an alternative to the more conventional roasting or pressure oxidation techniques with the following advantages: • Greatly reduced capital costs for small to medium size plants. • A relatively flexible and easily controllable process requiring relatively unskilled labour for operation. • Improved gold recovery. • A process that is environmentally friendly. The principal disadvantage of bacterial oxidation is the relatively slow kinetics compared to pressure oxidation and roasting, a plant residence time of 4 to 5 days typically being required to obtain complete liberation of gold from refractory sulphide minerals. Bacterial activity is also slow to recover from disruptions such as air supply failure or contamination by toxic species such as cyanide. Optimum plant performance depends on judicious management and sound training of operators.

Jan 1, 1993

By J. M. Tranquilla

EMR Microwave has developed several unique processes for the pretreatment of refractory gold and copper ores. This report describes a recent large scale pilot project involving a carbonaceous gold-bearing whole ore. Pilot plant testwork conducted jointly by EMR and Bateman Engineering Inc. has shown that 90+% cyanide soluble gold recovery is obtainable from refractory (sulphide and carbonaceous) Carlin, Nevada gold ores. Typical cyanide soluble gold recoveries for untreated material is 20%. AC energy consumption was found to be between 58.l kWh/ton and 15.5 kWh/t for an assumed heat recovery of 50% and 80% respectively. The plant was operated at reduced temperatures ( 400°C) from previous testwork on similar ore at 600°-700°C.

Jan 1, 2000

By C. A. Fleming, C. J. Ferron, I. Dymov

An oxidized gold/silver ore from Mexico has been evaluated at Lakefield Research in order to develop an economically viable treatment flowsheet for the recovery of gold and silver. Initial cyanidation test results indicated that at least 20 kg/t cyanide was required for maximum gold and silver extractions, due to high cyanide consumption by an oxidized zinc mineral present in the ore. A process was developed for the recovery and recirculation of the cyanide from the leach liquors. The proposed flowsheet included direct cyanidation, CCD and Merrill-Crowe, followed by precipitation of the zinc associated with cyanide with sodium sulphide and recycling of the regenerated cyanide liquor to the leach circuit. The process was demonstrated during a continuous pilot plant. A mill has been erected recently in Mexico and has been operating using this flowsheet.

Jan 1, 1997

By H. D. R. Browner, D. A. Marsh

The need for a product dewatering step between the milling/classification and leach/carbon stages of gold plants has traditionally been performed by thickeners. Whether these be the 'conventional' or 'high-rate' types both require considerable initial capital outlay even without provision for standby facilities. In addition, their sensitivity (both mechanically and metallurgically) to changing feed conditions often results in these being considered 'high-risk' items of equipment, requiring a high degree of attention from operating personnel.

Jan 1, 1992

By Robert Snow, Yingxue Yu, Patrick Zhang

The FIPR/SAPR process is FIPR's third approach to develop a viable alternative to the Crago "Double Float" process for phosphate flotation. SAPR stands for Single-collector, All-anionic Phosphate Recovery. The FIPR/SAPR process - offers a universal flowsheet for any anionic reagent system and flotation feed of varying sizes. For an unsized or fine flotation feed, the FIPR/SAPR process consists of the following steps: 1) high-solids conditioning with an anionic collector; 2) anionic rougher flotation, with the rougher concentrate sized at 48 (or 65) mesh and the +48 mesh recovered as a final product; and 3) cleaning flotation of the -48 mesh fraction from step 2. In a variation of step 2, the rougher concentrate from the first two cells may be collected as a final product, and the rougher concentrate from the last two cells sized at 48 or 65 mesh. The new process was tested with a blend of anionic collectors, achieving single-digit Insol at 85 + % recoveries.

Jan 1, 2002

By Maurice Jackson et a1

Golder Moffitt and Associates (GMA)", were commissioned to reassess a large metallic low grade orebody. One of the aims of the study was to estimate recoverable reserves. Recoverable reserves are here defined as ore reserves for a specific mining block size. The mining block is that block on which the decision that the material is ore or waste is made. Recoverable reserves take into consideration mining methods. New methods for solving this type of problem were recently developed in Geostatistics and so for this reason GMA called for the technical assistance of the Centre de Geostatistique (C.G). The complete estimation was done using the geostatistical techniques and programs of the C.G together with some of the programs of GMA. As the mine was in production at the time the study commenced it was-possible to make frequent checks on the estimated values using blast-hole data. The ore reserves were also estimated using the more conventional interpolation method of inverse square of distance weighting.

Jan 1, 1979

By Stephen Leslie

A multimedia tutorial illustrating the geology and mineral resources of Gulf Coast salt domes has been developed as a pilot project for a course on Texas geology and resources at the University of Texas at Austin. The principal objective of the tutorial is to educate students with limited background in geological sciences about a major local geologic feature and its geologic and economic significance. The content of the tutorial represents materials generally covered in 4 hours of lecture and laboratory instruction. These materials are presented using a flattened hierarchy of topics, each accessible from a central menu, including salt-dome history, salt tectonics, anhydrite and calcite cap rocks, mineral resources, and geophysical character. Information concerning salt-dome geology is communicated using interactive software; sound and animation are used throughout to reinforce key concepts. Visual aspects include field views, hand specimens, and photomicrographs that were digitized from slides. Illustrations were created using a graphics program or scanned from available archives. Each visual element has an accompanying explanation, which in many cases is linked to other parts of the tutorial. Navigation is accomplished using hyper-links or a set of unobtrusive buttons. The program includes a glossary of the major minerals associated with salt domes available as a pull-down menu and digitized video footage of the Gulf of Mexico sea floor to illustrate the active environment of the formation of the salt-dome cap rock. In addition, a group of interactive questions is presented to assess the level of mastery. Technical aspects were accomplished using a Power Macintosh ? 7100AV and a variety of commercial software. Actual linking of information was done with Authorware? 3.0 Educational, an icon-based, multimedia authoring program. Graphic illustration was done with Adobe Illustrator ?; image processing was accomplished using Adobe Photoshop?; video was cap¬tured, edited, and compressed using Adobe Premiere ?. The interactive nature of the project was designed with regard to future means of dissemination, especially on the World Wide Web. This tutorial serves as a template to build additional modules covering the entire course. A modular approach to the coding of the project and extensive self-documentation should ensure the viabil¬ity of the project by allowing other workers with moder¬ate computer skills to complete other lessons within the curriculum framework.

Jan 1, 1999

By Frederick W. DeVries

EPA announced, when they proposed to set a potable-water limit on cyanide, in August, 1990, that they had never encountered cyanide in a :sample of potable water, but they felt this was a sufficiently toxic and common material that it should be covered with a specification. The writer worked with both the American Mining Congress and the Aluminum Association in responding to their proposed spec. of 0.2 ppm max. of "cyanide" in· potable water. Although there are many subcategories of "cyanide", they failed to specify which type they meant.

Jan 1, 1993

By L. J. Prosser, A. T. Iannacchione

From 1991 through 1995, 44 miners out of a total workforce of less than 2,000 were fatally injured in the stone industry. Of these, 12 occurred at underground mining operations with nine deaths resulting from roof or rib falls. A safer environment can be achieved by evaluating the nature of the hazardous ground and by developing more efficient and effective ground-control strategies. Roof and rib conditions were observed and assessed in 33 underground stone mines in Illinois, Indiana, Kentucky, Maryland, Missouri, Pennsylvania and West Virginia (Fig. 1). Hazard assessment indicated that the ground failures that occurred under moderate to substantial overburden, i.e., >30 m (100 ft), were caused by stress concentrations and geologic structures. Ground failures near the surface are caused by solution (water) processes. Selection of the mining horizon and mine-layout decisions

Jan 1, 1999

By Richard Kolada

If the emission of methane into any particular area of an underground coal mine remains constant, then the calculation of ventilation requirements is relatively simple. This is also true if the ventilation system is recirculatory. However, the emission of methane into a working area can vary considerably. There is always a risk that the ventilation will not be able to dilute the emission of methane to acceptable levels, because there are often short-lived peaks of emission which are very large. The ventilation design must therefore consider what is an acceptable level of risks and calculate the airflow requirements to meet this level. The acceptable level of risk can be calculated by examining the historical variation in methane emission into the area to be ventilated. For example, consider that an acceptable level occurs when methane emission peaks only exceed the capability of the ventilation one day in twenty. Then, from the history of methane emission, it is possible to calculate the necessary ventilation requirements. This method has been used since the early 1980s for conventionally ventilated districts. This paper examines the application of this technique to districts ventilated by recirculatory ventilation.

Jan 1, 1987

By S. K. Vidyarthi

Most wastewater clean-up processes suffer from a fundamental lack of specificity in that a Reverse Osmosis process removes all dissolved solids, an Electrodialysis Reversal process removes all ions, wanted or unwanted, etc. Most techniques require the use of a membrane or contact surfaces that are prone to foul-up and are ineffective in situations where solids may be present. A photochemical process for the metallurgical industry on the other hand has the ability to operate specifically on targets that can range from one selected ion to an entire group of homologous species such as all biologically active species. Processes can be designed to change the oxidation states of a target altering the environmental impact. Several processes are currently in operation ranging from Cyanide removal to disposal of radiation wastes. This paper describes applicable photochemical processes with the help of certain key model examples.

Jan 1, 1988