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By D. A. Peterson

Laboratory testing was completed to determine the effectiveness of a fiberglass cable bolt (FCB) as a cuttable rock support for a continuous, hard-rock mining method. The FCB consists of four Polystal tendons combined in a node/antinode fashion, with polyvinyl chloride (PVC) spacers forming the anti-nodes. The largest ultimate pull-out load achieved by the FCB was 22 t (48,400 lb) at 89% of the tendons' theoretical pullout load. This premature tendon failure is accredited to: • differential stresses within the tendons and • differential tendon displacement. An increase in pull-out resistance for a given embedment length is due to: • increased bond area, • reduced interfacial shear and • "wedge" effect. The critical embedment length was found to be 40% less than for conventional steel cable bolts (SCB) at a 127-mm (5-in.) node spacing. An FCB can have up to a 92% increase in load-carrying capacity over a conventional SCB at equal embedment lengths. The load carrying capacity is equivalent to SCB at a 960-mm (37.8-in.) embedment length. Though the FCB is 7.5% more expensive than the conventional SCB (installed), this cost may be offset by increased performance. FCBs are a potentially viable support alternative for continuous hard-rock mining.

Jan 1, 1993

By James A. Barclay

Results of investigations over approximately the last 10 years by the Bureau of Mines and others on technology for recovering cell-grade alumina from domestic nonbauxitic resources such as clay, anorthosite, alunite, dawsonitic oil shale, coal ash, and coal shale are reviewed. It is concluded that, although many innovative techniques have evolved from this effort and have been shown to be technically feasible, energy and economic considerations will prevent any of the processes from competing with the Bayer process under normal conditions. Based on the Bureau's experience, some variation of clay-HCI leaching, HC1 gas sparging crystallization has the greatest potential as an alternative to the Bayer-bauxite process.

Jan 1, 1984

Early experiences suggested autogenous mills were difficult to operate and consumed substantially more energy than conventional rod/ball mill circuits. As our understanding has increased and the technology has matured this perception has changed to the point where most new comminution circuits are ag/sag based. In addition many operators have replaced existing conventional circuits with this technology. The JKMRC has been studying ag/sag mills for over 20 years. During this time it has amassed what is probably the single largest and most detailed data base of pilot and full scale mill operations in the world. This has been used to help develop and refine its cur- rent commercially available mathematical model of ag/sag mills. A decade of its application has greatly helped simplify both design and operation of ag/sag milling circuits as well as helping to promote the effective use of recycle crushing, secondary crushing and closed-circuit operation. This paper describes the development of ag and sag milling in terms of our understanding and the evolution of the technology. In addition the application of mathematical modelling and simulation in designing and operating efficient circuits is described with the aid of practical examples.

Jan 1, 1998

By D. L. Watson

In spite of the deflationary state of the minerals business today, there will be opportunities for those who can fulfill future needs. Since there are abundant supplies of ores and fuels to keep prices down, at least in peacetime scenarios, future needs may be as much political and social as technical and economic. Engineers and economists will develop new and innovative ways to find, mine, process and pay for mineral deposits. Pressure from governments and non-governmental organizations and the public will combine with market forces to provide opportunities for highly competitive, risk-taking enterprises who can leverage the qualities of their orebodies and employees by being good neighbors and partners.

Jan 1, 2000

By D. Marinakis

Gas hydrates (GH) are crystalline compounds consisting of a water molecule lattice, in the cages of which suitably sized molecules, such as methane or other light hydrocarbons, are confined. Although this solid phase looks similar to common ice, it contains substantial amounts of natural gas. The necessary conditions for natural gas hydrate formation exist in some deep-sea marine environments and in permafrost regions. Despite the extensive research, which has been conducted in the fields of exploration and exploitation of natural gas hydrate deposits over the last decades, there is still great uncertainty over the estimated amount of hydrates that these reserves bear. The present work examines some key features of sediments which affect their capacity to host gas hydrates. The hydrate content of a natural hydrate formation is correlated qualitatively with factors such as temperature, effective porosity, mineralogical composition, bio-surfactants, pore pressure and compaction pressure.

Jan 1, 2006

By AKIHIRO YOSHIMURA, HIDEKAZU KATO, KOTA TAKATORI, YASUNARI MATSUNO

Chalcopyrite (CuFeS2) is the most refractory copper mineral when treated in conventional sulfate media leaching systems. This study is the first to examine the use of a dimethyl sulfoxide (CH3SOCH3), or DMSO, solution containing copper chloride (CuCl2) in the leaching of chalcopyrite. The DMSO solution containing CuCl2 could selectively dissolve the valuable metals of copper (Cu) and gold (Au) from chalcopyrite while leaving minerals with little economic value, such as pyrite (FeS2), and the penalty element arsenic (As) in the residues. Leaching chalcopyrite using a DMSO solution that contains CuCl2 offers a number of advantages, including eco-friendliness and easy operation.

By Oleg N. Tikhonov

The paper deals with computerized analytical design of separational mineral processing flowsheets for flotation, gravity separation, magnetic separation, etc. (without comminution). Initial data include fractional composition of the feed ore, separational characteristics of the unit operations, and optimality criterion. Computer-calculated results display optimal flowsheet configuration and optimal parameters of unit operations like tonnage, residence time, etc., which allows the choice of equipment. An example of apatite flotation flowsheet design is given. This analytical approach may be used for automatic process control purposes as well.

Jan 1, 1989

By Celeste Powell

Liquid carbon dioxide can be used as a replacement for organic solvents in the extraction of anionic PGM complexes from an aqueous phase. This can be achieved only if highly carbon dioxide-soluble chelating agents are developed because conventional chelating agent-metal complexes, such as trioctylamine-gold chloride, are not soluble in liquid carbon dioxide (although trioctylamine is CO,-soluble). Our novel CO,-soluble chelating agents have a fluorinated tail and a conventional amine head group. Both the chelating agent and the chelating agent-metal complex are soluble at ambient temperature at pressures between 7-35 MPa. Equilibrium constants in the 105 range have been measured (in Freon 113, a low pressure screening liquid for carbon dioxide), indicating that these compounds will strongly bind the metal chloride. For example, 93% of Pt-chloride was extracted into Freon 113 using a 3.5:1I ratio of a double-tailed fluoroalkyl amine chelating:metal chloride. 88% recovery of Pt-chloride into liquid carbon dioxide was achieved using the same chelating agent at a 3.5:1 ratio.

Jan 1, 1999

By D. Krzyszton, P. Czaja

Mining explosions in rocks originate stress waves of great intensity, which crush the surrounding rocks and are then propagated as a seismic wave. Seismic waves are the cause of dynamic loading of pillars and their subsequent destruction. In calculating safe dimensions for inter-room pillars, not only the stresses conditioned by overburden pressures should be taken into consideration, but also the dynamic stresses caused by explosion. This is of particular importance for pillars with great specific acoustic impedance which have been destroyed mainly by the reflected seismic wave. It is possible to take dynamic loading into consideration in the calculation of pillars when the parameters of the propagation wave, the dynamic elastic constants of rocks, the strength properties of rocks, the strength properties of rocks subjected to dynamic loads and the parameters of the blasting charge are known. An example of the calculation for the safe width of an inter-room pillar subjected to the seismic effect of an explosion is given and the possibilities of reducing the dynamic loading of pillars are discussed.

Jan 1, 1982

By G. F. Willis

Gold mineralization in the Mesquite district is hosted by a series of Jurassic amphibolite grade metamorphic rocks which have been intruded by a Cretaceous leucogranite pegmatite. A series of northwest trending, high angle, normal faults have apparently acted as a structural locus for mineralized epithermal fluids and thus economic concentrations of gold in the Big Chief orebody. Late Tertiary fault reactivation has bounded the fault and fracture controlled mineralization. Popular theories of ore genesis call on, (1) Tertiary detachment faulting, (2) the Cretaceous intrusive, or (3) the opening of a dilational jog between regional dextral strike-slip faults as a source powering the gold bearing hydrothermal fluids.

Jan 1, 1988

By Erich U. Petersen

Discussion by Erich U. Petersen Harbuck et al. (1990) present results of research on sulfuric acid leaching of a germanium-gallium ore and shed considerable insight on possible extraction methods for gallium and germanium. However, the presentation does not give sufficient details to evaluate the research, so some of the conclusions may not be as applicable as stated. The objective of this communication is to indicate that relevant and easily obtainable geological and technical information was omitted. Consequently, on this basis, alternative explanations for some of the data are possible. Discussed below are the omission of: • pertinent geological, mineralogical and geochemical literature; • details regarding the determination of germanium concentration in quartz by electron microprobe; and • details on the calculation of the amount of germanium locked in quartz. "These topics are important since the determination of the amount and locus of "unrecoverable, locked germanium" may have an important impact on the economics and methods of germanium extraction and the directions of future research. Harbuck et al. state that "A key to increasing germanium extraction is understanding the mineralogy of the ore." However, only two studies are cited that in some manner describe the mineralogy of the ores. In addition, both of these studies were very preliminary, of limited scope and examined very few

Jan 1, 1993

By J. Loredo

The region of Asturias, located in the northwest of Spain, has an extensive mining history; coal, gold, zinc, lead, copper, cobalt, mercury, iron, manganese, fluorspar and others have been extracted from the antiquity. In the Asturian Central Coal Basin, the closure of all open pit coal mines and their restoration, the progressive closure of underground coal mines that is happening from the 1980?s, and the restoration of spoil heaps, provides post mining lands for alternative uses. In relation to metallic mining, the abandonment of all mercury mines without restoration in the 1970´s, has left significant quantities of wastes and mining works. More than thirty years later most of them remain without restoration. In these sites the legacy of the historical mining activities is apparent in the form of shafts, galleries and transversals, old mining installations and spoil heaps. Mine wastes have eventually become important Hg and As pollution sources, resulting in a widespread contamination of the surrounding soils and surface waters. Abandoned mines of other metals such as copper, cobalt, iron, etc. and industrial minerals such as fluorspar, have also left a mining legacy to take into consideration. In this context of declining mining areas, some remedial options have been applied to specific areas resulting in alternative uses as pastures, agro-forestry, industry and socio-cultural activities.

Jan 1, 2008

By Z. F. Wang, W. K. Choi, A. E. Torma

The present study has investigated the bioleachability of low-grade and high-grade pyritic gold ores and the extraction of gold from the leach residues of bioleaching with thiourea solutions. Final gold extractions as high as 96% were obtained from the high-grade ore and above 93% from the low-grade ore. The gold extraction was found to follow the extent of pyrite biooxidation. Using a cyclic voltammetric technique and carbon-paste-FeS2 electrode it was found that the semiconductor pyrite oxidation involves many intermediate electrochemical reactions. Furthermore, the oxidation is solid-state diffusion controlled as suggested by chronoamperometric and chronopotentiometric measurements.Using Sand's approach, the activation energy of solid-state diffusion biooxidation of pyrite was determined to be AEa=22.4 kJ. A generalized model for the mechanisms of pyrite oxidation has been presented.

Jan 1, 1990

By Alan A. Campoli, Michael D. Zuber, Frank E. McCall, Gerald L. Finfinger

Injecting water under pressure to wet the coalbed in advance of mining reduces mining-generated respirable dust. Owing to economic and geological barriers, water infusion for longwall dust control in the United States is currently limited to the Pocahontas No. 3 Coalbed in Virginia. Water is pumped into the coalbed through underground boreholes drilled horizontally from the headgate toward the tailgate side of retreat longwall panels. This paper theorizes that the barriers to widespread utilization of water infusion for longwall dust control could be overcome by long-duration, low-pressure water infusion through vertical gob gas boreholes. Currently, 43% of the 72 longwall mines in the United States employ vertical gob gas boreholes. Computer coalbed reservoir simulation suggests that one vertical surface borehole could infuse the same longwall panel area as four horizontal boreholes in the current water infusion system for longwall dust control in the Pocahontas No. 3 Coalbed.

Jan 1, 1995

By William E. Little, William R. Sharp, Edward R. Kennedy

Cost o f mechanical tunneling requires the knowledge of many machine/rock parameters such as rock types, machine power, penetration rate, cutter life, maintenance schedule, etc. Capital investment, labor requirements, and project scheduling will all play an important role in defining the economics of the overall project. Knowledge of the cost sensitivity of different project parameters will improve the overall success of any particular tunneling project if this information is incorporated into an effective management plan. Through the use of an interactive graphic computer program written for a microcomputer, one has the ability to quickly evaluate relative costs for a variety of parameters for either an existing project or for a proposed site.

Jan 1, 1983

By Wen Tao Liu, Tong Tian, Fu Sheng Niu, Xiu Man Liang

The level of automation employed in flotation production is relatively low. In an actual concentrator, operators use their judgment to adjust the production state based on the visual characteristics of the flotation froth surface. There are shortcomings, such as strong subjectivity and lagging process operation, that easily cause the waste of manpower and material resources. Machine vision technology is introduced to replace human visualization, achieving a quantitative description of the visual characteristics of the froth surface. The state variable parameters are provided for the identification of the flotation conditions.

Little knowledge is available that considers the effects of continuous miner position on the possible respirable dust exposure of the remote mining-machine operator. Such information could be very useful for increasing the awareness of the remote operator as to those parts of an extended cut that generate higher levels of respirable dust. This data could be used to develop guidelines for positioning the remote operator to reduce his potential exposure. This work details the effects of continuous miner position on dust levels measured on the machine and at the remote continuous miner operator location.

Jan 1, 2000

By Steve R. La Brooy

Techniques for dealing with copper-gold ores are reviewed. Cyanide has little selectivity of gold over copper, and depending on the reactivity of the copper minerals cut-off grades for gold recovery by direct cyanidation are generally below 0.5% copper for oxide ores and 1 % for sulfide ores. Non-cyanide gold leachants also tend to be reactive to copper. The cheapest option for sulfidic ores is to produce a flotation concentrate for smelting, while transition ores generally need a sulfidisation pre-treatment. The requirement for the concentrate to have a high enough copper grade to be acceptable to a smelter may compromise copper and gold recovery. This can lead to significant gold grades in the flotation tailing, and copper levels in the tailing that are too high for direct cyanidation to be able to recover the gold. Oxidised ores, flotation tailing or other material not amenable to flotation represent the greatest grey area for gold recovery. Copper removal by acid, alkaline or ferric pre-treatment is possible though not generally used. Cyanide pre-leaching to remove copper, followed by copper and cyanide recovery represents a potential option that has been installed at one Australian gold plant, where copper is recovered onto carbon, ahead of the slower leaching gold. Actual cyanide recovery depends on ore mineralogy, allowing for losses as cyanate, thiocyanate, carbonate and ferrocyanide. Alternative options for gold recovery following cyanide leaching include precipitation, ion exchange and solvent extraction of the gold. Ammonia-cyanide leaching may offer another option for more selective gold dissolution from flotation tailing and oxidised materials. A plant is currently under construction in Mauritania.

Jan 1, 1992

By Lj. Obradovic

The aim of this paper is to study the feasibility of copper and gold recovery from the old flotation tailing dam at Bor, Serbia. Laboratory leaching experiments were carried out using a composite sample taken by drilling from 16 - 40 m depth. Different oxidation agents as FeCl3, Fe2(SO4)3 and H2O2 were used. An H2SO4 solution with a pH less than 3 was used for leaching. The influence of a number of parameters on the recovery of both elements as temperature, pH, duration of leaching and concentration of oxidation agents was also studied.

Jan 1, 2006

By G. L. Finfinger, F. E. McCall, A. A. Campoli, M. D. Zuber

Injecting pressurized water into a coalbed prior to mining reduces mining-generated respirable dust. Because of economic and geological barriers, water infusion for longwall dust control in the United States is now limited to the Pocahontas No. 3 Coalbed in Virginia. Water is pumped into the coalbed through underground boreholes that are drilled horizontally from the headgate toward the tailgate side of retreat longwall panels. This paper theorizes that the barriers to widespread utilization of water infusion for longwall dust control could be overcome by long-duration, low-pressure water infusion through vertical gob-gas boreholes. Currently, 43% of the 72 longwall mines in the United States employ vertical gob-gas boreholes. Computer coalbed-reservoir simulation suggests that one vertical surface borehole could infuse the same longwall panel area as four horizontal boreholes in the current water-infusion system for longwall dust control in the Pocahontas No. 3 Coalbed.

Jan 1, 1997