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By O. Ozcan, J. D. Miller, Z. S. Nickolov

The production of soda ash from trona (sodium sesquicarbonate, Na2CO3•NaHCO3•2H2O) resources has completely displaced the production of synthetic soda ash in the USA. Further, the utilization of other trona resources is under consideration in China, Turkey, etc. Recent research has been concerned with the development of flotation technology for the trona industry. In this regard studies on the flotation behavior of sodium carbonate salts: trona, sodium carbonate monohydrate and decahydrate, as well as the flotation behavior of sodium bicarbonate, are reported for both cationic (dodecyl ammonium hydrochloride) and anionic (sodium dodecyl sulfate) collectors. It has been found that strong flotation of sodium bicarbonate (NaHCO3) can be achieved with 100% recovery, while the other sodium carbonate salts do not float well. These results have been explained by FTIR analysis of aqueous solutions of Na2CO3and NaHCO3in a range of concentrations from very dilute to saturated conditions. The changes in the shape of the O-H stretching band of water are correlated with the flotation behavior of Na2CO3salts and NaHCO3. In addition, the absorption band of the carbonate ion at ca. 1385 cm-1is used to monitor its interactions with water and/or other ions in solution. The infrared results demonstrate thatNa2CO3acts as a water structure maker, leading to an extensively hydrated surface that accounts for the poor flotation of most sodium carbonate salts. In contrast, NaHCO3does not have this characteristic and consequently complete flotation is possible with both cationic and anionic collectors. These results support the previous water structure analysis for soluble salt flotation of alkali halides and other oxyanion salts.

Jan 1, 2003

By J. W. Leonard, D. A. Newman

By using physical and chemical means to increase the bulk density of newly broken coal freed from the mine face, the potential to improve coal mine productivity is significantly enhanced. It is estimated that by increasing bulk density, greater tonnages can be placed in fixed volume scoops and shuttles cars to improve production by as much as 10% to 20%. Such improved packaging to achieve new levels of volumetric efficiency might require only small and easy to implement changes to present downstream mining operations. Opportunities exist for improving broken coal bulk density from the moment of breakage, during transport across the continuous miner or loading machine, during discharge into the haulage unit, and after placement in the haulage unit. Physical/chemical methods for broken coal compaction in mobile, fixed volume units in underground operations are discussed.

Jan 1, 1990

By A. J. Neale

Much has been published lately about the application of advanced control strategies in the automatic control of autogenous and semi-autogenous grinding circuits. The application of adaptive control algorithms, self-tuning controllers, state estimation, and expert systems has been well documented. While these approaches can be very effective; experience has shown that quite often simply "fixing the fundamentals" can have a significant positive impact on overall grinding circuit performance. This paper will highlight the results of process optimization and process control work by the authors at a variety of autogenous and semi-autogenous installations. A review of one approach for quantifying the mill load/bearing pressure/power relationship is provided. Accurate monitoring of key mill process variables is a necessary prerequisite for both effective process analysis and process control. This paper discusses some of the concerns related to defining steady state operating conditions and the issues related to signal conditioning. The paper concludes with a discussion of an effective application of algorithmic constraint control which incorporates many of these considerations.

Jan 1, 1994

By Peter G. Mason

Pressure oxidation is now a well estab­lished process for the treatment of refracto­ry gold ores and concentrates. The process utilizes pure oxygen to oxidize mineral sulphides in an aqueous slurry at elevated temperature and pressure. Gold released from the sulphides becomes amenable to subsequent cyanidation. A major component of the operating cost of this process the supply of oxygen. The quantity required is dependent on the sul­phide grade, the extent of oxidation and the percentage utilization of the oxygen. As the sulphide grade is fixed and complete oxida­tion is generally required to maximize gold liberation, the only opportunity for saving in oxygen consumption is to improve its utilization. Under circumstances where the feed material contains substantial carbonate, oxygen utilization can be improved by strip­ping carbon dioxide from the autoclave vent and recycling the associated oxygen. Fluor Daniel Wright included an oxygen recycle circuit in the Getchell pressure oxidation plant, which is operated by First­Miss Gold in Nevada. FirstMiss Gold has applied for patent rights to the process as implemented at Getchell.

Jan 1, 1990

By Neville T. Moxen, Stuart K. Nicol, Malcolm D. Engel

Ion flotation is a process in which ions of interest are complexed with a suitable surfactant molecule. A dilute solution containing these complexes is then aerated, under which circumstance the surface-active complex concentrates at the air-water interface and is transferred to a froth. The present work describes some of the phenomenology of this process and experimental work leading up to the design and use of a pilot scale laboratory facility. Early experiments suggest that selective recovery of gold can be obtained in a manner at least equivalent to conventional CIP processing at low capital cost. Under favourable conditions, upgrade ratios of gold ions of the order of 180: l have been achieved from reclaimed residue dam water with as low an initial gold level as 0.2ppm. Successful development of countercurrent ion flotation for concentrating solids-free gold solutions may offer a lower cost alternative to existing gold ore processing technologies, or in more secondary applications such as concentrating dilute gold solutions or heap leach runoff. The technology may also have more generalised applications to other heavy metal processing.

Jan 1, 1990

By Y. Luo, S. S. Peng

Several issues deserve further attention to improve subsidence prediction accuracy. These include: subsidence initiation and development over a setup entry area; subsidence development after face stop; and subsidence over chain pillar. An intensive subsidence monitoring program has been carried out over several longwall panels. A large amount of subsidence data has been collected, analyzed and solution techniques developed. In this paper, some of the measured data. data analysis techniques and the developed prediction methods are presented.

Jan 1, 1992

By John W. Ahlrichs, E. Daniel Baker, Erich U. Petersen, William J. Tafuri, Douglas N. Halbe

The combined Bootstrap and Capstone deposits, located in the Bootstrap subdistrict (Section 10, T36N, R49E, M.D.B.M., Elko County, Nevada), are approximately 27 miles northwest of Ca-1I: Nevada. The contiguous Bootstrap Capstone deposits are located along the northeastern and northern flanks of Round Mountain, a horst block separated by grabens from the sheep Creek Mountains to the north-northwest and the Tuscarora Mountains to the east. Open-pit-minable gold reserves as of December, 1989, were 13.27 million short tons with an average grade of .057 troy ounces gold per ton and an overall waste-to-ore strip ratio of 2.5:1. Ore zones in Bootstrap are concentrated along north striking high-angle dikes localized along faults, while ore zones at Capstone are strata form and structural, occurring at the Devonian limestone/siliceous sediment interface and in high-angle fault-filling dikes. Pre-ore faulting produced a complex structural setting for Capstone, dominated by strong northwest fault sets cross-cut by northeasterly structures. Alteration associated with both deposits is silicification with a-strong argillic overprint. Dike emplacement, which post-dates silicification, marked the onset of mainstage gold deposition and argillic overprinting of silicified lithologies. Gold displays an affinity for moderately argillized sedimentary and igneous lithologies. Mineralogic and geochemical analyses of rotary percussion drill samples show good correlation between gold, silica, antimony, and arsenic.

Jan 1, 1990

By Ratnakar Singh, Raj Kishore, Kisor Kumar Sahu, Ranjeet Kumar Singh, Ganesh Chalavadi

The Falcon concentrator is capable of separating minerals in fine size classes based on their differential density. Separation of mineral particles depends upon the fluid flow characteristics and relative movement of particles in a fluid. In the present study, a fluid flow characteristic inside the Falcon concentrator was established through experimentation and modeling. The Falcon concentrator has two fluid entry points: (a) Fluid entering through gravity assisted feeding system and (b) Fluid entering through the fluidized hole on the concentrator wall. In order to identify the role of fluid entering the concentrator, a tracer was injected into the system. As per the tracer based experimentation, it was established that fluid entering through the gravity based feeding system is responsible for thin flowing film formation in the stratification zone where particles are stratified based on their relative density. The momentum balance and continuity equations were simplified for a high centrifugal force field, and the fluid velocity profile was estimated inside the thin flowing film. Estimated fluid flow profiles will help to simulate the particle trajectories inside the Falcon concentrator. The influence of rotational speed, fluid flow rate, and cone angle on the fluid velocity profile were investigated. Fluid thickness over the concentrator wall is also estimated, and it is typically of the order of ~150–200 μm.

By J. J. Antony

The Cactus Gold Mine is a joint venture comprised of Middle Buttes Partners Ltd. (CoCa Mines, Inc.--operator, T. Congdon and W. Carey) and Compass Mining, Inc. The project includes 2.4 sq. miles of contiguous mining claims and leases in the Mojave Mining District, Kern County, California, approximately B5 miles northeast of Los Angeles. The property is readily accessible year round by all-weather roads and is within 6 miles of the main line of the Southern Pacific Railway.

Jan 1, 1988

By Basilio Giurgola, Federico Bonaiuti, Norbert Fuegenschuh

The North East Boundary Tunnel (NEBT) project in Washington, D.C. requires design and construction of several SEM adits which have to be built between lateral shafts and the NEBT-TBM Tunnel. The paper describes ground improvements, the actual excavation, and also the final lining works. Schedule and sequencing restrictions provided some unique challenges which had to be considered when designing and constructing these mostly short, but essential portions of the project

Dec 1, 2022

By R. D. Begley, A. W. Khair

This paper presents an assessment of modeling techniques in predicting subsidence over longwall areas. Extensive instrumentation has been made, both at the surface and subsurface, at three longwall mines in northern West Virginia. Ground movements were monitored during a three- year period until subsidence ceased in these areas. A comparative analysis of empirical subsidence prediction techniques including graphical (NCB), profile function, influence functions (USBM, Bals', Knothe's, and zone area) will he presented. A brief geologic and topographic description of each site, along with the instrumentation and monitoring program, will also he presented.

Jan 1, 1990

By S. G. Sawyer

The Pittsburgh Safety and Health Technology Center (PSHTC) of the Mine Safety and Health Administration (MSHA) provides engineering and scientific support to the inspectorate personnel of MSHA. One of the Center's myriad roles is to assist in the investigation of mining accidents, especially those involving fatalities. Center personnel utilize forensics to help uncover the causes of accidents and to make technical recommendations on the prevention of future similar mishaps. To exemplify a typical forensic investigation, this paper documents the methodology used in determining the reasons for a boat sinking, which resulted in a double fatality on a mine company pond.

Jan 1, 1997

By John W. Carson, David S. Dick

The last few years have produced new methods of characterizing flow properties of bulk solids. Abrasive wear and particle attrition can now be accurately measured in a laboratory and scaled up to field condi¬tions. In addition, the effect of large par¬ticles on a material's flow properties (cohe¬sive strength, bulk density, wall friction) can be determined as well as the effects of var¬ious additives such as freeze conditioning agents. New developments have occurred with devices to improve the reliability of solids flow. Much attention has been paid to find¬ing ways, by using inserts, to provide a mass flow pattern with relatively shallow hopper walls. Such devices can also provide reli¬able in-bin gravity blending of bulk solids or completely nonsegregated discharge. Other developments have occurred in the area of belt-to-belt transfer chutes and sealing screws. The technology and hardware for running bench scale flow tests on bulk solids samples and transforming the results into reliable designs has been in existence for nearly 30 years (Jenike, 1964; Marinelli and Carson, 1986). It has been shown repeatedly that reliable materials handling systems can be designed to avoid the problems of no-flow due to arching or rat-holing, erratic flow, segregation, loss of capacity, or spontaneous combustion. Running flow properties tests and carefully designing a bulk handling system are not expensive, particularly when compared to downtime costs and continual flow problems. New developments in characterizing flow properties of bulk solids include: • a shear tester for measuring the properties of run-of-mine ores containing large par¬ticles; • attrition testers to simulate a wide range of flow conditions; • a tester to measure the wear rate of liners in bins, feeder parts, etc.; • a dustiness tester to measure the potential for dust and the effect of dust control meas¬ures; and • techniques for measuring the strength of frozen ores and the effect of freeze condi¬tioning agents. In the area of improving the flow of bulk solids, there are new techniques for ensuring reliable flow without using up excessive headroom. These include: • belt-to-belt transfer chutes to handle po¬tentially sticky, abrasive, and dusty ores; • designs for the interface between a bin/ hopper and apron or belt feeders to avoid hangups and minimize feeder loads; methods to feed solids reliably into a pres¬surized process; and designs for handling systems that will mini¬ mize attrition, avoid segregation, or auto¬matically blend materials together. Characterizing flow properties Large shear cell It has long been known that the cohesive strength of a bulk solid is due mainly to its fine fraction. However, the effect of the larger particles (that were assumed to re¬duce the strength) could not be measured. The development of larger scale (205 mm¬diam and 0.6 x 0.9 m or 8 in.-diam and 2 x 3 ft) shear testers has made it possible to measure the properties of a wider range of materials. Now cohesive strength measurements can be made with up to 100 mm (4 in.) particles. The results obtained from the large shear testers, together with the results of the nor¬mal shear tests on the fine fraction, are used in the design of reliable stockpile reclaim systems and crusher feed systems. A high percentage of large particles can reduce the measured shear strength of a bulk solid. However, segregation may alter the size distribution and should therefore be considered (Carson, Royal, and Goodwill, 1986). In addition, larger particles will

Jan 1, 1989

By H. V. Alminas

The U.S. Virgin Islands consist of three major islands (St. Thomas, St. John, and St. Croix) and some 50 smaller islands that are located primarily along the coasts of St. Thomas and St. John. St. Croix, the largest of the islands, is located approximately 160 km south-southeast of San Juan, Puerto Rico and is about 218 km in area (Fig. 1). St. Thomas, the second largest island is located 64 km east of Puerto Rico and incorporates approximately 77 km2. St. John is located immediately to the east of St. Thomas and incorporates approximately 49 km2. The climate in the U.S. Virgin Islands is maritime tropical. The average annual rainfall at higher elevations is 127-152 cm and at lower elevations 51-76 cm. There is no well-defined wet or dry season. Temperatures generally average in the 80's (F°) with only a 5°-7° F variation throughout the year.

Jan 1, 1987

By A. Galicia, A. Charest

The Marlin deposit is a low sulphidation Au-Ag, epithermal system, with reserves of more than five million ounces gold equivalent. Marlin was discovered in December 1998, after a nine months grassroots exploration program in western Guatemala, focused on volcanic terrains of the Sierra Madre. Before the Marlin discovery, several gold prospects were found along an east-west corridor of approximately 70 kilometers long, associated to regional faulting systems. The deposit is hosted in faults, within Tertiary andesitic rocks and bedded volcano-sediments. Host-rocks are argillized closer to the surface and propyllitized at depth. Mineralization occurs in multi-stage quartz stockworks and breccia veins.

Jan 1, 2004

By V. de la Garza

The La Cienega Gold District is located at latitude 25°01'01"N and longitude 106°19'00"W, in the NW part of the State of Durango, Mexico. Ore deposits at The La Cienega District consist of a series of sub-parallel, NE-trending veins which cut andesitic and rhyolitic rocks that belong to both upper and lower tertiary volcanic sequences. The veins are vertical to steeply-depping structures which consist of quartz, generally containing gold-silver and less than ten percent lead, zinc and copper sulfide and sulfosalt minerals. Supergene enrichment is present on the upper parts of known oreshoots. Tertiary volcanic rocks of rhyolitic composition are the main host rocks of the gold-bearing quartz veins in the District. Gold productionc from the La Cienega orebody is scheduled to reach 100,000 ounces per year, becoming the largest gold-producing District in the Sierra Madre Occidental Province.

Jan 1, 1994

By H. Reginald Hardy, Xiaoqing Sun

Rheological models are widely accepted as a means of describing the mechanical behavior of geologic materials. It has been found, however, that rheological models developed for a specific stress level on the basis of linear visco-elasticity generally are not satisfactory at other stress levels. It has been suggested that the parameters of such models should be functions of stress level (Hardy, 1965; Kim, 1971). In this paper, continuous functions of stress have been utilized to obtain the required variation of Burgers model parameters with stress level. The model developed using these functions provides a constitutive relation which reflects the real time-dependent behavior of rock materials. The new model is capable of predicting the creep behavior over a wide range of stress levels and also predicts mechanical behavior under different loading condition (e.g. constant stress rate). It is also interesting to note that the mechanical behavior of individual elements in the model appear to reflect the different stages of brittle fracture in rocks (Bieniawski, 1967), namely; crack closure, elastic deformation, stable fracture propagation and unstable fracture propagation.

Jan 1, 1986

By Nopadon Mantajit, Dallas W. Davis, Somsak Potisat, Prasert Kumalachan

For centuries Thailand has been a significant, though primarily unofficial, producer of gold. Panning has been the traditional way of making a living for innumerable villagers during the December to May dry season following the harvest. During this period groups can be seen working the streams, rivers, fields and dry valleys at as many as 90 localities in 28 provinces. Attesting to their efforts are the five and a half ton solid gold Buddha at Wat Trimit and much of the gold jewelry sold in Bangkok. This traditional panning will continue, and probably become more extensive, in harmony with commercial endeavors using modern technology suitable for extraction of gold from types of deposits for which gravity separation would give very low recoveries. Several such deposits have been discovered in the course of geochemical and geological surveys conducted by the Royal Thai Department of Mineral Resources with the object of contributing to early interpretation of the results of a country-wide airborne survey.

Jan 1, 1987

By William Petruk

Lithium bearing lepidolites from three deposits in the province of Goias in Brazil were investigated to determine whether there is a correlation between the lithium content of the mineral and the colour of lepidolite and associated tourmaline. Such a correlation can be a useful guide to field geologists for outlining high grade ore zones. It was found that mauve-pink lepidolite associated with pink tourmaline, and brownish lepidolite associated with black tourmaline have high lithium contents, but the colour of lepidolite is not due to lithium. The pink colour of lepidolite and tourmaline is likely to Mn3+, and the brownish tint of lepidolite and black colour of tourmaline to Fe3+. Lepido lites appear to be lithium-rich when the lepidolite and associated tourmaline contain relatively high amounts of Mn3+ and/or-Fe3+.

Jan 1, 1985

By Harry Holle, Gary Johnson

A plant trial was conducted at the Paddy's Flat plant of Dominion Mining Limited with the aim of comparing the ef evenness of oxygen and hydrogen peroxide as leaching oxidants. The Paddy's Flat plant is designed such that the leach train can be divided into two parallel streams, allowing the same or lurry to be eated in two identical trains. By effectively ehminatmg the influence of the ore variations on the results subtle differences in the performance of the two reagents hav been identified. . . The results of the plant trial indicate that the two reagents act m different ways, and that each may be more suitable than the other _for _the treatment of certain types of ore. In some cases a co bmation of the two reagents may be the most cost effective option. . or t e same chemical conditions in the leach pulp, including dissolved oxygen levels , the reagents achieve different gold leaching rates, and in some cases different ultimate leach extraction.

Jan 1, 1992