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By M. L. Fuller

IN connection with an investigation in this laboratory on the high-zinc side of the copper-zinc system, it was observed that well developed segre-gate structures of the Widmanstätten type were formed when a secondary phase precipitated from the solid solution of copper in zinc. This paper presents an analysis of the crystallographic relationship between the segregate and the solid solution matrix. The data to be presented are an interesting addition to the literature on segregate structures in that the plane of segregation is one of the less densely populated planes. In agreement with the generalization of C. H. Mathewson and D. W. Smith1 the plane of segregation in the matrix con-tains the direction of closest atomic packing of the lattice. Furthermore, the matrix and the segregate are both hexagonal close-packed, which has not been reported hitherto in the literature.2 The increasing com-mercial importance of zinc alloys containing copper makes this funda-mental study of value to the metallography of zinc alloys.

Jan 1, 1933

By C. J. Veal, C. I. House, S. R. Bellamy

INTRODUCTION Coal gold agglomeration (CGA) is a new concept in gold processing. It involves the recovery of oleophilic (oil-loving) gold grains by causing them to adhere selectively to the surfaces of coal oil agglomerates. Under optimum conditions very high recoveries of gold. can be achieved. The agglomerates are recycled to build up gold loading to typically 1000 - 5000 g/tonne. Bullion can be produced by burning the loaded agglomerates with subsequent recovery of gold from the highly loaded ash either by dissolution/electrowinning or smelting. A wide-ranging programme of laboratory testwork has been performed to investigate the response of different ore types to the process. This has shown CGA to be most applicable to ores in which the gold is liberated or easily liberatable, relatively coarse (ca 500 µm) and fine (<5 µm) gold grains being recoverable with equal ease. The best opportunities for CGA seem to be: • placers containing fine gold not recoverable by gravity concentration • low grade gravity concentrates to avoid multiple magnetic/gravity separation stages and amalgamation • free milling ores where the gold can be liberated at a reasonable ore particle size eg >d80 50 µm • tailings past or present from gravity concentration plants. CGA testwork ranging in scale from laboratory to pilot plant on tailings produced by gravity concentration in the 19th century Australian gold rush has already been reported (Bonney, C F, 1988; House, C I, Townsend, I C and Veal, C J, 1988). An economic appraisal for a Canadian free milling gold ore has also been published (Buckley, S A, House, C I and Townsend, I G, 1989). This paper describes results of a detailed laboratory programme to assess CGA as a means of recovering gold from a beach sand deposit in New Zealand. The area from which the samples were taken consists of quarternary interglacial marine, lagoonal, fluvial and eolian deposits. The heavy minerals present are predominantly ilmenite and garnet and small concentrations of gold. In certain locations the sands and gravels are consolidated by a limonitic cement. In the 19th Century some parts of the deposit were mined and the ore processed using stamp milling and gravity concentration. Gold recoveries were low, probably below 50%, due primarily to the fine size of the gold grains, the flaky nature of the gold and also imperfect liberation by the stamp mills. Our laboratory testwork was divided into three parts: i) Preliminary studies on an initial sample to assess the feasibility of treating the ore by CGA ii) Extended studies on further samples from various locations in the deposit to confirm predictions from (i) iii) Conventional gold recovery techniques. EXPERIMENTAL PROCEDURES All CGA tests were performed by agitating a slurry of ore in water in a 0.6 dm3 pyrex beaker fitted with four vertical baffles. When required, potassium amyl xanthate collector was added and the slurry conditioned for 5 min. Coal (ex BP Coal Australia&apos;s Tahmoor Colliery) previously ground to a d80 50 µm was added followed by a commercial grade of gas oil (density 840 kg/m3). The agglomeration time was 30 min. The agglomerates were separated from the tailings by screening, both were then dried and analysed for gold by fire assay. This test procedure provides a reasonably accurate estimate of gold recoveries that might be expected from our 1 tph pilot plant. Ore samples were ground either dry in an agate ring disc mill or wet in a steel batch tumbling

Jan 1, 1989

By M. Zanotto

[ ] A period of heavy rains caused the river Adda to flood parts of the Valtellina, one of the Alpine valleys of Northern Italy. The exceptionally high waters put under considerable strain the whole system of embankments and levees controlling the river and protecting the adjacent towns and lands. In some places the water breached and washed away the embankments, submerging large tracts of cultivated land, buildings, roads and railway tracks. The town of Talamona, in the lower Valtellina, was hit particularly hard: in its proximity the river overrun and then washed away 300 m (1,000 ft) of embankment (see vicinity map, fig. 2), depositing large amounts of riverbed debris onto over 400 hectares (1,000 acres) of fertile land.

Jan 1, 1992

By Ashok K. Kakar

THE occurrence of superplasticity in Al-Zn alloys is of interest because of its possible industrial exploitation.&apos; The eutectoid composition (78Zn-22A1) has been the most extensively studied;&apos;-= neck resistant flow and high strain rate sensitivity of flow stress (characteristic of superplasticity) are associated with a micron-size grain conferred on the alloy by an homo-genization and quench.5&apos;6 Compositions away from the eutectoid have received comparatively little attention, especially from the viewpoint of relating the structural

Jan 1, 1969

By Kenneth L. Zonge

Recently, extensive field use has been made of a digital minicomputer incorporated into a modified geophysical prospecting method. This is a generalized induced polarization (IP) system called complex resistivity (CR) and has been successfully used in sulfide mineral exploration. The ease of use, portability and cost effectiveness of this computer-controlled method has provided a viable exploration tool based on a complex data acquisition system. Without the computer, this method would still be relegated to tedious laboratory measurements and theoretical studies.

Jan 1, 1976

By J B. Collier, R M. Fraser, O Dahl, I M. Platten

Grade control is a process of maximising value and reducing risk, through the delivery of quality tonnes to the mill via the accurate definition of ore and waste. It essentially comprises data collection, integration and interpretation; local resource estimation; stope design; supervision of mining and stockpile management. The foundation of all grade control programs should be that of geological understanding led by high-quality mapping and sampling to drive appropriate estimation strategies and mining. Gold veins show various complex features relating to erratic grade distribution (nugget effect), variable geometry and internal architecture. These include variations in dip, strike and width, late-stage faulting/shearing effects and geometallurgy. Such variations generally require close geological understanding to ensure optimum grade, minimal dilution and maximum mining recovery. A well designed grade control program will prove to management and stakeholders that by applying geological knowledge, the mining process can be more efficient and cost effective. This paper reviews the issues of grade control in underground gold mines and focuses on integrated mapping and sampling through three case studies.

Jan 1, 2009

By C. E. Jordan

The Tuscaloosa Metallurgy Research Center of the Bureau of Mines, U.S. Department of the Interior, is investigating the recovery of phosphate from beneficiation slime, as part of the Bureau&apos;s efforts to conserve mineral resources through increased use of wastes. Phosphate equivalent to about two-fifths of U.S. production is discarded annually in the wastes. Exploratory flotation tests on the plus 5-um fraction of a slime sample showed promise for a classification-flotation technique. Onsite classification tests at six phosphate washing plants were conducted with a two-stage hydro cyclone system designed to recover the plus 5-um material. The cyclone underflows contained 8.3 to 19.1 percent P2O5, and the recovery of the plus 5-um PZOS values ranged from 81 to 95 percent. The percent P2O5 recovery from the total slimes ranged from 38 to 47 percent. Batch-flotation studies are currently being conducted.

Jan 1, 1978

By R. B. Krog

Airflow patterns in longwall bleeder systems are affected by gob permeability and porosity and the condition of the gateroad entries after mining. As longwall panels are mined, areas of the caved zone and portions of the remaining gateroad entries become inaccessible, making direct ventilation measurement impossible. Mine operators are left to estimate direction and amount of airflow in the gob and the surrounding gateroads. The most readily available locations are where air enters the worked-out area, approved measurement point locations (MPLs) and/or evaluation points such as bleeder evaluation points, intake evaluation points, and the outer bleeder entry. Ventilation models (network or Computational Fluid Dynamics, CFD) can model the gob and the surrounding bleeder system but calibrating these models is difficult without field data. NIOSH installed a tube sampling system ahead of a longwall face and, as the face retreated, released a slug of tracer gas (SF6) to determine transportation times and flow rates in the inaccessible gateroads. The data was used to calibrate both network and CFD ventilation models for a longwall panel. Both model types were used to predict the airflow patterns in the gob and to determine the airflow rate from the longwall tailgate corner back to the bleeders.

Jan 1, 2011

By Raymond L. Jones

With the inauguration of the open pit operation in Bagdad, plans were formulated for a large scale leaching operation. Dump stockpiling was started almost immediately, but actual production was not initiated until the spring of 1961. Like all neophytes, we started something about which, on a commercial scale, we knew next to nothing, either dump preparation or leach procedure, and as a consequence, we are still paying the piper. True, we had been through an extensive laboratory pilot program, but it soon became apparent that there was considerably more to increasing solution volumes than simple multiplication. Had we initially possessed our present acumen, the Cyprus Bagdad plant could be operated more efficiently and at a better profit. During the past several years, the art of dump leaching of copper has improved in many ways, primarily because of the application of scientific principles gleaned from general mining practice. Rigid pH control and the use of atomic absorption techniques for rapid," accurate assaying have probably played a leading role in this respect, although we cannot overlook the other sophisticated electronic controls lending improvement to acid addition and pumping, better piping materials, and lastly, the more efficient use of our pregnant liquors. Thin too, the years of experience have given us a greater understanding of dump behavior in general; and, we can, to a greater extent, measure, predict, and avoid some of the idiosyncrasies inherent in every dump. However, it is my firm belief that we will still be confronted with unexplainable dump behavior as long as we are involved in leaching. We have found our dump to be a wonderful money bank, but one that is capable of yielding a wildly fluctuating profit.

Jan 1, 1975

By G. Skybey

The Directional Drill Monitor (DDM) is an advanced instrument for real time in hole surveying. It was developed by Du Pont (Australia) to suit Australian gassy coal mining conditions. The instrument consists of three units: i. Down hole transmitter ii. Acoustic transducer iii. Data receiver processor unit (i.e. up hole unit). This paper describes the function of each unit in detail and highlights the importance of the DDM in long hole drilling efficiency. Surveying is carried out independent of hole depth. Each survey takes 2-3 minutes to complete, the frequency of surveying to control borehole trajectory is determined by the accuracy required for a particular hole. The DDM is currently being used successfully for long hole drilling in a number of collieries. A high degree of directional control has been achieved. Borehole trajectories were controlled to within +l¬2m of the planned path with intersurvey distances varying between 6 to 18 metres over distances up to 700 metres.

Jan 1, 1992

By Brian McIntrye, Bo Trygg

"The need for grinding mills of ever increasing capacity and greater feed openings has tended toward mill trunnion diameters being beyond the size limits for roller bearings.Hydrodynamic plain bearings need to be wide enough to achieve the necessary bearing pressure in order to obtain an oil film with sufficient carrying capacity at low rotational speeds. This greater width increases edge loading resulting from the deflection of the mill under load.Because of the high surf ace pressure involved, the life of support rollers and girth rings is often inadequate-fatigue leads to flaking on the contact surfaces. Heat treatment of the girth rings also has its problems.The hydrostatic shoe bearing permits unlimited trunnion diameter and a high carrying capacity. The self-aligning shoes compensate automatically for radial deviations and large deformations can be tolerated at the girth ring.The sliding surfaces are completely separated by oil under pressure, enabling negligible starting torque and good damping capacity to be achieved together with low rotational speeds.IntroductionHydrostatic bearings have been known within machine technology since 1865, when the Frenchman Girard received a patent for such a bearing. During the following 75 years, these types of bearings were used sporadically for thrust bearings, primarily in water turbines. The first usable radial bearing was not designed until 1938. Since the 1950s, when hydrostatic bearings started to come into use within the field of machine tools, extensive research and development work has been carried out at various institutions and research centres throughout the world. Many support problems are now solved by means of hydrostatic plain bearings and the primary factor in deciding to use them is their unique characteristics:• ability to carry high loadings• no starting torque• large damping capacity• no wear• large running accuracyThe hydrostatic shoe bearing has been developed specially for use in the heavy machine industry, with the requirements for high loadings and large support diameters which this market demands."

Jan 1, 1982

By Ming-yi Zhang, Zhong-nian Yang, Xiao-ming Guan, Quan-wei Liu

"In slurry balanced shield tunneling, how to ensure the safety of construction and to reduce the influence on the environment has arisen wide attention of scholars both at home and abroad. But now it is still in the stage of experience as to the instability mechanism of the slurry shield tunneling excavation and its stability analysis. Based on the large-diameter model tests and FLAC 3D, the effect of the different waterhead (non-water, 0.9m and 1.1m) on stability of excavation face of slurry balanced shield is investigated, and the stability mechanics is proposed. The results show that: waterhead heights play an important role on excavation face instability features of slurry balanced shield in sandy stratum, Regarding the different waterhead heights, the development mode of the excavation face instability features can be divided into non-water mode, lower-waterhead mode and higher-waterhead mode; soil arching is existed in the process of excavation face instability, the settlement of ground lags behind excavation face failure, the soil arching will block or eliminate the effects of ground settlement; excess pore water pressure need to be considered besides earth pressure and hydrostatic pressure when the supporting force is calculated. INTRODUCTION With the development of the society, for the cities all over the world, the exploitation of underground space has become an important measure to solve the problems about population, resources and environment and an important way to heal the city syndrome and implement the sustainable development strategy of city. Constructing shield tunnel with large diameter is the major trend for development of tunnel construction (Yin, 1999). Instability of excavation face caused by relief of shield soil stress is still one problem that needs to be solved (Xiang, 2001). How to reduce the effects of construction on surrounding environment? How to accurately determine the instability of shield excavation face and to effectively and reasonably select the supporting force? These are the crucial problems which need to be solved during shield construction."

Jan 1, 2016

By J S. Laskowski

Froth flotation process requires the use of frothers. These important flotation agents are commonly characterised as either æselectiveÆ or æpowerfulÆ and are chosen following general guidelines and verification by laboratory and/or pilot plant tests. Fundamental properties of the flotation frothers have been extensively studied over the last few years. These studies have led to the development of standardised procedures to characterise frothers in terms of their ability to reduce bubble size and to increase foam stability. In this research project, the performance of five frothers in flotation of coal is evaluated and related to the fundamental properties of these agents. Since the recovery of water in the concentrate is closely related to the non-selective transport of solid particles by entrainment, the tested frothers are also assessed in terms of their ability to promote the transport of water towards the froth collection zone, both in absence and in presence of solids.

Jan 1, 2005

By Carlos Siccha, Luis Alvarez

Este trabajo técnico se embarca en una exploración profunda de la intersección entre la tecnología de vanguardia y la industria minera, con una mirada crítica a cómo una arquitectura de datos sólida puede servir como un potente catalizador para el uso efectivo de Machine Learning (ML) e Inteligencia Artificial (IA). A través de un enfoque focalizado en la operación minera Antamina, este informe articula una comprensión detallada de los desafíos y las oportunidades presentes en el panorama de la gestión de datos mineros.

Sep 29, 2023

By K. Taylor

In surface coal mining, the performance of a shovel through blasted muck is one of the key performance indicators of the blast. Historically, performance has been measured qualitatively based on operator feedback or visuals of the muckpile. More complete shovel data, such as loading times and GPS location, is available from most fleet dispatch systems that are already in place at most truck and shovel operations. With some database and analysis skill, the drill and blast team can take advantage of this data to make targeted improvements to drill and blast designs. An area typically known to cause trouble for shovel operators at this operation are blast boundaries. Blast patterns with and without design changes along the boundaries were studied in this case study. The instantaneous loading times for each shovel pass were analyzed for 75 blasts across two subsequent benches with similar firing direction and shovel paths. The benches were split into three categories: Main body of pattern, boundary with design change, and boundary with no design change. The loading times from the main body of the patterns and where the design change was utilized in the boundary had similar prevalence of good loading times. However, boundary areas without the deign change had approximately 2% more prevalence of poor loading times compared to the main boundary of the pattern. Improving the dig rates through the boundaries up to the average loading time would result in approximately 280 hours taken off the total loading time for one bench. By quantifying the shovel’s performance by GPS location, the drill and blast team can decide how much of a design change is needed, can target precisely only the areas that require it and measure the impact of any changes made

Jan 1, 2024

A model was developed of a CIL/CIP circuit for recovery of gold and silver. The model uses a simple two rate representation of the leaching kinetics. Parameters for the leaching kinetics may be simply obtained by sampling the feed to a circuit and the tailings from each tank and assaying the solids for both gold and silver to obtain the assay profiles of the solids down the tanks. The parameters in such a leaching model would be expected to be a function of the ore type, the grind, whether oxygen was used and the general chemical environment. These parameters are primary inputs to the model for any simulation. Standard power law relationships are used to express the practical equilibrium between the gold and silver cyanides adsorbed on the active carbon and the tenor of the solutions. The parameters for this may be derived from solution and carbon assays for the same set of samples. The model is constructed by writing a mass balance for gold and silver in and out of each tank in the train and for the circuit overall. Other inputs to a simulation are the feed rate of ore, per cent solids of the slurry in the tanks, gold and silver loadings of the input æbarrenÆ carbon and the rate of movement of carbon through the circuit counter-current to the slurry. With appropriate practical parameters the simulation is able to reproduce typical tank profiles.

Jan 1, 2004

By R. K. Clifford

Chalcopyrite (CuFeSz) concentrates produced on the Lead Belt of Missouri typically contain 28 pct Cu and from 0.5 to 1.5 pct each of nickel and cobalt. Most of the nickel and cobalt are present as the mineral siegenite, (Ni,Co)3S4, almost none of which is recovered presently. The Bureau of Mines, U.S. Department of the Interior, has been conducting research on the chalcopyrite to produce a marketable fraction enriched in cobalt and nickel. Ferric chloride leaching of various chalcopyrite (copper) concentrates has yielded residues containing from 10.2 to 16.2 pct Ni and 8.3 to 11.4 pct Co with recoveries of approximately 79 pct. In another approach, laboratory froth-flotation tests have been conducted to investigate the effects of regrinding, roasting, baking, and steaming prior to flotation, with a variety of reagents. The best laboratory results were obtained after regrinding the copper concentrate to 94 pct minus 400 mesh and floating the chalcopyrite at natural pH (6.5) with 0.48 pound of sodium diethyldithiophosphate and 0.01 pound of sodium cyanide per ton of concentrate. This procedure yielded a tailings assaying 20.4 pct Cu, 5.2 pct Ni, and 3.45 pct Co. The tailings contained 67.2 pct of the nickel and cobalt and 15.9 pct of the copper originally in the copper concentrate; the remainder of the values reported to the flotation concentrate, which analyzed 29.6 pct Cu. To verify the laboratory flotation results, a 60 kg/hr process demonstration unit (PDU) was constructed in the Cominco American Magmont mill, Bixby, Mo.

Jan 1, 1978

The Sishen iron-ore-mine produces 3 pro= ducts with size gradings of 25 to 8 mm, 11 to 5 mm and 5 to 0,2 mm and has a product capacity of 20 Mtpa. Ore is produced at an average Fe content of 66,2 % Fe for the two coarser pro= ducts and an average of 65,3 % Fe for the fine ore product. Three stage crushing is practised to re= duce the run-of-mine ore to -90 mm after which it is screened into five different size frac= tions of which four are heavy media beneficiated in static baths and cyclones and the fifth frac= tion discarded to slimes dams. A final three stage crushing and screening process is employed to produce the final three Products which are homogenized by means of blen=ding systems nrinr to despatch.

Jan 1, 1987

By Lars Rossemyr, Terkel Rosenqvist

The equilibrium Mn + 2 IiCl = MnCl2(g) + H2 has been studied at 1090°C for pure manganese and for Mn-Si alloys. For this reoction a standard free energy of Fo1363, = - 19,700 i 300 col ioas found. Combined with other thermal data, the standard free energy of the reaction Mn(s, ß) + Cl2 = MnCl2(g) was derived: Fo=- 56,140 + 9.78 T log T - 40.10 T For the formation of the various manganese silicides the following free energies were obtained. 5 Mn + 3 Si - M1z5Si3 ?F°1363 = -41,500 i 1500 cal Mn + Si - h.lnSi ?F°1363= -10,000 i 500 cnl Mn + 2 Si = MnSiz ?F°1363= -11,500 ± 500 cal In the search for a method suitable for the study of thermodynamic properties of certain alloy systems, it was found that the heterogeneous equilibrium between the alloy and a gas mixture consisting of hydrogen chloride, hydrogen, and volatile metal chlorides has considerable advantages. In addition to giving thermodynamic information about the alloys, such measurements may be used to derive thermodynamic data for the volatile metal chloride itself. The present paper gives some results which were obtained for manganese silicides and manganous chloride. Similar studies are presently being carried out for the iron silicides. The phase diagram of the Mn-Si system is rather well known,&apos; but no information exists to the authors&apos; knowledge about the thermodynamic properties of manganese silicides or about the chemical activities in molten Mn-Si alloys. At elevated temperature, manganese may react with hydrogen chloride according to the equation: Mn(s, ß ) + 2 HC1 = MnC1, (g ) + H2 [ 1] with the equilibrium constant The value of K, may be determined from measurements of the gas composition in equilibrium with pure manganese. When this value is used in connection with measurements on manganese alloys, the chemical activity of manganese in the alloy may be derived. Initial calculations showed that around 1000" to 1200°C the equilibrium constant K1 has a value of a few thousand, i.e., the reaction is shifted far to the right. In order to study this rather unbalanced gas composition, a flow method was used in two slightly different modifications. For all experiments with manganese silicides and for some experiments with pure manganese the apparatus shown on Fig. 1 was used. A bed of the metal or alloy was placed in a tube furnace. The refractory tube had an internal diameter of 14 mm and the bed was 75 mm long. Electrolytic manganese of high purity and silicon, 99.95 pct Si, were used as raw materials. All alloys were prepared by melting weighed amounts of the elements in a high frequency induction furnace in argon atmosphere. The melting was done in a silica crucible which was placed inside a graphite shell. The alloys were crushed to - 10 +40 mesh and analyzed chemically. Also, for the pure elements, the same size fraction was used. A controlled gas mixture of purified hydrogen and from 3 to 12 pct HC1 was passed through the bed where it reacted with manganese according to Eq. [I]. The volatile manganese chloride was collected in a condenser placed in the cooler part of the furnace tube. The gas mixture before and after the furnace was sampled and analyzed by absorption of

Jan 1, 1962

By B. Dimitriades

The Bureau of Mines measured the reactivities of 19 hydrocarbons known to be prominently present in automotive exhaust and ambient air in a smog chamber. Results agreed well with those obtained using two other smog chambers. Reactivity scales were developed for hydrocarbons and aldehydes using the results of this work and those of a previous study. Application of the reactivity scales to automotive exhaust samples gave fair agreement between predicted and observed rate-of-N02-formation values; however, predicted and observed ozone yields were neither in agreement nor did they correlate well. This lack of correlation for ozone yield was attributed to the inappropriateness of (1) the individual component reactivity data, (2) the reactivity classification scheme used, and (3) the linear summation method. In seeking to understand this problem and to develop more appropriate reactivity scales, the data were examined from a reaction mechanism standpoint, and further studies were suggested.

Jan 1, 1975