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By J. R. Mihalisin

Phase changes in as-cast alloys in the Ni2 CoCr-Ni, Ti-NSAl system containing 0.1 wt pct C were studied after heat treatment at 1650°F. It was found that a vegion of CrCo-type s was developed in this system after I1000 hr. The tendency for s formation was dePendent upon the aluminum and litanium content, the s -forming tendency generally becoming more pro-nounced as the latter two elements are increased. s lended to form in interdendritic regioues and was associated with solutioning- of- carbide phases. Electron- vacancy computations for prediction of s formation on these alloys mere in sufficient agreement with what was observed experimentally to indicate that the method should be of value in assessing a-forming potential in cast alloys. However, the correlation of electrotz- vacancy numbers may not be as favorable in cast as cormpared to wrought alloys. THE increasing use of high-temperature alloys for longer times at higher temperatures has resulted in a real need for obtaining information on the phase changes taking place in these alloys since these changes often have a direct effect on properties. This paper reports on a study of the phase changes in Ni-Cr-Co-Al-Ti alloys after prolonged heating at 1650°F. The alloys were selected from the pseudo-ternary system Ni2CoCr-Ni3Ti-Ni3Al and this system was chosen because it is the basis of many of the newer cast commercial superalloys. The attempt here was not to define accurately the boundaries of s formation in the NizCoCr-Ni3Ti-Ni3Al system but to delineate the phase transformations taking place upon heating alloys covering a wide range of chemistries in this system. An addition of carbon was made to all alloys to further simulate commercial alloys. It was hoped that the information generated in this manner would be of more direct use to superalloy designers than an equilibrium diagram approach since commercial alloys generally have outlived their usefulness when equilibrium is attained. EXPERIMENTAL PROCEDURE The alloys were vacuum-melted from carbonyl-nickel pellet, vacuum-grade chromium, electrolytic cobalt, high-purity aluminum and titanium, and spec-trographic-grade carbon.

Jan 1, 1968

By A. K. Andersen

One of the prime examples of the versatility of the MARCONAFLO system, which is a body of technology comprising the means to handle, store, load, transport, discharge and reclaim mineral commodities in slurry form, is the direct application of this process to leaching ores. The initial approach was to provide a much improved materials handling system for the transport of copper ores; however, an extensive development program, inclusive of prototype and pilot plant tests, has established that a new leaching concept is possible with this system. Data are presented from the leaching operation of a 25 TPD pilot plant utilizing a copper-oxide ore, mainly chrysocolla. This pilot plant was designed to incorporate true countercurrent flow where the ore is actually in motion, as contrary to vat leaching operations, and the ore being successfully leached is fine crushed ore (3/8-inch x o), contrary to agitation leach circuits. Extractions in excess of 85% of the soluble values are common with only 15 hours of retention time in the MARCONAFLO leaching system.

Jan 1, 1975

By J. T. Kalala

Energy consumption and wear of grinding media and liners are the major cost factors in milling plants. Since the beginning of the last century, much effort has been directed at the prediction of the power draw as affected by the mill operating conditions. This paper explores the prediction of the liner wear using the discrete element method (DEM). A mathematical model taking into account adhesion, abrasion and impact wear which occur in dry mills is derived in order to predict the loss of material on liners. The mathematical model is implemented in the DEM code using an objective function in order to produce realistic simulated profiles. Our DEM simulated predictions are compared to published experimental and industrial data. Keywords: modelling; discrete element method; liner wear

Jan 1, 2004

By B. Tora

Coal mining activity is inextricably connected to waste production. These include coal slurries deposited in environment. Current knowledge in the field of mining and especially mineral processing allows extracting valuable fuel from deposit coal slurries. The article discusses of previous works devoted to coal slurries inventory in Jankowice Mine in Poland (Upper Silesia) and quality assessment of coal slurries. 12 samples of coal slurries deposited in waste pond of Jankowice Mine was taken for the investigation. Total amount of wastes deposited is more than 100 thousands tones. Keywords: re-flotation, coal wastes, waste storage, industrial verification

Sep 1, 2012

By Kwadwo O. Adutwum, George M. Potter, Todd J. Harvey

Ashanti Goldfields Company (AGC) is the largest gold mining company in Western Africa. Their jewel operation is a highly inte­grated set of mines and plants situated in Obuasi, in the Ashanti region of Ghana. This operation is responsible for mining 5.5 mil­lion tonnes of ore at 4.6 git annually from a series of open pits and underground mines. The sulphide ore is highly refractory with untreated gold recoveries in the range of 30-40%. The milling facilities are quite varied and include an oxide treatment plant (OTP), a heap leach, a sulphide roaster circuit (PTP), a tailings treahnent plant (TIP) and the most recent, a sulphide treatment plant (STP). The sulphide treatment plant, the world's largest stirred tank biooxidation circuit, was commissioned in early 1994. This plant treats approximately 800 tonnes of refractory gold con­centrate per day with overall recoveries of75-85o/o(ll, Biooxidation was selected for its ease of operation and less exotic maintenance requirements as well as its ability to achieve comparable gold recoveries. Unfortunately, despite stirred tank biooxidation being one of the lower cost methods of treating refractory ores, it is still too costly for low grade refractory materials. GeoBiotics, Inc. has developed a proprietary technology that allows the economic treatment of lower grade refractory gold ores through heap biooxidation. AGC has a significant resource of low grade refractory sulphide ore. This ore is too low grade to warrant BIOX™ sulphide treatment and its oxide plant recov­ery is low at 35-45%. GeoBiotics and AGC have completed pre­liminary testing and economic analysis of heap biooxidation for this material. Additionally, the feasibility of producing a gravity concentrate from the tailings of the sulphide treatment plant has been explored. This concentrate would be coated onto the low grade sulphide and biooxidized concurrently. Gold recoveries for the biooxidized low grade sulphide have increased to 75% and the gravity recovery from the STP tailings has achieved 80% uti­lizing a Falcon concentrator. The preliminary economics of the proposed full scale plant are very favourable with a pre-tax IRR of 233% and a payback period of 6 months. This paper details the biooxidation testing, flow sheet devel­opment and preliminary economics of employing heap biooxi­dation for low grade refractory ore treatment at Ashanti Goldfields' Obuasi operation.

Jan 1, 1998

By Richard B. Berg

Chlorite veins in the Silver Star district (40 km southeast of Butte) were of little interest to those who were mining gold and silver in the late 19th century. It wasn't until 1975 that unusually pure magnesian chlorite of the variety clinochlore was identified from a ?talc? claim in this district. In 1977 tests by Cyprus Industrial Minerals showed that this chlorite was suitable for use in ceramics. Mining begun in that year continues. These replacement veins of chlorite in Precambrian quartzofeldspathic gneiss differ from the metalliferous veins to the northwest in both attitude and mineralogy.

Jan 1, 1982

By G. A. Wierink

This paper discusses a new method to increase flotation recovery. As known from literature, fine and coarse particles have different flotation rate constants, hydrodynamic behaviour and require different reagent regimes. The device discussed allows separate processing of finer and coarser slurry by extraction of a third stream, carrying finer slurry, from the flotation cell. By separate treatment of fine and coarse slurry operational conditions and so flotation recovery for both may be optimized more efficiently. Extraction and classification of the third stream is accomplished by low speed centrifugation and Taylor-Couette flow separation. This Dual Outlet Device (DOD) can be installed in a traditional flotation cell without need for equipment replacement. In order to asses different design options for the DOD a transparent laboratory scale model was built. For this scale model Computational Fluid Dynamics (CFD) simulations using the RANS k-e and LES turbulence models were performed. Essential insight in the dominant flow systems relevant to optimal operation of the DOD was obtained from the CFD simulations and flow visualization tests with the laboratory scale model. Based on these findings a number of configurations were investigated at pilot plant scale in a 5 m3 Outokumpu flotation cell. The results of the pilot plant study show that utilization of the DOD provides a method for in-cell control over particle size distribution in the slurry. Use of the DOD in a flotation cell may enhance flotation recovery and decrease flotation reagent consumption significantly, against marginal investment and operation costs.

Jan 1, 2014

By R. B. Ellestad

Introduction Lithium has been known since 1817, when it was discovered by the Swedish chemist, Arfvedson, while working in the laboratory of Berzelius on the chemical analysis of the mineral petalite, LiAl(Si205)2. Development of the chemistry of lithium proceeded slowly, following the early work of Davy, Gmelin, Bunsen, and Matthiessen. Approximately seventy years elapsed before lithium products assumed any commercial importance, and for a considerable period it was a' very minor industry. Their chief early use seems to have been in medicine, and in the production of lithiated water. Other more important uses were gradually discovered, and the industry has had a slow but steady growth. Chemistry Lithium is classified as an alkali metal, along with sodium, potassium, rubidium, and cæsium. Like these, it is a silvery-white metal, which can be cut with a knife; it is harder than sodium, but softer than lead" It is remarkable in having a density of only 0.53 gram per cubic centimeter, which makes it the lightest metal. On ignition in air, it burns intensely to form chiefly lithium monoxide, Li2O. Like the other alkali metals, lithium reacts vigorously with water to form hydrogen and lithium hydroxide. The later is a strong base, and reacts with acids to form salts. The salts of lithium are in general analogous to those of the -other alkalies, but many of them have unique properties. For example, lithium chloride and bromide are extremely hygroscopic, and have a very high water solubility. Lithium fluoride, phosphate, and carbonate, on the other hand, are all relatively insoluble, unlike the corresponding sodium and potassium compounds. In this instance, lithium exhibits its frequent tendency to resemble the alkaline-earth group of elements (calcium, strontium, and barium). Many of the special and valuable properties of lithium are related to the extremely small size of the lithium ion.

Jan 1, 1948

By Subhas G. Malghan

Feldspathic deposits occur widely throughout the United States, but North Carolina, California, Connecticut, and South Carolina accounted for over 80% of the total domestic feldspar output for the year 1973.1 Pegmatites and granites constitute the major feldspar reserves of the United States, 2 and in addition, feldspar is produced as a byproduct by firms whose major products are spodumene and mica. 3 Feldspar flotation is practiced in the United States, Mexico, Finland, Norway, West Germany, Japan, and the USSR. According to the US Bureau of Mines estimates, the production of feldspar in the United States and rest of the world were 704,000 and 2,514,000 t, respectively. Feldspar is principally used as a flux in making glass, pottery, porcelain, enamel, tile, and other ceramic products. In recent years, the domestic feldspar industry is faced with a number of problems. As a result of increased cost of energy and the introduction in 1972 of new legislative programs relating to air, water, and noise pollution, land-use restrictions, and mined-land rehabilitation, the production costs have increased. Apart from the increased cost of operation, an operational problem exists with the feldspar producers in North Carolina, especially those in the Spruce Pine area. This problem is concerned with the use of hydrofluoric acid in the feldspar flotation. Feldspar producers in Spruce Pine, NC, have been discharging process waste water into the North Toe River. The mill waste water contains active fluoride ions. Fluoride in excessive concentrations is undesirable in waters used for drinking. It is stated that water containing 0.9-1.0 ppm fluoride will seldom cause mottled enamel on children's teeth; and for adults, concentrations less than 3-4 are not likely to cause endemic cumulative fluorosis and skeletal effect. Although the literature on this subject is rather confusing and inconclusive, the inference that concentrations over 4 ppm may affect bone structure is clear. According to the recent Federal Register,4 maximum fluoride level of 1.4 ppm at 79°-98°F is considered to be adequate and safe for the protection of health of the consumers. The EPA and state environmental agencies have accelerated their drive to reduce water pollution on a faster schedule. By 1977, the EPA specifications for maximum contaminant level of fluoride ions in the discharge waters of feldspar milling operatins is expected to be reduced to 2.0 ppm. The other problems of using hydrofluoric acid are the following: toxicity, hazards of handling and storage, and high cost as compared to other inorganic acids (almost 16 times the cost of sulfuric acid). In order to reduce fluoride levels in mill discharge waters, mining companies have taken the following steps: I) Recirculating a part of their mill water. Even though recirculation of mill water seems to be a novel method of reducing fluoride contamination of the discharge water, there are certain operational and handling problems. 2) Conducting research on the treatment of fluorides in mill waste water. The technology of treatment of fluoride ions has received considerable interest in the recent years. A recent research report5 estimates that the cost of fluoride ion removal to meet the present specifications in the feldspar industry is approximately $0.25/t of ore processed, and about $0.50/t of feldspar produced. At the request of the feldspar producing industries in North Carolina, the North Carolina State University (NCSU) Minerals Research Laboratory has taken up a research program directed towards overcoming the fluoride ion pollution problem. After a close study of the operational, technical, and economic aspects of feldspar flotation, it was decided to attempt to replace the conventional hydrofluoric acid process. Conventional Feldspar Flotatin Using Hydrofluoric Acid Since the inception of the feldspar flotation process using hydrofluoric acid by O'Meara2,6 the process has achieved a great commercial success. In the conventional flotation separation of feldspar-quartz, hydrofluoric acid is used to suppress quartz and activate feldspar, and a long chain amine salt (acetate or chloride) is used as a collector. The bulk of amine collectors used in current feldspar operations are applied as the water-soluble acetates of the free-base amines. These products are pastes or waxy solids which are available in a range of acetic acid neutralization levels generally 50 to 100% neutralized. In spite of the problems mentioned in connection with the use of hydrofluoric acid, this process is extremely stable with respect to changes in the process variables. With the exception of a few operations, alaskite and pegmatite are the major sources of feldspar.7 In the flotation treatment of a pegmatite that contains iron-bearing minerals (heavy minerals), mica, feldspar, and silica, a logical order of removal presents itself considering the following:8 1) Mica is readily floated by an amine collector in a pulp pH 3.5. Some iron-bearing minerals will usually respond to amine collector in acid circuit with the mica concentrate. 2) Since iron minerals tend to occur invariably in the feldspar concentrate, it is desirable to remove most of these prior to feldspar flotation. A fatty acid or a petroleum sulfonate collector used in this flotation step in acid circuit will float iron-bearing minerals. 3) Using hydrofluoric acid to maintain pH of 2.5, an amine collector employed in a final step will float feldspar away from silica, usually leaving the latter in the tailing as a high-grade silica concentrate. The problems connected with the flotation separation of feldspar-quartz arise due to the similarities in their chemical structure. Therefore, any reagent system that is likely to succeed in feldspar-quartz separation should have adsorption affinity towards one of the minerals and depression effect towards the other mineral.

Jan 1, 1979

By W. J. Loring

It is proposed to describe in this paper as accurately as possible the present practice at the Utica mills, of which I am superintendent. The Utica Company operates three mills, the Madison (40 stamps), the Utica (60 stamps), and the Stickle (60 stamps). My description will be based on the last-named, in which I have experimented more than in either of the other two; but the practice is the same, under the same management, in all three. Everything is run by water-power, under about 420 feet fall at the Utica mill, and 425 feet at the Stickle mill, giving a pressure of about 185 pounds to the square inch. The Madison mill is situated about three-quarters of a mile below the Utica and Stickle mills, and has only some 100 feet fall from one place, and 38 feet fall from the other. The water that runs the Utica and Stickle mills, and all machinery connected with the corresponding mines, is conveyed through ditch and pipe to the Madison mine and mill, where it develops power for the air-compressor and the 40-stamp mill. The mill is run by a

Jan 1, 1899

By Kevin Galvin, Simon Iveson

Fine particles are the most valuable because they are the most liberated. However, they are also the most expensive and difficult to recover and concentrate. The Reflux Classifier is a novel invention that combines many of the virtues of existing fine particle separation technologies in a way that provides profound synergies. Multiple parallel narrow channels create a laminar-shear separation zone. The laminar flow provides a well-defined velocity gradient that exposes particles on the wall to a conveying velocity that is approximately proportional to their size, thus reducing the dependence of elutriation velocity on particle size. The high shear rate in these channels generates a hydrodynamic lift force that selectively lifts low-density particles off the channel wall and thus causes them to be preferentially conveyed out in the overflow. Particles that are not elutriated slide back down into the mixing reflux zone beneath the inclined channels which gives them multiple opportunities to re-enter the channels. The resultant suspension of both coarse and fine high-density particles in the fluidized bed zone at the base of the unit generates a strong autogenous dense medium that helps to direct large low-density particles back up to the overflow. The fluidization water also simultaneously de-slimes the high density underflow product. When placed in a centrifuge, the benefits of these features multiply with the improvements in capacity and selectivity that arise from high G-forces. When inverted, these features can be used to perform flotation well beyond the conventional flooding limit. Hence this invention platform has the potential to dramatically improve both gravity and flotation separation performance across the minerals processing industry.

Jan 1, 2014

By H. Saroglou

The anisotropic behaviour of Athens Schist has been brought out through the testing of specimens with varying orientation of schistosity with respect to the major principal stress under uniaxial, triaxial and dynamic conditions. A large number of results from tests on intact rock specimens of the Athens Schist were statistically analysed and evaluated.

Jan 1, 2004

By Jenna Wundrack, Evan Thibaud

The advanced cryogenic treatment is a post-manufacturing metallurgical process that involves subjecting off-theshelf materials to extremely low temperatures, significantly improving wear resistance and reliability. These case studies explore whether the claims of Enrich Bits & Tools benefit metals and their specific in-field application to drill bits in the blasting industry. This paper reviews the application of the treatment to button drill bits for enhanced wear resistance in two operations. The first is a civil construction project with highly abrasive rock. To confirm the remarkable benefits of the treatment, a second case study was performed. This case study utilized measure-while-drilling technology in consistent rock characteristics to reduce variables in the field study.

Feb 1, 2024

Scope / Agenda ? What is Situation Awareness (SA)? ? Background on SA theory ? SA is critical in a wide variety of domains ? SA and human performance ? Consequences of poor SA ? Significant challenges for SA in mining operations ? Technology centric design ? SA-oriented design methodology ? Goal-Directed Task Analysis ? Design ? SA Measurement and Evaluation ? Applications of SA-oriented design

Aug 1, 2013

By Ian Hutchison, Ted Sluder, Jack Caldwell, Don Moore

Introduction The Cannon mine at Wenatchee, WA has recently been brought into operation to recover gold from the sandstones of the Swauk formation. The mine is a joint venture between Asamera Minerals (US) Inc. and Breakwater Resources. A tailings impoundment was constructed to impound 2.7 to 3.6 Mt (3 to 4 million st) of tailings at 1.8 kt/a (2000 stpd) over about five years. This paper describes the design and construction of the impoundment. In particular, it describes the 100 m (300 ft) high earthfill embankment that is the main feature of the facility. Project environment The project is located on the outskirts of Wenatchee, a town of about 40,000 people. The town is situated on the flat alluvial terraces beside the Columbia River. The Cascade Mountains rise from the terraces in a series of ridges and valleys. The mine is at the foot of the Cascades. The tailings impoundment is in one of the steep valleys. The climate is mild and dry (Table 1). Site selection Twelve alternative sites within a 16-km (10-mile) radius of the mine were examined. Decision making theory was used to select the most suitable site. Advantages of the chosen site include its proximity to the mine and its low visibility from points of common public access. Also, the area was already heavily impacted by an existing silica quarry. The major disadvantage of the site is the need to pump tailings over a distance of 1.5 km (1 mile) and against a static head of 200 m (655 ft). Also, it is located in a gulch just upstream from the town of Wenatchee. Site geology The impoundment is generally underlain by interbedded sandstones and siltstones. The siltstones are often shattered. The sandstones are often friable. Both rock types are extensively jointed. Some isolated faulting of the sediments occurred before the area was covered with basalt flows. About 10,000 years ago, at the end of the ice age, the basalts were covered by 3 to 10 m (10 to 33 ft) of wind blown loess - a fine sandy clay and silt. River deposits filled the base of the valley to depths between 5 and 25 m (16 and 82 ft). Under the main part of the embankment, these materials were removed to expose bedrock. Ground water flow is generally through the more permeable layers. The permanent water table is about 5 m (16 ft) beneath the ground surface. Project and impoundment layout Figure 1 shows the layout of the mine, the mill, and the tailings impoundment. The tailings deliv-

Jan 8, 1986

By N. Kubo

Sumitomo Toyo Copper Smelter and Refinery was commenced in 1971, and its production capacity of sulfuric acid was 550tpd at the beginning. In 2001 Toyo Copper Smelter and Refinery projected to expand its copper production capacity to 450,000tpy, and now the project is still in progress. To achieve this expansion project, 4,000tpd of sulfuric acid production capacity is necessary to the acid plant. So as a part of this project, the construction of the new converting and absorbing line and the improvement of the existing converting and absorbing line were carried out from 2001 until 2005. Then the production capacity of these 2 lines has already reached the target, 4,000tpd of sulfuric acid. Moreover, at the design of the new line, we adopted several latest technologies and materials in order to construct the world's leading acid plant. Basing on the operation performance of the new line, we have improved the existing line in 2005. Both of these 2 converting and absorbing lines are working quite well and contribute to big energy saving and excellently stable operation. Cu2007

Jan 1, 2007

By A. M. Gaudin

This year the American Institute of Mining, Metallurgical and Petroleum Engineers has chosen to give me its Robert H. Richards Award, a distinction which is widely regarded as the highest honor in the field of mineral engineering. I am deeply moved by this tribute, which suggests not only regard for my service to the profession but also the affectionate esteem of my fellow mineral engineers. You have made me happy at the prospect of the permanent association of my name with that of Robert Hallowell Richards and of the distinguished recipients of the award, Arthur Fay Taggart, Frank R. Milliken, John F. Myers, Edward William Englemann, C. Harry Benedict, Edward W. Davis and Arthur W. Fahrenwald. I wish to thank you all for an honor so generously bestowed. Professor Richards is known to us all as a legendary figure, and we can read about him in the Richards Memorial Volume of our Transactions. Some of us have even had the good fortune of knowing him. I count myself among those lucky few. In its intangible attributes the Award recalls those things for which Professor Richards stood: for Science in Art, for thoroughness, for meticulous accuracy, for bold imaginativeness, most of all for professional integrity. Now, as in his day, these attributes are central to an engineer's creed. They are appropriately needed in a formulation of a definition of the mineral engineering profession.

Jan 6, 1957

By G. S. Tint, M. Herman, V. V. Damiano

Dislocation arrays and substructures were studied in cadmium doped zinc crystals using a newly devised etching technique. Cadmium precipitates delineating the dislocations were revealed by etching a surface closely parallel to the (0001) slip plane. Cinephotomicrography of the continuous etching process revealed the three-dimensional aspects of dislocations in the bulk crystal. Dislocation etch patterns were studied in both deformed and annealed crystals after suitable aging at room temperature. The effect of annealing was evidenced by a rearrangement of the dislocations into low-angle boundaries and hexagonal networks. ETCH pit techniques have been used extensively to study dislocations in both deformed and annealed bulk metal crystals. Ideally one hopes to obtain a one-to-one correspondence between the etch pits and the points of emergence of the dislocations at the surface. One then attempts to deduce the way in which dislocations are arranged in the bulk crystal from the arrangement of etch pits on the surface. It is clear that one can obtain only limited information of the dislocation configurations inside the crystal from etch pit studies of single surfaces. Considerably more information is obtained if one is able to follow the course of the dislocations through the crystal using progressive etching technique. Techniques of this sort were used by Gilmanl to study dislocations on the slip planes of NaCl crystals and by Damiano and Tint2 to study dislocation arrangement in zinc crystals grown from the melt. The present paper makes use of a technique first described by Tint and Damiano3 to observe and continuously record the dislocation structures which appear while a crystal surface was being progressively etched. Studies were made on cleaved (0001) surfaces to reveal the dislocations along their length on the surface closely parallel to the slip plane. The technique for revealing segments of dislocations along their length by etching is well known. Wilsdorf and Kuhlmann-wilsdorf4 revealed disloca- tions along their length in aluminum containing a few percent copper, when precipitates segregated along the dislocations. The technique was used by Low and Guard5 to study dislocation configurations on the slip plane in Fe-Si alloys containing carbon. In the present work the technique was applied to zinc containing cadmium since it was shown by Gil-man6 that a cadmium-rich phase could be made to precipitate from supersaturated solutions along dislocations in zinc. Segments of dislocations delineated by the precipitates were revealed by etching a surface prepared by cleaving the crystal. The three-dimensional nature of dislocations and substructures was thus studied from the cinephotomicro-graphic record of the continuous etching process. EXPERIMENTAL Single crystals of zinc containing the order of 0.1 pct Cd were prepared by slowly lowering a graphite crucible containing the melt through a temperature gradient of 15°C per cm at a rate of 1.5 X 10-3 cm per sec. "As grown" crystals were aged for periods of 1 month at room temperature, then cleaved in liquid nitrogen, and etched according to the procedure used by Gilman.' The etchant containing 32 g of CrO3, 6 g of hydrated Na2SO3 in 100 ml of water behaved as a chemical polish for zinc and etch pits were produced at the site of precipitates or inclusions. After the precipitates or inclusions were removed from the surface, the etch pits left behind were eventually polished smooth. This behavior enabled one to continuously observe the surface while the specimen was immersed in the etchant. Best results were obtained when the specimen surface was vertical and the reaction products of polishing were continuously removed by gravitational convection. Some crystals were heavily deformed in excess of 25 pct strain, others were lightly deformed the order of a few pct by compression such that the deformation occurred essentially by basal glide. Some crystals were etched immediately after deformation, others were allowed to age at room temperature for several weeks prior to etching. Heavily deformed crystals were annealed at various temperatures and etched on the cleavage plane immediately after annealing, others were allowed to age at room temperature for several weeks prior to etching. The etched structures of deformed and annealed structures were studied. Similar experiments were conducted on 99.9999 pct pure zone refined Tadanac zinc crystals which

Jan 1, 1963

By Bish Chanda

In the minerals business, like any other commodity-based business, management faces the daily challenge of holding down costs while the real prices of products are continually falling on an inflation-adjusted basis. Since the marketplace sets the prices, often without any premium attached for product quality, being one of the lowest-cost producers is the most viable competitive strategy. Continuous improvement is the mantra that can make the difference in terms of long-term survival of a mining company. Yet, this message has not always been followed, especially during periods of prosperity ushered by high commodity prices. More often than not, the need for improvement is only triggered by a crisis. This may be caused by events such as the onset of a severe economic recession, a prolonged oversupply situation due to an optimistic expansion of capacity during the period of prosperity, or simply falling profits alerting management to bring costs under control. At that time, there would be a need to implement a new cost-saving program, bring in a consultant to find ways to reduce costs, or re-activate an old program that had been shelved for some time.

May 1, 2003

By W. K. Tolley

This report presents data collected during research by the Bureau of Mines on corrosion of grinding media. Corrosion rates of eight alloys commonly used in grinding media were tested in synthetic mill water using an ultrasonic grinding device especially designed for this work. Electro-chemical measurements showed variations in corrosion rates for these alloys between 9.8 mpy for medium-carbon steels and 0.14 mpy for high chromium white irons. Bureau data are discussed along with data from the literature to indicate that corrosion causes less than 10 pct of the wear of grinding media in commercial grinding mills. A comparison of corrosion rates for various types of grinding media shows that alloying elements and electrochemically active inclusions in steel affect the corrosion behavior of the media.

Jan 1, 1984