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By Stoyan N. Groudev, Ioannis Paspaliaris, Plamen S. Georgiev, Irena I. Spasova, Kostas Komnitsas

"The uranium deposit Curilo located in Western Bulgaria for a long period of time was a site of intensive mining activities including both the open-pit and underground mining techniques as well as in situ leaching of uranium. The ore was rich in pyrite and, apart from uranium, contained some non-ferrous metals. The mining operations in the deposit were ended in 1990 but since that time the deposit is a permanent source of acid drainage waters. The generation of these waters is connected mainly with the oxidation of pyrite and other sulphide minerals by the indigenous acidophilic chemolithotrophic bacteria.Laboratory and pilot-scale studies revealed that an efficient clean-up of the above-mentioned waters was achieved by means of passive systems of the wetland type. In 2001 a wetland was constructed in the deposit to treat a portion of the acid drainage waters which were discharged to a small ravine. This ravine reaches into the Teina, a small river that is a tributary of the upper reaches of the Iskar river.The wetland was constructed in the ravine and its bottom was located on intrusive rocks with a very low permeability. The rocks were covered by a 30 – 50 cm layer consisting of a mixture of soil, plant compost and crushed limestone. The wetland was characterized by an abundant water and emergent vegetation and a diverse microflora. Typha latifolia, Typha angustifolia and Phragmites australis were the prevalent plant species in the wetland but species of the genera Juncus, Eleocharis, Carex and Poa as well as different algae were also well present.The acid drainage waters treated by the wetland had a pH in the range of about 2.5 – 4.1 and contained uranium, radium, some heavy metals (iron, manganese, copper, zinc, cadmium, lead), arsenic and sulphates in concentrations much higher than the relevant permissible levels for waters intended for use in the agriculture and/or industry. The watercourse through the wetland covered a distance of about 0.2 – 1.0 l/s."

Jan 1, 2003

By Eric R. Skonberg

"Technology exists today to blind drill a mine shaft 20 feet in diameter, unlined, over 3,000 feet deep. These shafts must be lined in the most economical, safe and expedient manner possible. A new technique of stacking precast concrete cylindrical sections in the unlined shaft has been developed to yield a dry and hydrostatically lined shaft .These sections must withstand an external radial pressure of 3,000 feet of water yet take up as little room as possible in the shaft . Using high-strength concrete, wall thicknesses may be kept at 2 feet. The outside diameter of the sections has been chosen to be 18 feet to allow for some annular space between the liner and shaft wall. The concrete sections are produced in segments 10 feet long weighing 75 tons each. During drilling operations, the concrete sections are cast and cured. After drilling operations are complete, a headframe is situated over the shaft. The unlined shaft remains full of fluid. A special liner running tool is mated with the section in three steel ports at the bottom of the section. The section and running tool are lowered into the hole, and the tool is disconnected and returned to the surface. Subsequent sections are lowered and stacked using the same operation. Grout is placed behind the liner to result in a dry shaft."

Jan 1, 1981

By John J. Cioston

THE steadily rising flood of gold production from all parts of the world has created an avalanche of rumors regarding the stability of the present price of this metal. Markets have been unsettled from Johannesburg to London from New York and Toronto to Melbourne, despite repeated denials from, American and British authorities of any immediate intention to alter the price. Various economists and financial writers have blossomed forth with predictions that the price would be set at the old level of $20.67 per oz.; some have even been so brash as to state That a price of $15 would be necessary to bring production within control. These effusions, based entirely upon monetary theories and with no regard to production costs, serve to confuse rather than clarify the situation.

Jan 1, 1937

By AIME AIME

Change of Meeting from Birmingham to Chattanooga. In consequence of the disturbed conditions attending a long¬continued labor strike in Alabama, the meeting of the Institute was changed from Birmingham, Ala., to Chattanooga, Tenn., where it will. begin on Thursday evening, Oct. 1, 1908. Information. of this change bad been sent to the newspapers through the Associated Press, and by circular to all members, when news was received of the sudden and unexpected termination of the strike referred to. It was, unfortunately, too late to change once more the arrangements for the meeting. But it is hoped that the cordial invitation of the citizens of ,Birmingham may be renewed and accepted at a future time, not too remote. Office Facilities for Visiting Members. A separate room in the suite occupied by the American Institute of Mining Engineers on the ninth floor of the United Engineering Society Building, has been equipped with furniture and telephone extension for the temporary use of members of the Institute or of sister societies, or visitors suitably accredited. Members of the Institute visiting New York for a short time, who need office facilities during their stay, or members residing in the city. who need temporary office accommodation, can arrange to have set apart for their exclusive use a room, equipped with office furniture, telephone, etc.,. in the suite of the Institute. It is not the intention to give possession of the room to any individual for an indefinite time, but to offer to members of the Institute an opportunity to acquire a well-located, well-equipped business headquarters to carry on transactions which

Jan 9, 1908

Steel Ladle in Bhilai Steel Plant, SAIL, India, passes through VAD & LF-RH route and this exposes refractory lining to a severe operating conditions. Ladles are lined with in-house manufactured MgO-C refractories. Lining life used to be 35 heats, out of which 18-20 heats were through VAD/LF-RH, hence, ladle availability had become a constraint. Laboratory studies were carried-out to optimize granulometry and composition. Granulometry was developed by adopting Andearssen packing model. A suitable plasiticiser was identified to eliminate inconsistency caused due to variation in resin quality and weather condition. It reduced variation in green bulk density from 6 to 1.3%. Abrasion and slag erosion studies were conducted, which shows that with increase of carbon, abrasion resistance decreases and corrosion resistance improves. Based on these studies, graphite in slag zone was increased from 10 to 12.5% and in metal zone it was reduced to 7.5%. Different process parameters of brick making were optimized to make MgO-C bricks of maximum bulk density with reduced coke porosity. Modified bricks have bulk density of 2.99-3.02 g/cc and coke porosity of 9.5-10.5%. Further, shape of the bricks were changed from side arch to mini keys and thickness was increased from 80 to 100 mm. Mini key bricks are pressed from sides, thus eliminating variation in thickness which is critical dimension for dry joints. These modifications improved average lining life of steel ladles to 64 heats, which includes 37-40 secondary heats. Maximum life obtained is 87 heats.

Jan 1, 2006

By H Kurth

Geoscan is used for multi-elemental analysis of conveyed bulk materials in real time. It has been used for coal analysis since the 1990s, in the cement industry, and since 2003 for measuring mineral ore quality. Geoscan-M has proven performance and demonstrated paybacks of weeks or months, in iron ore, manganese, copper, zinc-lead and phosphate industries. Geoscan-M measures continuously through the full bed depth and is unaffected by belt speed, particle size, layering and dust levels. Increments of two minutes (typically one to five minutes) are accurately measured and provide the plant operators with tonnage weighted results of each element within seconds.A Geoscan installed after crushing is able to measure quality shortly after mining. The analysis results can be used to divert the increments based on composition, such as diverting waste for disposal and diverting marginal material to a stockpile for processing at a later date. The bulk sorting process allows different qualities to be placed into relevant stockpiles for subsequent blending. Material meeting product DSO (Direct Shipping Ore) quality can bypass a beneficiation circuit to prevent unnecessary treatment costs. An analyser in a blending application enables proportioning of different quality feed materials from multiple stockpiles to achieve a desired compositional consistency for process feed. The parameter used for decisions may be; a) primary metal content, e.g. Cu, Fe, P, etc. b) deleterious component content, e.g. Mg as an indicator of talc content, c) process parameter content, or a combination of these. Process parameter content may be the elemental ratio between critical components, e.g. Cu:S ratio, Fe:Si ratio, basicity, Lime Saturation Factor, etc. or the content of an “indicator” element, e.g. Si as an indicator of material hardness or grindability.Measurement of the composition in real time enables prompt feedback to the mining operators and also feed forward to the process operators. Compositional variability can be critical in the process and advance warning enables appropriate reactions prior to processing. This may include modifying the feed rate, changing the feed blend (through additives), or modifying reagent dosing in anticipation of a change in feed quality. Benefits include, but are not limited to; reducing waste processing, improved feed grade stability, reducing energy, water and grinding media consumption, producing less tailings, increasing process efficiency, higher metal recovery, better plant utilisation, reducing plant downtime, better utilising mined material, all achieved using the same process plant throughput capacity.CITATION:Kurth, H, 2015. Optimising plant feed quality and process performance using Geoscan elemental analysis, in Proceedings MetPlant 2015, pp 373–380 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

By Randolph C. Specht

A two year study was made of the waste disposal of the pebble rock phosphate industry. Solid slimes are impounded in large settling areas and the process water is re-used. Clear effluent was not found to be toxic to fish, or animal life in field tests or in controlled experiments.

Jan 1, 1950

In subterranean mining operations, access to communication networks deep underground is critical for transporting data, voice and video, and other supporting applications that are essential for efficient and safe operations. Whether accessing sophisticated ERP or maintenance management systems, engaging in fleet management, video surveillance, or access control, or protecting miners with wireless locator systems, these networks serve as a literal lifeline between workers deep within mines and surface operations. For this, mining networks require more than permanently installed network cabling, it also requires unique deployable systems designed for quick installation, extension and even relocation as the active mine site area moves, or equipment is moved in and out.

Mar 1, 2014

By J. G. Stevens, S. W. Colley

"Selective separations of metals and ions in mineral extraction and refining are becoming more challenging as ore bodies become more complex and environmental pressures increase. The separation and containment of mercury produced in gold mining are a factor in the profitability and operability of mines. This paper will discuss the development and implementation of the Johnson Matthey HgFree selective mercury removal process. The process is designed to selectively recover co-leached mercury from either heap leach pregnant solutions at ambient temperature and low mercury concentrations, or electrowinning pregnant solutions at elevated temperature and high mercury concentration, without affecting gold or silver recovery. The process utilizes a highly selective adsorption-desorption step in which mercury is removed quantitatively by the HgFree adsorbent without adsorption of gold, silver or other metals present. Development of the original HgFree adsorbent has resulted in a process whereby mercury can be recovered as an inert salt and is never present as the free metal. The HgFree adsorbent can be regenerated and recycled in situ, and is capable of being reused multiple times. The overall process is compatible with existing gold mining and recovery practices and offers significant environmental and sustainability benefits, including reduction or elimination of the need to retort mercury with a subsequent reduction in potential mercury air emissions. Development of the HgFree adsorbent and process will be discussed along with a pilot operation at two operating mines.INTRODUCTIONMany gold ore bodies contain high concentrations of mercury which when extracted with cyanide, co-extract with the gold and other metals. This mercury is carried through the process with the gold, posing environmental and technical issues when it is separated from the doré. This paper describes a method to selectively adsorb mercury from the gold recovery circuit while it is in a soluble form, leaving gold to be processed as normal. The removal of mercury from the circuit eliminates the need for mercury retorting of doré and so reduces the potential environmental impact of fugitive emissions of elemental mercury."

Jan 1, 2016

By S. Maleksaeedi

On-site evaluation of strength using hardness is common for different materials. The lack of such relation for aluminum alloys has always been felt. In this work, a finite element analysis of plastic deformation and its distribution in Brinell hardness testing is presented. The analysis has been performed for different strength levels of aluminum alloys. By utilizing the Von Mises equivalent strain in hardness, it is tried to derive a correlation between hardness and strength values for the alloys under consideration. The derived correlation is verified using the experimental values available in literature.

Jan 1, 2004

By John J. Sammarco

Mining has one of the highest annual average fatality rates among major US industries. Health and safety dangers have been inherent to mining since the early days of picks and shovels. Even though miners' health and safety has improved over the years, mining is still one of the most dangerous occupations. Mining was traditionally a low tech industry. It is now driven by competitive pressures to go high-tech by using programmable electronics (PE) for machine control, atmospheric monitoring and material processing. The industry's experience with the functional safety of PE is limited compared with other industries. Thus, PE is an emerging technology for mining that can potentially create or worsen hazards. The US National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory in Pittsburgh, PA is addressing the safety of this new technology. NIOSH has a proactive project to generate recommendations for addressing the functional safety of PE-based mining systems before the technology proliferates. The recommendations take the form of a safety framework encompassing the entire life cycle for a PE-based mining system.

By Paul B. Crawford, Melvin B. Burton

A procedure is given which describes how the gelatin model may be-used to study the effect of mobility ratio on areas swept before and after breakthrough in fluid injection programs. Differences in mobility ratio are achieved through the proper selection of electrolytes for the invading and displaced fluids. The progress of the front is followed visually and photographed or traced onto plates (it desirrd positions before and after breakthrough. Example applications to standard flooding pattrrrls, vertically and horizontally fractured reservoirs and the in-situ combustion recovery process ore presentrtl. INTRODUCTION In water flooding, gas cycling and other fluid injection programs, the sweep efficiencies and swept areas after breakthrough are known to depend on the mobility ratio. Previous investigators have described the application of the X-ray technique, stepwise use of the poten-tiometric model and numerical procedures for studying these problems.1,3,4,6 Others have described the application of the electrolytic and gelatin models for studying sweep efficiencies at a mobility ratio near one.2,5,7,8,9 It is a purpose of this paper to describe a procedure for using the gelatin model to study swept areas at mobility ratios other than one. PROCEDURE The technique developed for gelatin model studies is composed of four phases: the construction of the model, the selection and preparation of electrolytes, the running procedure, and the recording of the swept areas. Each phase is discussed independently in order that the over-all procedure will not be confused. Construction of the Model Since some of the advantages of the gelatin model are its economy, and speed, it is desirable to have as small a model as is possihle without creating error through the inability to follow visually the progress of the colored front. For this work, it was found that a distance of 4 to 6 cm between salt bridges is convenient to use. Since the size is relatively small, it follows that the gelatin layer must be thin. For this study, 1/8 in. was used as the gelatin thickness in each case. The model was constructed on a flat 1/2-in. plastic (Lucite) base with boundaries constructed from 1/8-in. plastic strips. The well pattern to be studied was outlined with the 1/8-in. plastic strips on the base with narrow apertures (- - 2 mm) in the boundary to represent the wells. Behind each well opening, a rectangular area of some 8 to 12 sq cm was outlined by additional plastic strips. The plastic strips were fastened to the base by any suitable non-conducting cement so that the boundary system was liquid tight. The electrodes were constructed from sheet copper in a fashion that would allow easy removal. In this work, it was found that by simply forming a large U-shaped clip from a strip of the copper that would slip over the boundary was satisfactory and easily removed. The electrodes should be as wide as one of the sides of the rectangular area behind the well opening. If a fractured pattern is studied, fractures inside the well pattern may be represented by strips of copper of the desired shape mounted in some easily removable fashion. The reason that apertures (or salt bridges) were used for wells instead of metallic electrodes is that the plating of the electroactive ion at the cathode and the introduction of an electroactive ion at the anode has a detrimental effect on the swept area outline if these operations \rere permitted to be carried on within the well pattern itself. The anode may be used within the well pattern

Jan 1, 1957

By R. P. Aikman, F. G. Miller, J. M. Podgursky

As part of a larger study of the mechanism of froth flotation of coal, the rates at which coal particles of various size and specific gravity react to froth flotation were investigated. Results of this study show that in flotation: I) recovery rate increases, but selectivity decreases with a decrease in particle size down to 100 mesh, and 2) recovery rate is constant for all sizes between 100M and 325M. n response to the growing demand for low-sulfur coking coal for iron making, the coal industry is continually striving to perfect methods for cleaning coal to acceptable ash and sulfur levels while maintaining maximum product yield. By present standards the industry has adequate processes for cleaning coarse coal, i.e., + 28 mesh, at almost any desired specific gravity. However, in the case of fine coal, i.e., —28 mesh, neither of the two existing processes - froth flotation or hydrocycloning — in its present state of development yields products that are comparable in ash and/or sulfur content to products normally obtained from coarse coal processes. The work outlined in this paper is part of a larger study directed toward maximum exploitation of froth flotation for fine coal processing. The concepts and data presented are now serving as a basis for designing fine-coal circuits in which improved efficiency is obtained by optimum use of froth flotation with other fine-coal processing methods. The paper includes: 1) A discussion of the value of a detailed wash-ability study as a method of assessing the problems associated with fine coal processing, 2) A general discussion of hydrocyclone principles, included to serve as a basis for understanding the mechanism of coal flotation, and 3) A detailed discussion of the mechanism of coal flotation, as well as the research leading to the optimum use of froth flotation in combination with other fine-coal cleaning methods to provide efficient fine-coal processing. Our study of the rates at which coal particles of various size and specific gravity react to flotation shows that in flotation: 1) recovery rate increases but selectivity decreases with a decrease in particle size down to 100 mesh, 2) recovery rate is constant for all sizes between 100 mesh and 325 mesh, and 3) the flotation process effectively rejects only those extremely fine particles which do not contain surface carbon. (Because of this feature, froth flotation is an excellent method for rejecting clays - the only extreme fines in - 325-mesh coal that are always carbon free.) Washability studies of flotation products are used to assess flotation efficiency. These studies show that: 1) the increase in percent sulfur in flotation products above the theoretical sulfur content as defined by the washability study is due almost entirely to flotation of fine high-specific-gravity particles that are part coal and part pyrite, and 2) in a given size range particle floatability decreases with an increase in particle specific gravity. Error curves are explained and are used to compare the mechanisms of coal flotation and hydrocycloning. These comparisons show that hydrocyclone performance is affected primarily by particle mass, i.e., particle specific gravity and size, whereas coal flotation performance is dependent on both the particle mass and the coal surface available for bubble attachment. Since the error curve is a basic tool for rating the efficiency of any coal processing system, it will be useful to quickly review the principles of error curve construction. RATING COAL-PROCESSING EFFICIENCY BY THE ERROR CURVE The organic component of coal is of lower specific gravity than its impurities, and the most effective principle for coal concentration is therefore separation on the basis of specific gravity. However, since there is no sharp dividing line between pure coal and pure ash components, specific gravity must be closely controlled if the product is to have acceptable quality at maximum yields. In turn, the basis for close control in any coal processing system is the reference standard provided by precise laboratory washability studies. In these studies, coal is carefully separated into a series of progressively higher specific gravity fractions to establish a relationship

Jan 1, 1968

By Rodrigo Afonso Hatwig

Os aços inoxidáveis duplex (DSS) e superduplex (SDSS) são ligas que se caracterizam por apresentar uma microestrutura composta por frações volumétricas similares das fases ferrita e austenita. Dependendo da composição química e do tratamento termomecânico aplicado, a microestrutura dos aços inoxidáveis DSS e SDSS poderá apresentar, além das fases ferrita e austenita, fases intermetálicas deletérias. Neste trabalho, um estudo termodinâmico-computacional foi realizado com o objetivo de acompanhar a evolução das fases de aços superduplex no intervalo de temperaturas entre 300°C e 1.200ºC. Para tanto, fez-se uso do software de simulação termodinâmica FactSage v. 6.4. Os resultados descrevem de forma eficaz as fases principais e secundárias em função da temperatura e composição química.

Aug 8, 2018

By Hong Yong Sohn

Keywords: Barium sulfate, Barium sulfide, Environment, Kinetics, Pollutants, Sulfur dioxide conversion, Thermodynamics Nonferrous smelters and coal gasification processes generate sulfur dioxide streams, most of which are treated to produce sulfuric acid with the accompanying problems of market shortage and transportation difficulties. While the conversion of sulfur dioxide to elemental sulfur has many environmental advantages, no processes exist that are environmentally acceptable and economically viable. A method for converting sulfur dioxide to elemental sulfur by a cyclic process involving calcium or barium sulfide and calcium or barium sulfate without generating solid wastes has been developed. In this process, the sulfate, as the starting raw material, is reduced by a suitable reducing agent such as hydrogen to produce the sulfide, which is used to reduce sulfur dioxide producing elemental sulfur vapor and regenerating the sulfate. The latter is then reduced to reproduce the sulfide. This paper describes work on the BaS/BaSO4 system. Thermodynamic analysis and experimental results indicated that the BaS-SO2 reaction produces mainly sulfur vapor and solid barium sulfate and that the gaseous product from the BaSO4-H2 reaction is mainly water vapor. The rates of the two reactions are reasonably rapid in the temperature range 700-1050°C.

Jan 1, 2005

By A. L. Engel

[Thi;. re:9ort presents re3ults of investigations of problema a3signed as ore-testing projects to the Ore-Dressing Section, t.fetal1urgica.l Div:biion, of the Bureau of Ii.fines at the .fississippi?Valley E>"'1lcrimcnt Station in rtolla, Ho., durine the fiscal year ended June 30, 1940.]

Jan 1, 1941

By A. L. Engel

[This report presents results of investigations of problems assigned as ore-testing projects to the Ore-Dressing Section, Metallurgical Division, of the Bureau of Mines at the Mississippi Valley Experiment Station in Rolla, Mo., during the fiscal year ended June 30, 1940.]

Jan 1, 1941

The results of studies to ameliorate acid mine drainage by retarding the rate of oxidation of pyrite at source are discussed. In the transpassive region, pyrite oxidizes by reactive dissolution, mass transfer through the product layer and diffusion in the bulk solution. One can decrease the rate of pyrite oxidation by inhibiting either oxidation reactions or cathodic reactions. It is demonstrated in this study that some surface active reagents extend the passive region by affecting both the anodic and cathodic processes. The extension to higher potentials occurs by inhibition of the anodic dissolution process whereas to lower cathodic potentials through decrease in the rate of reduction of molecular oxygen and/or ferric ions. To retard the oxidation of pyrite by ferric ions, which is considered to be the dominant oxidant under conditions of acid mine drainage, it would be necessary to restrict mass transfer or promote complexation of ferric ions at the surface. Imidazoline based reagents were found to be most effective in meeting this goal.

Jan 1, 1994

"There mines are located in out of the way places, where timber is scarce and its price high, the problem of protecting it from fire risk is of considerable practical importance. Scarcity of timber for mining purposes is commonly met with in the more arid parts of the country, where, so, mine timbers are most likely to become dry, and inflammable, and where, therefore, the risk from fire is accentuated. Any effective and cheap method of securing adequate protection of such timber at the lowest possible cost is worthy of careful investigation. The use of magnesite cement has been suggested in this connection.The necessary qualities for any substance for the use suggested above may be summarized as follows: It should be resistant to abrasion, and to impact and structural stresses. It should be durable when subjected to the action of the elements, and stable to any minor derangements of the base on which it is placed. It must be relatively unaffected by changes in temperature, by the action of water, and should adhere to the material on which it is placed, and it should also be free from shrinkage cracks due to setting up the material, Magnesite cement appears to fulfill the various conditions outlined above.The elasticity of such cement is the outstanding quality which makes it desirable for exterior work. It also possesses the ability to adhere to all materials in a marked degree. Its freedom from expansion and contraction after setting is one of the principal reasons for its adhesive quality. It may be applied to old brick or stone walls, even tho they have been repeatedly covered with paint, and the quality of adhearing to wood makes it possible to secure a weather-proof protection to the wooden casings and trim of exterior openings. The quality of adhesion and elasticity is easily proved by applying a 1/2"" layer to a 1"" board which has been first covered with metal lath. Such a board, about 8 feet long, may be repeatedly deflected about 3"" in the center without breaking the bond to the board, or causing any cracks to appear in the magnesia cement. The ability to resist fire as well as the possession of insulating qualities are also desirable characteristics of magnesia cement stucco.Magnesite cement stucco should be applied in two coats, each 1/4"" thick on various surfaces such as wood lath, metal lath, sheathing board, brick, hollow tile, or stone; care being taken as regards the presence of lime, unless the same has been rendered, or become inert as with very old, walls. The first coat made up to a consistency that works easily under the trowel is applied in the usual manner. No water should be added to the liquid chloride as it would alter its density, and injure the work. The second or finishing coat is then applied. The aggregates are different in each, and no other dry material should be added to them as they come to the trade. The cement may be applied in zero weather without damage. Setting is quite slow under such conditions, but the cement ultimately becomes hard. It should always be applied to a dry surface excepting that under certain conditions it is desirable to apply a solution of magnesium chloride before using the stucco."

Dec 1, 1919

By J. B. Hiskey

INTRODUCTION The extraction of gold and silver from ores, concentrates, and various metallurgical products can be achieved by a number of hydrometallurgical techniques. The solvation properties of alkali cyanide solutions on gold and silver were recognized 200 years ago. A cyanidation process for leaching gold from its ore was patented in 1887 and 1889 by MacArthur and Forrest. The solvent action of thiosulfate on gold and silver was observed over 100 years ago. Recently, several patents have been issued for processes using ammonium thiosulfate as lixiviant for precious metals, Berezowsky, et. al (1978) and Kerley (1981). Tozawa and and coworkers also examined the dissolution of gold in ammoniacal thiosulfate solution. Thiourea leaching of gold and silver initially discussed by Plaksin and Kozhukhova in 1941 but has received only limited attention since that early work. Use of thiourea as an alternative to cyanide was the topic of several papers presented at the 1981 AIME annual meeting In Chicago, Illinois. Hiskey provided a review of the fundamental chemistry of the dissolution of gold and silver in acidic thiourea solutions. Pyper and Hendrix reported on the leaching of a finely disseminated gold ore using thiourea as a lixiviant. The review article(6) previously presented was fairly comprehensive covering Important contributions to the chemistry of thiourea and the processing of gold and silver with acidic thiourea solutions. A search of the technical literature was made to determine recent (since 1981) progress and developments in applying thiourea to the processing of gold and silver. This review reveals that Soviet and Eastern European scientists are continuing to make major contributions to our understanding of thiourea/precious metal systems.

Jan 1, 1984