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By Ch. Apostolaki

Eighty samples from Roman wall paintings from ancient Corinth were studied by means of optical and scanning electron microscopy coupled to an energy dispersive analyzer, X-ray diffraction and image analysis techniques. The goals of the study were the identification of the exact nature of the pigments and the technical features of paint application (binding medium, adherence to plaster, thickness of the pigment layer), which would provide evidence about the painting technique (fresco or secco). The main plaster is calcitic with secondary calcite as a cement binder to the primary calcite grains. All pigments, except Egyptian Blue, were naturally occurring ochres or pigment minerals, such as limonite, goethite, hematite for yellow, brown and red hues, cinnabar for red hues and celadonite for green color. The presence of specific elements such as Ni and Cr or minerals such as olivine, in the yellow, brown and red pigments, gave an indication about the provenance of the original pigments, which seems to be from Cyprus. The black color was represented using charcoal. It seems, finally, that for the pigment application the fresco technique was used, while secco is also apparent.

Jan 1, 2006

By Robert Dimock

The successful management of large dispersed mineral operations is dependent upon accurate and timely decision making. The plant locations providing the data to support the decision making process are generally separated by distances which elongate the time required to accumulate the data at a central focus. The need exists to examine operational data in context with total mining operations, and in relation to target projections and historical trends. The use of microcomputers for local information tasks is an established capability. Grouping microcomputers into local-area networks is rapidly becoming established. Interconnecting multiple local-area networks to provide a free flowing stream of information between all operational locations of a mining enterprise is possible with use of some emerging technologies. The benefit of the potential interconnections and rapid transfer of information can readily be seen from a production reporting perspective. Numerous other advantages exist' by providing routing to enable a workgroup to be established between separated work functions.

Jan 1, 1989

By J. B. Zachwieja

Cationic reagents have been utilized in mineral processing since the mid 1930's and are based upon fatty nitrogen derivatives. The initial commercial development was centered around a flotation collector capable of separating potassium chloride from sodium chloride - potash flotation. The first commercial sale for Akzo, known then as Amour and Company, was realized in the summer of 1940 to a potash producer in Carlsbad, New Mexico for the flotation of potash. The success of the potash flotation collector led to the development of other cationic mineral processing reagents. Flotation collectors for iron ore, phosphate, calcium carbonate, silica sand, feldspar, and other silicates materialized into a large commercial business. Another area that realized commercial success was the development and use of anticaking/antidusting reagents for hygroscopic salts, fertilizer mixes, and granular fertilizers. A more recent development has found use in the trona industry as a defoamer and crystal growth modifier during the crystallization of sodium carbonate liquors. A review of cationic reagent chemistry and applications will be given and the potential for new application areas will be explored.

Jan 1, 1994

By J. J. Moore, B. Mishra, D. L. Olson

The production of radioactive and reactive metals, such as plutonium, uses various pyrometallurgical techniques that generate significant quantities of waste salts contaminated with hazardous, reactive or radioactive materials. Health concerns, environmental regulations and economic considerations require proper mitigation processes to recover the valuable components and for recycling or unrestricted release of these salts. The Oxygen Sparging Process converts soluble metal halides, such as chromium-, plutonium-, cerium chlorides, into insoluble oxides and/or oxychlorides which can be consolidated and separated for long-term storage or further processing. The matrix salt phase, viz. calcium and/or alkali chlorides, are clean after oxygen sparging and fit for recycling. This method has been described and its optimized parameters discussed to show that RCRA regulated elements, such as, chromium, lead, cadmium, etc. report to the consolidated phase making the salt recyclable. Salt Scrub Reduction Process for the recovery of radioactive and RCRA metals from the waste salts has been developed. The process uses a Ca-Ga intermetallic alloy which recovers over 98 percent of the reactive metals. The matrix salt phase in this process, viz. calcium or alkali metal chlorides, are clean after salt scrub reduction.

Jan 1, 1995

By R. L. Garrett

The quality of mineral additives used in a drilling fluid (mud) can dramatically affect the fluid's properties and the overall cost of drilling an oil or gas well. The principally wed minerals are bentonite, barite, barite/hematite blends, and hematite alone. The high specific gravity minerals, barite and hematite, are used to increase drilling fluid density. Bentonite clay is used to increase drilling fluid viscosity and gel strength and to provide a low permeability filter cake. A multimillion dollar investment in a well and the safety of the personnel on the drilling rig can depend on how effectively these mud additives perform with other constituents in the mud. This paper points out effects caused by small amounts of certain carbonate and sulfide mineral impurities in barite or hematite and how polymeric extender additives in bentonites contribute to unpredictable behavior of a mud. Effects like these are the reason oil companies using these materials sometimes set their own quality standards beyond those already specified in APZ Spec. 13A. Also discussed in this paper are the current standardization activities of API Committee 13 on these minerals.

Jan 1, 1988

By L. G. Austin

Using an instrumented laboratory high-pressure grinding rolls mill, the grinding force, gap dimension, mass flow rate and net mill power were measured for six coals and a crystalline quartz. A technique was developed to estimate the compressive stress-strain curves for compression of the materials in the mill plus the effects of elastic decompression. To reconcile the mill power and grinding pressure results, it was necessary to allow for the energy recovery on decompression. No clear correlation was obtained between the form of the stress-strain curves or the variation of specific mill power factor with the Hardgrove grindability index (HGI), although coals with the lowest and highest HGIs (i.e., 44 and 106) gave results significantly different from the other coals. Feeds below 140 mesh (105 µm) flowed more rapidly than coarser feeds and would not build up high grinding pressures. This indicated shearing and fluidlike properties rather than compression as a locked bed.

Jan 1, 1998

By Weixiang Meng, Zhao Song, Ming Guo, Zhigao Liu, Shoubao Zhang

"There are many multi-layer coal reserves in China which account for nearly 20 to 25% of the existing proven reserves. When the coals are mined in a descending order using the fully mechanized long wall mining method, they usually have roof collapse with cavity and air leak in roadways and long wall stopes; this is especially relevant when the thickness of the rock between two coals is less than 5.0 m, as the roof stability of lower seam would be greatly reduced. At the Wuhushan Mine, such abnormal strata behavior occurs, including abnormal support stress, irregular period roof pressure, and roof falls in the face. The main reasons for these behaviors include smaller roof thickness, lower rock strength, and mining influence of upper coal; these reasons were determined by analyzing the in situ conditions. A mechanics-based model of the mine geometry was set up to study the sources of stress, the stress evolution of coal, and the discriminant method of roof stability; to obtain the smallest safe thickness of roof between two coal layers, numerical modeling was applied to analyze the relations between the roof thickness and its displacement distribution. Based on the above research, the No.1001 face was divided into easy roof caving zone (ERCZ), roof caving transition zone (RCTZ), and unlikely to roof caving zone (URCZ). In the ERCZ, comprehensive grouting to reinforce the roof was implemented; in the RCTZ, local grouting to reinforce the roof was implemented. Furthermore, a face stability control index and its range were developed in a fully mechanized face combined with mine pressure observation. After implementing this strategy, there have been no unexpected roof caving or other serious strata behaviors.INTRODUCTIONChina is the country with the largest coal production in the world, and the conditions for its coal seams are particularly complicated. For example, in China’s Datong, Wuda, Pingdingshan, and Qinshui mining areas, there are a large number of multi-layer coal seams. The thickness of these coal seams ranges from 1.3 m to more than 10 m, and the spacing between layers is from under 1.0 m to over 30 m. A common problem with these coal seams is that one layer of mining has a large impact on other coal seams, which are customarily referred to as close-distance coal seams. According to statistics, close-distance coal seams account for about 20–25% and 15–18% of China’s coal reserves and production, respectively.From the reference research of Huang (1999, 2002, 2018) and Tu (2010, 2011) we can learn that in the mining process of close-distance coal seams, downward mining is mainly used. When the upper-layer coal is mined, it has a huge mining disturbance effect on the floor (that is, the roof of the lower coal). The mining disturbance increases the mining fissure in the rockmass and weakens the strata strength. The mining problem formed by this issue is that when the lower coal is mined, problems such as difficulty in roadway support, collapse of stope roof, and difficulty in ventilation are often encountered. Especially for the mining of medium-thick coal seam groups with a layer spacing of less than 5.0 m, there has been a large-scale roof collapse accident with a fall height of more than 10.0 m. In response to such problems, domestic and foreign scholars and engineers such as Tan, Zhao, and Xiao (2010), Xie et al. (2017), and others have also carried out targeted theoretical and practical research."

Jan 1, 2019

By Robert H. Shannon

Coal is the primary fuel for U.S. electric per generation -- over 78% of U.S coal production. In 1987 over 56% of electric per generation was from coal-fired plants. Areas of concern confronting the expanded use of coal for per generation include environmental, political and the nation's energy security and economy. These matters and available alternatives and options directed to the expanded use of coal are reviewed.

Jan 1, 1989

By Michael J. Shulman

During-all phases of exploration limited resources must be allocated among exploration methods and among exploration prospects. This problem,, an exercise in optimization, can be treated mathematically. For three objective functions - maximizing return, return to cost and return minus weighted cost - theoretical results exist which enable the exploration planner not only to gain valuable insight into the problem, but also to estimate the resources necessary and to allocate these resources for' at least-two stages of exploration prior to initial field work. A two-stage exploration strategy for volcanogenic-sedimentary iron in northern Egypt illustrates, how the results can be used. Stage 1 consists of an aeromagnetic survey to map the structure of five areas;" stage 2 consists of field reconnaissance work. For the three objectives, lower bounds are calculated as a function of exploration expenditures for each stage in order to facilitate the choice of an-optimal exploration budget. Nomograms are then presented which, based on the Kuhn-Tucker Conditions', enable the incremental allocation of airborne and reconnaissance effort among the five areas.

Jan 1, 1989

By A. D. Paul, Yoon R. H., C. I. Basilio

Considerable amounts of Fe3+ ions are released into solution when coal is exposed to 1-3 M acid solutions. These ions superficially oxidize the coal surface, and are reduced to Fe2+ ions. When provisions are made to generate the Fe3+ ions in solution, e.g., by inserting an anode whose potential is above the reversible potential for the Fe3+/Fe2+ couple, considerable amounts of mineral matter are liberated from the coal matrix. With many eastern U.S. bituminous coals, this mineral liberation is achieved selectively without significant breakage of the coal. It is believed that this process is induced by the osmotic pressure set-up in the crevices between the mineral matter and coal that are exposed to the solution. A theoretical model predicting the osmotic pressure is presented in this work, along with some results obtained with different coal samples.

Jan 1, 1992

By Kostas Fytas, Pierre Bousquet, Bill Evanelou

Acid mine drainage (AMD) is a serious environmental problem that preoccupies the Canadian Mining Industry. Considerable amounts of money are spent every year in an effort to prevent or reduce the acid mine drainage phenomenon. AMD occurs when sulphide minerals (ex. pyrite) contained in rock are exposed to air and water and subsequently oxidise to produce low pH water. This acid effluent has the potential to mobilise any heavy metals contained in the rock. Coating the sulphide minerals with silicates is a new promising technology to reduce AMD. Pynte is treated with a solution containing H2O2, sodium silicate and a buffering agent. H2O2 oxidises a small part of pyrite producing ferric iron (Fe3+) ions. These ions subsequently react with the silicate ions to produce ferric hydroxide-silica that precipitates on the pyrite surface producing a passive coating. This silicate coating can protect the grains of pyrite from oxidation. This paper presents a series of experiments that confirm that silicate coating can considerably reduce AMD.

Jan 1, 2000

The transfer of Langmuir-Blodgett (LB) monolayers of collector molecules to the surface of mineral crystals is an excellent method for the study of collector adsorption phenomena and is of particular significance in the understanding and development of improved flotation separations. The fatty acid/fluorite and amine/sylvite potation systems were investigated by the Fourier transform infrared/internal reflection spectroscopy (FT-IR/IRS) examination of transferred LB monolayers of collector molecules at the surfaces of the mineral crystals. The [ir]-A isotherm study of fatty acid and amine, typical anionic and cationic collectors, showed the different packing trends dependent upon the pH and/or type of subphase. This result clearly reflects the effect of pH on compound formation and dissociation of the collector molecules. Identification of the collector adsorption state and confirmation of the validity of the FT-IR/IRS adsorption density equation were included in this research effort. This allowed for a detailed discussion of collector adsorption phenomena. As a result of these experiments, it is possible to relate the hydrophobic character of a surface to the nature of the adsorbed collector structure and thus describe flotation behavior in greater detail. For example, it appears that in the case of oleate/ fluorite the equivalent of an LB monolayer can form spontaneously during adsorption from solution, and this structure is known as a self-assembled monolayer (SAM). Such a state is significantly more hydrophobic than the oleate structure which forms on the calcite surface at an equivalent adsorption density.

Jan 1, 1996

By A. G. Royle

Although these exhibit similar structures overall, there are more acute valuation problems in alluvials. Most of this description will therefore be about alluvials with comments on bedded vis-a- vis alluvial deposits where necessary. Although geological comments refer mainly to lateritic deposits the method of valuation described applies to all bedded deposits, e. g. coal, limestone, phosphate. In general, the more a deposit suffers alteration during or after its formation and the more the sampling process disturbs its material, the greater the difficulties of valuation. Emphasis is laid on structure, as in any kind of deposit valuation cannot proceed until its structures are understood. Not all the structures found in alluvials will occur in bedded deposits, of course.

Jan 1, 1982

By Byron C. Hardinge, E. R. Palowitch, Albert W. Deurbrouck, David J. Akers, Edward R. Torak

During 1983, 42.2% of the 686.0 (624.3 Mt) million tons of coal reported, 289.6 (263.5 Mt) million tons were mechanically cleaned, of which 107 (97.4 Mt) million tons were cleaned by dense media (magnetite and sand) processes.' The percentage of bituminous coal and lignite cleaned mechanically by dense medium processes increased from 7 to 38% between 1938 and 1983. The Electric Power Research Institute estimates that 150 million tons (137 Mt) of coal were cleaned by heavy-media processes in 1986, and that this number may increase to 265 million tons (241 Mt) by 1990.2 Dense medium separations include those coal preparation processes that clean raw coal by immersing it in a fluid having a density intermediate between clean coal and reject. As there is a general correlation between ash content and specific gravity, it is possible to achieve the required degree of removal of ash-forming impurities from a raw coal by regulating the specific gravity of the separating fluid. Dense medium processes generally offer the following advantages over other coal cleaning processes: • Ability to make sharp separations at any specific gravity within the range normally required even in the presence of high percentages of raw coal whose specific gravity is near the specific gravity of separation. • Ability to maintain a separating gravity that can be controlled within + 0.005 sp gr units. • Ability to handle a wide range of coal sizes. • Ability to change specific gravity of separation to meet varying market requirements. • Ability to handle fluctuations in feed, in terms of both quantity and quality. Unfortunately, dense medium processes can have the following disadvantages: • Relatively high capital costs caused primarily by the need for equipment to collect and recycle the medium. Relatively high operating costs caused primarily by operation of medium recycle equipment and loss of medium.

Jan 1, 1991

By R. B. Tippin

Great Salt Lake Minerals & Chemicals Corporation (GSL), a subsidiary of Gulf Resources & Chemical Corporation, is located on the east side of the Great Salt Lake, approximately 20 miles from Ogden, Utah. GSL processes brine from the north arm of the lake to produce potash, salt cake, salt and magnesium chloride brine. Potash fertilizer, in the form of K2SO4 is GSL's primary product. The GSL Sulfate of Potash Complex The GSL potash complex (depicted in Figure I) is divided into a solar evaporation pond system and the process plants. The solar,evaporation system consists of a 17,000-acre (68.8 Km2) ponding operation where the various salts deposit during the summer evaporation season, and a harvesting operation which recovers the deposits during the remainder of the year. The harvest is either preconcentrated in the flotation plant or processed directly in the chemical plant where sulfate of potash (SOP) is produced. The chemistry of the lake brine results in a solar deposit con¬taining primarily kainite (KCl-MgSO4.3H20), schoenite (K2SO4?MgSO4^ 6H2O), and halite (NaCI), with some carnallite (KCl.MgCl2.6H20) and epsomite (MgSO4.7H20). Other minor minerals may be deposited, depending upon the weather during the evaporation season. Each year, the solar deposit in the evaporation ponds will greatly depend upon the summer weather conditions, which have in the past proven to be quite unpredictable. Weather may alter both the quantity of the solar deposit and the composition of this deposit. During, a "short" evaporation season, the tonnage deposited decreases, but depending upon the short-term weather, the potash mineral content

Jan 1, 1977

By H. R. Bullis

Lupin is located on the shores of Contwoyto Lake at lat. 65° 48'N, Long. 111° 15'W and lies about 80 kilometers south of the Arctic Circle. Since start up in 1982 the mine has produced over 2.15 million ounces of gold from 6.66 million tonnes of ore grading 10.63 gm/tonne. Total remaining reserves at 1993 year end were 5.1 million tonnes at a grade of 9.11 gm/tonne (1.65 million ounces). This is sufficient for 7 -8 years at the present annual production rate of about 200,000 ounces. The Centre and West Zones of the deposit are open to depth. The deposit is in an Archean metaturbidite sequence of the Contwoyto Formation, which has been mapped as part of the Yellowknife Supergroup of supracrustal metasedimentary and metavolcanic rocks making up part of the Slave Geologic Province. These rocks have been subjected to regionar and contact metamorphism and to several phases of deformation. Six stages of Archean plutonism have been identified and all Archean rocks have been cut by Proterozoic diabase dyke swarms. Gold mineralization in the Lupin deposit is commonly fine grained and associated with pyrrhotite and arsenopyrite in amphibolitic banded iron formation. The gold-bearing portions of the host iron formations are characterized by the presence of multiple quartz veins and the pervasive replacement of grunerite by hornblende. In sparsely mineralized portions of the host iron formation, zoning of sulfides about quartz veins is clearly seen with the arsenopyrite halo being more restricted around the veins than the pyrrhotite halo. In well mineralized portions, quartz vein densities approach one vein per metre along strike. In these areas pyrrhotite distribution in the iron formation is more pervasive and the rock takes on the appearance of a banded sulphide rock.

Jan 1, 1995

By D. A. Elgillani

Oxidation potentials have been measured in the presence of various concentrations of cyanide, ferrocyanide, and ferricyanide and ethyl xanthate at various values of pH and related to flotation response. Eh-pH diagrams are constructed and show that the formation of surface ferric ferrocyanide is probably responsible for depression when cyanide is added. The influence of cyanide in the depression of pyrite with xanthates as collector has been the subject of many investigations (1,2,3,4,5,6), and from these studies several theories on the mechanism of depression have evolved. Wark and Cox (7) and Gaudin(8) have suggested that the depressing effect is due to a competition of cyanide ion with xanthate ion for the surface. Cook and his colleagues (9,10,11) have explained this phenomenon in terms of competition between hydrocyanic acid and xanthic acid. Sutherland (12) has shown that both of these theories describe accurately the relation between pH value and cyanide addition at constant collector addition but fail to describe the relationship, between pH value and the amount of collector required to cause flotation. Taggart(12) suggested that depression in these systems is due to the formation of a reaction product between ferric ion at the pyrite surface and ferrocyanide ion derived from solution. Majumdar(4,6) has attempted to prove this hypothesis by measuring the contact angles of pyrite in the presence of 25 mg/liter ethyl xanthate and different concentrations of potassium ferrocyanide and ferricyanide. In all cases the contact angles were quite high up to pH 10; these results indicate that pyrite should not be depressed by either potassium ferrocyanide or ferricyanide. In view of these facts, Majumdar has assumed that the compound Fe(CN)2 forms at the surface.

Jan 1, 1968

By R. C. Richardson

Barite Worldwide barite production for 1985 decreased 1.3%, while US barite production increased 1.4%, according to US Bureau of Mines statistics. The increase in US production is attributed to heavy demand for oil and gas drilling during the first quarter and an unrealized heavy expected demand in oil and gas markets for the last quarter. Nevada accounted for 82.1% of the 807 kt (890,000 st) of barite produced in the US last year, according to the Bureau. Other producing states were California, Georgia, Illinois, Missouri, Montana, Tennessee, and Washington. In 1985, the US imported 1.8 Mt (2 million st) of crude barite and 64 kt (71,000 st) of ground barite. China led the way with 43.3% of the total. Imports from India accounted for 21.6%; Morocco, 15.5%; and Thailand, 5.6%. The 1.8 Mt (2 million st) of crude barite imported is an 18.8% increase over 1984. Apparent consumption of barite for 1985 was about 2.6 Mt (2.9 million st), a 15.7% increase from 1984. Due to very low drilling rig activity during the last quarter of 1985, actual consumption is probably less as crude barite inventories at mines and plants increased. According to the Bureau, 90% of barite consumed in 1985 was for the oil and gas market. Paints, rubber, glass, and other chemical uses consumed the other 10%. With the price of oil falling dramatically early in 1986, the outlook for oil and gas drilling looks to be significantly lower than 1985. This lower demand for barite, coupled with the high year-end inventories, should lower both imports and domestic production. Significant lower prices on imported barite are expected, especially from China, Morocco, and India. This also could further lower US production of barite this year.

Jan 5, 1986

By Angela Binder, Oliver Langefeld

"The future of mining will be characterized not only by the application of modern technology, but also by the harmonization of economic, environmental and social issues. These areas set major future challenges which are complex and demand extensive knowledge. As an example, mining of highly complex orebodies for the supply of often critical raw materials, needs to consider technically demanding and cost-intensive extraction issues. The amount of tailings, which need to be stored, increases with the amount of ore mined. Therefore, the negative impact on environment and society increases. Hence mining becomes expensive with regard to all three aspects: economy, environment and society. In view of a sustainable mining practice this challenge should be used as an opportunity. The positive impact should be maximized for present and future generations. The objective is to create and use the mining openings in an optimum way related to sustainability. The approach of Blue Mining, which focuses on energy and ergonomics in the field of Sustainable Development, enhances the closure planning by recommending subsequent usage of such openings for energy storage. The approach fosters among others the implementation of the 7th Goal for Sustainable Development defined by the United Nations with the assurance of access to affordable, reliable, sustainable and modern energy for all. The usage of underground storage increases the stability of solar and water power usage, which are otherwise unreliable. Blue Mining embeds these issues in the main planning effort long before groundbreaking. This approach involves experience from past and current projects. This paper introduces the concept of Blue Mining with respect to post-mining utilization of a mine for energy storage. Methods and perspectives are presented with examples covering best-practices and lessons-learned."

Jan 1, 2017

By Thomas V. Mullen

Some 146 kt (4.69 billion oz) of gold have been mined throughout history. Of this, 70% has been mined in this century alone, with 17% produced from 1985 through 1996 (Fig. 1 and Table 1). Until the mid-19th century, placers were the chief source of gold. Advancements in mining, metallurgy and geological thinking have resulted in underground mining (first of veins plus stockworks and later of Rand-type deposits) becoming the principal source of gold. With the demise of the South African deposits and the move towards lower grade ores, the primary source of gold will be from disseminated deposits exploited through large, open-pit mines. For the past 200 years, there has been a fairly constant ratio of about 31 g (1 oz) of gold to each person alive. If this ratio is to be maintained, annual gold production will have to rise from about 2.3 kt/a (73.9 million oz/year) to more than 3.1 kt/a (99.7 million oz/year) by the year 2000. To effect this increase, an unforeseen breakthrough in exploration or metallurgy is needed. Barring this, there will be pressure for an increase in the price of gold. This article traces the historical production of gold from 4000 B.C. - the earliest record of gold mining - to today and relates this 6,000-year record to advances in geological thinking, mining engineering and extractive metallurgy. It also proposes that man's thirst for gold, reflected in the price he will pay for gold, and his ability to find, mine and refine gold have combined to effect an equilibrium based loosely on the historical ratio of 31 g (1 oz) of cumulative gold production per each man or woman alive.

Jan 1, 1998