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By G. J. Joy, J. P. Rider

Technical advances in longwall mining over the last several years have resulted in much larger and faster shearers that have the capability of mining at speeds over 30 m/min (100 fpm). This has resulted in a substantial increase in the amount of dust that is generated at the shearer and during shield advances. Meanwhile, increased underground coal production has put a greater demand on longwall dust control systems as some operators have had difficulty maintaining consistent compliance with federal dust standards. To address this need, the U.S. National Institute for Occupational Safety and Health (NIOSH) is investigating the effectiveness of a water spray manifold mounted on the tailgate end of the shearer body. The sprays are oriented parallel to the tailgate ranging arm, and these sprays create a water curtain confining the dust plume near the face, preventing the dust from drifting into the walkway. This redirection of dust provides a clean air envelope for the tailgate shearer operator and jacksetters working near the tailgate drum. Three different tailgate spray manifold designs were tested and evaluated at the Office of Mine Safety and Health Research (OMSHR) Pittsburgh Longwall Test Facility. Manifolds were equipped with hollow cone or flat fan water spray nozzles and evaluated at three face air velocities — 152, 213 and 274 m/min (500, 700 and 900 fpm)— and at water pressures of 689, 1,034 and 1,379 kPa (100, 150 and 200 psi). Reductions in dust concentrations were observed at six face sampling locations for all the tailgate manifold systems at each of the tested spray pressures and face velocities. Average reduction efficiencies of at least 90 percent were seen at the three sampling locations closest to the shearer for all three manifold systems at nozzle spray pressures greater than 689 kPa (100 psi). Based on results from the laboratory tests showing reductions in dust concentrations at sampling locations downwind of the shearer, a spray manifold was fabricated and evaluated at an underground operation.

Jan 1, 2016

By J. Perlacia, J. M. Eguiluz

"INTRODUCTION The Bulk Handling Technology has suffered an important development in the recent years, allowing the use of conveyor belts in the most important and critical applications. As a consequence of this, the reliability and lasting performance of the conveyor belt components is becoming more and more significant, thus the implementation of preventive maintenance programs is a must. The rollers are one of the consumables in the conveyor belts, which have to be changed once arrived to the end of life. The actual ways of detecting this moment always require intensive use of labour and they are not very accurate. Indeed, if the rollers get broken before replacement, the consequences could be very important, generating additional costs and operational losses. The R&D Department of ULMA Conveyor Components, has been working since early 2012 on the development of Monitored Rollers along with a Management Software to provide users the capacity to Manage and Monitor the rollers from its desk, getting continuous online information on the internal temperature of the bearings, on the working status of the rollers as well as the identification of the rollers close to their end of life so that they could be changed during the next maintenance stop of the conveyor belt. In short, a system of Preventive Maintenance for Conveyor Belt Rollers BACKGROUND AND CURRENT STATE The malfunction of a single roller in certain conveyor belts can suppose the standstill of the whole installation until its replacement, due to the risk of greater and more expensive failures like the rip of the belt. In the case of a bulk handling installation where a continuous supply of material is necessary, a bare stop of one hour could entail huge economical losses. What’s more, many conveyor belts are several kilometers length or the access to some parts of them is very complicated. Due to these difficulties the inspection and maintenance operations can become expensive and hard going, with staff going over the whole area checking the correct condition of the conveyor and rollers, which means a dangerous activity. In addition, it’s quite common to find rollers working in very harsh conditions, completely exposed to the elements or working in corrosive closed environments like underground mines. These tough working conditions together with the very demanding features of Bulk Handling sector (high loads, speed, dangerous materials etc.) can bring the unexpected failure of a roller, even being designed to support them. Thus, to have the working conditions of the rollers real time is clearly required, in order to achieve an actual predictive maintenance of the system and avoid fatal failures. Nowadays the most common procedures to identify a broken roller is to hear how it sounds or use thermo-graphic cameras to measure their internal temperature, both of them implying workers inspecting the whole length of the conveyor while the conveyor is running. This means intense use of workmanship and operational safety level reduction."

Jan 1, 2018

By Van E. Housman, Stephan Hoffman

Introduction Based upon the 1980 Bevill Amendment to the Resource Conservation and Recovery Act (RCRA), a 1986 Regulatory Determination decision, and subsequent rulemakings, the Environmental Protection Agency (EPA) exempted all extraction and beneficiation wastes and twenty mineral processing wastes from regulation under RCRA Subtitle C (hazardous waste) regulations. These twenty mineral processing waste streams were studied in a 1990 Mineral Processing Report to Congress. For purposes of regulatory classification, EPA made special distinctions between extraction/beneficiation and mineral processing. Wastes determined by EPA to be from the extraction/beneficiation of ores and minerals retain the exemption, while wastes found to be mineral processing, except for the “special" twenty mineral processing wastes, fall within RCRA Subtitle C jurisdiction. For those wastes that are subject to RCRA Subtitle C, § 3004(m) of RCRA requires EPA to set levels or methods of treatment, of any, which would substantially diminish the toxicity of the waste or substantially reduce the likelihood of migration of hazardous constituents from the waste so that short- term and long-term threats to human health and the environment are minimized. These treatment standards are developed by EPA under the Land Disposal Restrictions (LDR) program. Under § 3004(g) (4) of RCRA, EPA is required to promulgate treatment standards for any waste that is newly identified or listed as hazardous. As part of the settlement agreement in Environmental Defense Fund (EDF) v. Reilly and Chemical Waste Management, Inc. v. EPA (1992), EPA has agreed to propose a rule by June 30, 1995 and promulgate a final rule by June 30, 1996. This rule is commonly referred to as the "Phase IV" LDR rule and will address newly identified mineral processing wastes. Other wastes that will be addressed in this rule include newly listed dyes and pigments and wood preserving wastes. Therefore, in the Phase IV rule EPA will develop treatment standards for all mineral processing wastes that have lost their Bevill exclusion. EPA is currently collecting information on the waste characterization, treatment alternatives, and disposal capacity data currently available on these wastes. EPA is also soliciting data and information on opportunities for

Jan 1, 1995

By L. Adler

INTRODUCTION The purpose of this paper is to describe in engineering terms the singular and basic operational kinematics of all excavating and bulk handling equipment. The safe and efficient use of equipment will be fostered by enabling the engineer to conceptually duplicate the operators' "tasks" in directing and controlling it. A simple graphical and notational scheme will be introduced to define the essential gross repetitive motions. The significance of this effort includes filling a vital analytical gap at the work face, and in establishing direct communications between the engineer and equipment operator. Since all types and sizes of earth- moving equipment are covered, a major concern has been to integrate equipment specialties into d single encompassing discipline. Equipment types are closely related to the working conditions, and their selection and evaluation are also considered. The extension to human factors analysis is natural and predictable. Since human [actors are involved, the operational analysis can also be considered a catch-all for many subtle vagaries. BACKGROUND Symbolic modelling linked to a notational system will be developed and intensively used. This constitutes the "language of science," providing a shorthand method which gives immediate recognition, is fluent, explicit, reinforcing, unequivocal and provides limitless associations. Many examples of symbolic modelling exist in chemistry, physics, the military, engineering sciences and it is a major tool in mapping. Its use is so ubiquitous that it often goes unnoticed. On the other hand it must be realized that something is lost in simplifying and idealizing what is an extraordinarily complex occurrence. The components describing the basic operational kinematics of equipment include: (1) the vehicular motions as a rigid body and (2) the job-end motions focussing on excavating (Adler, 1985). These provide all of the components in the load-haul-dump sequence (L-H-D) , and will yield three dimensional expressions. Complex patterns can also be assembled from these simple elements. An existing equipment designation employed in earthmoving will be integrated into this approach (Carson, 1961). Along with the basic motions, corresponding working conditions will be noted.

Jan 1, 1986

By C. Williard

Computer based mine monitoring and control systems represent a relatively new technology to be applied in the U.S. mining industry. While computer assisted engineering, design, and planning have been accepted as tools for specific technical and engineering jobs within the industry, integrating mine-wide monitoring and control systems into mining operations has been slow. This paper reviews the state of the art of mine monitoring and control systems and provides insights into future trends and developments.

Jan 1, 1988

"Longwall shearers are widely employed in underground coal mines. The reliability of such machine has significant importance for successful mining operations. This paper aims at studying reliability of a longwall shearer using failure data recorded for a year. Data was pre-processed, sorted and selected for analysis. Selected data is then examined using statistical models. Distribution fitting of time-between-failure (TBF) and time-to-repair (TTR) are accomplished using three different models. Goodness-of-fit criteria is used to ascertain the best fitting model. Reliability in terms of mean-time-between-failure (MTBF), and mean-time-to-repair (MTTR) are calculated using the model which best represents the failure data. Exponential distribution best represents the time between failure and lognormal distribution the time to repair data. A well-known risk management technique Failure Mode Effect and Criticality Analysis is used to evaluate the critical breakdowns. Critical system/parts, experiencing regular failures is delineated based on this analysis. INTRODUCTION Mining is a capital intensive process, and huge monetary investment is required to develop and operate a mining project. Heavy and expensive equipment’s are employed in development and operation of these projects. In order to ensure timely completion of set milestones, it is mandatory that equipment’s perform their required task productively. Delays are not unusual owing to breakdown of these equipment’s. Breakdown or failure experienced by any of the equipment pose heavy financial burden. Moreover, frequent times, companies have to employ and dedicate additional resources to make up for such delays. Delays in project is not only detrimental to company’s image in market, but it also interrupts customer commitments. Mines having history of not fulfilling their promise usually get lower commodity price. Penalties are also imposed on the companies defaulting its obligations. Especially, in today’s world where competition among the companies are growing, success means keeping up the commitments in a timely manner. Heavy machinery and equipment are instrumental in success of any project. These machinery and equipment’s have to reliable in a sense that they can perform the set task in given time period. Reliability of these equipment plays a pivotal role in success of any project. The reliability analysis of mining equipment has long history. Many researchers have applied different statistical models for analyzing the reliability of mining machines (Samanta, Sarkar [1]. Kumar and Klefsjö [2] demonstrated the use of the power law process model for reliability assessments of repairable mining machines. Barabady and Kumar [3] performed the reliability analysis from failure data of the crushing plants."

Jan 1, 2018

By James J. Brady, Kenneth L. Faught, Chadi El Mohtar, Chaoshi Hu

"During construction of a 9.5-ft. diameter sanitary sewer tunnel, the City of Edmonton encountered a large pocket of flowing sand that flooded their TBM and caused significant surface subsidence, stopping further tunneling by the TBM through this zone. A unique collaborative effort ensued between the authors representing the city, consulting engineers and academic researchers to develop the optimal strategy for grouting the problematic soils. The site has a layer of very find sand between 20 and 30 ft. in depth with fines contents ranging from 5% to more than 40%. The collaboration extended from requesting additional site investigation efforts to shipping samples to the UT-Austin laboratories for grout testing plus ground and grouting characterization tests resulting in field recommendations for a full scale ground improvement program. New research information on the grouting of fine sands along with a collaborative framework for the design of in-situ grouting projects are the key topics presented. INTRODUCTION Encountering a large unexpected pocket of flowing sand with an open-faced TBM while excavating a tunnel below the groundwater table is never a good thing. This was certainly true for the City of Edmonton when one of their Lovat TBM’s became inundated by flowing sand while excavating the 9.5-ft. diameter Millwoods Double Barrel Replacement Tunnel in September 2013. However, since the City of Edmonton self-performed this work, a rare situation existed where the site could be investigated objectively, without the prejudice of contending parties selectively influencing how information was gathered and presented, to accurately examine site conditions with a goal of identifying the best remediation measures."

Jan 1, 2016

By Byron R. Berger

Epithermal Ag-Au deposits form at low to moderate temperatures in near-surface environments. Historically, these deposits have been the source of high-grade ores. Increases in the market prices for gold and silver make lower-grade ores economically viable when available in large tonnages. Both the high-grade and bulk-tonnage ores are a consequence of the same processes, and general models of epithermal systems can be useful in the search for new precious-metal resources. A detailed study of deposits at Round Mountain, Nevada; Balei, Russia; Creede, Colorado; Guanajuato, Mexico; and Chanarcillo, Chile, indicates that the hydrodynamics of the fluid systems as determined by fracture geometries, the permeability, and composition of the host rocks are the key factors in the creation of both high-grade and bulk-tonnage epithermal deposits. End-member models that explain the range of observed deposit characteristics are: (1) the hot-springs deposition model; (2) the stacked-cell convection model (where mineral deposition occurs laterally along the interface of two partially separated fluid reservoirs); and, (3) the closed-cell convection model (where deposition occurs in vertical zones due to the relatively unimpeded vertical flow of hydrothermal fluids). Boiling and fluid mixing appear to be agents of precious-metal deposition with the self-sealing of the hydrothermal system being an important adjunct to boiling. Imaginative application of model concepts in exploration has led and can lead to the discovery of new high-grade and/or bulk-tonnage precious-metal deposits.

Jan 1, 1982

By McCarthy. Richard E.

The prime movers of the Centralia Project, the surface coal mine and the power plant, private utilities are very aware of public attitudes. They have established and maintain the reputation for leadership in public service and are genuinely concerned that this project initiate the pro-grams and design the hardware to answer the question :What will be the impact of the mine and the plant on the physical environment, i.e., the air, soil and the water." So in the beginning almost as soon as the decision had been made to go ahead with the project, officials of the two private utilities, Washington Water Power and Pacific Power & Light went on record and publicly stated time and again that the overall approach of the Operators would be to do all that was reasonably possible to safeguard the environment. This attitude became part of the thinking of the project planners, part of the design of the power plant and part of the plan for the surface mine. The coal to be mined is from the Skookumchuck formation. The formation is Late Eocene and is made up of poorly consolidated marine and non-marine deposits. The major overburden removal equipment is a bucket-wheel excavator -conveyor system and a 56 yard dragline. Mining of the coal will be done with truck and shovel. The coal is processed, washed and crushed to 1 ¼ " for delivery to the power plant. The muddy water created by the washing process is chemically treated and the solids removed by a thickener-vacuum filter system.

Jan 1, 1971

By T. Hayes

Track-type tractors remain one of the most cost-efficient stripping tools available to coal miners. Whether they are "sweetening up" a dragline operation with pre-benching or serving as the primary stripping tool, dozers can play an important role in driving down mining costs. This paper reviews the application zone of track-type tractors. In addition, it provides tips on site set-up, equipping of tractors, and machine operation which the audience can take home and apply.

Jan 1, 1996

By A. L. Frank, Benton

INTRODUCTION The selective sensitivity of plastic nuclear track detectors (PNTD's) to low energy 4He particles in an environment which also contains gamma and beta radiations has made these detectors prime candidates for the dosimetric measurement of the concentrations of radon and its daughter products in mine air. Their passive, integrating mode of measurement, small size, low weight and inexpensiveness are attractive characteristics for large scale personnel dosimetry. The detectors can be used in either active or passive dosimeters. In active devices, the PNTD is placed in close proximity to a sampling filter. The filter collects, from a calibrated air flow, all the daughter nuclei which are in suspension. As the daughter nuclei pass through the decay chain, through 214Po, a fraction of the 4He particles emitted are registered as latent tracks in the plastic. In passive devices, the PNTD is placed in direct contact with the ambient air containing the radio-nuclei concentrations to be determined. The active dosimeters have the advantage of excellent sensitivity, and the measured track densities yield very close approximations to accumulated Working Level (WL)** exposures. They have the disadvantage that the simplicity of the passive PNTD is lost, since a battery-driven constant flow-rate air pump is a necessity. The passive dosimeters are simple in construction and use, but they have the disadvantage that WL exposures are not directly measured and certain assumptions concerning radon and daughter equilibrium conditions must be made in determining WL exposures from the measured track densities. Also the sensitivities, in track densities per Working Level Hour (WLH) exposure, are much less than for active dosimeters. Dosimeters of both types have been investigated. Passive devices have been tested extensively both in the laboratory and in mines. Active devices have been laboratory tested. In our earlier measurements, cellulose nitrate plastic detectors were used exclusively, since this material had the highest sensitivity of the PNTD's then in use. When the properties of CR-39 plastic were discovered (Cartwright, 1978; Cassou and Benton, 1978), this material was used, where possible, to take advantage of its superior sensitivity. The results of our earlier work have previously been published (Frank and Benton, 1977). * Research sponsored by the Bureau of Mines, U.S. Department of Interior, under Contract No. JO-188003. ** A Working Level is defined as any combination of the short-lived radon daughters containing 1.3 x 105 MeV of potential 4He-particle energy per liter of ambient air. PASSIVE DOSIMETRY In the earliest testing of PNTD's for passive WL dosimetry, a single strip of cellulose nitrate plastic was used to determine the total cumulative 4He-particle activity in the air of simulated uranium mine and uranium mine environments (Rock, 1968; Rock [et al], 1969; White, 1969). The measurements yielded a close relationship between track densities and WL exposures in a controlled, static environment, but poor accuracy in the active mine tests. It was assumed that equilibrium differences contributed largely to the variations found. The response of PNTD's to airborne 4He-particle emitters, derived by Lovett (1969), demonstrated that detectors such as cellulose nitrate, which has a sensitivity cutoff at 4He-particle energies below the emission energies of radon and its daughters, are equally sensitive to the activity concentrations of radon, 218po(RaA) and 214Po(RaC'). Since radon does not contribute to WL as it is defined, and since, under normal ventilated uranium mine conditions, the radon activity constitutes about 40% to 70% of the total 4He-particle activity, the WL exposures calculated from measured track densities are very sensitive to the particular radon daughter equilibrium conditions. Also, the detector does not weight the individual daughter activities in proportion to their importance to WL. The equation for WL is WL = 0.00103C2 + 0.00507C3 + 0.00373C4 (1) where C2, C3 and C4 are the activity concentrations of RaA, RaB and RaC-C', respectively, in pCi/[L]. The detector leaves C3 unmeasured and weights C2 and C4, equally. [This problem has been approached by Domanski et al (1975, 1979), for some non-uranium mines, by measuring equilibrium conditions throughout the mines to determine a mean value for A, the inverse of the Working Level Ratio (WLR = 100 WL where C1 is the activity of radon-222 in pCi/[L].) The distribution of values allowed Domanski to determine probable errors in calculating WL exposures from track densities. However, measurements of equilibrium conditions in U.S. uranium mines (Breslin et al, 1969; Holub and Droullard, 1978) indicate that this method would not be accurate enough for uranium miner personal dosimetry.] A two-element dosimeter was designed at our laboratory to compensate for equilibrium variations. The first element is a radon detector; the second is a detector for the total 4He-particle activity in the ambient air, just as in the single element dosimeters cited above. The addition of the radon detector allows the equilibrium conditions for the individual nuclei to be determined, given certain assumptions concerning the interrelationships between the nuclei concentrations in mine air. The two detectors and the problems involved in calculating WL exposures from their measurements are discussed below.

Jan 1, 1981

By D. Diekman

Perlite is not a trade name but a generic term for naturally occurring siliceous volcanic rock. A distinguishing feature which sets perlite apart from other volcanic glasses is that when heated to a suitable point in its softening range, it expands 5 to 20 times its original volume. This expansion is due to the presence of 2% to 6% combined water in the crude perlite rock. When quickly heated above 1600°F (871°C) crude perlite pops in a manner similar to popcorn. The combined water vaporizes and creates countless tiny bubbles in the heat softened glassy particles. It is these tiny glass sealed bubbles which account for the amazing lightweight and other exceptional physical properties of expanded perlite. The bulk densities of the expanded perlite generally range from 3 pounds per cubic foot (48 Kg M3) to 10 pounds per cubic foot (160 Kg H3).

Jan 1, 1985

By Lisa Shevenell

Three pits at the Getchell Mine contained water during a hiatus in mining activity (1968-1983). For this period, expected concentrations of As, C1, SO4 and TDS resulting solely 16om evaporative concentration were computed. Computed values are 1.6 to 2.3 times greater than those measured in local groundwaters. However, computed values fix As, SO4 and TDS are lower than measured values in the pit lakes. In some cases, the computed values are only 8% of the measured pit lake values, indicating a major control on water quality via water-rock interactions. In contrast, computed C1 values exceed measured pit lake concentrations.

Jan 1, 2000

By S. Subramanian, K. A. Natarajan, D. N. Sathyanarayana

FTIR spectroscopy is used to study the ad¬sorption of an oxidized starch on hematite, corundum, and quart: substrates. The difference spectrum of the adsorbed starch on hematite indicates surface reactions involving -CH2OH and -COH groups and shows striking similarities with that of the ferric-starch system, suggesting chemical interaction between the iron of hematite and the starch adsorbate. The IR spectra of starch adsorbed on corundum and quart: show no evidence of chemical interaction, although hydrogen bonding is apparent. The extent of adsorption of starch on hematite. corundum, and quartz decreases along the series. The evidence for chemical interaction of starch with hematite is further obtained by the X-ray photoelectron spectra of starch adsorbed on hematite, showing noticeable decrease in peak positions of O(Is) and C(Is) of free starch. The Mössbauer spectrum of hematite with stanch adsorbed on it complements these findings.

Jan 1, 1990

By Y. Topkaya, R. E. Johnson, B. R. Palmer, Bruce E. Kurtz, Anatoli Omelian, John I. Choi

This paper relates to hydrometallurgical studies on the recovery of soluble aluminum values from aluminum-bearing ores, i.e., Georgia clays. At least 50% of the soluble alumina values were recovered by leaching the calcined clays from aqueous solutions, comprising simultaneously contacting a stream containing an effective amount of a reducing agent such as sulfur dioxide and a stream containing an effective amount of an oxidizing agent such as chlorine gas for a time sufficient to dissolve alumina. The recovery of alumina from this aqueous slurry of the calcined clay by leaching with sulfur dioxide and chlorine gas showed much better results than that by leaching with concentrated sulfuric acid and/or concentrated hydrochloric acid at 100O C. The leaching reactions between the aqueous slurry of the calcined clay, chlorine gas, and sulfur dioxide were strong exothermic reactions for several hours, requiring no external heating.

Jan 1, 1993

Energy Developments Ltd. (EDL) has developed power plants at two Australian coal mines that featuring 94 gas-fueled Caterpillar G3516 engine/generator sets. They will convert to electricity 145 kt/a (160,000 stpy) of coal-seam methane gas for sale to a local utility. The $100-million project will cut the sites' methane emissions in half, provide a low-cost energy source and offset mine operating costs. The project began in May 1995. It is located at the Appin and Tower longwall underground mines, 80 km (50 miles) south of Sydney in New South Wales. The installation is one of the first to capture coal-seam gas from mine ventilation air and gas drainage systems. Coal- seam gas contains 40% to 60% methane, which fluctuates constantly. The system is expected to convert 578,000 m3/d (20.4 million cu ft/d) of coal-seam gas to 94 MW. It will also reduce greenhouse gas emissions by 3.5 Mt/a (3.8 million stpy) of CO, equivalent emissions. The Appin and Tower mines each produce 2 Mtla (2.2 million stpy) of clean coking coal. They operate around the clock with about 400 workers per site. The mines are owned by BHP Steel, Collieries Division, which will share the revenues from energy sales. The Appin Power Partnership consists of EDL and Lend Lease Development Corp.

Jan 1, 1997

By J. G. Pippenger

The Coteau Properties Company's Freedom Mine is a surface lignite mining operation located near Beulah, North Dakota. As part of the mining process, Coteau removes and replaces thin layers of suitable plant growth material (SPGM) generally ranging in thickness between one and five feet. Historically, tractor-scrapers completed this work; however, rising tractor-scraper costs and increasing haulage distances sent Coteau in search of a lower cost method resulting in the acquisition of a backhoe/truck fleet in 1995.

Jan 1, 1997

By B. Ceccarelli

Many public domain programs useful in mining engineering, e.g., MULSIM, DZTAB, and EXPAREA, require tedious data input and generate pages and pages of printed output. To eliminate the tedium and to enhance the output, ETI U.S., Inc. developed GEM, Graphics for Engineering and Mining, a collection of application programs and underlying interface tools for VAX/VMS computers. This paper presents an example of how an application program in GEM enhances a specific public domain program. It describes how GEM provides automated graphics assisted input and output. The paper describes how this program uses the GEM User Interface: the 3D GKS device independent graphics, server and drivers, various mining, mathematical and statistical algorithms, the means of handling graphics, data including IGES, and the foreign language interface.

Jan 1, 1992

By F. M. Doyle, Jiang Tao, Xu Shi, Chen Jin, E. Peters

Tafel curve technique and leaching tests have been applied to study the kinetics of gold leaching with thiosulfate. Results show that cupric ions and ammonia play the part of catalysts in the leaching of gold with thiosulfate. The activation energy of gold dissolution is calculated as 27.99 KJ/mol in the absence of both cupric ions and ammonia. However, the energy is reduced to 15.54 KJ/mol in a solution of 0.01 mol/L Cu (NH3)2 4* and 0. 5moVL total ammonia. The reaction order of Cu (NH,) g is one in the range of 0.001~0.1mol/L. These results support the electrochemical-catalytic mechanism pro- posed by the authors and explains the behavior of cupric ion and ammonia (Jiang Tao, et al., 1993)

Jan 1, 1993

The mining industry is one of the three pillars of the Namibian economic development, besides tourism and the fishing industry. Generating 20 % of the GDP and more than 50 % of the export income, half of this amount derives from the diamond mining industry. In 2008, the annual production of 2.2 mio carat achieved an income higher than 1.44 billion Namibian Dollars (more than 750 mio Euro). After the global recession in early 2009, which also caused a significant downcrease in production to only 0.93 mio Carat, the diamond mining industry easily restored itself and the production figures for 2010 are expected to be even higher than those achieved in 2008. Compared to other diamond producing countries, Namibia is mainly producing diamonds of highest quality (jewellery quality), with less than 10 % of the mined diamonds not falling into this category. This high quality stands also for the worldwide highest prize achieved per carat. With 370 $US per carat it is more than four times higher than that of the average South African stone. In 1908 the finding of the first diamonds in the Namib desert close to the coastal town of Lüderitz was reported by a Mr Stauch, railway inspector for the then German colonial railway company. This event immediately triggered a Diamond Rush and subsequently the set-up of the restricted diamond mining area ?Sperrgebiet? through the German colonial administration. In 1913, only five years after the first mining operations had started, the steadily increasing production allowed for more than 20 % of the diamond production worldwide. After the First World War, the new South African government concentrated all mining activities in one organization, CDM (Consolidated Diamond Mines of South West Africa) which in following decades conducted an extensive and detailed exploration of the whole Sperrgebiet and started numerous new diamond mining operations.

Jan 1, 2011