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P. W. SHIMER, Easton, Pa. (written discussion*).-When lump calcium cyanamid is immersed in the melt of mixed chlorides of the alkalies and alkaline earths in the manner described in the paper, the amount of sodium cyanide formed in the melt, as shown by numerous analyses, is but a small fraction of that formed by the reaction referred to by Mr. Johnson. The case-hardening effects in my process are, however, at least as good as when the common cyanide baths are used. Moreover, when compared with the cyanide baths, the gases evolved in the new process are harmless, consisting of nitrogen, carbon monoxide (which burns to carbon dioxide on the surface of the melt), and occasionally a little carbon dioxide. These gases are not irritating or poisonous, whereas the vapors arising from cyanide baths are both irritating and poisonous. The complex chemical reactions that take place in and on the surface of the melt are being investigated by the writer, who hopes, in due time, to communicate the results of his work.

Jan 7, 1919

By Frank Firmstone

IT is proposed to consider here only comparisons made between results obtained when the materials employed are precisely the same, two furnaces at the same works for example, or the same furnace under different conditions as respects temperature of blast, method of charging, etc. With this limitation, the most important point in the comparison is the amount of fuel consumed per ton of iron. This, in fact, is the only item in the prime cost of the iron which can properly be said to vary in consequence of changes in the furnace process ; for of the other principal items, the ore used per ton of iron, and also the amount of fluxing material, will depend on its richness, which, under the assumed conditions, will be practically invariable when taken over any considerable period; the labor cost also, from its nature, should be very nearly constant when estimated on the ton of iron. Moreover, as it consists principally in handling and moving material, it is greatly affected by circumstances quite independent of

Jan 1, 1876

There is considerable variability in the level of detail incorporated in prefeasibility studies relating to mining developments. Hence, when undertaking a review or audit, it is critical to attempt to ascertain at an early juncture precisely who has compiled the various facets of the study, for what purpose it was intended and the terms of reference given to the authors. Likewise, when commissioned to undertake an audit it is preferable to have proper terms of reference and to be aware of the purpose to which the audit will be put.These factors will influence the degree of detail an auditor would expect to find in the study and consequently, the degree of effort/time required for the audit process. In most instances audits do not imply recalculation of the entire study or modifying it in anyway, but involve an overall assessment of the methodology used, combined with spot checking of detail. One of the most difficult aspects is to determine a realistic order of accuracy for the overall study when the accuracy of the individual components may differ markedly.

Jan 1, 1990

By W. F. Pruden

On June 30, 1960, ground was broken for the construction of the facilities to mine, concentrate, and agglomerate the iron ores of the Atlantic City, Wyo., area which has become known as the "Atlantic City Project." This was a historic occasion for Columbia-Geneva Steel Division of United States Steel Corp. When completed, the installation will be the first integrated iron ore beneficiation plant west of the Mississippi River producing an agglomerated product. This Project, named for a nearby ghost mining town, is located in central Wyoming on the south-east flank of the Wind River Mountains. It is 16 miles north of the South Pass, where the early pioneers who followed the Mormon and Oregon Trails crossed the Continental Divide. White men first penetrated into this area in October, 1812, when Robert Stuart Party brought the returning Astorians through South Pass on route to St. Louis from the Columbia River area. Further interest in the area developed when gold was discovered in the sands of Rock Creek and the towns of Atlantic City and South Pass City were founded.

Jan 5, 1961

By Martha Caudill

When planning for the required amount of storage capacity at a proposed open-pit coal mine or determining when additional storage capacity should be added to an existing operation, the decision must be based on a breakeven- analysis relating the discounted cost of capital for storage capacity to the marginal costs incurred for additional crew call-outs on weekends and demurrage charges. The model developed in this paper uses simulation techniques applied to two coal mines in the Powder-River Basin to determine how much storage capacity is needed and when it is needed. The paper also generalizes the simulation model so that it can be applied to any type of open-pit mining operation. Two important results of the model are (1) all of the mines in the Powder River Basin have excessive amounts of storage capacity, and (2) management is provided with estimates of the total number of hours that crews will have to work on the weekends as annual tonnage increases, and the levels of demurrage costs incurred.

Jan 1, 1986

To reduce the possibility of injury to operators and damage to equipment caused by collision of mining vehicles during coal loading. Approach An energy-absorbing bumper was developed and tested underground on a continuous miner. How It Works The bumper, a long box-like weldment backed by five energy absorbers, is attached to a continuous mining machine by a hinge behind the cab. See Figure 1. When a shuttle car collides with the bumper, or when it is otherwise struck, the energy absorbers are compressed. This absorbs and dissipates part of the kinetic energy of the colliding vehicle, thereby reducing or eliminating its destructive effects. Each energy absorber consists of two chambers separated by a freely-moving piston. One chamber (Figure 2) contains hydraulic fluid. The second chamber contains a gas. When a collision causes the absorber to compress, the hydraulic fluid in the first chamber is forced past a metering pin and through an orifice. The hydraulic fluid then pushes against the piston, compressing the gas in the second chamber.

Jan 1, 1978

By D. Harris, M. Osterberg

This paper examines the economics of acquiring mineral exploration rights by royalty-rate bidding when the royalty basis does not provide for full cost recovery. Bidding takes place prior to exploration and the documentation of actual tonnage and grade. Consequently, it increases considerably the risk to exploration capital when the fraction of cost recovered is small and the product price exhibits large fluctuations. Price and grade risk are demonstrated on a 360-Mt (400-million-st) porphyry copper deposit by Monte Carlo simulation of discounted-cash-flow analysis. Copper price is modeled as a stochastic price process, and costs are based on US Bureau of Mines cost models. When both grade and price risk are considered, the probability for a negative NPV is 0.54, given a royalty rate of 5% applied to a basis that allows the recovery of costs up to 50% of product price. Investment risk could be considerably reduced by defining the royalty basis to allow greater cost recovery. Although such a basis would require society to share in the risk, society would benefit from greater resource development.

Jan 1, 2000

By D. Seke, E. Katsande, R. Khumalo, K. Seerane

Palabora Mining Company (PMC) processes a multi-component ore body using a circuit consisting of two AG mills in parallel, closed with vibrating double deck screens and hydrocyclones. The bottom screen undersize feeds the hydrocyclones, but the screen oversize products can be treated in a variety of ways. The top deck screen pebbles can be crushed and then combined with the bottom deck oversize and recycled to the AG mill. Alternatively both the top and bottom deck screen oversize can by-pass the recycle crusher and be recycled directly to the mill. A full tap-off is a configuration when both the top and bottom deck screen oversize streams are stockpiled. The other configuration is when the bottom deck screen oversize is recycled to the mill while the top deck screen oversize is stockpiled - termed partial tap-off. This article reports the findings from the surveys performed to evaluate the performance of the PMC auto mill circuit when operated under the four different configurations discussed. Ore characterisation tests were performed to assess the deportment of the key ore components for the different configuration.

Jan 1, 2012

By M. T. Holroyd

Digital computer applications to minerals exploration remained largely an experimental alternative to manual techniques until well into the 1960's. Due to the high cost of computer time, and the lack of digital data and appropriate software, the most favoured applications in the early days were computationally intense tasks - those which produced the most results with the least demands for programing and data input, e.g. forward modeling. When large digitisers and plotters became affordable, the computer took over simple labour intensive tasks such as data transcription, and when software caught up, more complex tasks such as contouring. Digital data acquisition systems and superminicomputers made total computerisation of geophysical compilation and cartography possible and affordable. Applications continued to develop into areas of much greater logical complexity. Software, the new labour intensive process, still lagged behind. The microcomputer made computer applications potentially available everywhere to everyone. Desk-top micros as powerful as the minis of ten years ago can take on any geophysical exploration task currently done by computer - when the software becomes available.

Jan 1, 1989

By Quanzhong Gu

Stability of a pre-exnacted recovery room plays a vital role when longwall face approaches and during a longwall face move. In an attempt to extend the application of pumpable cribs into recovery room support and to limit roof bolt installation when a longwall face approaches the recovery room, yieldable and cuttable pumpable cribs (YCPC) were employed in the recovery room at the northern West Virginia mine. The YCPC consists of two layers of materials with different strengths. This allows considerable deformation from the floor and/or roof by sacrificing the soft layer while maintaining relatively high load capacity under mining¬induced front abutment loads. The thickness and stiffness of the soft layer, installation and quality control are the key factors when using the Yieldable and Cuttable Pumpable Crib to stabilize longwall recovery room- Underground observation and monitoring results show that the Yieldable and Cuttable Pumpable Crib is a viable solution to insure stability of the recovery room and can save at least two days for a longwall face move at the mine.

Jan 1, 2004

By Bill M. Stewart

The Bureau of Mines conducted laboratory tests to determine the effects on the physical properties of coarse coal waste of adding large amounts of fine coal waste. Maximum laboratory dry density, optimum moisture content, shear strength, and permeability tests were conducted on samples that contained 18 to 60 pct minus No.4 (U.S. Standard sieve size) coal waste. For the nonslaky materials, maximum laboratory densities were highest and permeabilities lowest when the samples contained between 30 and 40 pct minus No.4. Shear strength increased rapidly when the proportion of minus No. 4 was increased from 20 to 40 pct, but then increased only slightly or leveled off when the minus No. 4 was increased to 60 pct. Optimum moisture content and permeability were the physical properties most affected by the addition of fines. Optimum moisture content increased as much as 3 pct, and permeabilities decreased up to three orders of magnitude. Slaky coal waste material had physical property reactions to the addition of fines substantially different from those of nonslaky material.

Jan 1, 1981

The common approach of designing blasts on a trial and error basis is quickly coming to an end. When utilizing the full scale blast environment, trial and error can quickly become cost prohibitive and leaves much to be desired in terms of true blast diagnostics. In these situations testing is usually only continued until a perceived improvement is achieved and when the gross undesirables in blast results are removed. This does not preclude, however, that further improvements of up to 100% or more can not be obtained.

Jan 1, 1994

Generating short- and long-term mine production schedules in isolation and independently from each other means that only a local optimum can be achieved when each scheduling phase is carried out. The globally optimal solution however, can be achieved when integrating scheduling phases and accounting for the interaction between short-term and long-term activities simultaneously. This paper addresses the task of integrating short- and long-term production plans by combining the short-term objective of minimising deviation to targeted mill feed grade with the long-term objective of maximising net present value (NPV) into a single mathematical model. A case study is presented which compares the present values of the same stope data set scheduled via separate long and short-term models and than by the proposed integrated model which applies a predetermined penalty for each tonne of metal deviation to target for the respective ore tonnage being processed. This allows an operation to obtain a globally optimal scheduling regime when taking into consideration the cost and loss of value resulting from fluctuations in grade to the mill over the short-term.

Dec 6, 2010

By M Simpson

Greywackes of the greater Auckland Region (Brynderwyn Hills to Hamilton), when considered on a regional scale, have characteristic ranges of physical, mineralogical and other properties. Some properties (eg density, porosity, crushing resistance, clay index) generally cluster and correlate with the basement greywacke facies, regions and terranes recognised by geologists, and their diagenetic/metamorphic level. Other local factors, particularly variations in mineralogical composition, nature of matrix cement, grain size, and degree of weathering may produce aberrant properties. Some of these local variations, when extreme, have the potential to affect the aggregateÆs performance in roading or the concrete industries.   Smectite and the zeolite laumontite are the major deleterious minerals occurring in fresh greywacke rocks of the Auckland region, although weathered rocks may contain halloysite, an expanding member of the kaolin clay mineral group. These minerals, when found in abnormally high levels in greywackes cause expansion effects in the aggregate. Currently there are inconsistencies in the detailed correlation of shrinkage, clay index, clay mineral content and intrinsic expansion data that need further research to resolve them.  

Jan 1, 2007

By Samuel P. Harteis

Many mining operations rely on retention bulkheads to provide a barrier between impounded water and active mine workings. However, bulkhead failures can cause catastrophic flooding that puts the underground workforce at risk. Underground observations and evaluations of existing bulkheads indicate that a systems approach is required when building an underground water or slurry retention system. In addition to engineering the bulkhead, the designer must ensure the quality control of materials and workmanship of the bulkhead, the reaction of the mine strata when exposed to water under pressure, and methods to monitor the performance of the retention system. Researchers from the National Institute for Occupational Safety and Health (NIOSH), with the assistance of the Mine Safety and Health Administration (MSHA), conducted an extensive review of bulkhead permits submitted to the MSHA Technical Support office in Bruceton, PA. In addition, the researchers visited accessible bulkhead installations at undeground mining operations to gather information related to construction practices, maintenance issues, and monitoring and emergency response procedures. Several key items were identified that must be considered when permitting the installation of an underground fluid retention system.

Jan 1, 2008

By R. P. King

The essential features of an image analysis system for the measurement of mineral liberation are described. Good procedures for image acquisition and image processing prior to image analysis are defined. The basic stereological methods for the measurement of volume fraction, surface area per unit volume, particle size distribution and liberation spectra are given. The appropriate methods for fractal correction when measuring perimeters of irregular features and for frame correction when measuring linear intercepts are developed. Practically useful and accurate procedures for the stereological correction of particle size and liberation distribution methods are given.

Jan 1, 1995

By Katherine Harding

This Bureau of Mines publication describes a practical approach to sampling that does not require elaborate statistical techniques. Simple steps are given for finding a cutoff point in the response from a repetitive survey. This procedure can be used to estimate the aggregate value of the characteristic being measured without waiting for a complete count from the survey. This is a useful technique when the reference periods are repeated at frequent intervals, such as monthly and quarterly, and when the statistical collecting agency is engaged in publishing timely data which must be accurate economic indicators.

Jan 1, 1971

By Robert McClure, Carlton Lehman

Rendering safe explosives in an urban environment presents a unique challenge due to the safety concerns and disruption to the general public. Potential damage to the surrounding homes, businesses, utilities and transportation infrastructure are some of the major concerns when planning the render-safe operation. Engineering controls to mitigate blast effects, such as damaging air over pressure levels, material ejection and ground borne vibration, need to be implemented as part of the operation. Monitoring of seismic and air overpressure during these operations are needed to protect against potential claims when controlled or unplanned detonations occur.

Feb 1, 2020

By V. F. Parry

[Approximately 7-1/2 million tons of subbituminous coals are mined annually in Colorado, Wyoming, and Montana, of which 50 percent probably reaches domestic consumers. The moisture of these subbituminous coals is high, averaging about 25 percent when they are mined. The coals are non-caking end stack to a variable degree when exposed to normal atmospheric conditions. They are good domestic fuels, are considered to be smokeless in most furnaces, and have been used for many years in hand-fired domestic furnaces in which the practice is to employ large lutes for efficient combustion.]

Jan 1, 1941

By W. D. Delahaut

Sampling tests performed at the Paradise Peak Mine compared various blasthole samplers and reverse circulation sampling methods. Statistical analysis of the data indicates that be-low-the-deck bag sampling produced a 24 to 29 percent error when compared to bulk sampling methods. Use of a chip pile wedge sampler reduced error to 17 percent. Reverse circulation sampling upgraded over bulk blasthole sampling by 7 percent for gold and 11 percent for silver. These results indicate that bias sampling conditions exist when small volume bag sampling is employed in production blasthole drilling.

Jan 1, 1991