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By Jerry Harrington, Brad Wigglesworth, David C. Beling

Commercial operations at the open pit, heap leach Crofoot Mine commenced in April, 1988. Approximately 13,600 tonnes (15,000 st) of low grade pregnant solution are treated daily using a Merrill-Crowe circuit. Acceptable gold recoveries from these low grade solutions can be obtained by optimizing solution pre-treatment prior to zinc addition.

Jan 1, 1990

By Tim Avery, Steve Klein, Mark Schmoll

Tunnel boring machine (TBM) performance in hard rock is highly dependent on the geologic conditions, including the type of rock and hysical properties like the rock strength, hardness, and the spacing of the fractures. This paper examines TBM performance relative to the geologic conditions and rock mass properties at four recent TBM-bored tunnels in California.

Jan 1, 1995

By Gary PE Beerkircher

A brief history of banana screen development and evolution will be presented along with the operational advantages of the large banana screens available in the industry today. Applications of the large banana screens will be presented as well as the economic advantages that the use of large banana screens can offer to the Mining lndustry today. Banana screen installations in metal, non- metal and coal mining applications will be presented.

Jan 1, 1997

By Tien H. Wu, Pinnaduwa H. S. W. Kulatilake

The concepts of conditional probabi1ity and geometrical probability are used to establish a relation between the probability density of the trace length and the probability density of the discontinuity diameter. The discontinuity is represented as a thin circular disc. A numerical solution scheme is used to obtain the probability density of the disc diameter from the probability density of the trace length. An example was used to illustrate the possibly large difference between the mean discontinuity diameter and the mean trace length.

Jan 1, 1986

By Ferdi Camisani

The ‘Bible’ 1977 & 1981 ‘South African Mine Valuation’ by C. D. Storrar. Proved reserve (=’measured ore’ USA; ore reserve = the payable portion of the proved reserve) -Fully developed (…immediately available…) -Partly developed (…not immediately available…) -Undeveloped (…unavailable…) Probable reserve (=’indicated ore’ USA) Possible reserve (=’inferred ore’ USA) Life-of-mine reserve (Proved + Probable + Possible)

Jan 1, 2003

By Z. B. Yin, R. W. Bartlett, P. R. Taylor

Tube furnace experiments have been performed to evaluate the lime roasting of pyrite in air. The sulfur volatilized was measured over time. Variables studied included: form of lime, sodium sulfate additions, temperature, air flow rate, lime to pyrite weight ratio and pyrite particle size. It was found that more than 98% of the sulfur can be retained at a reactor temperature of 650°C, with a slight excess of calcium hydroxide. The roast products are primarily hematite and calcium sulfate.

Jan 1, 1990

By S. Bozinis

In this paper, blast design considerations and implementation that lead to reduced vibrations will be presented. In addition, blast vibration data collected during hard and semi-hard rocks blasting in the proximity of an inhabited area will be analyzed and presented. In all cases maximum vibration levels are kept below the limits set by DIN 4150.

Jan 1, 2006

By James R. Aggson, Verne E. Hooker, Dennis R. Dolinar

The stability of underground openings and mining systems is closely related to the in situ stress field. This paper presents a short discussion of the three-component borehole deformation gage and overcoring technique which the Bureau of Mines uses to measure in situ stresses, and a summary of stress data that the Bureau has gathered in the process of evaluating ground control problems. Specific ground control problems and stress distributions are discussed as examples.

Jan 1, 1982

By A. Mai, J. S. Wakeman

The progress results of a pilot plant study on the effects of ball top size and other mill operating parameters are reported. Test series on taconite and quartzite crude ores using a 1.7-m diam primary mill in closed circuit with a vibrating screen indicate clear trends on the improvements of mill throughput and power consumption when using larger diameter balls. Possible effects on mill liner and ball consumption as well as future research plans are discussed.

Jan 1, 1987

By S. K. Kawatra, S. Bagley, T. C. Eisele

To meet federal air pollution guidelines, it is necessary to remove a considerable quantity of sulfur from many North American coals. This may be accomplished by oxidizing the sulfur to water soluble forms, followed by washing the coal. Selective oxidation of the various sulfur forms can be accomplished through the use of a variety of types of bacteria. In this paper, the various bacteria and their requirements are described, and processes using bacteria to remove coal sulfur are discussed.

Jan 1, 1988

By Lester A. D. Chin

The cost of bauxite is a multiple of the Bauxite Consumption Factor and the Unit Cost of Bauxite, and is a major cost item at most alumina plants. Bauxite Consumption Factor can be reduced by increasing alumina recovery during processing. Unrecovered aluminas are analyzed and possible research identified, using the framework below: 1. [Unextracted Aluminas] 1.1 Aluminous goethite 1.2 Boehmitic alumina 1.3 Diasporic aluminas 2. [Chemically-Bound Aluminas] 2.1 Desilication product 2.2 Phosphorus precipitate 2.3 Solid-phase lime-reaction products 3. [Alumina Reprecipitated on Red Mud] 3.1 Red mud separation and washing 4. [Physical Loss] 4.1 Liquor 4.2 Alumina dust

Jan 1, 1984

By G. J. Lindenburg, T. L. Wilson

The Velvet uranium mine is located in the Big Indian district of the Colorado Plateau. The uranium ore body lies within the lower Triassic Chinle Formation, and the ore is associated with west-south-westerly trending fluvial sand systems. Exploration and mining are directed by longhole drilling and radiometric sampling. Results of the gamma probing, face scanning, and geologic mapping guide mining decisions and planning. Three people are directly involved with the geologic procedures: two geologists and a mine supervisor. The two geologists map, do rib scans, and direct longhole drilling. The third man involved, the mine supervisor, has last minute directive action based on shot hole probe data.

Jan 1, 1992

By Rex C. Bryan

An application of geostatistics to financial decision analysis is the linking of reserve parameters estimation precisions to a mine economics computer program calculating profitability. The estimates of economic reserve parameters are obtained by the kriging method, while precision are calculated by a technique more akin to the polygon method. To indicate the effect of the variables probability distribution on a distribution of profitability, their values are sampled by a Monte Carlo technique and entered into a mine economics modelling program developed by T. R. Ellis. The distribution of profitability calculations are in essence, a superior method of sensitivity analysis. The method is applied to a roll-front uranium deposit in the Powder River Basin, Wyoming.

Jan 1, 1982

By R. Spears, J. B. Vincent, S. Donald, J. Litaker

Previous efforts to remove and concentrate heavy-metal ions from wastewater streams via metalloprotein affinity metal chromatography (MAMC) were limited to the metal transport protein transferrin. Extension of the technique to the enzymes carbonic anhydrase and carboxypeptidase A, which possess different metal affinity properties, is described. Preliminary results indicate that the technique is capable of selectively removing and separating late first-row transition metal ions from aqueous solution. The results suggest that by properly choosing the matrix, i.e., protein or enzyme, MAMC may he applicable to problems involving a wide range of heavy-metal-hearing aqueous solutions.

Jan 1, 1996

By J. Herbst, J. A. Kitchner, J. P. Anfruns, G. Poling

Measurements have been made of the rate of capture of single particles of strongly hydrophobic, surface-methylated, quartz, of sizes ranging from 12 to 40 pm diam., by single rising bubbles of diam. 0.5 to 1.1 mm. The results agree closely with the theoretically calculated hydrodynamic collision rates, indicating that, in this system, every collision results in capture and retention of a particle.

Jan 1, 1976

By Ing. Alois Adamus, Ing. Václav Pošta, Ing. Lubomír Hájek

This paper reviews experiences connected with the use of nitrogen in the Czech coal industry. Special attention is focused on the first use nitrogen In the Czech Republic, it is probably the first case of fighting a mine fire using nitrogen in all the World. Discussion dwells on the present-day use of nitrogen, its sources, consumption, technological equipment, and the theoretical evaluation of nitrogen flushing.

Jan 1, 1995

By F. J. Susko

The US Bureau of Mines is using Fourier-transform infrared (FT-IR) analysis to investigate the bonding mechanisrn that occurs during the dewatering of clay slurries. High-molecular-weight polymers are used as flocculating agents in these processes. This investigation presents the results of an FT-!R study of calcium-exchanged montmorillonite treated with polyacrylamide (PAM) and polyethylene oxide (PEO). Both thin film and attenuated total reflectance (ATR) spectroscopic techniques were employed to study this clay polymer system. Results suggest PAM is adsorbed to the clay via the nitrogen atom of the polymer. A waterbridge is involved in the bonding between the clay at d PEO. Evidence also suggests that PEO may be adsorbed directly onto the surface of the clay.

Jan 1, 1991

By Sheldon Shepherd

Fifty years ago, belt scales were mechanical devices based on a complex weight balancing design. Today's systems use load cells to assess material weight, belt speed sensors and microprocessor-based integrators to continuously compute the rate of material transferred along a conveyor. Belt scales have become important assets to a plant. They help maximize the use of raw materials, control inventories and aid in the manufacture of a consistent product. Choosing and installing a belt scale system may seem complicated but it can be simplified by following a few guidelines.

Jan 1, 1999

By Mark W. Springett

The sampling of precious metal deposits entails inherent problems due to the low mineral abundances, high mineral specific gravities, skewed grade distributions and wide ranges of mineral particle sizes. Sampling practices and precautions are discussed with particular attention to each of the tripartite stages of sampling - sample acquisition, sample preparation and sample assaying. Practical examples of approaches to the sampling problem are given and some examples of significant sources of error are provided from gold and silver deposits in North America.

Jan 1, 1992

By D. R. McGregor, B. V. Clingan

A practical application of recent design concepts makes it possible to design a column cell to fit a specific set of conditions. The design and operating parameters of a column cell installation that replaced a conventional two-stage copper flotation cleaning circuit at Magma Copper Co., San Manuel, AZ, using these design concepts is described. A survey of other mineral processors using column cell technology was conducted. The results of this survey are also discussed.

Jan 1, 1988