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By R. L. Grayson

Based on the relationships between severity measure vs. productivity and other factors, this paper presents a comprehensive analysis of US underground coal mine injuries in 1996 by mine size. From the 1996 data, it was concluded that, generally, the larger the mine, the more productive it is (in tons per employee-hour) but the more severe is its injury experience (r = 0.65). However, within very large, large and medium mines, the more productive the mine, the less severe is its injury experience (r = -0.43, - 0.36 and -0.26, respectively). For small and very small mines, a deeply nested analysis would be required to understand relationships. Other interesting relationships and comparisons are presented.

Jan 1, 2002

By Qingguo Xue, Jingsong Wang, Yingli Liu, Guang Wang

In the dropping zone of blast furnace (BF), primary slag absorbing ash of pulverized coal and coke become to be intermediate slag. Due to viscosity and surface tension of slag and the pore between cokes, some slag remained in coke layer and affected the permeability of blast furnace. The flow behavior of slag with different basicity (0.55–1.10) and Al/Si (0.35–0.50) were studied. Meanwhile, the viscosity and surface tension of slag were calculated. The results showed that, with the increasing basicity of slag, surface tension increased and viscosity decreased. With the Al/Si increase, surface tension and viscosity increased. The smallest pore that all slag can pass through was 4.5 mm. However, the height between slag droplets and the bottom of crucible indicated that the ability of slag to pass through pore were weakened with the increasing basicity and Al/Si. Thus, slag which absorbed ash from fuel become difficult to pass through coke layer.

Mar 1, 2017

By Edward F. Divers

A new nonclogging water spray system for continuous-mining machines has been developed under contract with the Bureau of Mines. This paper presents installation and operating guidelines for the system, which consists of improved and easily maintained machine-mounted hardware, including an inline Y-strainer, a hydrocyclone, a backup filter, and two quick-opening valves for flushing particulates from the strainer and hydrocyclone. Underground tests with continuous-mining machines have shown that when properly installed and maintained, the new sys tern virtually eliminates nozzle clogging and thus greatly reduces spray maintenance. The sys tern is relatively inexpensive and has been installed on typical continuous-mining machines for a total cost under $1,000.

Jan 1, 1976

By Billy L. Crowder, John M. Fairfield

The implantation of B+ , P+, and As&apos; into silicon has been studied with the purpose of making shallow p-n junctions. The influence of such parameters as 1) ion energy, 2) target orientation and temperature, 3) total dose, and 4) annealing schedule was investigated. An energy range of 70 to 300 kev was used for boron and phosphorus implants and up to 500 kev for arsenic. It is found that the experimental projected range agrees well with theory and that shallow junction depths can be made reproducibly. ION implantation has received much attention recently as a technique for doping semiconductors. Specifically, it has the potential of supplementing or replacing the diffusion process as a method for making p-n junctions. In a few specific cases it has been used successfully to make semiconductor junction devices. Potential advantages of ion implantation doping over diffusion techniques are: 1) It affords greater control of shallow junction depths (< 0.2 µ) while maintaining high peak concentrations. This is particularly important for high-speed switching devices, since lower junction capacitances and resistances can be achieved. 2) More precise registration of small planar structures can be realized if proper masking procedures are employed. This advantage is especially useful in the design of high-density integrated circuits. It has been used to advantage in FET fabrication since the edge of the source or drain can be aligned precisely at the edge of the gate electrode.&apos; 3) Ion implanatation permits lower temperatures than diffusion techniques. This factor alleviates the problem of compatibility of diffusivities often encountered when designing multiple-junction structures. Also, the lower temperatures create fewer thermal defects and dislocations, which may account for the high efficiency of some ion-implanted solar cells.2 4) Impurity profiles can be more easily tailored to resemble ideal distributions. Successful exploitation of the potential advantages of ion implantation techniques will depend on increased knowledge and understanding of the subject. The factors likely to be influential in determining impurity distribution profiles in ion-implanted single-crystal targets have been reviewed by J. F. Gibbons.3 In addition to the mass and energy of the implanted ion, the total dose, target orientation, and target temperature are important parameters. The annealing temperature required for removing lattice damage and incorporating the implanted species on an electrically active site is very important. This paper describes an investigation of some of these factors. Implants of boron, phosphorus, and arsenic into silicon have been studied. Energy ranges of 50 to 300 kev were used for boron and phosphorus and up to 500 kev for arsenic. In addition to the implantation energy, the effects of total dose, target temperature, and post implant anneal have been investigated. EXPERIMENTAL PROCEDURE The implantation targets were silicon wafers cut from Czochralski-grown crystals, lapped, and chemically polished. The orientations were (111), (110). and (100) with misorientations of up to 7 deg from the principal axis. For this study, accurate target alignment (i.e., within 0.1 deg) was not available and quoted misorientation values should be regarded as approximate . The implantation equipment consisted of an ion source, a 300-kev linear accelerator tube, an electromagnetic separator, and the associated target supporting and beam focusing assemblies. The ion source was a simple oscillating electron type source,4 which has been described elsewhere.5 The gaseous compounds BF3, PF5, and AsH3 were used as ion sources for B+, P+, As+, and AS+&apos;. Analyzed current levels of up to 20 pamp could be obtained; however, for this investigation target current levels of 1-3 µ amp were usually employed. The analyzed ion beam was collimated through a double slit (1.4 x 0.4 cm) and swept perpendicularly to the long axis of the slit such that an area of about 2 sq cm on each target was covered. Dosages of around 1015 cm-2 were normally employed, but smaller amounts were also used for comparison. A uniform flux density over the bombarded area was assured by the continuous use of profile monitors similar to those described by Wegner and Feigenbaum.6 Post-implant annealing was accomplished in an argon atmosphere in a temperature range of 600" to 950°C. It was not part of the purpose of this investigation to study the annealing kinetics; however, some isochronal and isothermal anneal experiments were conducted to determine the time and temperature necessary to render a reasonably high portion of the implanted ions electrically active (i.e., higher than 50 pct). Post-implant anneal temperatures of around 900° and 600°C were required for boron, and arsenic and phosphorus implants, respectively. Arsenic and phosphorus implants increased in conductivity rather abruptly at the proper anneal temperature of the isochronal curve, but boron increased more gradually over a wider range. Isothermal anneal curves were reasonably flat after 10 min, so an anneal time of 1/2 hr was used for the experimental results described below. The profiling techniques were: 1) neutron activation analysis, 2) differential sheet resistance,7 and 3) junction staining.8 The differential sheet resistance technique is commonly employed in this type of study. Its principal disadvantage is the uncertainty of the ef-

Jan 1, 1970

By H. Hao

This paper outlines the development of a 2-D axisymmetric mathematical model to predict the evolution of temperature during the Direct Chill (DC) casting of AZ31 magnesium billets. Model predictions of temperature have been compared to measurements made on an industrial DC casting machine at Timminco Ltd, in Haley, Ontario. These measurements have been used to fine-tune the thermal boundary conditions employed in the mathematical model, The model, which is based on the commercial finite-element code ABAQUS, has been developed as part of a strategic project aimed at improving the DC casting process for light metals through a reduction in casting related defects and increased productivity.

Jan 1, 2004

By J. L. Gillson

In a brief summary of the many occurrences of fluorspar in our western states, it is not possible to go into detail in regard to the geology, mining and milling methods, and reserves about individual deposits. Rather a broad review is made of the occurrences and an analysis of how the western deposits may fit into our future domestic economy is presented. General Statement on Fluorspar Situation Fluorspar has been used for years as a flux in the manufacture of basic open-hearth steel, in foundry cupolas for melting pig iron, in the manufacture of opalescent glass and in the preparation of hydrofluoric acid. In 1880 the annual production of fluorspar in the United States was around 4000 tons per year. By 1900 it was up to 21,656 tons and between 1902 and 1908 it averaged about 40,000 tons annually. Prices were then so low, by present standards, that it seems impossible to believe now that mining could have been performed profitably at the price levels then prevailing. In 1890 fluorspar sold at the mines for $6.70 per ton, in 1901 for $5.81, in 1916 for 85.92. When the United States entered World War I, flyorspar production and price skyrocketed; the production reached 263,817 tons in 1918, with prices above $20.00 per ton, and prices were even higher in 1919 and 1920. After 1920, the domestic production fell from the 1918 level to about 125,000 tons annually and the average price dropped back to about $18.00 per ton. By 1935 the average price had fallen to $15.00, but in 1940 with a rising demand the average price of all grades had gone back up to $20.31. Today it is 75 per cent higher than in 1940 and presumably the price of acid grade at .least would be even higher if it were not for price ceilings. The first subsequent year that the domestic production exceeded that of 1918 was 1941, and the 1944 production is expected to exceed 400,000 tons, or over one and a half times that of 1918. In five-year periods, average production and imports were as are shown in Table I. Many people concerned with the consumption of fluorspar believe that the postwar period ahead will show a repetition of price trends of the last such period. They believe that imports will be again an important factor in the available supply and the price will fall back gradually toward the prewar level. The following basic factors are pertinent in analyzing this conclusion:

Jan 1, 1948

By J. L. Gillson

In a brief summary of the many occurrences of fluorspar in our western states, it is not possible to go into detail in regard to the geology, mining and milling methods, and reserves about individual deposits. Rather a broad review is made of the occurrences and an analysis of how the western deposits may fit into our future domestic economy is presented. General Statement on Fluorspar Situation Fluorspar has been used for years as a flux in the manufacture of basic open-hearth steel, in foundry cupolas for melting pig iron, in the manufacture of opalescent glass and in the preparation of hydrofluoric acid. In 1880 the annual production of fluorspar in the United States was around 4000 tons per year. By 1900 it was up to 21,656 tons and between 1902 and 1908 it averaged about 40,000 tons annually. Prices were then so low, by present standards, that it seems impossible to believe now that mining could have been performed profitably at the price levels then prevailing. In 1890 fluorspar sold at the mines for $6.70 per ton, in 1901 for $5.81, in 1916 for 85.92. When the United States entered World War I, flyorspar production and price skyrocketed; the production reached 263,817 tons in 1918, with prices above $20.00 per ton, and prices were even higher in 1919 and 1920. After 1920, the domestic production fell from the 1918 level to about 125,000 tons annually and the average price dropped back to about $18.00 per ton. By 1935 the average price had fallen to $15.00, but in 1940 with a rising demand the average price of all grades had gone back up to $20.31. Today it is 75 per cent higher than in 1940 and presumably the price of acid grade at .least would be even higher if it were not for price ceilings. The first subsequent year that the domestic production exceeded that of 1918 was 1941, and the 1944 production is expected to exceed 400,000 tons, or over one and a half times that of 1918. In five-year periods, average production and imports were as are shown in Table I. Many people concerned with the consumption of fluorspar believe that the postwar period ahead will show a repetition of price trends of the last such period. They believe that imports will be again an important factor in the available supply and the price will fall back gradually toward the prewar level. The following basic factors are pertinent in analyzing this conclusion:

Jan 1, 1948

By Kurt Stock

The grades of spelter demanded by the consuming industries were not definitely established until the American Society for Testing Materials undertook to fix specifications, based on the varying percentages of the common impurities (lead, iron, and cadmium) as follows: Total, Not Leap, Iron, Cadmium, Over. Per Per Cent. Per Cent. Per Cent. Cent. A. High grade.................. 0.07 0.03 0.05 0.10 B. Intermediate................ 0.20 0.03 0.50 0.50 C. Brass special................ 0.75 0.04 0.75 1.20 D. Prime western............... 1.50 0.08 The question which grade was the best for certain purposes and why was left unanswered. The conservatism of the zinc-smelting industry and the unwillingness of the spelter-consuming industries to engage in research work prevented the full benefits being obtained that such standardization promised. The custom smelters, producing spelter in pigs or plates, found it impossible to adhere closely to the established limits on account of the variety of ores treated; and the smelters with long-established and known brands, or those manufacturing their metal into marketable products, like sheet zinc, did not have to abide by the newly established grades based on chemical percentages. Smelters engaged in the smelting of custom ores had occasional complaints about the quality of their metal, as some of the consumers, especially brassmakers and some galvanizers, used the rigid standards of the A. S. T. M. as a basis for obtaining redress from zinc smelters whenever some of their work was faulty. Indirectly, much good resulted from such complaints; for while the brassmakers and galvanizers, on the whole, did not know what was wrong, the metallurgists in charge of zinc smelters were induced to abandon their conservatism and study the influence of impurities in spelter from the point of view of the consumer. For some of us, spelter gradually ceased to be considered merely spelter; it

Jan 1, 1925

By Daniel Su

Approximately 90% of the primary roof bolts used in CONSOL?s Pittsburgh seam coal mines is 2-piece, 8-foot long, 7/8? (or ¾?), high-strength, resin assisted, mechanical shell tensioned bolt. The remaining 10% is the 2-piece, 8-foot long, 7/8? combination bolt, which employs 4 feet of fast resin to anchor the deformed rebar at the top of the hole. In either system, a 1-3/8? hole is required to accommodate the mechanical shell and the coupler. The cheaper torque-tension rebar system, which is typically fully-grouted with 2-speed resin and which typically provides low bolt tension, is not used in CONSOL?s Pittsburgh seam mines. Rather, it is used in CONSOL?s Central Appalachia mines, where the roof rocks have CMRR rating of 50 or higher. Fully-grouted headed rebars, on the other hand, are used in CONSOL?s room-and-pillar mines. The selection of tensioned versus non-tensioned, fully-grouted bolts for coal mine primary roof support has been debated for the past thirty years. Many researches have been conducted to understand the theoretical bases behind the two systems. This paper describes CONSOL?s experience of using a new fully-grouted, mechanical shell tensioned bolt in the Pittsburgh seam with the development of low insertion force resin.

Jan 1, 2007

By Frank Arthur Forward

FRANK ARTHUR FORWARD was born in Ottawa and attended the University of Toronto, where he received a B.A.Sc. in chemical engineering in 1924. From 1924 to 1929, he was a smelter operator and research metallurgist with the Consolidated Mining and Smelting Company of Canada Ltd. (Cominco) at Trail, B.C. Moving to Australia in 1929, he was assistant smelter superintendent, Mount Isa Mines Ltd., Queensland, until 1934, when he returned to Canada, spend-ing one year as metallurgist with B.C.

Jan 1, 1970

By Arthur H. Leigh

Anode mud, the residual material collected from the bottom of the electrolytic cells during the refining of copper is leached, roasted, fire-refined and cast into Dore1 metal anodes. Dore1 metal is a gold-silver-copper alloy containing 80 percent silver. The metal is processed electrolytically using the Moebius system to refine silver and separate gold, platinum and palladium. The Moebius cell cathodes receive a deposit of silver crystals which are melted and cast into 1000 ounce silver bars with 999 Fine minimum purity. Gold mud is collected in fabric bags and cast into gold anodes for further refining in the Wohlwill cells. Wohlwill cells are unique in that gold, the noble metal, can be put into solution electrolytically without the use of aqua regia. Gold is collected on high purity gold foil cathodes and cast into 400 ounce bull ion with 999.7 Fine minimum purity. Platinum and palladium remain in the electrolyte progressively increasing in concentration and are finally separated and purified by precipitation.

Jan 1, 1973

By Rogers F. Davis

This publication has been prepared to supply manufacturers and industrial users a listing of mobile diesel-powered equipment and subassemblies approved and certified by the Bureau of Mines for use in noncoal mines. Testing of diesel-powered equipment is one phase of the Bureau&apos;s program of health and safety that concerns approval of electrical and diesel equipment designed to prevent explosions, fires, shocks, or toxic hazards in underground mines, when such equipment is used and maintained properly. Manufacturers submit machinery and component parts to the Bureau for study of their design, safety features, and use. Equipment must pass exacting tests and must meet strict requirements established through research and experience and listed in the Bureau&apos;s permissible schedules before the Bureau approves it as permissible for safe use in mines.

Jan 1, 1963

By Chu Yong Cheng

Synergists can be used in solvent extraction to improve the selectivity of extractants for metals. Research work carried out by the SX group at the AJ Parker Cooperative Research Centre for Hydrometallurgy / CSIRO Minerals has shown that the pH isotherm of nickel with Versatic 10 was significantly lowered by the addition of the synergist Acorga CLX50. The paper discusses how this synergistic shift can be used to alleviate a gypsum formation problem at Bulong nickel laterite operation in Western Australia. Metal pH isotherms were obtained with Versatic 10 and synergist CLX50 using synthetic leach solutions. In terms of pH50, the extraction order of the metals with 0.5 M Versatic 10 alone was Cu > Zn > Ni > Co > Mn > Ca > Mg, whilst the extraction order with Versatic 10 and 20% by volume CLX50 was Cu > Ni Zn > Co > Mn > Ca > Mg with the pH50 (Mn-Co) significantlyincreased. This is significant because the isotherms of valuable metals Ni, Cu, Co and Zn shift more towards low pH than those of the waste metals Mn, Mg and Ca, resulting in a possible good separation of Ni, Cu, Co and Zn from Mn, Mg and Ca. The use of intermediate precipitation, solids/liquid separation and re-leach in the three Western Australian nickel plants make these processes complicated and costly in capital and operation. The research work carried by the SX groupat the AJ Parker Centre has led to the development of direct SX (DSX) processes to recover nickel and cobalt from leach solutions using synergistic organic systems. Semi-continuous tests with a BHP Billiton pilot plant leach solution showed that Ni and Co together with Zn and Cu were separated from the major impurities, Mn, Mg, Ca, and Cl, in the first SX circuit. The co-extracted impurities were easily scrubbed. After stripping, Ni and Co together with Zn and Cu were concentrated, resulting in a much smaller second SX circuit in the down stream processes.

Jan 1, 2003

By John J. Mortvedt

Application of some by-products of the metals industry which contain plant nutrients to agricultural lands could constitute resource recovery instead of costly disposal. Some industrial by-products contain appreciable concentrations of heavy metal contaminants, such as Cd, Cr, Ni, and Pb. After land application, these metals may be absorbed by plants and enter the human food chain or be leached to groundwaters. Plant uptake of these heavy metals varies with plant species:, soil pH, soil texture, and the particular metal. Certain leafy vegetables can absorb significant amounts of heavy metals, while absorbed metals are usually poorly translocated to cereal grains. Allowable heavy metal concentrations in fertilizers now are not regulated, but EPA is considering such regulations. Heavy metal impurities in animal feed supplements are regulated by the states; so some by-products may not be permitted for this use.

Jan 1, 1992

By Ye Chen, Jianhua Chen, Meng Liu, Yuqiong Li, Xiao Mu, Cuihua Zhao

"Sulfidization-amine is the most effective method for the recovery of smithsonite (ZnCO3), however the interface interaction details remain unclear. The sulfidization-amine flotation mechanism of smithsonite has been studied by Density Functional based Tight Binding (DFTB+) method in this paper. The slab model of ZnCO3 (101) surface was built and the adsorptions of a monolayer of HS- and S2- ions were conducted to model the sulfidization effect on the ZnCO3 (101) surface adsorption. DDA hardly interacts with the hydrated ZnCO3 (101) surface. Under the low concentration of Na2S, HS- ions form a Zn-SH-SH structure on the ZnCO3 (101) surface, which hinders the interaction between DDA and surface Zn atoms. Under the high concentration of Na2S, a layer of ZnS is formed on ZnCO3 (101) surface, which is favorable for the adsorption of DDA on the surface. This is consistent with the flotation practice where smithsonite flotation requires a large amount of sodium sulfide. The results could provide a microscopic investigation into the sulfidization-amine flotation mechanism of smithsonite.INTRODUCTIONSmithsonite (ZnCO3) is an important and typical oxide mineral of zinc. It is a semi-soluble salt mineral with a solubility product constant of 1.46 × 10-10 (Weast, 1973). The most common and effective method to recover oxidized zinc ores is froth flotation (Caproni et al., 1979; Pereia and Peres, 2005; Kashani and Rashchi, 2008). It is well known that the flotation of oxidized zinc minerals is much more difficult than the flotation of zinc sulphide minerals (Hosseini and Forssberg, 2007).The recovery of zinc oxide ores with poor floatability attracts more and more attention due to the depletion of easy-recovered of zinc sulfide ores.Sulfidization-amine flotation, which using Na2S as sufidizing agent and amine as collector (Mckenna et al., 1949; Rey, 1954; Abramov, 1961; Rey, 1979; Hosseini and Forssberg, 2007). This method is the most successful technology used for zinc oxide minerals flotation in large-scale industrial applications since it was invented in the 1950s (Önal et al., 2005; Pereira and Peres, 2005). There have been numerous experimental researches on the sulfidization-amine flotation of smithsonite. Shi et al., (2013) studied solution chemistry of smithsonite flotation system. Feng and Wen (2017) studied the formation of zinc sulfide species on smithsonite surfaces and its response to flotation performance. Wu et al., (2017) investigated the sulfidization behavior of smithsonite with the use of zeta potential, inductively coupled plasma (ICP), scanning electron microscope (SEM), and X-ray photoelectron spectroscopic (XPS). Their measurement results confirms the chemisorption of sulfur ions and the formation of ZnS film on the smithsonite surface after Na2S treatment, however the influence of HS- ions on the surface and the influence of sulfidization on the amine adsorption have not been discussed."

Jan 1, 2018

By G MORRIS

The mining industry has been rightly proud of its environmental achievements and it would be fair to say that in some areas the Australian mining industry is at the forefront of world practice in environmental management and mine rehabilitation. The `environment&apos; has certainly been a growth area over the past three decades with growing awareness in the 1960s, some large battles and the of significant legislation in the 1970s. The most important period however has been the 1980s and so far the 1990s where, in addition to the of some more rigorous legislation, we have seen the practical application of environmental management/rehabilitation Techniques.

Jan 1, 1992

By H. E. Stauss, G. Sandoz

AN increase in the value of magnetostriction1 * is known to result from the annealing of some ferromagnetic alloys in a magnetic field. Similar increases may be anticipated in the value of the magnetostriction of alloys that are of interest because of their normal high values. Two were selected for trial, 87 pct Fe-13 pct Al(Fe,Al) and 69 pct Co-31 pct Fe, the latter being used as a representative of the Co-Fe alloy series. The influence of a magnetic field present during annealing is explained by the domain theory of magnetism." The field orients the domain vectors in its own direction when the alloy is at or below the Curie temperature, and holds them there until the metal is cold. During cooling the interaction stresses between neighboring grains are largely relaxed. Interaction stresses will reappear, however, if the state of magnetization of the specimen is changed in any way, and will be larger the more the new state of magnetization differs from the one existing during the magnetic anneal. In this connection the 180" reversal of a magnetization vector is not considered a change because a simple reversal does not tend to produce a change in shape of a magnetized region. When the field existing during the anneal is removed after the metal is cold, the domain vectors can turn back only to the nearest crystallographic directions of easy magnetization because return to random

Jan 1, 1953

By N. Sacks, N. B. S. Magagula, I. Botef

"Low-pressure cold gas dynamic spraying was used to deposit WC-4wt%Ni and WC-4wt%Ni-1wt%Mo coatings onto mild steel. Dense coatings with very low porosities were produced. No decarburization occurred during deposition and no deleterious phases were formed. The coatings were subjected to standardized material characterization tests, as well as slurry abrasion testing to assess their wear behaviour. The wear tests were conducted in synthetic minewater-silica slurries, while distilled watersilica slurries were used as a control. The hardness of the coatings, 512HV0.3 and 458HV0.3 for WC-4wt%Ni and WC-4wt%Ni-1wt%Mo respectively, are comparable to those achieved using high-temperature coating processes. The abrasion wear rates for both coatings were less than 5 mg/min and 10 mg/min in the distilled water-silica and synthetic mine water-silica slurries respectively. The approximately 50% increase in wear rate in the synthetic minewater slurry is attributed to a synergistic corrosive wear mechanism. The predominant wear mechanisms were identified as binder smearing and delamination, with carbide grain fracture and pull-out. IntroductionSlurry abrasion is a common phenomenon in mining operations, particularly in pipelines transporting, for example, sand-water slurries. This type of wear can cause pipeline fracture, shortened operational lifetimes, and impede pipeline efficiency. To reduce or limit abrasion, thermally sprayed tungsten-carbide-based coatings are often used as pipe linings (Kanchan et al., 2010). This is due to their attractive mechanical properties, which include high wear resistance, stiffness, hardness, compressive strength, and tensile strength. These properties are provided by the coating microstructure and composition, which is a blend of hard, wear-resistant tungsten carbide (WC) particles embedded in a fracture-tough metallic binder phase (Brookes, 1997). Cobalt (Co) is the most commonly used binder due to its excellent wetting of the WC phase and moderate mechanical properties; however, its application is limited to non-corrosive environments as it has a low corrosion and oxidation resistance (Andren, 2001). Nickel (Ni) may also be used as a binder, and has been shown to have superior oxidation and corrosion resistance, but in some applications may not have the required mechanical properties (Kim et al., 2006)."

Jan 1, 2016

The Australian mining industry can expect to be working internationally competitive high quality coal mines during the twenty-first century. Cost efficient mining methods such as high productivity longwall units with heavy reliance on remote control will be standard and worked by well paid and intensively trained operators. Major changes in mine ventilation engineering can be expected in the use of computers and mine telemetry, the understanding of the mine environment and the frequency of mine disasters, the utilization of mine air contaminants for profitable purposes and the provision of a pleasant and comfortable work environment. New approaches to mine ventilation such as air recirculation will have been considered. There will be an increased need for highly trained ventilation engineers. With the present pace of technological change, quite revolutionary new approaches to mining and ventilation can be expected by the end of the twenty-first century.

Jan 1, 1988

By Richard M. Foose

MOST of the roofing granules produced in Pennsylvania are made by two companies at three plants. The Advance Industrial Supply Co. has three quarries and a mill at Gladhill Station, in southern Adams County. The Funkhouser Company is actively engaged in mining, quarrying and milling at Charmian, about one mile west of Gladhill Station, and at Delta, in southern York County. These three plants produced approximately 100,000 short tons of granules in 1943. The production of roofing granules in 1937 for the whole country was only about 500,000 tons, generally indicating the large growth of the industry since that time. The fundamentals of producing roofing granules were discussed comprehensively by G. W. Josephson in a paper before the Industrial Minerals Division in October 1943 (Mining Technology, March 1944). The purpose of this paper is to describe the actual methods of mining the rock and milling it to make roofing granules, as practiced by the three Pennsylvania plants. MINING AND MILLING Funkhouser Company (Delta) The Funkhouser Company, near Delta, in southern York County, Pennsylvania, operates three joined quarries and a mine in the Peach Bottom slate. The joined quarries extend 1200 ft. in a northeast southwest direction along the strike of the slate cleavage and are about 200 ft. wide. The working face is about 45 ft. high. The quarrying operation is rather simple: Ingersoll-Rand Jackhamers, 1-in. and 1 1/4-in., with hollow drill steel, are used to undercut the quarry face with10-ft. holes. The face is "blown" and allowed to slump on the quarry floor. Loaded by a Marion electric shovel into trucks, the shattered rock is taken to the primary crusher 2500 ft. away. In addition to the normal quarrying operations, a drift into the northeast wall of the middle quarry was begun about 1935 and has advanced about 2000 ft. since then. Rooms have been driven at angles to the drift along choice beds of slate. The drifts and rooms have a roof more than 35 ft. high and the main drift and rooms are all more than 40 ft. wide. There is no cribbing at any place in the mine. Several of the rooms were driven upward on a 5º slope and in some of them there was stoping. Ingersoll-Rand Jackhamers are used, and only wet drilling is practiced. When visited in January 1940, an electric shovel was operating at the head of the drift, scooping up the slate blasted out of the working face. This, too, is trucked to the primary crusher. Some of the better quality slate is saved for making slate shingles. The primary crusher, which is a No. 30 McCulley gyratory, receives the slate from the trucks and crushes it to about 2-in. size (Fig. I). This product travels by a 30-in. belt conveyor to Niagara vibrating screens with 2-in. holes. The minus 2-in. product moves to a storage silo by bucket

Jan 1, 1945