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By Henry M. Howe

A discussion of the paper published in Bi-Monthly Bulletin, No. 20, March, 1908, pp. 227 to 237, and No. 22, July, 1908, pp. 615 to 620. PROF. HENRY M. HOWE, New York, N. Y. (communication to the Secretary *) :-Mr. Hibbard's definition of steel would be the best yet offered were it not for its one defect, the vagueness or equivocalness of "fusion-process." Puddling is surely in one sense a fusion-process, and so are the charcoal-hearth or knobbling-processes. But what he says suggests the following definition, which seems to me a good one: " Steel: any variety of iron which is usefully malleable at least at some one temperature, and is either cast when molten into a malleable mass, or if not so cast can be much hardened by sudden cooling." It is not necessary in a definition that quantitative bounds should be set up, for instance, that the exact height at which dwarf apple-trees cease and standards begin, or at which hills cease and mountains begin, should be stated. These quantitative measures are proper for specifications and contracts, but are not necessary for purposes such as the present. HENRY D. HIBBARD, Plainfield, N. J. (communication to the Secretary t) :-Professor Howe's criticisms of my definition of steel are not, it seems to me, well founded, for the . following reasons: The term "fusion-process" has been used during the past quarter or half century to distinguish the crucible, Bessemer and Siemens-Martin processes from the puddling- and cementation-processes, and probably no one at all conversant with the art of iron-metallurgy would now mistake its meaning. Moreover, no steel-metallurgist is in doubt of the meaning of the term "hardened? as applied to steel. If it were really necessary to describe what is meant by the term then it would

Nov 1, 1908

By A. M. Gaudin

THE so-called Kick law' is generally accepted to . mean that for each reduction to one-half in particle diameter, in a unit weight, the same amount of work is required. In crushing-efficiency calculations on crushing tests it is customary, when basing the calculation on Kick's law, to assign ordinal numbers to each standard sieve size. These ordinal numbers increase by a constant difference with each successive sieve aperture, because standard sieve apertures are in constant ratio. Minus 200-mesh is generally assumed as equivalent to 37 microns in size. By definition, the ordinal number multiplied by the per cent material of any size is equal to the energy units in the material of that size in a unit weight of sample. The sum of all energy units is the energy units content of a unit weight of sample, whether it be crusher feed or product. The difference between the energy units in the product and that in the feed is the tangible result of the work input per unit weight of feed. From this the amount of work necessary for one energy unit may be calculated. This has been done for a quartz crushing-test made at the Intermountain Experiment Station of the U. S. Bureau of Mines at Salt Lake City, in which the net work going to crushing was carefully measured. The results of this crushing test are given in Table 1.'

Jan 1, 1929

By W. -D. Schneider, B. Schwab

Like all metals, zinc can be recycled theoretically without end. To demonstrate environmentally friendly use of zinc, it is necessary to increase the recycling rate. In this regard, the Imperial Smelting Process developed in the forties and fifties in the United Kingdom has become more and more important. This unique process combined with a sinter plant, hot briquetting, and direct injection through the ISP furnace tuyeres offers ideal possibilities to recycle all kinds of zinc and lead bearing materials. Possible secondary materials include Electric Arc Furnace (EAF) dust, zinc-containing sludges and even zinc/carbon batteries. This high temperature process also destroys all organic materials, like dioxin, and can be seen as a sink for many harmful substances.

Jan 1, 2000

By Alain Jardy, Thibaut Quatravaux, Denis Ablitzer

"A numerical model of the Vacuum Arc Remelting process has been developed and applied to simulate remelting of various metallic materials, such as specialty steels, titanium and zirconium alloys. In practice, electromagnetic stirring is sometimes used, resulting in a complex 3D molten metal flow. After having validated the numerical model for different remelting conditions, we can use it to study the effect of applying a constant or alternated magnetic field on the thermohydrodynamic behaviour of the melt pool. The intensity of flow turbulence, computed with a classical k-E model, is shown to depend strongly on the nature of electromagnetic stirring.IntroductionThe principle of the Vacuum Arc Remelting (VAR) process, illustrated in figure I, consists in melting a consumable metallic electrode of the required grade under a high vacuum, in order to obtain a sound ingot of good structural quality.During remelting, an electric arc is maintained between the tip of the electrode and the top of the secondary ingot, in order to ensure melting of the electrode. The metal droplets fall through the arc plasma and progressively buid up the ingot, which solidifies in contact with the walls of a water-cooled copper crucible. The secondary ingot formed in this way contains three distinct zones, corresponding to the liquid pool, fully solidified metal and intermediate mushy zone. In order to stabilize the arc, it can be confined with the aid of a magnetic field created by an external induction coil. This field can also be used to stir the liquid metal, the rotation induced being in the orthoradial direction. By reversing periodically the coil current, stirring can be alternated."

Jan 1, 2004

By N. Sarmady, Mei Li, N. C. Parson, W. J. Poole

"The mechanical behaviour of AA6082 is a function of the extrusion conditions and in particular, the quench rate after extrusion. It is well known that precipitation of Mg-Si phases on grain boundaries during quenching can negatively affect the ductility of the alloy. In this study, AA6082 alloys containing 0.5 wt. % Mn and 0.15 wt. % Cr were direct chill (DC) cast, homogenized and then extruded to produce 3 mm x 42 mm strips. The microstructure in the as-extruded strips was unrecrystallized due to the Zener-Smith drag from the Mn/Cr dispersoids. It was shown that a solution treatment of 5 minutes at 560°C did not significantly affecting the as-extruded microstructure but if the as-extruded strip was cold rolled prior to heating, recrystallization occurred concurrently with the solution treatment. As such, 3 initial microstructures were produced, i.e. unrecrystallized and recrystallized with a grain size of 9 and 40 µm. After the solution treatment, controlled cooling experiments were conducted using the Gleeble 3500 thermomechanical simulator with cooling rates of 10, 25, 80°C/s as well as water quenched. The mechanical properties (e.g. yield stress, fracture stress and fracture strain) were determined from tensile tests for the different combinations of initial microstructure and cooling rate. The relationship between the quench rate and precipitation of Mg-Si phases on grain boundaries was examined by FEG-SEM. It was found that the yield stress decreased as the cooling rate decreased and that there was complex relationship between the fracture properties and the microstructure.INTRODUCTION As the automotive industry strives to reduce fuel consumption and CO2 emissions with the goal of reducing the environmental impact, there is a need for lighter vehicles. As a result, aluminum alloys are gaining popularity to replace steel parts as structural components. An exemplar of this is the Ford F-150 pickup truck which has an aluminum body and is ˜750 pounds lighter than the previous steel version of the vehicle. The structure includes a mix of aluminum sheet, extrusions and cast alloys. The current research is concerned with the performance of aluminum extrusions in applications such as side rails, crash tubes and other structural parts. These components experience a combination of bending, stretching and folding both during the forming of the part and in service, e.g. crash of a vehicle. There is a need to have detailed information on the influence of processing on final material performance, in particular the cooling rate after extrusion."

Jan 1, 2018

By L. A. Roe, John Jan

Iodine is a soft, lustrous, grayish-black nonmetallic element with a density of 4.9. It is the least active of the four members of the halogen family. The other members are, in order of increasing activity, bromine, chlorine, and fluorine. Iodine is a solid at ordinary temperatures, while bromine is a liquid and chlorine and fluorine are gases. Iodine melts at 113°C and volatilizes at 184.4°C to a blue-violet gas with an irritating odor. It occurs in nature only as iodates and iodides or other combined forms. It was discovered by Bernard Courtois in France in 1811, who noticed its presence as an unknown substance in crude soda ash obtained from burning seaweed. Gay-Lussac recognized it as a new element and named it iode, from the Greek word "ioeides or iodes" for violet color (MacMillan, 1970). The world production is not known with any great certainty, but it is probably between 25 and 35 million lb per year, of which about 30% is consumed in the United States. Geology and Mineralogy Iodine compounds occur as a minor constituent as a mineral in the Chilean nitrate deposits and in solution in brines and seawater. According to the US Geological Survey, it is the 47th most abundant element in the earth's crust. The minerals lautarite, Ca (I03)3 (calcium iodate), and dietzeite, Cat (103)2 (CrO4), (calcium iodate-chromate) are found in Chilean nitrate deposits which are located in Antofagasta and Tarapaca provinces on the eastern slope of the coast range in a desert area. Various brines contain iodine compounds. Seawater contains about 0.05 ppm of iodine and some seaweeds will extract and accumulate it up to 0.45% on a dry basis. Some coals in West Germany also contain iodine compounds. The known and potential sources of iodine reported in 1968 are given in Table 1. Table 2 lists estimated world iodine reserves. Iodine has been recovered from brines in Java, Indonesia, France, England, and the USSR. Iodine has also been recovered from seaweed in Ireland, Scotland, France, Japan, Norway, and the USSR. The indicated reserves and future resources of iodine are large but have never been adequately measured. Analysis Iodine as the free element can be detected by the characteristic blue color it gives to a starch solution. Quantitatively it is determined as the free element by titration with standard thiosulfate solutions using starch as an indicator. Colorimetric methods are also applicable. Markets and Prices Iodine and its compounds are generally marketed in the form of: iodine, crude; iodine, resublimed; calcium iodates; calcium iodide; potassium iodide, sodium iodide, and numerous organic compounds. Product Specifications Crude iodine, World market: 99-99.5% 12. Crude iodine, US produced, average: 99.8% 12. Crude iodine, USP XVII Specs: not less than 99.8% percent I2. Resublimed iodine is usually 99.9% and ACS specifications call for not over 0.005% total bromine and 0.020% nonvolatile materials (Anon., 1971). Prices, c.i.f. United States, for iodine have been steadily increasing from $1.18 per lb of crude in 1967 to $6.37-7.27 in January 1981 (Anon., 1981). In 1980 the price of iodine increased by 50%.

Jan 1, 1983

By G. A. Irona

Solids injection into non-ferrous converters and furnaces is becoming increasingly important for concentrate injection, removal of impurities, and recycling of dusts and other waste materials. The fundamental design aspects of these technologies will be reviewed, including gas and particle trajectories, lance clogging, heat transfer, and mass transfer including reaction rates and mixing. The use of soda ash for removal of impurities such as antimony and selenium will be used as an example of versatility of powder injection processes.

Jan 1, 1993

By Guanghui Li, Xuling Chen, Zhiyun Ji, Min Gan, Tao Jiang, Xiaohui Fan, Zhiyuan Yu

With the increase of proportion of biochar(without modified) replacing coke breeze, the physical strength of sinter decreases due to the faster burning speed of biochar. An investigation upon passivating biochar with boric acid was then conducted to strengthen sintering in this paper. A layer of thin film of B2O3 distributed in the surface of biochar was observed, which could reduce the contact between reaction gas and biochar. So the burning speed of biochar was decreased properly after passivation, and the combustion efficiency increased due to the inhibition of carbon gasification. The comprehensive effects of above changes could increase the maximum temperature of sintering bed, which facilitated to the mineralization of sintering mixtures. Eventually sintering indices got reinforced. Thus the indices of sinter as applying 40% passivated biochar were comparable with that of 100% coke breeze.

Jan 1, 2015

By J. Tomlinson

Shuttle car trailing cable splices were tested for resistance to failure upon being subjected to repeated bending, abrasion, and tensile shocks using a new testing method that closely simulates shuttle car induced stress. The results show that under normal stresses, splices can be made to withstand the equivalent of three months of operational use. Restoring the tensile strength to the conductors is found to be as critical as restoring flexibility. Splices in which the conductors are of slightly unequal length did not present as serious a workmanship problem as previously thought since test results show that the conductors tend to equalize when longer cables, in contrast to short cables employed in previous testing methods, were used. Dynamic recordings of cable tensile stresses are presented for a shuttle car and the new simulated testing method. Two simple but effective methods for removing insulation using a knife and a pair of pliers are described. None of the designs tested for a sacrificial splice covering were satisfactory.

Jan 1, 1979

By H Cifuentes, D J. Williams

Despite the recognised importance of tailings management, there remain little data on the potential benefits of biological treatments compared with physical and chemical treatments. The operation of the majority of tailings storage facilities (TSFs) continues to employ mainly physical solutions, such as sub-aerial tailings slurry deposition, with increasing adoption of thickening, paste and filtration to dewater the tailings involving the addition of chemicals such as flocculants and coagulants. However, with tailings production continuing to escalate rapidly due to the increasing demand for commodities and reducing ore grades, available technologies have not demonstrated cost-effective performance at high tailings production rates. This paper examines the emerging role of bacteria to better manage tailings, reducing risks and optimising storage capacity. Bacteria have the potential to enhance tailings dewatering, maintain their permeability, delay the onset of desiccation cracking, and improve their shear strength. Bacteria-treated tailings may be suitable for use as construction materials. Bacteria also have potential in limiting the dusting of tailings and facilitating rehabilitation on closure. The paper describes a series of laboratory involving the addition of harmless bacteria to a range of tailings. The bacteria form a compact material called calcite (a common and stable form of calcium carbonate), which immobilises the tailings particles, releases water, and cements the tailings in a stable and natural matrix. The water released can be recovered or evaporated, depending on site objectives. The bacterial reactions are linked to physical and chemical processes, providing the potential for an optimal mix of technologies for particular tailings and site conditions.CITATION:Cifuentes, H and Williams, D J, 2018. Potential improvement of tailings geotechnical behaviour using bacteria, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 228–238 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By Gordon O. Prickett

In two case studies we look at strategies of acceptance that the analyst can employ to gain entrance and to see his problem solution out to use. The first example comes from metal mines. The problem area was excessive usage and cost of wear parts in the concentrator and an atmosphere of crisis over frequent and unexpected breakdowns. The second case pertains to coal exploration. Better methods were being sought for representing coal quality in developing reserve tonnages. The first strategy is - Develop a detailed Human Impact Statement. The second strategy is - Write down in plain language with the keeper of the problem what he will consider as success in dealing with his problem.

Jan 1, 1978

By Marco D. Boscardin, Benjamin H. MacKinney, Kenneth R. Allard, Kenneth A. Pidgeon, Adriane G. Boscardin

This paper presents a case history for a unique application of a system of vertical micropiles with horizontal soil nail bracing and shotcrete facing for underpinning. The system was used to support and protect an existing 2-story hospital building during demolition and renovation. The goal was to limit building movements and have the building remain in use during construction of an abutting addition. Soils at the site consisted of clean, loose to dense, sand and gravel. The original underpinning design was revised after the initial excavation revealed unsuitable soil conditions for traditional underpinning pits. An alternative system consisting of vertical micropiles (hollow bars) through the footing, combined with shotcrete and soil nails was proposed, accepted by the owner, and successfully constructed. Excavation depths were up to 15 feet (4.6 m) below the existing footings. Wall movements were monitored at regular, horizontal and vertical intervals along the hospital wall, and less than 0.6 inches (15 mm) of settlement and 0.1 inches (3 mm) of horizontal displacement throughout underpinning and construction were reported. The challenges with the original proposed support of excavation design and other alternative approaches considered will also be discussed.

Oct 1, 2022

By Leena Suopajärvi, Karin Käär, Marcin Szumny, Jari Joutsenvaara, Md Ariful Islam, Helmut Mischo, Georg Meissner, Ossi Kotavaara, Catalina Vrabie

This study outlines implemented tactics and results for community empowerment through participation in questionnaire surveys, educational programs, and discussion on sustainable sourcing from new critical raw materials (CRMs) projects. Utilising questionnaire surveys, including the Public Participation Geographic Information System (PPGIS), the research gathered public opinions from Estonia, Germany, Poland, and Zambia, receiving 1,068 responses. These responses addressed various social, economic, and environmental issues related to CRM projects. Feedback from educational courses with participants from over 25 nations and public events provided additional insights. The collected data and feedback offer crucial input for advancing sustainable and responsible CRM sourcing strategies in these regions.

Feb 1, 2025

By R. L. Grayson

"Compliance standards for respirable dust, which are reduced because of high quart: concentrations, have become an industry-wide problem. Research on the physical and chemical character of quart-classified particles in respirable coal mine dusts indicates that they may exist in intermixed layers or may be coated by clay or coal material. The relative amount of intermixing varies with the coal seam being mined. If most of the quart: particles of a mine dust are ""pure,"" then the dust may have a high fibrogenic risk potential because of truly free silica and the compliance standard should be lowered. lf, however, quart: is locked inside another material matrix, or coated, a reduced compliance standard may not be appropriate.Although much research has been done on coal workers' pneumoconiosis (CWP) over the past decades, the etiologic agents of the disease still have not been pinpointed. The predominant methods of characterizing respirable coal mine dusts were bulk analysis techniques for determination of elemental and mineralogical concentrations, the results of which were used in statistical analyses to determine relationships between dust composition and the occurrence of CWP. These methods are incapable of finding the etiologic agents in the dust primarily because of complicated and confounding physiochemical factors, which may be discovered if the focus of characterization was done on a dust particle level.The SEM/EDXA-based research discussed here shows a significant difference in the number of ""pure"" quartz particles in respirable dusts collected from different mines. Some of the results have been reported previously (Grayson, Andre, and Simonyi, 1988). Concurrent research by other investigators (Wallace et al., 1989) demonstrates an SEM/EDXA-based methodology to pinpoint the location of the ""contaminating"" substance(s ) in a quartz-classified particle. The research of the European Economic Community has also begun analyses on the respirable-dust-particle level (Robock and Bauer, 1988).Since the compensatory and intangible costs of CWP are substantial in the United States, it is important that the etiologic agents be determined and then either controlled or neutralized in a cost-effective way. This line of research is especially important consid-ering the forecasted. near-term growth of coal production and the evolution of high productivity longwall panels (an immediate problem in compliance) and continuous mining sections ( a probable future problem).This need has been accentuated now that nearly all respirable dust samples submitted to MSHA are analyzed for free silica (Tomb, Parobeck, and Gem, 1986). Today a real problem exists in the coal industry, both underground and surface, because of high quartz levels in respirable dusts causing substantially reduced compliance standards (Murphy, 1989).The combined results of the respirable dust particle investigators indicate that conventional bulk sample analyses may not faithfully represent the amount of biologically available or active quartz in all mines with a high level (greater than 5% ) of quartz in the dust For example, some mine dusts might contain predominantly occluded (or coated) quartz particles where bulk analysis would result in anomalously high ""free silica"" measurements. The same result would occur when quartz particles are intermixed substantially with other minerals that can alter the surface of the composite particle away from a quartz-behaving character."

Mar 1, 1992

By Gérald Riverin, Bernard Boily, Daniel Bernard

"The Donalda gold deposit is located in the southern part of the Noranda camp, approximately 2 /em east of the Horne deposit. Combined past production and current reserves total over 1.5 Mt grading 6.9 grams of gold per tonne.The deposit consists of two main veins which are both narrow but persistent structures. The No 1 Vein, hosting about 80% of the gold ore, consists of an EW-striking banded quartz vein dipping on average 25° to the south. Although variable in thickness, it averages lessthan1 metre. TheNo2 Vein, located 300 m below the No 1 Vein, is similar to it except that it dips 50° south. Gold occurs mostly as fine native gold disseminated in quartz, with 2-3% pyrite and trace amounts of various sulphides and tellurides. The wall rocks are only weakly altered and mineralized with pyrite, hematite and sericite.Structurally, the Donalda deposit is centered on the Horne Creek fault (HCF) where the HCF is intersected by the ENE-trending DonaldaandCentralfaults.NorthoftheHCF,theNo1Veinishosted by the Quemont Rhyolite, whereas south of the HCF the vein is hosted by magnetic basalts and diorites of the Wilco Andesite Formation. The No 1 Vein extends across the HCF with only minor displacement, whereas the No 2 Vein has not yet been traced south of the HCF.A preliminary structural analysis of the mine shows that the HCF, which strikes 275° and dips 70° north in the mine area, has a reverse movement a lid that the flat dipping No 1 Vein is a tension vein. Both probably developed in response to the same stress conditions. Although the absolute age of the Donalda veins is not known, structural relationships indicate that they formed during the latest movements of the HCF, but prior to the intrusion of the Proterozoic D' Eldona Diabase. The occurrence along the HCF of gold-rich synvolcanic massive sulphides and much younger vein-type gold deposits (such as Donalda) indicates that the HCF was a very long-lived, deep-seated (?)structure which has controlled the circulation of gold-rich fluids over a long period of time."

Jan 1, 1990

By P. R. Taylor

Diamond films have been successfully formed in an inductively coupled plasma (ICP) chemical vapor deposition (CVD) system from several gas mixtures: CH,-H,, C2112-112, and C2112-112-02' Our previous thermodynamic study indicated that the substrate temperature could be lowered by the presence of oxygen species at moderate system pressures (0.3-0.5 atm) and that higher volumetric growth rates required a high temperature source and a moderate pressure system in CVD processing. The principal experimental results were consistent with the thermodynamic predictions. The deposited films were characterized by laser Raman spectroscopy, scanning electron microscopy, and X-ray diffraction. The films were well faceted and uniform, with the growth rates over 10 pm/hr on molybdenum substrates. The crystal size ranged between 1 and 2 microns for a two hour experiment. It was possible to decrease the substrate temperature to below 800 °C in this system.

Jan 1, 1995

By Brent Wilkins

The project team was tasked with the design and installation of a deep foundation system to support an expansion to a power generating station in Glenrock WY. Cast-in-place piles installed by a fixed mast drilling platform were assessed to be the most efficient foundation system for the subgrade conditions and range of design loads for the project. It was determined that conventional augered, cast-in-place piles could not be installed to the required pile toe elevations. Subsurface materials consisted of interbedded coarse- and fine-grained soils to about 23 ft to 30 ft depth below the ground surface, underlain by carbonaceous shale (claystone) with interbedded sandstone. The overburden materials varied from very soft to medium stiff and loose to dense. The claystone was typically foliated and very weak to weak whereas the sandstone was typically massive and very weak to weak. The site characterization consisted of a variety of field and laboratory programs including soil borings with Standard Penetration Tests, pressure-meter testing, and geophysical testing. A load test program was performed involving the compressive, lateral, and tensile testing of piles ranging from 14-in to 24-in diameter. Compression test piles were instrumented with vibrating wire strain gages. The paper includes a discussion of the regional and local geologic and geotechnical parameters, particularly the results of the various in situ and laboratory test programs. The selected foundation system is introduced. Load test results are then presented along with analysis and discussion of these results with regard to performance of the piles in the claystone.

Jan 1, 2009

By L. K. Nenonen

"Given the properties, locations and quantities of material to be hauled and the dump locations and capacities, the designer wishes to select the type and number of trucks and loading equipment required. Accordingly, software is being developed to assist in creation of the equipment, material and road network data bases, in selection of equipment, materials and road networks from these data bases, and in evaluation of the expected productivities both in a rapid, non-interactive, approximate fashion and a more detailed interactive fashion which permits the user to act as superintendent, if he so chooses. The basic technology has been developed and applied to an open-pit copper mine and is being refined and generalized for oil sands and coal mining applications.BackgroundA set of mathematical and interactive computer models are under development to aid in the selection of equipment and operating policies for an open-pit oil sands mine being planned by Canstar Oil Sands Ltd. This paper describes the computer models being developed of truck haulage systems. Although the interactive truck haulage model is based primarily on a model developed by the National Research Council in collaboration with Glenayre Electronics Ltd. of North Vancouver and Lornex Mines Limited(2).(3l, substantial changes and improvements are being incorporated to greatly increase its generality re equipment types, road network characteristics, dispatching and supervisory policies, etc. Although this paper is principally devoted to the truck haulage model, discussion is included concerning its interactions with other models."

Jan 1, 1982

By Kenneth W. Luke

In the development of the ultimate pit limits for a narrow ore body, pa¬rameters necessary in the design of a functional, or working, pit become highly sensitive factors in the determination of ore reserve levels and their associated waste to ore stripping ratios. Through the use of geologic cross sections, ore reserves can be roughly calculated by utilizing a straight line approximation for pit wall slopes. The optimum position of the pit floor can be substantially altered from such a preliminary design though with the introduction of functional mining parameters, such as a ramping network, and working bench heights, berm widths, and bench to bench wall angles. Originally a computer program was developed to quickly evaluate changes in cross-section pit design with minimal alteration of input data. After developing a satisfactory technique of cross-section evaluation which incorporates working mine parameters, an optimization algorithm, or procedure, was developed and included in the program to eliminate much of the tedious manual decision-making required in determining the optimum location of the pit floor on each cross section. Optimization in this case implies the maximum profit pit. When pit and processing costs are defined or hypothesized, this computer program can be used to design the maximum profit pit, constrained by the recognized functional mining parameters. A second way of stating the optimization is that the program can be used to develop a pit design which minimizes waste stripping at any desired ore reserve level. The basic method of cross-section evaluation parallels present manual methods. Program input is a combination of data obtained directly from cross sections developed for, geological interpretation and pit design parameters selected by the mine planner. As a result it is easy for the mine planner to comprehend what the program is accomplishing, and thus participate in the development of the computer assisted design.

Jan 1, 1971

J. S. UNGER, ? Pittsburgh, Pa. (written discussion ?).-Firebricks intended for, the same purpose, but supplied by different manufacturers, may be of entirely different clays, contain different proportions of flint, calcined and plastic clays; the particles may vary widely in size; the water used to make the brick will vary; the pressure in molding will vary, depend-ing on whether the brick is hand made or power pressed; and the degree of burning in the same kiln will differ. These variables affect the melting point and the strength of the brick when heated. An important property, of a firebrick is its ability to resist heat and, at the same time, weight or load without serious deformation. The soft-ening point and the melting point of a firebrick may be several hundred degrees apart, and two bricks may show considerable difference in their softening points, but the melting points may be approximately the same. Bricks are not usually employed at temperatures close to their melting points. If they must withstand very high temperatures, the firebrick is discarded and a brick of more refractory material is used. Under these conditions' it is doubtful whether the determination of the melting point of a brick has much practical value. If the determination of the melting point is necessary, the test should he made on a portion of the original brick and not on a specially prepared sample. A small triangular pyramid with a base about 1 1/2 in. and 3 in. high can be sawed from the corner of the brick with a thin-bladed car-borundum wheel, without injuring or destroying the size of particles, the bond, or degree of burning of the original brick. This specimen can then he compared with standard Seger cones or tested by any other method desired.

Jan 12, 1919