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By David E. Fogelson, James J. Olson

Rock mechanics as a guide to a safe underground operation is gaining importance as more is under- stood of rock behavior under stress and of the competency of rock after blasting. The U. S. Bureau of Mines' Twin Cities Mining Research Center and White Pine Copper Co. personnel undertook a joint research program recently to define how the rock adjacent to a newly opened underground working could be left as undisturbed as possible. The goal was to leave a competent structure which would tend to limit rock falls and thus decrease the incidence of fatalities from this greatest of all underground hazards. High-amplitude stress waves and borehole gases create a crushed zone in the rock, the thickness of which is about equal to the borehole radius. Beyond the crushed zone, additional structural damage occurs to the rock from the microstructural level up to visible fractures that may extend several feet. This type of rock damage near the final excavation lines reduces rock strength and increases the possibility of failure of the openings from subsequent vibrations or stresses.

Jan 9, 1969

By Behram H. Wadia, Robert S. Lehto

A new metallurgical treatment for capturing as much of the values as possible from zinc refinery feed has been devised by personnel in Cerro de Pasco's Peruvian operation at La Oroya. Results from a pilot test illustrate that 50 metric tons of throughput can be maintained whereby substantially all the silver and copper report in the sponge iron while zinc and lead with indium and cadmium volatilize in the fume. This new technique named the Zileret (zinc leach residue treatment) process complements the electrolytic system used in the refinery so that all values in a zinc concentrate are economically recovered. In the system, dried zinc leach residue is pelletized with soluble zinc sulfate which already exists in the leach residue and a finely divided reducing agent such as anthracite coal. Upon heat addition, the loose anthracite in the charge maintains a reducing atmosphere while the free space above the charge has an oxidizing nature. When the charge reaches the reaction zone at about 1100°C, metals such as zinc, lead, cadmium and indium volatilize from the pellets, are oxidized in the upper kiln atmosphere, and are then carried in suspension as an oxide fume to the cooler and baghouse. The copper and silver content in their reduced forms, along with the iron, discharge from the kiln as a calcined product which is then cooled to below 130°C before being exposed to the air.

Jan 9, 1969

By John V. Beall

Homeland of the Republic of China, the island of Taiwan looks on the map like a seal, muzzle pointed south, resting complacently on the emerald waters of the China Sea. Any notion of placidness is quickly dispelled by going to that country where the visitor gains the impression of almost violent busyness in tearing up streets, pushing up buildings and tilling the fields. Driving from the airport downtown to Taipei, the capital city, one sees roads, streets and thorough-fares which seethe with bizarre traffic. From water buffaloes to buses, transportation takes every conceivable shape, size and color in between. The load being transported need not conform in any way to the capabilities of the vehicle. Twenty- foot lengths of pipe may be trans- ported on a bicycle. A family of five may go to town on a motor- cycle. Impossible? Count them. The streets and buildings of the city appear unrestrained, or without margins. Shops do not end at the doorway but overflow with a variety of goods onto the sidewalks and into the streets where the marginal traffic, on foot or on wheels, intertwines unconcernedly with the flotsam from the shops. Signs, dry goods, hardware and the continuous hubbub make the view colorful, lighthearted and fascinating. The island is 230 miles long by 75 miles wide with a central mountain spine. To the east, the mountains descend steeply to the ocean whereas to the west, beyond the foothills, there is a broad coastal plain. Only about 25% of the land is suitable for cultivation but the tropical climate permits several harvests a year. At the same time the mountains, which are high enough to sometimes have snow, offer an agreeable change of temperature. In this setting, society has created an economy that is growing at such a rate on all fronts that it would seem to be fairly bursting at the seams.

Jan 9, 1969

By Edward C. John, Wilbur H. Smith

At the Bingham Canyon pit operated by Kennecott's Utah Copper Division, the demand for geology has recently grown and diversified so rapidly that it has necessitated a revolution in geologic mapping techniques. The most significant changes in method have been in the preparation of the base map and in the computer application of collected data. Formerly maps were prepared by surveying with a transit or plane table. Now, however, a photogrammetric map with a scale of l in. to 200 ft is prepared semiannually and updated continuously to keep pace with the removal of more than 350,000 tons of material a day. Larger-scale bases of areas with specific problems such as un- stable slopes are prepared with aerial and terrestrial photography and photo-mosaics. Note sheets designed for computer application speed the processing of data. The multiplying applications of geology at the Bingham mine now include studies of the effect of structure, rock type, and alteration on slope stability, the relationship of sulfide mineral distribution to concentrating results, the effect of rock and mineral types on waste dump leaching, and the requirements of a reliable internal source of silica flux for smelting, as well as many others.

Jan 9, 1969

By K. Tajrych

Time and again, lives are lost in underground cave-ins only be- cause there is no quick, sure way of locating the victims. When such accidents happen, rescuers must usually depend on the testimony of eye- witnesses for information on the whereabouts of trapped miners. Seldom is this information reliable. The witnesses themselves have just been through a traumatic experience that has distorted or destroyed their sense of time and place. A far more reliable method of finding men underground has recently been developed by the Coal Mining Research Institute of Ostrava, Czechoslovakia. With this system, a miner can be located with adequate precision even if he shows no sign of life. For the system to work, the miner need only have his electric cap lamp somewhere nearby. The system consists of a minute radio transmitter operated by the lamp battery (Fig. 1). This tiny transmitter continuously emits high- frequency electromagnetic waves that can be picked up by a sensitive direction-finder receiver in case of accident.

Jan 8, 1969

By Tuncel M. Yegulalp, Malcolm T. Wane

In general, many problems relating to the exploitation of mineral deposits are probabilistic in nature. This derives from the fact that the geologic universe is inherently random. Probability theory and statistics have been found useful for forecasting the behavior of natural events that occur in the geologic universe. The objective of this paper is to outline the application of the theory of extremes to this forecasting problem. Consider the design of an underground structure or the design of a rock slope. The initial step is the formulation of the various possible structural actions which result from the geometry of the layout. For a given structural model, various intensities of behavior are possible depending upon the load, deformation, and material characteristic spectra, respectively. Of popular interest to mining people is the failure behavior or condition. A necessary feature of the analysis is the rupture strength of the material. Information on the rupture strength is derived from testing either in situ or in the laboratory and the usual outcome is a variation in the test results. This variation is overcome by constructing a frequency distribution of rupture strengths, and then determining a measure of central tendency and variability. The main feature of interest in the analysis is the failure characteristic and its percentage chance of occurrence. Hence, one is naturally led to examine those areas of a distribution curve which are termed the tails. The statistical concepts which can most efficiently handle such areas are contained within extreme value statistics.

Jan 8, 1969

By A. H. Smallbone, R. Lathe

Considerable efforts have been expended to apply multiple regression techniques to quantitative determinations in x-ray fluorescence analysis. Multiple regression has been shown to be an effective method for correlating x-ray fluorescence intensities to elemental concentrations. Although many other techniques have been devised to solve the problem of matrix effects in x-ray fluorescence analysis, there are few as efficient in terms of storage requirement or ease of programming for digital computers as the multiple regression method. In the case of ore slurry, it has the additional advantage of allowing a unified approach to the problems of slurry density correction and matrix effect corrections. The data used in the present work were obtained with an on-stream x-ray analyzer capable of analyzing 15 slurry streams for as many as nine elements simultaneously. One of its fixed monochromators was set to accept scattered radiation at a discretely selected wavelength as a means of monitoring the slurry's pulp density. The data were reduced to obtain the correlation equations and a computer program combining slurry density with matrix corrections was written in FORTRAN IV to calculate concentrations.

Jan 8, 1969

By John V. Beall

Monotonous flood planes flanked either side of the road as we drove in the embassy car from the airport to downtown Seoul. We crossed the brown waters of the Hann River, meandering over mud flats. A great, gnarled tree bore beautiful fall colors of gold. "That is a Ginko Tree, the oldest living fossil, probably a hundred million years old;" said Jean W. Pressler. Compared to other cities of the Far East, the traffic in and around Seoul was sedate. Few motorcycles or bicycles, and little superfluous horn tooting. "This is the best season in Korea. We have long beautiful springs and falls," said Pressler, chief of the mining branch of USAID, and he continued with a briefing on the country.

Jan 8, 1969

By Virgil W. Carmichael

In the Fort Union formation of western North Dakota, eastern Montana and northeastern Wyoming there are immense tonnages of lignite and subbituminous coal that have not yet been evaluated in terms of present economic conditions. The general lack of detailed geologic and topographic maps of this region, coupled with a considerable interest in some of its deposits, has spurred the North American Coal Corp. to develop a rapid, economical method of producing its own maps on which to base a quantitative evaluation of the coal reserves involved. The techniques the company employs in this mapping and evaluation program are simple photogeologic and photogrammetric procedures that can also be applied to other exploration and mining work. The air photos, in addition to being used for photogeologic interpretation, have been successfully applied to locating drainage cuts, haul roads, and road metal deposits as well as for various property studies and general mine and reclamation planning. The present discussion will deal primarily with North American's photogeological reconnaissance method of mapping and evaluating relatively flat- lying to shallow-dipping coal beds with limited topographic control and a minimum of core drilling. The field tools employed under this method include aerial photographs and pocket stereoscopes, engineering levels, aneroid barometers, portable transceiver radios and core drills. Field information developed on the photos is transferred to maps for measurement of reserves and overburden. To date this method has been used to map and analyze nearly 6 billion tons of Fort Union lignite and subbituminous coal.

Jan 8, 1969

By C. O. Brawner

Simple, specific rules for achieving slope stability in open-pit mines are impossible to devise. Each pit has a different mining program and a different set of environmental conditions, and its final slope design must be based on an individual evaluation of the actual site. The overall philosophy of pit stability, however, is tending towards a limit design concept. Since slope angle has a great influence on the economics of most open-pit mines, efforts are being made to reduce the theoretical factor of safety for slope stability to very near 1.0. (Factor of safety is here defined as shear strength/shear stress on the most probable plane of failure.) Actually, where detailed, statistically significant testing has been done and a comprehensive ground control program is being instituted to warn of movement at an early stage, safety factors as low as 1.1 or 1.2 may be justified. The cost of the necessary procedures, however, is high. There are many factors that influence stability, but this article will be confined to three-rock structure, groundwater, and blasting.

Jan 8, 1969

By John M. Karpinski, David S. Cahn

For many years the green and dry compressive strengths of pellets have been considered as possible criteria of pellet performance during induration. Little attention, however, has been given to standardizing the unfired pellet compressive strength test or to determining the characteristics of this test. The purpose of this study was to compare the constant deformation rate test with constant loading rate tests. In addition, the dependence of these tests on such pellet properties as size and weight was to be investigated.

Jan 7, 1969

By Kent E. McElhattan

Selecting efficient machinery for an underground mining operation is a highly skilled art that still depends largely on human judgment and experience. In a coal mine, for example, there is no better way to predict the results of operating with a cutting machine or a continuous miner than to go underground with a sharp-pointed miner's pick. The trained eye can detect the depth of point penetration, cleavage planes, roof and floor strata, and many other conditions impossible to determine in a laboratory. Even so, however, an entirely new set of conditions may lie unexposed just a few feet behind the solid face. The candid truth of the matter is that practically nothing is known of the phenomenon of extracting a mineral from a solid. Consequently, the selection of mineral extraction machinery and systems must be based on results obtained elsewhere under apparently similar conditions. A recent study of the problem of equipment and system analysis was conducted in the coal mining regions of West Virginia. This state was chosen for study because it afforded representative sampling. The 172 coal mines investigated ecompassed seam heights ranging from less than 30 in. to over 84 in. and covered virtually all known coal mining conditions except two. The exceptions are the extreme pitch of coal seams in the western United States and British Columbia and the "bumps" encountered in the Rocky Mountains. Both of these extreme conditions are worthy of individual study.

Jan 7, 1969

By H. T. Mulryan

For the producer of industrial rocks and minerals, marketing is often the only means of survival. His material must be sold. There is little of the impersonal force of the market regulating supply and demand. No commodity exchanges facilitate his efforts to dispose of the material he produces, and the success or failure of his business depends primarily on prompt and correct response to market needs and requirements. This response is particularly vital where materials of low unit value must be shipped to distant consumers owing to a relative rarity of suitable deposits. The advantage of positive response to change can best be illustrated by hypothetical cases showing how problems can be turned into opportunity through marketing ingenuity. Three such cases dealing with materials of unit values in the range of $5 to $100 per ton are outlined below.

Jan 7, 1969

By H. C. Rolseth, R. H. Kohler

Jet channeling made its entry into the granite industry in 1955 and quickly gained acceptance as an economical method of quarrying. Developed by the Linde Division of Union Carbide Corp., this method employs a small rocket-jet burner with a high-temperature, high-velocity exhaust flame that causes granite to disintegrate. It can thus make continuous vertical cuts to free large blocks from granite formations. The Thermal Spalling Process The effect of a thermal device on rock depends upon the rock's spallability. In simplest terms, spalling is the decrepitation resulting from differential expansion of rock crystals due to thermally induced stresses.1 the individual rock properties influencing the spalling characteristic are so numerous and their interaction is so complex that it has so far been impossible to predict with accuracy the reaction of any particular rock to a high-temperature source of heat. Perhaps computers will eventually make such predictions possible, but for the present it is necessary to impose the thermal shock conditions on a sample of the rock to establish its spalling characteristics. The properties most favorable to a high degree of spallability are: (1) Large linear thermal expansion at temperatures below 700º C. (2) High thermal diffusivity at temperatures below 400º C. (3) Equigranular interlocking structure with little or no fine-grained clay or mica alteration products. (4) No significant amounts of soft, low-melting, or elastic minerals or materials which yield after thermal decomposition.

Jan 7, 1969

By S. Terry, W. Callender, R. J. Cornelius

When a dry ball-mill grinding circuit was in- stalled at the pellet plant of Hamersley Iron Pty. Ltd., it was something of a pioneering venture, since this was one of the first instances where such a circuit had been applied to iron ore on a major scale. The Hamersley pellet plant is located in Dampier on the coast of Western Australia. The feed for it consists of -8mm fines produced as a screened product at the Mt. Tom Price mine 186 miles inland from Dampier. It was these fines that encouraged the choice of a dry grinding facility for the plant. At the outset, tests had shown that the fines could not be filtered satisfactorily with a wet grinding system. At the pelletizing plant, the fines are stockpiled, reclaimed, dry ground in ball mills, formed into pellets on balling discs, hardened on an indurating line, and stockpiled for shipment overseas. These operations are shown in Fig. 1.

Jan 7, 1969

By E. Pothas, P. R. Jochens, L. B. McRae, D. D. Howat

Discussion H. J. S. Kriek*: During 1956 Iscor became interested in the acid smelting in a blast furnace of siliceous ores containing 15 per cent silica. This interest was as a result of the successful acid smelting in Germany at a CaO/SiO2-ratio of between 0.4 and 0.8. Acid smelting can become an economic proposition due to a reduction in slag volume accompanied by a lowering of the coke rate. Paschke and Hannel1 found that a free flowing slag (i.e. viscosities of less than two poise) would not be obtained at C/S-ratios lower than 0.82 and that the addition of 3 to 4 per cent alkalies became necessary. In titanium bearing slags it was established that maximum fluidity is obtained with 10 per cent TiO2. Acid smelting resulted in increased sulphur pickup with decreasing O/S-ratio and desulphurization with soda-ash outside the blast furnace was necessary. At Iscor Mr B. B. Segal established that, for slags with (CaO+MgO)/SiO2-ratios of 0.5, 0.6 and 0.7, the addition of alkalies and TiO2 resulted in a substantial decrease in melting point and also of viscosity. At a (CaO+ MgO)/ ratio of 0.53 the addition of 10 per cent TiO2 is as effective as the addition of 3.75 per cent alkalies. This means that a blast furnace can be run without the addition of alkalies and consequently the detrimental effect of alkalies on the lining can be avoided; also that fluid slags with 5 to 15 per cent MgO and 8 to 10 per cent Al203 can be obtained with 10 per cent TiO present. (CaO+ MgO)/SiO2-ratios smaller than 0.5 the addition of titania resulted in a decrease in melting point and also in an increase in viscosity. In ceramic crucibles the slag did not become more viscous with time but thickened appreciably when held in graphite crucibles. No titanium carbonitride could be detected and only Ti20a was found. Prof Howat also did not obtain the TiC-TiN solid solution and therefore it appears that the thickening of the slag is not solely due to the formation of the titanium carbonitrides. This is in agreement with the work of Michailov and Belyakova2 who found that TiO2 decreased the viscosity of acid slags and increased the viscosity of basic slags; that titanium sesquioxide (Ti203) and titanium monoxide (TiO) increased the viscosity of both acid and basic slags and that titanium carbide, which is found in larger amounts in basic slags than in acid slags, considerably increases the viscosity of both acid and basic slags. Patzak et al3 describes the following oxygen deficient titanias, viz Ti2O, TiO, Ti203, Ti3O5, Ti4O7, Ti5O9, Ti6O11- Ti10O9,Ti7O13,Ti8O15 and Ti9O17. Until about 1959 a fair amount of data was available on the viscosity of normal slags to which titania was added2, 4, 5, 6, 7, 8, 9. At Iscor an electromagnetic viscometer based on the viscometer developed by Bockris10 was built. Progress was very slow as our main attention was centred around problems associated with the operation of the Rotor process. During 1962 and 1963 two papers containing fundamental work on the viscosities of slags in the systems CaO-SiO2-TiO211 and CaO-SiO2-TiO2 at 0 per cent A1203, 10 per cent Al203 and 20 per cent Al20312 appeared. The work of Ross and Ohno obviated the necessity of any further work by Iscor on the viscosity of blast furnace slags containing titania. Ross gave the following optimum compositions for blast furnace slags containing titania. Titania % Lime % Silica % Lime/Silica-ratio 20 30-42 38-50 0.6-1.10 30 27-36 34-43 0.63-1.06 40 24-32 28-36 0.66-1.14 The optimum temperature is 1,500°C because at this temperature the largest workable composition range exists. Higher temperatures result in narrower optimum composition ranges and in increased rates of thickening. The factors affecting the rate of thickening were also investigated by Ross and Ohno, as the main problem with slags containing titania is not finding compositions which are fluid at operating temperatures but the thickening due to a lack of oxygen. With these slags when there is insufficient oxygen to co-ordinate each silicon atom with its own individual shell of four oxygen ions, some sharing of oxygen ions must occur, resulting in the formation of large silicate ions and a rise in viscosity. The formation of oxygen deficient titania can be prevented as long as iron oxide or manganese oxide remain in the liquid slag. Iwase13 and also Viens, Camp bell and Rogers14 obtained in the experimental smelting of ilmenite ores fluid slags with more than 3 to 5 per cent manganese oxide and ferrous oxide in the slags. It appears that titaniferous ores can be smelted in blast furnaces under the following conditions: (1) Acid slag operation, i.e. at C/S-ratios from O.6-1.0. (2) Dolomite can be used as a flux as MgO is a network modifier. (3) The Al2O3-content must be less than 15 per cent as alumina promotes thickening of the slag and decreases the optimum composition range. (4) The hearth temperature must not exceed 1,500°C. According to Ross a definite amount of energy is required for each ton of iron produced and in order to increase production an increase in heat

Jan 6, 1969

By Frank E. Briber

In the years ahead, the industrial minerals producer will face several major challenges. Not only will he have to market increasing quantities of his product economically, but he will have to do so from lower grade deposits that are farther away from the marketplace. At the same time, he will have to comply with more regulations controlling the handling and disposal of waste products and get along with relatively less available labor than he has at present. Accordingly, industrial minerals developments of the next 30 years will be directed primarily toward helping the producer meet these challenges. There will be greater raw materials usage, new processes, new marketing practices affecting plant location, size and complexity, and maximum automation-all aimed at producing more materials at lower cost. Processes To Make the Most of Materials In future processes for industrial minerals, there will be great emphasis on more or total use of the initial raw materials or plant feed stock. This approach will result in the application of more and more concentration methods to the treatment of industrial minerals-both conventional processes and new ones that might be developed in conjunction with pyro-processing. High-intensity and electrostatic separation are certainly two areas which will see greater use in the field.

Jan 6, 1969

By Jacques B. Wertz

Even with the best geological maps, there is a constant need for further information and a constant demand for new clues, particularly in exploration work. New ideas and new thoughts are a necessity for progress. In the structural study of an area, be it in Arizona, Africa, or British Columbia, the basic fracture pattern has to be determined first. There is, however, no assurance that the trends shown on the map are really meaningful because they often are secondary in nature, having occurred as a consequence of an intrusion, of doming, or of gravity faulting. Thus, such trends often are a weak basis for assuming the presence of ancient and important zones of fractures that could constitute useful guides to mineral exploration.

Jan 6, 1969

By C. A. Stiles, J. W. Nyhus

Erie Mining Co. is a 10.3-million-tpy pellet producer on the east end of the Mesabi Range 60 miles north of Duluth. Its complex includes facilities for mining, crushing, grinding and beneficiation in addition to a pellet plant and power plant. A 74-mile railroad links the mine and plant to Taconite Harbor on the shore of Lake Superior. The concentrate recovery ratio at Erie is about 1: 3, and this, along with stripping activity, makes it necessary for the company to mine nearly a million tons of material a week. At the outset, all crude ore mined at Erie was hauled entirely by rail, but with expansion into additional mining areas, the company made a gradual transition towards truck-to-rail haulage. Today, in Erie's 11th year of operation, over 50% of all crude taconite mined is transported by truck to loading pockets where it is transferred to rail cars. Future years will see more taconite moved in this manner. Thus, the company has an increasing interest in tire performance.

Jan 6, 1969

By John V. Beall

As recently as 1964, the situation in the Australian iron ore industry was chiefly one of potential. The only producer was the Broken Hill Pty. (BHP). That company mined about 5 million tpy from deposits in the Middleback Range in South Australia and at Yampi Sound in Western Australia. No ore was exported from Australia. Now, just five years later, and after expenditures amounting to approximately one half billion dollars, BHP and seven new companies exported about 15 million tons (long tons) of iron ore and pellets as well as meeting Australia's own annual requirements of approximately 8.5 million tons of ore. Early this year, the volume of iron ore on order stood at 328 mil- lion tons to be delivered over a period of 15 years, but Cliffs Western negotiations for sale of Robe River iron ore have boosted the volume to the new high of 466 million tons. All of this has meant a great deal to Australia in terms of new income. In fiscal year 1967 (ending June 30, 1967) exports of iron ore amounted to $52 million; in 1968, $128 million and by 1'972 the Bureau of Mineral Resources expects the value of exports from iron ore to reach $242 million. In achieving the position of major- supplier of iron ore to the Japanese steelmakers, it was necessary to build a great many new facilities, mostly in Western Australia. Three railroads, 70 miles long, 182 miles and 265 miles were constructed. A new port was created at Dampier; Port Hedland was deepened and otherwise improved; both of these ports are in Western Australia. In Tasmania, Savage River developers built an offshore shiploading station that has received the recognition of engineers internationally. At least a half dozen new communities have been founded. The narrow gage railroad from Kalgoorlie to Perth and Freemantle was replaced with a standard gage line.

Jan 6, 1969