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By Howard E. Kremers

Although more than 100 thorium-rare earth minerals are known, only a few have any commercial significance. Monazite, thorite, bastnasite, and some exotic thorium rare earth ores are reviewed Commercial interest is presently centered on monazite from the Union of South Africa, and thorite from this country. Thorium became commercially important with the development of the incandescent gas mantle about 75 years ago, Gas mantles consist of thorium oxide with small amounts of cerium oxide. The thorium nitrate used to make gas mantles was first obtained from rare thorium minerals, As a matter of fact, this use of thorium is still important and is one of the largest commercial uses for thorium materials. The discovery of monazite sand placer deposits along the coasts of Travancore, India, and in some Brazilian beach s .s, and the development of the old North and South Carolina monazite stream placers gave the mantle industry of 30 to 40 years ago a comfortable inventory of thorium ore. Even today, the thorium industry depends largely upon monazite ores for its source of thorium. This paper will briefly describe some of the major thorium ores and their principal deposits insofar as they relate to the thorium industry in this country. Because of similar chemical and physical properties, thorium always occurs with the rare earth elements and with varying amounts of yttrium. Thorium may predominate over rare earths, as in thorite-type minerals, or may represent only a fraction of the rare earth content. Typical ratios of thorium to rare earths in various minerals are given in Table 1, The average thorium content of the earth's crust is about 12 grams per ton, and in this respect thorium approximates lead, molybdenum, and some of the rare earths in abundance. The ore minerals of greatest importance to the-thorium-rare earth industry are monazite, thorite-type minerals, bastnasite-type- ores, and the family of minerals which is characterized by a preponderance of the heavy rare earths and yttrium. The latter classification includes xenotime, gadolinite, samarskite, euxenite, etc, The first two, monazite and thorite, are of greatest significance.

Jan 1, 1958

By O. M. Arafat, J. A. Finch

"The Functional Performance Equation calculated from a plant grinding survey defines two distinct ball mill circuit efficiencies and how they relate to total production rate through the target grind size. The survey data are also used to calculate a complete ball mill size distribution model, represented by the energy specific grinding rates, not just through the target grind size, but through all the size classes. Cyclone separation performance is represented by individual size recoveries to underflow. When these two unit operation performances are entered into the circuit modelling program (Streamline™), along with the circuit feed rate and size distribution, all the circuit survey size distributions and mass flows are perfectly regenerated by the program. The many issues associated with the historical Epstein (breakage-selection) models are eliminated. Once the circuit program is populated, pump and cyclone performance changes can be evaluated using a step-by-step procedure in order to maximize Classification System Efficiency. Mill water use and media sizing opportunities are also diagnosed in order to maximize Mill Grinding Efficiency at the size of interest. An example is provided. This circuit analysis and modelling system, and related training, is provided through a web-based application. INTRODUCTION Since its development (McIvor, 1988), the Functional Performance Equation for ball milling has facilitated new understanding of industrial circuit cause and effect relationships, leading to significant strides in operational performance. Success stories of this refreshing approach to plant circuit performance improvement are now too numerous to list. Finch and McIvor (circa 1986) also discovered that the Functional Performance “Mill Grinding Rate” at the size of interest was the same cumulative grinding rate that is calculated from mill feed and discharge size distributions using a first-order rate equation. By calculating these cumulative grinding rates for all screen sizes, a complete ball mill model is generated (as used by Finch and Ramirez, 1981). Others in industry, Hinde and Kalala (2009), for example, have noted the same. Lacking the complexity needed to maintain their interest, most researchers have ignored this model, broadly opting instead for Epstein’s (1948) characterization of grinding as a chemical reaction, combining “selection rate” and “breakage size distribution” functions. The much simpler ball mill model presented here has previously been incorporated into a proprietary circuit modeling program (McIvor, 2005) and used for plant improvement work (for example, see McIvor and Finch, 2007, and McIvor, 2014). Now, by combining this extremely business-friendly ball mill model with optimization criteria from Functional Performance Analysis, a circuit modeling system (including the needed supplementary steps to assure successful plant implementation of circuit design changes) is at the disposal of every plant metallurgist, grinding equipment/material provider, and circuit designer."

Jan 1, 2017

By Werner Wenzel

Whisker growth during the reduction of iron ores The phenomenon of whisker growth can be observed in a number of solid-state crystallisation reactions, which, apparently, appear in6 the first instance as though they are two independent processes. From such reactions, one can find the whisker type of crystallisation on solid bodies. These examples show, that the whisker growth is neither due to certain crystal forms with predetermined temperature and pressureranges, nor to parameters, which, ad hoc, are necessary for the crystallisation. In all cases the whisker formation seems to depend on nucleation and the availability of crystallizing material in direct environment of such a nucleus, under given parameters of a system. One can generally state, that the research of whisker growth with the aim of establishing proper physical laws, to determine the foundamentals of whisker formation and whisker growth, is at present under active study. We can conclude that, although a great number of hypothesis have been proposed; no concluding theory has yet been arrived at. In the institute for ferrous metallurgy of the technical university of Aachen, research works are undertaken to find an explination to various metallurgical phenomena through help of whisker growth which was observed under varying conditions of iron ore reduction. This was possible by using refined microscopic techniques through which the whisker growth on solid oxyde substrates is detected. This refined technique combines the latest methods of surface examination with the help of stereo-scan-electron-microscope and proper and carefull preparation of surface to be stereo-scanned.

Jan 1, 1971

By Joe B. Rosenbaum

Waste solutions from sea water desalination processes are enriched in minerals by a factor of two or three. This suggests that extraction of selected mineral components from the concentrated brine might help pay desalination costs. The possible recovery of gold has received particular mention. Sonstadt, in 1872, reported the gold content of sea water as 65,000 micrograms per cubic meter, or 65,000 parts per trillion. At $35 an ounce, this is equivalent to $0.065 per ton of sea water. Fritz Haber, however, after his abortive venture to restore Post War I Germany to economic health by recovering gold from the sea, concluded the gold content was 4 micrograms per cubic meter. Haber's analysis is equivalent to 0.0004 cent per ton. In the past 10 years, investigators using advanced analytical techniques reported from 4 to 27 micrograms per cubic meter. Our brief experiments to determine a threshhold value for the gold in sea water employed solvent extraction for initial concentration, evaporation of the gold-loaded organic for further concentration, and atomic absorption analysis of the gold in the concentrated organic. Radioactive gold was used as a tracer for monitoring the gold through the concentration and analytical steps. Our method established that sea water contains about 11 parts gold per trillion parts sea water, or 0.001 cent worth per ton. This agrees closely with results of recent studies by other investigators employing ion exchange resins and neutron activation techniques.

Jan 1, 1969

By J. L. Fuller

Thousands of mine air samples are taken underground each year by MSHA inspection personnel in order to further assure that miners have a safe and healthy environment in which to work. While most air samples are taken with stain tubes, many samples are obtained in evacuated containers and returned to a laboratory for more accurate analysis on a gas chromatograph. In order to enhance the accuracy, reliability and repeatability of the samples taken with evacuated containers, improved procedures have been developed, which are described in this report, for filling two different types of evacuated sample containers using either mechanical or electrical pumps. In those instances, such as when sampling strata gases in drill holes, where mathematical calculations may be required for proper sampling, example calculations are provided. The use of a third type of evacuated container, which is generally restricted to non-specific sampling of the ambient mine atmosphere, is also described.

Jan 1, 1986

By Allan M. Johnson

Dewatering is a major operational cost at sane mines. Under certain conditions, costs associated with water disposal may continue beyond the productive life of the mine. For mines with mineralized waters, this is of special concern. Since 1974 experience has been gained from the examination of a number of closed underground metal mines that exhibited drainage problems. It was observed in certain cases, that had appropriate steps been taken prior to closure, that the resulting drainage problems could have been largely avoided. The pre-closure steps would have involved alteration to the "plumbing system" of the mines: i.e., the drifts and crosscuts interconnecting the workings of the mine. This could have best been accomplished by the placement of bulkheads and/or selective drifting. In addition to reconfirming that hindsight is 20-20, a lesson learned from these case studies shows that a relatively simple hydrologic evaluation prior to mine closure may avoid a troublesome and costly drainage problem.

Jan 1, 1983

By Joel S. Leventhal

The roles of organic matter in ore deposits are complex and represent a specialized effort in the larger subject of the geochemistry of ore deposits. The organic carbon cycle can be considered with particular emphasis to ore deposits in order to understand the origin and genesis of the organic matter. Organic matter may play one, several, or none of the following important roles in the formation of ore deposits: leaching, transport, concentration, reduction, and precipitation of metals. For deposits that contain organic matter, detailed field relationships and laboratory characterization of the organic matter are required to make an ore deposit model that Includes the organic matter and specifies its role(s). Examples of the involvement of organic matter in several types of uranium deposits are contrasted as being direct or indirect, syngenetic or epigenetic, and necessary or unnecessary. Examples of organic matter in deposits containing gold and lead-zinc, and In metal rich shale are discussed with respect to ongoing work and critical questions.

Jan 1, 2013

By R. D. Coursen

Tin has been one of the very few commodities which has been covered by an international commodity agreement. It is the only metal so covered. The reason behind tin's prediliction for an agreement has been the inconsistency of the price pattern for tin during the entire 20th century. It is not surprising in view - of the wide and wild fluctuations in its price that tin has been called the Cinderella metal. An examination, for example, of prices in 1977 alone attests to the erratic behavior of the tin markets. The high was recorded on October 27 at M$1,895 per picul and the low on January 3 at M$l,314 3/8, on the Penang market, a spread in Malaysian dollars of $581 for a picul weighing 133 1/3 pounds. The first steps in international cooperation on tin were taken after the price bonanza of the First World War. Despite a lack of increased consumption, and in spite of the fact there was no shortage of mining production during the war, prices boomed. Shipping shortages and thinning stocks brought about a situation where in the U.S., industrial stocks were only 1/6 of what they had been in 1914. The boom busted early. In 1921 the tinplate industry of the world had cut its output in half and total world consumption of tin fell by 1/3. Tin producers became so concerned that they created what was called the Bandoeng Pool. It accumulated stocks held by countries now known as Indonesia and Malaysia, amounting to 28 percent of the combined production of the two countries and about 15 percent of the total world for 1921. The pool holdings were shortly exhausted and thereafter in the years 1924 to 1928, general boom conditions existed for tin.

Jan 1, 1978

By Keith Whitworth

The USSR, over the last 20 years, has continued to increase its out-put year by year and it is now almost four times what it was at the end of the Second World War. In 1975, it exceeded 700 million tons of run-oi-mine coal (all ranks) which amounts to over 20 percent of world output. This rapid progress has been due to modernization of the industry, by means of increased mechanization and automation and the development of new machines and systems for underground workings and by the expansion of open-pit workings and the development and implementation of larger earthmoving machines.

Jan 1, 1977

By Ramon B. Santos

The Atlas Concentrator, reputedly the largest in the Far East today, is located on the island of Cebu in the Republic of the Philippines. It started operation on a 4000 TPD capacity in 1955. An expansion program, coupled with significant improvements both in the Crushing Plant and the Mil, made the Atlas Concentrator what it is today, treating about 14,000 tons of ore per day at a comparatively low cost of about $0.50 per ton treated. The Atlas Copper Mine is at present mainly an open pit operation, with ore supplied from two pits (Lutopan and Biga) north of the Concen¬trator. Development of an Underground Mine, situated on the main ore body at Lutopan, which will be a block caving operation, has been underway since 1963, and this underground mining operation is expected to b e in full production by the latter part of 1966.

Jan 1, 1966

By Maurice L. Madden

An investigation was undertaken for a ground water discharge plan for the Chino mining complex near Hurley, New Mexico. Operations which impact ground water include dump leaching, storage reservoirs, and tailings seepage. The investigation included both hydrogeological data collection and laboratory analysis. A conceptual understanding of surface water and ground water was then developed. Surface water and ground water models were used to match existing conditions and predict the impact of operational modifications. The study concluded that runoff and resulting leach reservoir overflows were primarily responsible for the ground water degradation. Tailings seepage represents a smaller part of the impact.

Jan 1, 1984

By Yung Sam Kim

The study of ultrasonic-wave propagation in substances has been remarkably advanced in recent years in most engineering and science fields. The main object in studying the velocity of ultrasonic-wave propagation in solids, is to determine dynamic properties of these materials. The present paper, however, presents some other possible applications of ultrasonic-wave propagation in the study of rock mechanics as follows: Investigation of the mechanism of microseismic activites of geologic materials, (a) at initial or low stress level, (b) at final or fracture stress level, and (c) under fatigue loading condition. Also, correlations among stress level, density, and the velocity of ultrasonic-wave propagation in rocks are discussed in this paper.

Jan 1, 1973

By Douglas M. Smith

The town of Tayoltita, Durango is located at the bottom of the 2000 m. deep Rio Piaxtla canyon on the axis of the rugged Sierra Madre Occidental mountain range. Throughout most of the year access to the town is restricted to travel by mule or STOL aircraft. Silver and gold have been produced from epithermal veins in the north side of the canyon since 1757. During the last seventy-three years more than 4,588,000 kg. of silver and 76,322 kg. of gold have been produced from approximately 6,000,000 metric tons of ore. The Tayoltita mine is developed within a fault block bounded by normal faults which strike north-northwest and have opposing dips. A thickness of at least 1300 meters of late Cretaceous or early Tertiary volcanic rocks is exposed in the mine. These range in composition from andesite to rhyolite. Andesite predominates in the upper 750 meters of the section. The volcanic rocks were passively intruded by quartz-monzonite and andesite stocks during middle (?) Tertiary time. Mineralization spatially and temporally (?) related to the stocks occurs along the east boundary fault and in intersecting footwall fissures which strike east-west and northeast. Ore was deposited over a vertical range of up to 600 m. prior to tilting of the volcanic rocks 35 to 45° to the east. With few exceptions, the ore bodies are found within the lower 400 to 500 m. of the andesite. Argentite (acanthite), stromeyerite, jalpaite, electrum and native silver are the principal ore minerals. They occur in gangue composed of one or more of the following: quartz, calcite, bustamite, adularia, chlorite, and albite. Base-metal sulfides make up less than 1.5 percent by weight of the ore.

Jan 1, 1974

By Robert M. Mann

The Ag/S specific ion electrode has been evaluated for analysis of both free and total cyanide. Metal cyanide solutions were prepared from reagent grade compounds and by stoichiometric fixture of the metal with a potassium cyanide solution. Solutions containing Cu+1, Ni+2, Fe+2, Fe+3 and Zn+2 complexes were analyzed prior to and following EDTA pre treatment. This effort provides an understanding of the effect of each metal cyanide complex on the SIE analysis of free and "total" cyanide.

Jan 1, 1981

By M. Eyll-Vetter

The operation of large opencast mines in a densely populated area in the centre of Europe involves an inevitable interference in the region. Thus, this is only possible with general acceptance by the regional stakeholders. In order to achieve this general acceptance, it is necessary to develop sound common concepts and to engage in a continuous dialogue with the stakeholders. The aim is to create seminal structures of relevance to the regional economy, taking into account the interests of the various stakeholders like e.g. authorities, local governments, the regional public, and churches. The recultivation of the mined-out areas represents the offset for the mining activities. RWE Power has reached high acceptance of its recultivation. This high acceptance is illustrated by various examples, from biotopes to high-yield agriculture and recreational areas. Thus, recultivation covers all the elements of sustainable development from social compatibility to ecological as well as economic aspects. This is only achievable through an intensive stakeholder dialogue in the region: The communities concerned are intensively involved in the planning and approval process for the new landscape. As far as social compatibility - one of the aspects of sustainable development - is concerned, the necessary resettlement of whole villages is one of the principal challenges. Over the last few decades, RWE Power has developed an approach that is broadly recognised by the stake-holders in the region. The best proof for this is the high proportion of resettlees taking part in the joint resettlement scheme offered. This can only be achieved by constant involvement of the stakeholders in the resettlement process. In conclusion, it can be stated that RWE Power has implemented a well-functioning stakeholder dialogue that guarantees the general acceptance necessary for mining operations.

Jan 1, 2007

By H. Colijn

The problem of the freezing of moist raw materials, such as concentrates, in railroad cars during winter shipment has been a continuing source of both economic and operational trouble to the industry and to the railroad companies. The difficulties center around the discharging of frozen cargoes into the plant materials handling system. Because of cargo freezing, appreciable delays in car-dumping schedules occur each winter and cause additional expense for demurrage charges and for slowdown of plant operations. In one plant during one winter, a car dumper rated at 40 cars per day could dump only 3 cars per day in bad weather. Delays became so serious one winter, that 500 cars held in the yard became so badly frozen, that they were sent to the southern part of the United States to thaw after they accumulated an average of two months demurrage charges. These delays in car unloading become critical if unit or integral train concept is applied to the movement of raw materials. Anticipated savings in transportation costs through better equipment utilization are largely based on rapid loading and unloading cycles of whole trainloads. If freezing problems cannot be adequately solved, unit train operations cannot be operated to achieve the potentially large reductions in transportation costs. The freezing problem may tend to become even greater in the years ahead, because the unit train concept will allow the trains to run faster and consequently the heat loss will be accelerated due to the larger heat transfer coefficient. A compensating factor, however, will be the shorter travel time. Further, the sources of raw materials being mined are located farther north than before and the ambient temperatures during transit are going to be lower.

Jan 1, 1976

By Adam Zanker

Smooth roll crushers are widely used as secondary crushers, operating most effectively when set for size reductions in a ratio between 3 or 4 to I. The feed supplied to these units varies from 13 to 102 mm in size and the product obtained ranges from 13 mm to about 20 mesh. Smooth roll crushers produce very few fines and absolutely no oversize. The diameter otfhe rolls varies with the clearance between them, feed size, and the coefficient of internal friction ofmaterial to be crushed, Detailed calculations of this relationship may be found in Unit operations of Chemical Engineering, (McCabe, W. L., and Smith, J. C., 1967, McGraw Hill, NY, Chapter 26, pg. 825). The geometrical arrangement of the roll crusher is shown on the accompanying sketch. A relatively simple relationship between the diameter of feed, the roll, and the gap between them is as follows:

Jan 6, 1980

By S. M. Hsiung

Chain pillar design formula under weak roof condition was developed by statistically analyzing the results from the three dimensional finite element parametric analyses. The parameters such as mechanical properties of the roof and floor strata, overburden depth, panel width and length, and coal strength were incorporated in the formula. A conversion formula which transfers a rectangular chain pillar into a square chain pillar of equal strength is proposed. The influence of high in-situ horizontal stresses, which are often encountered in the coalfield, on chain pillar stability is also discussed.

Jan 1, 1984

By William C. Ellis

Underground water is part of a continuing hydrologic cycle, which involves all elements of water occurrence. All groundwater of economic importance is in process of movement through a porous rock stratum from a place of intake or recharge to a place of disposal. Groundwater moves and is contained in fractures in the rock and/or in intergranular spaces of porous formations. Where there have been no water developments by man, groundwater is in a state of approximate equilibrium and the forces of replenishment and discharge are in balance. Thus, groundwater, unlike other mineral resources, is constantly being replenished in most areas at a rate which is measurable and which is important in the planning of its utilization. As illustrated by Figure 1, replenishment of groundwater supplies results from the direct penetration of rainfall through the soil to the water table, by seepage from surface streams or ponds, and/or by subsurface movement from an adjacent groundwater body. Under natural discharge conditions, water is commonly consumed by transpiration of trees and other types of vegetation, by flows from springs, by evaporation from shallow depths below the surface, and seepage into streams that traverse the area.

Jan 1, 1964

By E. M. Spokes

A.B. Rushton The work and resulting publications of the Committee on Underground Coal Mine Safety and The President's Commission on Coal were appropriate at the time of publication. The statistics cited in the publications appeared to be valid, and the actions proposed by the committee had merit. Although the actions proposed to achieve further improvements in safety may have been worthy of repeating, to associate statistics (Table 1) that are seven to eight years old with company names is bad. Statistics are readily available from the Mine Safety and Health Administration (MSHA) and are usually within three months of being up to date. A review of the most recent Coal Controlling Co. Report will reveal significant changes in the rankings. The more recent statistics should have been cited, or at least compared with those used in the article. Westmoreland Coal Co. is listed as having a 21.1 disabling injury rate for the period (1/78-12/80). The disabling injury rate for the Company for the year ending 1985 was 7.4 for the underground mines and 6.25 for the total facilities. Through March 1986, the disabling rate for the underground mines was 2.86. The management and employees of Westmoreland Coal Co. are committed to safety. The improvements achieved over the past five years attest to that commitment. We are justifiably proud of the achievement and dislike being misrepresented as in the April 1986 article. Reply by E.M. Spokes I regret that the lapse of time since the original work gives a picture of safety practice that is no longer true today. That Westmoreland has reduced its disabling injury rate by 65% to 7.4 in 1985 is most commendable, and I congratulate you for this accomplishment. It is typical of the progress sought by the National Academy of Science and National Research Council when they funded the original study and published "Toward Safer Underground Coal Mines" in 1982. If a significant number of companies do as well as Westmoreland, the report will have served its purpose. Since the paper was primarily a condensation of the original report, it would not have been appropriate to seek access to later statistics. The purpose in seeking its publication at the time of presentation was to reach those who might have missed the original report. The fact that publication was delayed has not voided that purpose and may have reminded some who were aware of the original that its recommendations still apply to improvement of underground coal mine safety.

Jan 6, 1986