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By Duluth Engineers' Club, Engineers' Club of Northern Minnesota

"In recent years, much has been said and written on Lake Superior ores, giving the impression that the quality of the ore is deteriorating in grade and that the reserve of high grade ore is rapidly being depleted. Average analyses of ore produced in this district since 1902 show that the average quality has been practically uniform since 1910, and now closely approximates the average for the total reserves of merchantable ore.The accompanying tables and charts show the average analyses for the past ten years, weighted according to tonnage: The chart above shows graphically the average natural iron content for the old range, Mesabi, and grand total Lake Superior ore shipments since 1902.During the last ten years the decrease in iron content for shipments from all ranges except the Menominee was only' .05 of 1 per cent, while for the Menominee ores there was an increase of .052 of 1 per cent. These tabulations and the chart prove that the average quality of the total annual production of iron ore from the Lake Superior district is uniform. Mining men of the district know that all of the merchantable ores of every ore body are being mined out cleanly, and therefore the present average iron ore content of total annual shipments from the district may be expected to continue as long as the present merchantable ore reserves last. There is no logical reason to expect a decrease in the average iron content. Furnaces require ore of definite quality, and if this quality of ore cannot be produced from the natural ore bodies, it must be produced by mechanical means—that is, by concentration of low grade ores or iron formation."

Jan 1, 1920

By Dan Nilsson

INTRODUCTION There are many mine planning factors in sublevel caving, as in the other mining systems, which when varied can substantially alter mining costs and profit¬ability. In this chapter, the following four topics are addressed with regard to economic optimization of sub¬level caving: production planning, haulage level spacing, orepass spacing, and extraction cutoff. The costs used here are the right order of magnitude but since each mine is unique, they should be considered only as examples. The objective is to demonstrate the tech¬niques which can be used. In a real mine, the evalua¬tions must be done using actual costs and conditions. It is difficult to predict exactly the costs involved, and therefore it is valuable to perform a sensitivity analysis to evaluate the effect of making incorrect as¬sumptions. Since the mining industry is very capital intensive, the effect of the interest rate must also be studied. PRODUCTION PLAN FOR AN IRON ORE DEPOSIT Introduction The first and most important thing to do before de¬signing an underground mine is to establish a long-range production plan. Such a plan is necessary for all eco¬nomic evaluations and should provide information about the lifetime of the mine, how much ore and waste must be handled per year, how much development per year is required, etc. An example is given in the following section. Problem In an iron ore mine sublevel caving is used. The iron content is 42%, and the mine supplies a pelletizing plant with an annual capacity of 3 million t/a. The ore body is shown in Fig. 1. The length of the ore body is 1000 m and the width is 100 m. Each slice is 10 m high, and there are 10 m be¬tween crosscuts, each of which has an area of 20 m2. The density of the ore is 3.5 t/m3. The spacing between rings is 2 m, and the extraction is 100%. The iron con¬tent is 66% in the pellets and 6% in the tailings. The problem is to develop a detailed production plan. A typical sublevel caving sequence is shown in Fig. 2. Solution Amount of ore per meter of crosscut: 20 X 3.5 = 70 t. Number of crosscuts per slice= 100. Length of crosscuts per slice: 100 X 100 = 10 000. Ore from crosscuts per slice = 10 000 m X 20 m2 X 3.5 = 700 000 t. Number of sublevel caving rounds per slice: 10 000/2 = 5000. Area for each blast in sublevel caving: 10 X 10 - 20 = 80 m2. Amount of ore per blast: 80 m2 X 6 m X 3.5 = 560 t. Extraction: 100% (see extraction curve Fig. 12). Loaded ore per blast: 75% or 420 t. Loaded waste per blast: 25% or 140 t. Total: 560 t. Total amount of rock from each blast in the sublevel caving: Ore: 560 t of which 2 X 70 = 140 t from develop¬ment work and 420 t from sublevel caving. Waste: 140 t. Total: 700 t. The ore needed per year is 3 X (66-6)/42-6 5 mil¬lion t. Necessary number of blasts per year= 5,000,000/ 560 = 8929. Distance to develop per year = 8929 blasts per year X 2 m per blast 17 858 m. Total amount/year: Ore from development work 17 858 m x 70 t/m = 1.25 million t/a Ore from sublevel caving: 8929 blasts per year X 420 tons per blast = 3.75 million t/a 5.00 million t/a Waste rock dilution: 8929 blasts per year X 140 tons per blast 1.25 million t/a Total amount to hoist 6.25 million t/ a The amount of ore from development work will in¬crease a little if the horizontal drift is placed in the ore body and not in the footwall. In this example the ore loss in 20%, and the waste rock dilution is also 20%. After taking the ore loss into account, the lifetime for 100 m of the ore body will be:

Jan 1, 1982

By S. E. Phifer

The Haile gold mine was the largest gold producer east of the Mississippi River before 1942. It was the first gold mine in the Southeast to reopen following deregulation of the gold price by the United States Government. The Haile mine was also the first gold mine in the Southeast to use heap leaching and carbon recovery for gold production. Current production involves mining and heap leaching about 1.8 kt/d (1600 stpd). Carbon is used as a recovery medium. Due to the clay and excessive fines in the oxidized ore, agglomeration using portland cement is required before leaching. Agglomerated ore ranges in screen size from 50 mm (2 in.) to less than 75 µm (200 mesh). The agglomerating step combined with certain other conditions has enabled Piedmont Mining Co. to achieve recoveries of about 90% or better.

Jan 1, 1987

By W. Jacobi, B. Haider, D. Regulla, J. Huber

[Introductory Remarks] Thermoluminescence (TL) detectors are widely used for the dosimetry of X- and[ y]-rays. Also filter devices for radon daughter monitoring have been developed in which the a activity on the filter was measured with TL-detectors (Breslin et al., 1977). For this purpose normal LiF-tablets with a thickness of 0.4 - 1 mm were used. However the lower detection limit of such TLmonitors for radon daughters is relative high, especially in areas with a high [y]-background, due to the low [a /-y]-sensitivity ratio of such thick LiF-detectors. This [a/y]-sensitivity ratio can be increased if TL-detectors are used whose thickness is comparable with the range of [a]-particles. On the basis of this consideration we have developed a simple light weighted and sensitive TL-monitor for the measurement of the cumulative radon daughter exposure in air. [Description of the "Monitor] The monitor consists of two parts: The sampling pump with the accumulator, and the sampling probe which contains the air filter and TL-detector system. Both parts are connected with a plastic tube. For operation in mines a light weight, portable air sampler with a built-in accumulator (DuPont model 125 and 200, 400 g) is used which enables an adjustable, constant flow rate in the range of 7.5 -12 1/h. These air samplers allow a sampling period of 10 hours before recharging is necessary. For radon daughter measurements in houses this pump is replaced by a larger, netoperated pump with a flow rate of 180 1/h. Figure 1 shows a schematic cross section through the sampling probe whose weight is 40 g. The radon daughters are collected on a hydrophob membrane filter (Sartorius) with an effective filter diameter of 11 mm and a pore diameter of 3 µm; its collection efficiency for radon daughters is [>] 95%. Above the filter the detector system is mounted. It consists of two thin Tm-activated CaSO4-TL films of 8 mm diameter on a Al-carrier foil manufactured by Matsushita Inc., Japan. The thickness of the TL-film is 6 mg/cm2, which is comparable with the range of a rays. The first detector is faced in 3.5 mm distance above the filter; in addition to the ambient y background this detector is exposed to the [a] and ß radiation from the radon daughters on the filter. Between the first and the second TL-detector is an Al-absorber of 0.5 mm thickness which shields this detector against the [a] radiation and partly also to the ß radiation from the filter. Both detectors have the same [y] shielding. After air sampling both TL-detectors are read-out with a commercial, hot-air reader (Matsushita Inc. / Japan, Model 505 A). The glow-curves are identical for [a and y] rays (Regulla et al., 1980). The integral TLsignal from both detectors is displayed in mR-units (or mR-equivalent). The difference between the response of the unshielded TL-detector above the filter and the shielded TL-detector is proportional to the time-integral of the filter activity, integrated over the sampling period. Calibration and Intercomparison Measurements] The linearity of the a response was checked with a 241Am-source for an [a] fluence on the detector surface of 5400 [a's/cm2•s] in the range of 102 -105 mR-equivalent. Within the experimental error of 15% the response function is linear. The TLD-monitor was calibrated for radon daughters in air by comparison with a calibrated integrating, monitor (WLM-meter) equipped with a Si-surface barrier detector and a direct electronic read-out; this instrument was developed by us for area monitoring some years ago (Haider et al., 1976). The results of simultaneous measurements with the TL-monitor and the electronic WLM-meter in mine areas and in indoor air of houses are shown in figure 2. On the abscissa the mean potential [a] energy concentration (in WL) during the sampling period is given which was derived from the measurements with the electronic WLM-meter. On the ordinate the corresponding response of the TLDmonitor to radon daughters (difference between both TL-detectors) is displayed, expressed in terms of mRequivalent per liter sampled air. It follows from this comparison a linear relationship over the whole range of 0.005 - 5 WL with a standard deviation of 10%. The resulting calibration factor for the TLD-monitor is 18± 2 mRequiv per WL • 1.

Jan 1, 1981

By Richard W. Kimball, Fred B. Estep, Dwayne E. Easterling

This paper discusses the overall challenges to construct a 15,125.7 m (49,625 LF),wastewater drainage tunnel in Cobb County, Georgia by a joint venture of Gilbert Southern Corp. and S.A. Healy Co. and a construction manager Parsons, with Jacobs Associates as a subcontractor. The goal of the project is to provide wastewater retention during peak usage and is connected to a treatment facility near the Chattahoochee River. The primary component of the project is the TBM-driven hard rock tunnel. Additional works include drill and blast areas; four intake interceptors, two construction shafts and a 33.5 m (110 ft), diameter pump station shaft.

Jan 1, 2003

By T. J. Dudek

To be competitive in automotive applications, polymer composites must be processable by high production rate processes like injection molding (IM), reaction injection molding (RIM), structural rim (SRIM) and compression molding. With current fiber reinforced composite materials, performance properties are sometimes compromised to make them compatible with these processes. This is done by decreasing the amount and length of the reinforcing fiber and the viscosity and molecular weight of the polymer matrix. Sheet molding composite (SMC) and thermoplastic polymer blends are examples of polymer composites which are cost effective in many applications and meet the high speed processing requirements for automotive parts.

Jan 1, 1993

By E. G. Kelly

Many methods of evaluating the efficiency of mineral separations have been described in the literature. In most cases, these present the efficiency as a single number. This paper argues that single-number measures of efficiency are inadequate because they seldom allow reliable comparisons, and are unlikely to correspond to the optimum operating conditions. To realistically make comparisons, it is necessary to distinguish the particle-induced component from the equipment- induced component. In a number of situations where the separating property can be identified (such as in gravity concentration and classification), this can often be done. However, in more complicated systems, such as flotation, this has not been possible. A technique is described whereby particle and equipment contributions to efficiency can be distinguished without the need to define the separation property. Because smelter schedules define a boundary correlation between grade and recovery, they generate some of the better single¬-number measures of efficiency, but even these have limitations.

Jan 1, 1991

By J. E. Hoffman, Massimo Maccagni, T. J. Keefe, Marco Olper, O&apos

The research laboratory of B.U.S Engitec has identified and patented a new process for electrolytic production of lead from lead sulphide concentrates with simultaneous production of elementary sulphur. The process occurs in an aqueous solution, at atmospheric pressure, utilizing a solution of ferric fluoroborate in fluoroboric acid as the oxidizing and solubilizing medium for lead sulphide. After the filtration and separation of a residue composed of elementary sulphur and the gangue which accompanied the concentrate, the solution containing lead as fluoroborate and iron reduced to a ferrous state is sent to a diaphragm electrolytic cell where, in the cathode compartment, the lead is deposited in a compact form on the stainless steel permanent blank. The exhaust solution stripped of lead is sent to the anode compartment where the oxidation of ferrous fluoroborate into ferric fluoroboratetakes place, reproducing the oxidizing solution for new leaching. Depending on operating conditions, it is possible to selectively solubilize the lead from the other metal values present in the concentrate. The sulphur produced from the reaction may be separated from the gangue by extraction with solvent or by flotation.

Jan 1, 1993

By Louise H. Michaud

An interactive mine planning system that employs recent advances in 3D computer graphics capabilities and 3D geologic modelling to aid with the tasks involved in producing dragline mine plans was developed. As well as offering large potential saving in the time required to carry out the planning tasks, the system offers immediate visual feedback to the planning engineer. This can greatly aid in the conceptual understanding of complex geology and mine plans. The package incorporates the generation of a three dimensional Gridded Seam Model (GSM) as the basis for the development of the geologic database. This modelling method is capable of accurately representing rugged topography and multiple coal seams, including folding and faulting. The GSM is then integrated with an interactive graphics mine planning system in order to develop one model and one database for the generation of the mine design, the depletion of the coal resources and the movement of spoil material. The gridded structure of the model also provides the foundation on which all mine and spoil pile volumes are calculated.

Jan 1, 1992

By R. Y. Wan, J. R. Parga, J. D. Miller

The direct recovery of precious metals from a1kaline cyanide solution is frequently accomplished by the well-established Merrill-Crowe process involving zinc-dust cementation. This is particularly true for silver. Plant data from two operations are presented and analyzed in terms of intrinsic reaction features. In such Merrill-Crowe plants a plate-and-frame filter press acts as a semicontinuous fixed-bed reactor with a distribution of particle retention times. For the plants studied, 99Yo of the silver is recovered with a solution retention time of less than 2 min. Differences in plant operating conditions and product characteristics can be related to the nature of the surface deposit of silver which forms on the zinc particles. From laboratory experiments and plant samples it has been found that the presence of lead in the system activates a change in the silver deposit morphology to the dendritic state which affects the rate of silver deposition as well as the filter cake porosity. Finally the plate-and-frame press is considered from an engineering perspective as a semi- continuous fixed - bed reactor to describe the behavior of the system.

Jan 1, 1987

By R. L. Wiegel

Several mineral process modeling and simulation packages are currently available for use in evaluating the performance of alternative process flow schemes. A critical link that has been missing from these packages is the ability to quantitatively model the effect of size reduction on the liberation of the valuable and waste minerals in the ore being processed. Although there have been several approaches taken to this problem over the past 25 years, none of them has led to a satisfactory conclusion. A technique was developed for measuring the effective liberation characteristics of magnetic taconite ores, and a program was constructed that makes use of these liberation characteristics in simultaneously simulating both size reduction and mineral liberation as it occurs in tumbling mills. This is an especially important step in the modeling of magnetic taconite processes, where magnetic rejection of low-grade wastes between grinding stages mandates that a predictive capability be available. The current application is specific to magnetic taconite, but it is possible that a similar approach could be used for other types of mineral systems. Key words: Modeling and simulation, Size reduction, Mineral liberation, Taconite, Magnetic concentrator

Jan 1, 2003

By P. J. Lechler

A review of the geology and mineralogy of several of the better known hydrothermal platinum-group metal (PGM) deposits is undertaken. Along with new data from two recently discovered occurrences in Nevada, a number of common characteristics of these deposits are identified. Newly described PGM occurrences in Nevada are the abandoned Gibellini mine workings characterized by limestone-hosted hydrothermal Mn-V-Zn-Ni mineralization and the granite-hosted base-and precious-metal veins of the Gingerload claims.

Jan 1, 1989

By Omid Frough, Hossein Changani

Application of Tunnel Boring Machines (TBMs) is one of the main solutions to achieve a safe and high-performance method of construction in hard rock and soft ground tunneling. In order to adequately assess the progress and potential impacts of the tunneling operations with the TBM, it is required to record a series of data during the tunneling and process of the data to evaluate the TBM performance. Applying the right machine parameters during the excavation not only delivers an optimum penetration rate, but also prevents extra downtime due to over excavation or wear of cutting tools. In this paper, the effect of machine and operational parameters on TBM downtimes has been studied and supported with the real examples of TBM operation data.

Dec 1, 2022

By Robert B. Fulton

The objective of this chapter is to discuss the interrelationship between industrial minerals and chemical manufacturing. It is intended to supplement rather than duplicate the commodity chapters. Particular emphasis is given to the pertinent chemical element and to market factors. Condensing this broad subject into a few pages of this handbook permits treating only the most important elements derived from industrial minerals. Hydrocarbons, which quantitatively dominate as raw materials for the chemical industry, are omitted, as are the metallic elements and the minerals covered in other "use" chapters such as phosphorous, potassium, and nitrogen for fertilizers, and titanium dioxide for pigments. The remaining six elements of major importance are: boron, bromine, chlorine, fluorine, sodium, and sulfur. These elements are treated individually under separate headings. [Table 1] affords an overview of the main industrial minerals, the chemical products derived from them, and end uses of the products. Salt brines have particular importance as raw material sources for the chemical industry. Table 2 is a chart of the chemical compounds derived from four types of brines: (1) Owens Lake-type brines, which are sources of boron and sodium compounds; (2) Midland-type brines, from which bromine, iodine, and chlorides of calcium, magnesium, potassium, and sodium are derived; (3) Searles Lake-type brines, yielding boron, bromine, lithium, magnesium, potassium, and sodium compounds; and (4) Silver Peak- type brines, produced mainly for lithium. MARKET ATTRIBUTES Some of the important market traits common to industrial minerals used by the chemical industry are: 1. They are international commodities, such as fluorspar and sulfur, which largely move to foreign consumers. 2. Grade, and freedom from deleterious elements are important factors affecting their usability in chemical processes. An example is salt (NaCl) used in electrolysis where ultrapure evaporated salt is required to meet rigid specifications. 3. Purified products take on the characteristics of specialty items and command a distinctly higher price than the basic commodity from which they are derived. 4. In practically all cases, chemical users require some sort of cleaning or beneficiation of the naturally-occurring mineral to bring it to specification, and individual specifications may vary from user to user for essentially the same use. 5. In some instances it is necessary to strike a balance between what the vendor can supply and what the buyer requires, with the result that specifications have to be eased to afford the needed materials in marginal cases. 6. Because they tend to be bulk commodities, low cost for handling and transportation are important and such costs may limit the area from which a chemical user can draw his supply. 7. Shipments are usually in bulk and frequently in multiple-car, full-trainload or full-shipload lots to reduce transport costs, which in turn may require large terminal investment facilities. 8. Purchases are generally by contract of one year or longer term, with spot buying playing only a minor role. 9. Contract prices are usually fixed in short term commitments, but may vary according to assay, with premiums and penalties for content above or below the norm; however, general practice is for specifications to be fixed in the contract with minimums being set for the desired material and maximums for undesired elements. In longer term contracts, prices are often escalated on labor, fuel, and other vendor processing costs. 10. Suppliers of individual commodities to the chemical industry tend to be limited in number and are generally medium- to large-size producers that supply a few major consumers. 11. The bulk of the mineral volume is for basic chemical uses, sulfur suppliers to sulfuric acid producers and fluorspar for hydrofluoric acid producers being typical examples. These basic chemical products then are used for the production of other products. 12. Shortage of a supply of adequate quality leads consumers to seek substitutes. In the case of fluorspar, much work is being done on recovery of fluorine from phosphate rock. Success in the form of fluorosilicic acid and/or hydrofluoric acid production could, in time, affect the hydrofluoric acid chemical industry. 13. Markets tend to be characterized by cycles of shortage followed by oversupply, with attendant wide price fluctuations. 14. Baniers to trade can have an adverse effect on the necessary movement of industrial minerals used by the chemical industry in international trade. Antidumping laws, quotas, and tariffs can disrupt or dislocate normal markets. 15. Chemical industry consumers may back-integrate for security of supply or for favorable economics, sometimes by joint ownership and often with experienced mining partners.

Jan 1, 1994

By P. C. Kapur

The hierarchical relationship between three broad kinds of grinding models for a spatially homogeneous, linear, time-invariant batch grinding system are first established. Limiting and asymptotic arguments for arriving at approximate but simpler models are employed in all three cases. These parsimonious models -provide alternate and, in some respects, more incisive and convenient tools for the analyses of grinding processes and simulation of comminution circuits. In the discrete-size, discrete- time class of models, a reduced mill matrix is derived, which is seemingly adequate for those grinding circuits whose identification otherwise is difficult because of limitations on the quantity of data and its quality. In discrete-size, continuous-time types of models, parameter lumping has been employed for obtaining a G-H solution which is quite accurate and exceptionally useful for graphical display of data, model verification, and parameter estimation and simulation. In continuous-size, continuous-time models, a similarity transformation is used for solving the integrodifferential equation of grinding. This solution provides a unified framework for a number of apparently diverse empirical grinding phenomena such as self-preserving behavior of ground particle size distributions and energy laws.

Jan 1, 1987

By Byron N. Cooper

The Revenue Act of 1926 provided for five simple categories of natural resources to have the benefit of depletion allowances. In the 1947 Revenue Act, the number was increased to twenty-five, and in the 1951 Revenue Act to fifty-four. Of this number, fourteen were allowed 5 per cent; nine, 10 per cent; twenty-nine, 15 per cent; one, 23 per cent; and one (oil and gas), 27.5 per cent. The 1951 Revenue Act created a host of difficulties, including application of the "end- use criterion" and determination of the commonly accepted meaning of such terms as limestone, dolomite, chemical- and metallurgical-grade limestone, marble, calcium carbonates, and magnesium carbonates. Dolomite, for example, was listed at 10 per cent depletion allowance, but without definition. In the great amount of litigation growing out of the 1951 Revenue Act and its administration, it became essential to understand the derivation and subsequent usage of these common geologic terms. One thing that became clear was that our definitions changed significantly between the time that the 1951 Revenue Act became law and the time that later cases were tried. Some geologists neglected to learn about first usages of such terms as metallurgical limestone, and about meanings that were applicable when the 1951 Revenue Act was written and passed. Legal meanings in this paper are discussed in the light of certain famous cases that have been tried and settled.

Jan 1, 1966

By A. T. Visser

The expansion of surface mining has led to the development of very large off-highway trucks capable of hauling payloads in excess of 290 t (320 st). Mine haul roads have historically been designed empirically, relying heavily on local experience; the trend in increasing truck size will thus render the current pavement systems inadequate. Because truck haulage costs can account for 10% to 50% of the total costs incurred by a surface mine, not only would the maintenance costs of existing roads of inadequate design increase, but vehicle operating and maintenance costs would increase prohibitively. Thus, there is a need for improved design technologies encompassing the construction and management techniques of mine haul roads appropriate for the wheel loads of vehicles now in use. This paper presents the different components of a mine haul road design and management system and demonstrates the value of its application through case studies. The system has been applied at several South African surface mines, and distinct benefits have been derived. The improved structural design of a new road resulted in a 29% saving in construction costs and provided better service, while the optimal selection and management of wearing course materials provided better functionality at lower total transportation operating costs.

Jan 1, 2000

By J. J. Crowhurst

The modem open pit-heap leach operation by Pegasus Gold Ltd. at Zortman and Landusky in Phillips County, Montana, is a new chapter in the mining of gold in these districts. The discovery of bulk tonnage ore bodies and their development and ultimate production was based on a long history of mining and exploration in that part of Montana. Gold was originally discovered in the Little Rocky Mountains as placer deposits by Pike Landusky and Lou Myers. This discovery in the 1880s was not significant, but Pike Landusky continued prospecting for lode deposits, and he eventually located the Gold Bug and Little Ben, two of the larger Au-Ag producers in the district. Eventually two camps, Landusky and Zortman, grew in the LittleRocky Mountains. By the time Landusky was killed in 1894 by Kid Curry, the district was still a discontinuous small producer. Steady production commenced in 1907 with the organization of the August Gold Mining Co. Eventually high grade ores on specific veins were exhausted by selective underground mining and the district was idle by May 1942. After World War II in the early 1950s. E.A. Scholz tried to continue selective underground mining, but he realized the stockworks surrounding the larger veins constituted bulk tonnage targets. Ultimately in the 1976- 1979 period he organized two exploration efforts, one each for the Landusky and Zortman areas, and brought these into production as the Argo and Pegasus gold mines. By the time of his death, Apr. 8, 1980, both operations were producing gold. Later the two companies were merged as Pegasus Gold Ltd. Upon the death of Scholz, V.F. Hollister continued as the geological consultant, Ed Roper was engaged as general manager, and J. J. Crowhurst was given the responsibility of executive vice president. The discovery of open pittable ores and the application of heap leach technology was important in the development of mining. Both contributed to the low cost operation that continues to this day. The attached article by L.M. Rogers, then chief geologist, and M.S. Enders, his assistant, describes the geology of the deposit. It was presented at the Northwest Mining Association meeting in 1982.

Jan 1, 1990

By M. T. Smith

In a 2,000 square mile area of Polk, Hillsborough, Hardee and Manatee Counties in Central Florida is located one of the richest known deposits of the life-giving mineral, phosphorus. Under layers of sand and clay are found millions of tons of phosphate rock, best source of this element which is necessary to all forms of life - plant, animal and human. Phosphorus is an irreplaceable ingredient in all complete plant foods, and more than 90% of Florida's vast production goes to enrich the croplands of the United States and many other areas of a hungry world. In addition to this, it has wide industrial use in the manufacture of many products - detergents, baking powder, carbonated beverages, steel, matches, munitions, glass, insecticides, dyes, water softeners and innumerable others. Not only does phosphorus make life possible for us - it also helps us to live longer and better.

Jan 1, 1962

By T. W. Camm, J. C. Johnson

"Most engineers are bright, hard-working, reliable, and prefer to avoid conflict. An engineering curriculum tends to self-select these characteristics. By most standards, you would expect workers exhibiting these traits to require minimal supervision. But is this true? Is this how most current engineering managers lead? Looking at some current theories on leadership combined with personal anecdotes, this presentation will look at some common misconceptions about leading engineers. INTRODUCTION Engineers are different. There, I said it. From cartoons to movies to television shows and more, there is a reason stereotypes of engineers resonate. Yes, you can find a lot individual variation among specific engineers that you may know, but they do not detract from some of the overarching commonalities that engineers are known for. CLASH OF CULTURES What distinguishes a professional? Raelin (1985), in his book Clash of Cultures, describes professionals as having superior intellectual training, maintaining their own standards of excellence, and being supported by associations that maintain the quality of the profession. Engineers obviously fit all three of these ideas: an engineering degree is still regarded as one of the most difficult to attain; we maintain our own standards both through peer-review and in academia through ABET accreditation; and through professional associations like SME to promote the discipline and foster technical growth. Six characteristics representing professional status are described by Raelin (1985, p. 9): Expertise—prolonged specialized training in a body of abstract knowledge. Autonomy—the freedom to choose the means to solving a problem. Commitment—Primary interest is in pursuing the practice of one’s own chosen specialty. Identification—identifying with the profession and with fellow professionals, both through formal associations and through peers external to the organization. Ethics—providing service without concern for oneself or without becoming emotionally involved with the client. Standards—committed to help in policing the conduct of fellow professionals. Engineers are smart—in the vast majority of cases they are hired specifically for their expertise. At a typical mine the ventilation engineer knows more about mine ventilation than anyone else on site; the same is true for the rock mechanics engineer, the explosives engineer, the planning engineer who uses sophisticated computer software—each is the expert for their particular area at the mine, that is why they have that responsibility. This can present a dilemma for the manager for each (sometimes all) of these engineers. The manager needs to keep everyone on task and focused on the objectives of the organization. Because they have reached their position by following the norms and expectations of the organization, managers tend to have a certain amount of loyalty to that organization. Engineers, on the other hand, tend to have mixed loyalties, having as much loyalty and affinity for their profession as they do for the particular company they happen to be working for at any given time. This dynamic can often lead to power struggles between the managers, based on their positional authority in the organization, and the engineers, based on their specialized knowledge (Camm, 2013)."

Jan 1, 2017