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By Ulick R. Evans

I Should like to commence by saying how much I appreciate the honor which the American Institute of Mining and Metallurgical Engineers has done me in inviting me to visit your country, and to deliver this lecture before you. In choosing a subject, and in deciding what to include and what to omit, I have endeavored to discuss as far as possible work carried out recently in Europe with which you may not be unduly familiar. It would be poor return for your hospitality, and a mistaken sort of compliment indeed, if I were to load the lecture with accounts of researches carried out in your own country—researches with which you are probably better acquainted than I. Not that I have in any way excluded work done on this side of the Atlantic from my survey; one would indeed find it difficult to write on this, or on any other branch of science, without mentioning American work. But I have endeavored as far as possible to concentrate on aspects of the case which will, I hope, be comparatively fresh to you, and I feel fairly certain that this will be in accordance with your own wishes. Films Produced at Elevated Temperatures If a strip of iron is heated strongly at one end, the other end remaining cold, there is produced over the heated portion a layer of oxide scale, the thickness of which diminishes steadily with the distance from the hot end. Somewhere in the middle of the strip, the thickness of the oxidized layer will become comparable to the wave length of light, and over this region the thin films give rise to a series of beautiful interference tints, commonly known as "temper colors." The colors are caused by the fact that two trains of light waves are reflected respectively from the outer and inner surfaces of the oxide film, and the possibility arises that the "crests" of one series of waves may coincide with the "troughs" of the other, thus diminishing the intensity of the light of some particular wave length. The state of affairs in this part of the strip is shown diagrammatically in Fig. 1, in which the film thickness is enormously exaggerated, of course, in comparison with the length of the strip; the

Jan 1, 1929

By R. K. Amankwah, E. K. Asiam

Changes in the thermal-oxidation behavior and other properties of gold-bearing waste activated carbon when milled in both a ball mill and a vibratory mill were investigated. It was found that significant changes occurred in the oxidation temperature of the vibration-milled waste carbon as a result of increases in surface area and mechano-chemical activation. The mechano-chemical action brought about modifications in the crystal structure of the waste carbon. As a result, the vibration-milled sample was completely oxidized at a temperature of 450°C. Thus, the study established that vibration milling is a better way of lowering the temperature of oxidation of the waste carbon. Furthermore, the gold was found to be concentrated in the ash and, when leached with cyanide for 20 hrs, the gold recoveries from a sample having a head grade of 2 kg/t was 99.5% for the vibration-milled sample and 82% for the ball-milled sample. The lower gold recovery for the ball-milled sample was attributed to sintering of the ash, which was caused by the higher temperature required for its oxidation.

Jan 1, 1997

By R. V. Whetsel, Valentin R. Garfias

Mexican petroleum production for 1928 was approximately 50,000,-000 bbl., the lowest in 12 years, showing a decrease from 1927 of over 14,000,000 bbl. The steady downward trend for the past 7 years has allowed Russia to outrank Mexico by a wide margin for third position and if the expected decline continues during 1929 it should place Persia ahead of Mexico as fourth in rank. The year 1928 was characterized by a continuation of the reentrench-ment previously begun by the oil industry in Mexico in an attempt to adjust itself to the adverse conditions caused by the steady depletion of the fields, the rapidly increasing competition from Venezuela and the United States and the as yet unsettled petroleum legislation and taxation situation. With the exception of the Isthmus of Tehuantepee, drilling in proved fields was considerably curtailed and although the number of wildcats completed exceeded those of the previous year, no extensive drilling programs were undertaken. Practically without exception, the major companies reduced personnel and operations to a point where they could meet existing conditions and mark time while awaiting a more stable basis for the future testing of unexploited regions. Many terminal and transportation facilities were abandoned during the year. Development Only 371 wells were completed during 1928, as against 583 in the previous year and 808 during 1926, and although the percentage of producers in 1928 was 34 per cent., compared to 26 per cent. in 1927, the initial production of -wells was considerably lower than during the previous year, a great number of the wells showing salt water and becoming "strippers" from the time they started to flow. Development is summarized in Table 1. Drilling in the Northern fields did not prove any new pools of importance, the most successful wells being located in the old producing areas of Cacalilao, Panuco and Topila. (Fig. 1 Very few of the producers made more than 1000 bbl. daily, and a great many less than 300 bbl. a day.

Jan 1, 1929

By C. H. Curtis

The Esperanza mine of the Copper Division of Duval Sulphur & Potash Co. is located in the Twin Buttes District, 32 miles southwest of Tucson, Ariz. Records of mining activity in this vicinity date back to the 1850's. The New Year's Eve mine, which was last active briefly during the years of World War II, made the first actual penetration into what is now Duval's Esperanza property. Duval's exploration department became interested in the Esperanza in the fall of 1954. The first test hole was started on May 8, 1955. Two years of intensive exploration work together with metallurgical studies developed the basis for the decision to establish an operation.

Jan 11, 1961

By J L. Mauk

The Favona low-sulfidation epithermal deposit in the Hauraki Goldfield is less than one kilometre southeast of the world-class Waihi deposit. The veins are hosted by Miocene andesite of the Waipupu Formation, have a total strike length of over 900 m, a vertical extent of at least 350 m and are on average 1-3 m wide. Individual veins have been traced for 200 m with vein widths up to 25 m. The dominant vein textures are massive, crustiform and colloform banded veins and vein breccias, with subsidiary textures including comb, zonal, flamboyant, lattice-bladed, ghost-bladed, microbotryoidal, feathery, ripple and dune, and mosaic. Quartz is the dominant gangue mineral in the veins at Favona. Accessory gangue minerals include pyrite, chlorite, adularia, illite, calcite, and apatite. Electrum is the only gold-bearing mineral and is associated with acanthite, tetrahedrite, pyrite, sphalerite, chalcopyrite, and rare galena. Whole rock geochemical analyses indicate that gold grades correlate with textures/vein types. The highest gold and silver grades are associated with vein breccias and banded veins, with the former containing 28 g/t Au and 136 g/t Ag on average. To date, veins with significant base metal sulfide minerals, and massive and crystalline quartz veins lack significant precious metals (Au and Ag), except for one banded base metal sulfide-rich vein at Favona. An overall zonation of the veins exists, with base metal sulfide minerals dominant at depth (1050 m RL) of the system are characterised by massive quartz veins.Fluid inclusions from a total of 31 quartz, amethyst, and platy calcite veins reveal homogenisation temperatures of ~190-250¦C, with final ice melting temperatures between 0.0 and -0.8. Ice melting temperatures correspond to apparent salinities of 18O value of the water that formed these veins is approximately -4.3 per mil, which is similar to meteoric water-dominated, near neutral chloride fluids in geothermal systems in the Taupo Volcanic Zone.

Jan 1, 2002

By S. F. Emmons

" The obscurity which still veils from us the true nature of veins will become more and more cleared up when they can be considered in connection with the geological structure of the regions in which they occur."* These words, according to Lossen, the biographer of the late Dr. A. von Groddeck, of Clausthal, were the last received by him from that eminent man, perhaps the most far-sighted and carefully progressive of recent writers on ore-deposits. They seem to me to form a fitting text for what I am about to say; since I find that many of the conclusions at which I have arrived by my own study of the structural relations of ore-deposits, or, in other words, of the structural and dynamic geology of the regions in which they occur in this country, have been similarly determined by him within recent years in Europe, and especially in his home field of work, the Hartz. I shall not enter upon a detailed account of how far other workers may have arrived at similar conclusions with myself, since these questions of priority are of little interest, except to those immediately concerned; but will briefly present the methods by which, in my work in this country, I have arrived at certain generalizations, and will point out the practical bearing which they may have upon the work of mining engineers. In my first thorough and systematic examination of an important group of ore-deposits, viz., that of Leadville, Colorado, I was enabled, through the generous facilities afforded me by the then Director of the Geological Survey, Mr. Clarence King, to make a most elaborate and detailed study of the geology, not only of the immediate vicinity of the mines, but of the adjacent mountain regions, based upon accurate topographical and underground maps, and

Jan 1, 1888

By V 9. 0 / 300 dpi

ATHOUGH turquoise mining was, so far as we know, the first large, well-organized mining operation,' gem mining, from the Roman con-quest of Egypt until the opening of the South African pipe diamond mines some 50 years ago, was largely carried on' by individuals 01' small companies in a relatively primitive way. Now" however" gem mining does not yield in efficiency or in scale of operations to the mining of other mineral products. In 1926 the diamond mines of the world milled some 9,000,000 cu. yd. and produced 0,43 cu. yd. diamonds, a remarkable example of concentration. The Premier Diamond Mining Co. up to Oct. 31, 1927, had milled 116,455,550 loads (each of 16 cu. ft.) from which 26,-217,144 carats of diamonds" worth £29,897,971 2s, 9d., were recovered. The Burma Ruby Mines, Ltd., operating sever-al alluvial mines in Burma in 1911-12, mined and milled 1,479,845 truckloads of gemmiferous earth for 15c. per load. We of the industry can there-fore, with good grace, disclose some of the myths and also describe some of the primitive mining methods of the, dark ages of our industry. The methods, so far as I know, were not patented, and if they were, the patents have expired, so that engineers in other branches of the art are free to use them if they see fit.

Jan 1, 1928

By G. M. Ritcey

Purification of solutions can involve various treatment methods. In the normal sequence of metals recovery by hydrometallurgy, the ore is initially prepared for leaching by grinding to the desired optimum mesh size as dictated by the leaching parameters. Following leaching and liquids- solids separation, the resultant solution is ready for purification. The use, or introduction of solvent extraction into a plant, can be either a major or a minor part of the metal recovery process as shown by the following list where solvent extraction is normally considered: a) recovery of a metal by a simple leaching of the broken ore, e.g., copper from dump leaching where there are only the three main steps of leaching, solvent extraction, and electrowinning (1);

Jan 1, 1978

By Saieb Haddad, Henry Pate

"Building retaining walls in an urban area is becoming more diffi cult due to right-of-way restraints. Using standard concrete cantilever walls requires a construction easement behind the walls for installation, which for the most part is unavailable. To install these types of walls in a limited right-of-way requires extensive temporary walls to minimize the construction easement. Top-down construction walls utilizing tie-back anchors for support require either the purchase of the right-of-way or underground easements in the area of the anchors.These problems faced the Department on Interstate 75 widening in Knoxville, TN in an area of a large cut. A multi-story Insurance Building and a large commercial Retail Center were located at the top of the cut. To prevent any impact on the buildings, the walls had to be placed within a limited area. The option of buying the properties was prohibitively expensive. Due to the height of the two walls and the variability of the underling rock line, contiguous caisson pile cantilever walls were contemplated as the only wall type that would be appropriate. The cost of the two walls was estimated to be very close or even higher than the cost of purchasing the two buildings. The Department believed that there must be a better way to deal with the problem. A vertically tied-down pile frame wall constructed from the top-down with a concrete facing was developed. This allowed the construction of the walls to be restricted to the available limited area and provided substantial savings for the State. INTRODUCTIONThe widening of I-40/75 has been a major transportation project in the Knoxville area which is being constructed by the Tennessee Department of Transportation. The project includes 18 Retaining Walls and 13 Bridges. Two of the 18 Retaining Walls, refer to Figure 1, are to support two valuable properties, one being an insurance company housed in a multi-story offi ce building and the other a suburban shopping center which were appraised at $13.0 million and $5.0 million respectively. Due to the 31 ft. (9.5m) maximum height of each of the two Retaining Walls and the limited Right-of- Way of 15.0 feet (4.6m), a contiguous caisson pile cantilever wall was proposed for each of the two retaining wall sites with an estimated cost of $12.0 million each. The contiguous pile cantilever Wall is comprised of a line of caisson piles socketed into underlying competent bedrock. The design required that 4 ft. (1219mm) dia. piles be installed at 6 ft. (1.83m) centers, socketed into rock in order to provide lateral stability and restrict lateral wall movement to acceptable limits. The line of caissons would be fronted with a cast-in-place concrete face wall."

Jan 1, 2007

By M. Bender, H. D. Goodfellow

"Belt conveyors, because of their low capital and operating costs and inherent flexibility in handling a wide variety of products, have numerous applications in the mining industry. With the increased emphasis on improving the workplace environment, dust emissions from belt conveyors at transfer and other points have become a significant problem for many applications.The paper reviews belt conveyor dust control technology and compares dust emissions from belt conveyor systems with other possible materials handling systems. Technical information on existing belt conveyor installations which have been designed to minimize or eliminate dust emissions is summarized. The important features of good design as well as the necessary input from operating and maintenance personnel are highlighted. The status of research and development work on dust control on belt conveyor systems on a world-wide basis is discussed. A proposed methodology for field measurements of emission factors from belt conveyor systems is presented. Data collected from such a test program can be used to establish a design basis for new dust-free belt conveyors.IntroductionBelt conveyors have proven themselves over the year s in the mining industry as a reliable and low-co st method of moving bulk material at high tonnage rates. Because of the above, as well as their inherent flexibility in handling a wide variety of products, belt conveyors are often called the ""workhorses"" of bulk material handling systems. For many processing plants, belt conveyors serve as the ""vital link"" in providing feed to the plant and the removal of the finished product. As would be expected, there has been considerable engineering effort in designing rugged and reliable belt conveyor systems.It is also well known that belt conveyor systems are a primary source of respirable dust emissions. The major sources are from the tail pulley where material is received and the head pulley where material is discharged, from the return idlers, due to the fine material attached to the return belt, and from the take-up pulley. It is usually considered that for dust particles less than 10 microns, these particles will remain airborne and thus can have a profound effect on the workplace environment."

Jan 1, 1982

By Bryn Harris

Answer to the question is given as 42! Asked the wrong question So got the wrong answer How does this apply to the mining industry? And particularly to this session on Water? Water is just one aspect of mining/minerals/metals Should not be looked at in isolation Need to adopt a ?holistic? approach

May 1, 2013

Full sets of 149 Vols., including 4 Indexes, covering 1871-1940 incl. Indexes to Vols. 1-35, 36-55, 56-72, 73-117 (set of 4 Indexes)

Jan 1, 1940

By G. P. Salas

I.- In order to keep pace feeding its fast growing population, Mexico with only about 20% of its surface suitable for intensive agriculture, will need the application of modern foodgrowing techniques. To assure greater crop yields it will be necessary to apply more fertilizers than used at present (yearly average of 29 Kgs/hectare)** For its fertilizers production Mexico still depends mostly on imports of phosphate concentrates from Florida, U.S.A., Morocco and Spain. To reduce or eliminate this dependence on foreign providers, the Consejo de Recursos Minerales -a Federal Government exploration Institute- started in 1974 an exhaustive exploration program for phosphate deposits more amenable to commercial exploitation than the phosphatic limestones contained within the La Caja Formation of Upper Jurassic, found along the Sierra Madre Oriental. After studying literature on the origin and deposition of marine phosphate and visits to deposits in Florida, U.S.A., the Baja California peninsula was selected as most favorable for starting this program because of its geologic and sedimentary history and also for its geographic location, where the cold California and warm Counterequatorial currents meet. Exploration activities executed by FORNOS, S. A. (1956) led to the disco very of low grade phosphate (3 to 5% P2O5) in the recent beach sands along the Bahia de Magdalena (Fig. # 1). In his doctoral thesis Bruno D'Anglejan Chatillon (1965) reports the presence of nodular phosphate on the continental shelf, between Isla Margarita and the Vizcaino peninsula. He estimated reserves of up to 1.5 million tons. A Mexican-American marine exploration company attempted in 1966 the evaluation of this deposit with negative results.

Jan 1, 1978

By Venancio Astucuri

"El presente texto describe las cuatro competencias que debe poseer un ingenierio de minas para un desarrollo sostenible de la minería. Dichas competencias se dividen en personales, académicas, profesionales y de ingeniería. Este grupo de competencias pueden ser usados también para un proceso de autoevaluación, donde cada uno pueda medir sus competencias con el fin de determinar brechas y superarlas, de forma que las empresas puedan plantear requisitos mínimos para sus diferentes posiciones laborales y, finalmente, para que en las instituciones educativas, estos puedan diseñar de forma adecuada sus respectivos planes de estudio."

Feb 1, 2017

By D. H. Davis

HAND picking was the earliest form of coal preparation, first practiced to improve the outward appearance of the coal being loaded and to remove any pieces that might appear objection- able to the buyer. It is still extensively practiced on the plus 1-in. sizes and particularly on the plus 4-in. and larger sizes. The percentage of ash reduction that can be obtained by hand picking depends entirely upon the amount of free impurity occurring in the coal. In a particularly dirty seam, where a considerable quantity of rock occurs with the coal as mined, hand picking produces sizable reductions in ash. If the coal is prepared clean at the working face hand picking is a final check; in some cases, on the smaller sizes, it is practiced only to show that an effort is being made to prepare a clean product. Because of the variety and different methods of handling coal, the early plants were not always adapted for efficient hand picking. At most mines an attempt is made to remove the visual impurities at one or more of the following places in the surface plant? (1) in the tipple during screening; (a) on picking band, belt, or shaking conveyors;*(3) during the loading of the coal as it goes into the railroad car. Whatever the physical arrangements of the plant may be, the usual practice is to run the coal over the screen, picking table or boom at such a rate that each piece of impurity is exposed to the view of the picker. Coal should be uniformly sized and spread out on the table so as not to exceed one particle in depth. The flow should be even in tonnage and the speed of travel should be from 30 to 60 ft. per minute and not exceed 80 ft. per minute. The dirtier the coal, the slower the speed required for a fixed number of pickers. Actually, picking capacity depends on the number of particles per minute that can be picked out and rejected. The percentage of impurity removed is determined by this and the average weight of piece rejected. Handling a mixture of sizes from nut to the largest lump over the same picking table or conveyor is not conducive to efficient separation by hand picking because the lump hides the smaller

Jan 1, 1943

By F. C. Oliphant, George H. Fancher

Two samples of drilling mud from the Hastings oil field, Texas, were tested, and the solids in each were separated into small fractions of a limited range in particle size. The mineral composition of each fraction by X-ray analysis is reported, and the results are interpreted in relation to other measured quantities, such as the physical properties of the original samples and the density of the various fractions. It was found that only 7 to 8 per cent by weight of the solids was of colloidal dimensions and that neither of the samples contained montmorillonite but did contain illite. Considerable calcite was also found. These data should be useful to the geologist interested in the origin and history of sedimentary strata as well as to the petroleum engineer. Introduction The questions, What is good drilling mud? What constitutes bad drilling mud? are pertinent, because the proper use and control of drilling fluids has been a factor of great importance in the successful drilling and completion of oil wells since the days of Captain Lucas. Adequate control of the characteristics of drilling fluids has assumed greater significance comparatively recently because of the problems introduced by caving formations in deep wells, costly blowouts and impressive mud bills. Much is known about the solution of some of the problems but, despite extensive research directed toward a better understanding of the physical and chemical properties of clay suspensions, it is difficult to define precisely a drilling mud, and much more difficult to say what constitutes a good mud. It is generally believed that the smaller particles of a drilling mud greatly affect its physical properties. In fact, it is customary to blame the colloids in a mud for nearly everything that goes amiss, because colloidal properties have effects out of all usual proportion on viscosity, filtration rate and reaction to electrolytes. It is germane to know whether drilling muds possess colloids and if so, the quantity and kind. Source oF Samples Two drilling muds from the Hastings oil field, Brazoria County, Texas, were selected because it is generally agreed that in this oil field good natural muds made solely from formations penetrated by the drill can be used until the well is nearly ready for completion. Customary drilling procedure in this field is to spud in with water, set a protective string of pipe, drill to 2500 ft. and set the surface casing. Drilling is continued to 5500 ft. with no treatment of the drilling fluid other than addition of water to

Jan 1, 1943

By Richard Schellinger, Ronald H. Carlson, Robert D. Norris

INTRODUCTION A very important key to the success of an in-situ leach venture is proper choice of well field chemistry, in which type and concentration of oxidant plays a significant role. For proper design of well field and plant, an engineer must be able to estimate uranium production levels and their change with time. The rate controlling step in the uranium leach process is generally acknowledged to be the oxidation step (Goddard and Brosnahan, 1980; McKnight and Anthony, 1979; Mays, 1979). Uranium head grade is very dependent upon concentration of oxidant injected into the ore zone. If oxidant levels are too low, uranium production requirements will not be met; if levels ate too high, excess oxidant will be wasted in side reactions with gangue material and leach economics will suffer. To date, no reliable laboratory technique exists for generating data easily translatable to field conditions. Empirical correlations based upon lengthy field testing have been the major tools avail- able to the design engineer to date. During the past five years, FMC has developed lab- oratory techniques for studying uranium leach chemistry under conditions simulating as closely as possible the field situation. Both agitated batch and consolidated core leach procedures have been developed. Results of FMC agitated batch studies are described in detail in a companion paper (Carlson, et. al., 1980). This paper will focus on the technique developed for leaching consolidated undisturbed core under simulated down-hole conditions. Through use of a follow-up computer model (Winkley, 1980), generated data can be translated to expected field response, thus providing the design engineer with valuable information in a relatively short period of time. CHEMISTRY In addition to uranium (+4), other oxidant-consuming species present in uranium ore are iron sulfides and carbonaceous material. Iron sulfides are usually present in concentrations far exceeding those of the other two materials and, therefore, represent the major oxidant-consuming species present in uranium sandstone ore. Previous studies (Carlson, et. al., 1980) have shown that iron sulfides exist in both Texas and Wyoming ores as a mixture of pyrite and marcasite (FeSz); furthermore, uranium mineralization (existing as uraninite) was shown to exist as a fine granular material coating or imbedded in iron sulfide crystals and sand grains (i.e. quartz and feldspars). The leach chemistry of a uranium ore body can be described by the following equations using hydrogen peroxide (Hz021 as oxidant:

Jan 1, 1980

By F. B. Plummer, R. B. Newcome

The practice of introducing acid into oil wells to increase production of oil and gas has been in use since 1894, when it was first used in the Pennsylvania oil fields30.‡ It is only since 1928 that it has been used to any extent in the Mid-Continent18. The process has proved successful in increasing production, at least temporarily, in depleted oil fields where the producing formation is highly calcareous and where water drive is not too pronounced. In the Zwolle field in Louisiana, where the producing horizon is a chalk, increases of 100 per cent have been recorded25. In north-central Texas, where the oil is produced from the Marble Falls limestone, equally pronounced increases have resulted3. The production also in some fields yielding oil from quartz sand cemented with calcitc has been benefited. The evidence of actual increase in total recovery of oil, however, has been questioned by some engineers18. It has been pointed out that the results of the treatment of a well in a now district, where the process has never been tried out, can never be predicted with certainty, since other factors besides percentage of calcareous content of the oil sand play a large part in determining the success of the method. Numerous articles have been published on acid treatment and on the effects of acid on limestone1-35, yet very little has been written concerning experimental work on the actual effect of acid on capillary pores and larger oil-coated voids of oil sands. This is due partly to difficulties in duplicating field conditions in a laboratory and partly to the fact that the process has been carried out largely by contracting companies that have been unwilling to publish details of their results for fear of loss of business to competitors. The authors, using equipment developed to measure the radial permeability of oil-sand cores2', have developed a method of investigating the results of acid treatment which has enabled them to test numerous cores and to study in some detail the action of acid on the different types of rocks, particularly fine-grained rocks.

Jan 1, 1936

By A. C. Richardson

[During the past two and a half sears the U. S. Bureau of Mines and the University of Alabama, with the cooperation of the different coal operators, have been making an extensive studs of coal preparation in the State of Alabama. Considerable time has been devoted to the studs of the washing characteristics of the Mars Lee bed and the various methods used In preparing from it a low-ash coal suitable for the manufacture of metallurgical coke. One of the phases of this problem is the utilization of middlings products from the washing plants. This paper gives the results of treating jig middlings on a coal-washing table at the Bureau of Mines laboratory at Tuscaloosa, Ala. The sample used was secured from the Sayreton washery of the Republic Steel Corporation, Sayreton, Ala. WASHERY PRACTICE The Mary Lee bed is very bony, and operators find it difficult to produce from this bed a washed coal much under 10 per cent ash. Experience has shown that in the preparation of a coking coal from the Mary Lee bed it is best to use a process which permits the recovery of a middlings product. Middlings are desirable because separation according to specific gravity is never perfect, and a middlings product makes possible a low ash in the primary warned coal without excessive losses of combustible in the refuse. The general washery practice on the Mary Lee bed is to crush the run-of-mine coal through some maximum screen size and wash it upon some one type of jig without re-treatment of any of the products made. The maximum size treated varies from 3 inch to J inch. The middlings product from multiple-cell jigs is usually termed "boiler fuel" and when possible is utilized as such. At present the production of boiler fuel is often in excess of power requirements, and the surplus, due to its high ash content, becomes waste.]

Jan 1, 1931

By Donald P. Tuchman, Robert P. Vinson, Steven J. Page

Researchers at the National Institute for Occupational Safety and Health (NIOSH) have long used stationary tapered element oscillating microbalances (TEOMs®) in laboratory settings. They have served to assess the mass concentration of laboratory-generated particulates in experimental , dust chambers and they provide a reference method for comparison with other particulate- measuring instruments. Current NIOSH research is focused on further adapting TEOM technology as a wearable personal dust monitor (PDM) for coal mining occupations. This investigation's goal is to help identify, quantify, and provide means for resolving certain TEOM- related error. The present research investigated bias caused by thermal effects on filter assemblies. New filters used in the PDM for 8 h tests show an average positive bias of 25.5 pg, while similar tests of equivalent filters used in two 1400A model TEOMs show an average positive bias of 34.3 µg. The derived bias values allow correction of previously collected biased data. Also, pre- heating the filters for 24 h at 46° C shows significant bias reduction, with PDM pre-heated filters subsequently averaging -3.3 µg and 1400A TEOM filters averaging 5.9 µg. On a single-point comparison to gravimetric sampling, a 25.5 µg bias is only significant at low mass loadings. At 2.5 mg, this bias represents a negligible 1 % of the mass measurement. If ordinary linear regression is used, the bias is still insignificant. However, if the more valid weighted linear regression is used, it gives more weight to the smaller dependent variable values, which are more impacted by the bias. Consequently, what is 1% bias on a single high-mass value can translate into a larger bias percentage at high-mass values when performing a weighted regression on data that include a large number of low-mass values.