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By J. B. Clark

In 1933, R. paris1 published a phase diagram for the entire Mg-Ca-Zn system. He reported the existence of a ternary intermetallic phase, Mg5Zn5Ca2, which formed a quasi-binary with the magnesium solid solution. Since then, no extensive work has been reported on the system. Recently however, indications of the existence of a second ternary in-termetallic phase in equilibrium with the magnesium solid solution led to a reinvestigation of the solid phase equilibria involving the magnesium solid solution. The 335°C (635°F) isothermal section was chosen for study. Metallography and powder X-ray diffraction were selected as the best mutually corroborating methods for determining the solid phase constitution. Seventy-six alloys were prepared from singly sublimed (99.95 pct) magnesium, electrolytic (99.95 pct) zinc and USP calcium. The analyses of some of the alloys are shown in Fig. 1. The alloys were melted in a graphite crucible under a chloride flu and chill cast in a split graphite mold. Dif-fusion couples (see Fig. 2) were prepared by casting molten Mg-20 wt pct Zn alloy around a cylinder of Mg-30 wt pct Ca alloy. The alloy samples and the diffusion couples were sealed under argon in Pyrex vials and annealed in a furnace capable of controlling within 1/2°C of 335°C. At the conclusion of the anneal, the alloy samples were quenched in ice water and the diffusion couples were air cooled. Procedures standard for magnesium alloys were used for metallographic examination. Powder X-ray diffraction patterns were taken on a G. E. camera with a 14.32 cm dim using nickel-filtered copper radiation. The redetermined 335°C (635°) section of the Mg-Ca-Zn phase diagram is shown in Fig. 1. TWO ternary intermetallic phases, designated w and

Jan 1, 1962

By Norma Golumbic

The primary purpose of the Bergius (hydrogenation of coal) and Fischer-Tropsch (hydrogenation of carbon monoxide) processes is the production of synthetic liquid fuels. This objective is of importance in insuring an adequate supply of motor fuels and lubricating oils in the United States. In the urgency of the basic research and process development work on synthetic liquid fuels, the possibilities for the production of synthetic chemicals inherent in these processes have hitherto received little attention in this country. However, the by-products, as well as the primary products, from the Bergius and Fischer-Tropsch processes are rich source materials for organic chemicals. The overhead oil from liquid-phase hydrogenation of coal, for example, contains benzene, toluene, xylene, cyclohexane, methylcyclohexane, aromatic solvents, about 20 percent tar acids (largely phenol, cresols, and xylenols), and 3 percent nitrogen bases. Wax, alcohols, and acids are by--products of the Fischer-Tropsch synthesis. In addition, techniques have been developed which make possible the production of aliphatic hydrocarbons, alcohols, acids, aldehydes, and other oxygenated organic compounds. These chemicals are more valuable on a unit basis than gasoline. Because of continued rapid expansion of the plastic, resin, lacquer, and solvent industries, larger amounts of many of these chemicals will be needed in the near future.

Jan 1, 1949

By S. Ralph Austin

Emanation coefficients of 950 samples of domestic uranium ore were successfully and rapidly determined with fair precision by modifications of the closed-can, gamma-only assay method, using commercially available or similar equipment. Coefficients range from <1 to 91 percent. Emanation varies considerably within each mine and area, but distinct differences among major mining areas were found, ranging from 7.5 percent for Moss Back Member, Chinle Formation, Southwest Lisbon Valley, Utah, to 56.6 percent for Ft. Union Formation (?), Powder River Basin, Wyoming. Coefficients also vary with (1) uranium mineralogy; (2) radium mineralogy; (3) lithology of host rocks; (4) grain size of uranium and radium minerals; (5) comminution of ore; (6) estimated porosity and permeability; (7) moisture content; (8) ore grade; (9) supposed mobility of deposits; age of deposits is unknown but limited by (10) age of host rocks which shows only doubtful correlation with emanation. Data obtained may be used to evaluate effects of investigated parameters on radon concentration in mines and thus to select efficient control measures. Drill-core emanation data allow estimates of probable radon problems in undeveloped deposits.

Jan 1, 1978

By R. J. Matetic, David S. Yantek, David K. Ingram

The National Institute for Occupational Safety and Health (NIOSH) has investigated engineering noise controls to reduce sound levels in cabs on air-rotary drill rigs. A recent investigation revealed that some drillers are exposed to A-weighted sound levels exceeding 85 dB even though a cab is used. NIOSH studied the in-cab sound levels of one such rig. First, preliminary tests were conducted in a controlled environment using accelerometers and microphones with spectral analysis to identify the dominant noise sources for in-cab sound levels. The results indicate that vibration transmitted from multiple hydraulic pumps to the control panel produces a dominant spike in the sound level spectrum in the 400 Hz 1/3-octave band. Next, field tests were performed in a production environment to evaluate noise controls to reduce in-cab sound levels. It was found that utilizing hydraulic noise suppressors reduces the structure-borne noise transmitted to the control panel. Further, using hydraulic noise suppressors and enhancing soundproofing reduced the in-cab A-weighted sound levels by as much as 4 dB.

By Jean-Marc Lulin

"Depuis 1906, pres de 130 gisements ont ere decouverts dans la inture archeenne polymetallique (Cu, Zn, Au, Ag) du nord-ouest becois. Une etude regionale du developpement du potentiel inier est presentee puis detaillee pour quatre secteurs: RouynDranda, Val d'Or-Malartic, Bousquet-Cadillac et Matagami.L' analyse est conduite a l' aide des parametres suivants: temps, ethodes de decouverte, profondeur des gisements et poids metal. ~~ courbes cumulatives illustrant le nombre de gisements decouverts fonction du temps montrent une forme generale en ""S"" dont les i'iations de pentes correspondent aux variations dans les taux de ~ouverte. Initiation, realisation et stabilisation des cycles de decourte sont ainsi mis en evidence. Deux ""bourns miniers"", de 1922 a ~5 et de 1955 a 1965, rassemblent 72 % des mines identijiees squ' a present.La plupart des mines sont trouvees en subsurface: 90% ont leur fmet entre 0 et 100 metres de profondeur dont 70 % entre 0 et 10 etres. Dans le temps, il y ad' abord recolte par prospection puis par fphysique et enjin, developpement progressif du potentiel en proeur avec des methodes composites. Environ 80% du poids metal extrait de 4 camps miniers, couvrant 8% de Ia surface regionale quelques gros gisements dominent /a production.Ces donnees permettent de proposer une nouvelle approche pour lysed' une region miniere:La distribution de Ia profondeur des gisements en fonction du temps est indicatricede /amaturite d' uncampminieret peut servir a evaluer son potentiel residue/.L' analyse des courbes en ""S"" permet d' extrapoler les taux de succes relies aux differentes methodes et met en relief le role crucial de I' innovation dans I' exploration.ABSTRACTSince 1906, some 130 deposits have been discovered in the Archean polymetallic belt of northwestern Quebec. In this paper, the development of the mining potential is analyzed at the regional scale and for the following mining camps: Rouyn-Noranda, Val d'OrMalartic, Bousquet-Cadillac and Matagami.The analysis is based on the following parameters: time, discovery method, depth and weight of metal extracted. Curves showing the cumulative number of deposits discovered as a function of time are ""S"" shaped with slope variations corresponding to changing discovery rates. Initiation, realization and stabilization of discovery cycles are thus well represented. Two ""mining booms"", 1922 to 1945 and 1955 to 1965, account for 72% of the mines identified to date.Most exploitable orebodies have been found near the surface: 90 %have their top between 0 and 100 meters, including 70% between 0 and 10 meters. Early discoveries were made by prospecting, followed by geophysics while the progressive development of the depth potential is being realized by a combination of methods. Approximately 80 %of the metal extracted comes from four mining camps which cover 8% of the area, but most of the production can be allributed to only a few large deposits. Based on these data, a new approach to the analysis of a mining region is proposed:1) The distribution showing deposit depth versus time is indicative of the maturity of a mining camp and can serve to evaluate its remaining potential.2) The ""S"" curve analysis can be used to extrapolate the success rate of a specific exploration method and also stresses the crucial role of innovation in exploration."

Jan 1, 1990

By Jean-Marc Lulin

"Depuis 1906, près de 130 gisements ont été découverts dans la inture archéenne polymétallique (Cu, Zn, Au, Ag) du nord-ouest québécois. Une étude régionale du développement du potentiel inier est présentée puis détaillée pour quatre secteurs: Rouyn-Dranda, Val d'Or-Malartic, Bousquet-Cadillac et Matagami.L' analyse est conduite a l' aide des paramètres suivants: temps, méthodes de découverte, profondeur des gisements et poids métal. Les courbes cumulatives illustrant le nombre de gisements découverts fonction du temps montrent une forme générale en ""S"" dont les i'iations de pentes correspondent aux variations dans les taux de couverte. Initiation, réalisation et stabilisation des cycles de décourté sont ainsi mis en évidence. Deux ""bourns miniers"", de 1922 à 1945 et de 1955 à 1965, rassemblent 72 % des mines identifiées sqú à présent.La plupart des mines sont trouvées en subsurface: 90% ont leur mmet entre 0 et 100 mètres de profondeur dont 70 % entre 0 et 10 êtres. Dans le temps, il y a d' abord récolte par prospection puis par ophysique et enfin, développement progressif du potentiel en proeur avec des méthodes composites. Environ 80% du poids métal extrait de 4 camps miniers, couvrant 8% de Ia surface régionale quelques gros gisements dominent /a production.Ces données permettent de proposer une nouvelle approche pour analyse d' une région minière:La distribution de Ia profondeur des gisements en fonction du temps est indicatrice de la maturité d' un camp minier et peut servir a évaluer son potentiel résiduel.L’analyse des courbes en ""S"" permet d’extrapoler les taux de succès relies aux différentes méthodes et met en relief le rôle crucial de I' innovation dans I' exploration.ABSTRACTSince 1906, some 130 deposits have been discovered in the Archean polymetallic belt of northwestern Quebec. In this paper, the development of the mining potential is analyzed at the regional scale and for the following mining camps: Rouyn-Noranda, Val d'OrMalartic, Bousquet-Cadillac and Matagami.The analysis is based on the following parameters: time, discovery method, depth and weight of metal extracted. Curves showing the cumulative number of deposits discovered as a function of time are ""S"" shaped with slope variations corresponding to changing discovery rates. Initiation, realization and stabilization of discovery cycles are thus well represented. Two ""mining booms"", 1922 to 1945 and 1955 to 1965, account for 72% of the mines identified to date.Most exploitable orebodies have been found near the surface: 90 %have their top between 0 and 100 meters, including 70% between 0 and 10 meters. Early discoveries were made by prospecting, followed by geophysics while the progressive development of the depth potential is being realized by a combination of methods. Approximately 80 %of the metal extracted comes from four mining camps which cover 8% of the area, but most of the production can be allributed to only a few large deposits. Based on these data, a new approach to the analysis of a mining region is proposed:1) The distribution showing deposit depth versus time is indicative of the maturity of a mining camp and can serve to evaluate its remaining potential.2) The ""S"" curve analysis can be used to extrapolate the success rate of a specific exploration method and also stresses the crucial role of innovation in exploration."

Jan 1, 1989

By S. L. Weber, D. E. Banks

"Silicosis was first reported by the ancient Greeks and is apparently as old as human history. The prevalence of this illness peaked in the last half of the 19th century and the early part of this century, when mechanized industry was developing and the relationship between dust exposure and disease was less well understood. Yet, even today in devel-oped countries, sporadic outbreaks of silicosis occur when workers are consistently exposed to silica particles of respir-able size (0.5 to 5.0 µm in diameter) at levels exceeding those recognized to be safe.Silicon dioxide or silica. is the earth's most abundant mineral. Silica is considered to be either free (i.e.. unbound to other minerals) or combined. Minerals with high amounts of free silica include quartz (including granite) flint. Chert, opal, chalcedony, and diatomite. Combined forms of silica are called silicates and include, among others, asbestos talc and kaolin.In the crystalline form, silica exists as quartz, cristobalite, and tridymite (Fig. 28). Of these quartz is ubiquitous in the environment and occurs as sand and as a part of many rocks. Cristobalite and tridymite occur naturally in lava and can be formed by the heating of quartz or amorphous silica. Cristo-balite is more tibrogenic than quartz. Amorphous silica is noncrystalline and, therefore, is relatively nontoxic and does not cause silicosis. It occurs as diatomite (skeletons of pre-historic marine organisms) or as vitreous silica (glass), the result of carefully melting and then quickly cooling free crystalline silica. Heating diatomite with or without alkali (a process known as calcining), forms cristobalite and adds the respiratory toxicity of free crystalline silica.There are many opportunities for occupational exposure to respirable crystalline free silica. Some of the commonly en-countered occupations in which the risk of silicosis exists are reported in Table 20.Silicosis. the pulmonary disease caused by the inhalation of silica particles of respirable size, is most commonly cate-gorized by findings on the chest radiograph. The most typical presentations simple silicosis and progressive massive fibrosis appear different radiologically but are grouped under the category of classic silicosis because they are a part of the radiographic spectrum of this illness. Radiographically, simple silicosis appears as small (less than 10 mm in diameter), rounded opacities, typically predominant in the upper lung zones. Progressive massive fibrosis is the result of the coalescence of these small nodular opacities and appears as larger opacities (more than 10 mm in diameter), again typicallydistributed in the upper lung zones."

Dec 1, 1995

By V. F. Swanson

As part of the Bureau of Mines titanium resources examination program, samples of altered rock (saprolite) and unaltered rock from the Roseland anorthosite near Roseland, Nelson County, Va., were tested for amenability to beneficiation by flotation. A flotation technique was developed to produce bulk concentrates of ilmenite, rutile, sphene, and leucoxene. It was necessary to first float apatite using oleic acid as the collector, in an alkaline pulp with dextrine as a titanium mineral depressant. The titanium minerals could then be floated from the apatite tailing, using fluosilicic acid to depress the remaining apatite, morin to depress ferromagnesian minerals (when present), and oleic acid as the collector. A bulk titanium mineral concentrate, analyzing 66.0 percent Ti02 and 0.08 percent P205, was obtained from a sample of the unaltered rock which contained 5.45 percent TiO2 and 2.81 percent P205. Overall recovery in the concentrate was 47.1 percent of the total TiO2 in the ore. About 55 to 65 percent of the saprolite sample was clay and was removed by attrition scrubbing and decantation. The apatite prefloat procedure was applied to the saprolite sands; subsequent titanium mine: 1 flotation recovered 72.2 percent of the Ti02 in a bulk concentrate containing 65.1 percent TiO2 and 0.20 percent P205.

Jan 1, 1962

By Ali Kazmi, Wern-ping N. Chen

A load rating procedure was performed to evaluate safe load capacity of the Port of Miami Tunnel (POMT), FDOT Tunnel No. 871071 SR 887. The rating procedure performed on a total of eleven stations beneath roadways and with fill depth less than the tunnel exterior diameter (42 ft). Calculations on tunnel sections passing beneath roadways were performed to evaluate the structural response of the sections subject to moving vehicular loads, dead load, and earth pressures. Ratings were performed in accordance with AASHTO and FDOT guidelines. The procedure considered two types of vehicles (HL-93 and FL-120) and two rating levels (Design level and Permit level). As part of HL-93 vehicle, Tandem load was also considered for rating, separately. For HL-93 and HL-93 Tandem, inventory and operating level ratings were performed. The results show rating factors are high. The minimum rating factor is 16.8 using Inventory truck HL-93. For Permit level using FDOT FL-120 truck the minimum rating factor is 6.9. As can be seen, rating factors are higher than comparable analysis for bridges. This paper explains how the procedure can be implemented for tunnels and evaluates the rating results.

Dec 1, 2022

By Paul M. Tyler

Magnesite is of importance primarily as a refractory material for lining steel furnaces , although substantial amounts are used in the production of flooring compositions and other building materials and for certain chemicals , notably epsom salts . Since consumption for all of these purposes is largely in the eastern United States and domestic deposits are situated in California and Washington , this country's magnesite mining industry , which was created largely by war- time conditions , has subsequently been sustained by tariff protection .

May 1, 1931

Blasthole deviation is a frequent, well documented and undesirable occurrence in mining operations. It is caused by the drill string mechanics, operating variables and the interaction between the drill bit and the rock mass characteristics. It is composed of three distinct components: collaring or marking error, alignment error and trajectory deviation. This study has focussed on the dependence of trajectory or natural deviation on the geological features of the rock mass being drilled.

Jan 1, 1996

By R. A. Williams

The Pascua Lama Project is situated on the border of Chile and Argentina at an elevation of 4,800 m. The ore contains gold, silver and copper, and an initial milling production rate of 33,000 t/d is planned. The mineralogy of this deposit is unusual. The ore is hard and abrasive, and it contains a complex array of sulphate minerals, such as chalcanthite, jarosites and alunites. The sulphides are predominantly enargite and pyrite. A novel flowsheet has therefore been developed, which includes dry grinding and ore washing to remove and then neutralize the soluble salts, prior to flotation, cyanide leaching and Merrill-Crowe recovery of the precious metals. These metallurgical issues and challenges associated with plant design and construction in the high and remote Andes Mountains make this a particularly challenging project.

Jan 1, 2001

By Terry J. Close

Between 1986 and 1989, at the request of the U. S. Bureau of Land Management, personnel from the U. S. Bureau of Mines Western Field Operations Center studied the highly-mineralized, 25,335-acre, Crack Canyon Wilderness Study Area (UT-060-028A), to evaluate its identified mineral resources. The 16-mi-long, 2-mi to 4-mi-wide stud/ area is on the southeast side of the San Rafael Swell, about 40 mi southwest of Green River, Emery County, southeast-central Utah. The study area is underlain by Mesozoic sedimentary beds. Uranium, the principle mineral resource, occurs in two formations. The principle uranium deposits are in mudstone, sandstone, and conglomerate lenses in the 22-mi-long outcrop of the Triassic Chinle Formation which parallels and straddles the northwest boundary of the study area, Some small low-grade uranium occurrences and an extensive gypsum deposit are hosted by the Jurassic-age rocks that underlie the southeast part of the study area.

Jan 1, 1989

By Ricardo Burdisso, Rahul Kadam, Kyle Schwartz, Marty Johnson

Occupational exposure to hand transmitted vibration (HTV) arises from the hand held powered tools extensively used in the mining and construction industry such as rock drills, chipping hammers, chain saws etc. Regular exposure to HTV is the major cause of a range of permanent injuries to human hands and arms which are commonly referred to as hand-arm vibration syndrome (HAVS). In addition to this, the percussive tools generate overall sound power levels in excess of 110dBA in most cases. Such a high sound power level greatly exceeds the maximum permissible exposure limit (PEL) of organizations such as National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA). Long term occupational exposure to this noise has been diagnosed as the main reason for permanent hearing loss in the operators. It is therefore important to develop an understanding of the mechanisms which lead to these high vibration and sound levels and in order to do this a detailed computational model of a pneumatic chipping hammer has been made. This paper presents a nonlinear computational model of a pneumatic chipping hammer. In order to better understand the dynamics of the chipping hammer, the hammer was subdivided into components that are shown in figure 1 (a) (based on a chipping hammer manufactured by Atlas-Copco). The hammer mainly consisted of a center body, a moving piston and a chisel. Compressed air is used to drive the piston inside of a cylinder and on the downward stroke this piston impacts the chisel to create the hammer effect. The machine has one pneumatic valve and this valve regulates the air supply either to the upper chamber or to the lower chamber. The valve changes according to the relative pressures in the two chambers and the supply pressure. There are also twelve different exhaust ports at two positions along the cylinder labeled upper ports and lower ports. As the piston moves the ports can be closed or open (allowing exhaust). Fundamentally, the computational model was made up of two different sub-models, a fluid model and a structural dynamic model as shown in Figure 3 (a) and (b) respectively. The first sub-model takes into consideration the fluid dynamics of the machine since the hammer is driven by compressed air. Equations for the mass flow rate though bleed orifices (assuming an isentropic process) 1 is used to determine the mass flow into and out of the upper and lower chambers. From this the pressures in the two chambers and consequently the forcing on the piston can be calculated. The second sub-model deals with modeling the structural [ ]

Jan 6, 2006

By John C. Machisak

DATA ON INJURY experience at quarries and related plants of the United States are presented in this publication under the following general sections: A) General injury experience: Tables 1-4: Contain current data on number of injuries, injury-frequency rates, work location, accident agency, degree of injury, and related employment data. (B) Injury experience at different kinds of quarries: Tables 5-6: Current data on number of injuries, injury-frequency rates, work location, accident agency, degree of injury, and related employment data. (C) Injury experience by States: Tables 7-19: Current data on the number of injuries, injury-frequency rates, accident agency, degree of injury, and related employment data. (D) Selected injury data: Tables 20-30: Current data on various selected factors of operating conditions at different kinds of quarries, including employment size-groups, length of shifts, comparative severity of injuries, and injury data and related employment experience at dimension-stone and crushed and broken stone quarries, and underground quarries. (E) Mining methods and historical injury experience: Tables 31-32; Employment data and injury experience in the quarrying industries of the United States, by mining method and work location, 1953-58; and historical injury experience and employment data in the quarrying industry, 1911-58.

Jan 1, 1962

By A. F. Banks

"The last time I spoke to you the potash industry was at a low point. Markets were bad and the industry depressed. Many people had left and there was very little being done in terms of development. The current situation is very much changed. The oversupply conditions have given way to a very tight supply capability. All of the firms in the business are expanding in one way or another. These expansions will run from simple debottlenecking through to complete new projects.In New Brunswick, the Potash Corporation of America is proceeding with a new project and the Dennison - Potacan Project is in progress. In Saskatchewan, the Potash Corporation of Saskatchewan has an ambitious 2.5 billion dollar expansion program underway while those in the private sector are taking a somewhat less ambitious but equally significant approach to obtain further tonnage out of existing facilities.The significance of these expansions to mineral processors is that we can expect to see expanded employment opportunities and through necessity a surge in innovation and development in an industry that has been traditionally very conservative. This presentation will review potash processing with a view towards highlighting some of the more recent developments."

Jan 1, 1982

By Y. M. Zhao

The separating performance of a pilot dry beneficiation system using a gas-solid fluidized bed was investigated with coal from South Africa. The coal used for the study has a low inherent moisture content, a moderate ash content, a moderate volatile content, a low sulphur content and a high calorific value. Its washability is moderate. Experimental results show that the separating quality of the fluidized bed drops gradually as the feed-coal particle size decreases. The probable error, E, values for 50?25mm, 25?13 mm and 13?6 mm coals were 0.04 g/cm3, 0.06 g/cm3 and 0.09 g/cm3, respectively. The cause of the differences in separating characteristics was analysed by particle dynamics and numerical modelling. Furthermore, the pilot fluidized bed was employed to separate 50-6mm coal. In this experiment the coal ash content was reduced from 23.74% to 11.79%, with a probable error, E, value of 0.07 g/cm3and a recovery efficiency of 98.26%. This indicates that the fluidized bed is applicable to the separation of coal from South Africa and has good separating performance and wide applicability. Keywords: feed-coal particle size; gas-solid fluidized bed; dry coal beneficiation; numerical simulation.

Jan 1, 2010

By Axel Nitschke, Josef Arnold

Bochum’s Underground Lot 306 was characterised by a confined site and unique tunnelling methods. A highly mechanized construction concept was developed to achieve high progress rates. Bespoke backup systems for muck disposal and material supply were used. For the first time in suburban tunnelling, wet shotcrete, batched onsite, was applied. A three-storey underground car park had to be undermined with only1.5 m of overburden and had to be lifted several times by “compensation grout in.” An existing operational two-lane metro tunnel was enlarged without any major impact on train operation.

Jan 1, 2005

By Sam Ammermann, William Heasley

"The mining industry is on an ever accelerating path to complete mechanization. As companiesutilize more sophisticated and efficient methods of blasting, a more thorough look should begiven to the pros and cons of mechanized shaft sinking. Historically, Vertical Shaft SinkingMachines (VSSM) have been capital intensive, making it hard to enter lowest bidder marketssuch as the United States. As advances in safety and technology have occurred, VSSM methodsare becoming increasingly common in many countries outside the United States. Decreasedcapital requirements, a greater amount of competition within the VSSM market along withgreatly improved safety practices, have made it more competitive with traditional drill and blast(D&B) methods. However, VSSM technology has yet to be embraced by the United States. Alarge culture shift will have to occur before VSSM technology will become common in theUnited States. The history, and advent, of raised boring machines will be discussed and how itrelates to the current development of VSSM technology. The researchers will analyze the uniquerisks of D&B methods and how they compare with the unique risks of VSSM technology. Theresearchers will put an emphasis on risks directly affecting the safety of personnel working onthe shaft sinking operation. Many of these risks are identified by contracting companies withregards to geology, relative location of resources and the chosen shaft sinking method. Theresearchers will discuss specific risks a given shaft sinking company will want to consider whenchoosing between D&B and VSSM methods."

Jan 1, 2016

By R. J. Hundhausen

This report describes the exploration and recent utilization studies the Bureau of Mines conducted on the Iron King, Chambers, and Dry Camp chromite deposits in the John Day district, Grant County, Oreg. The field investigations were undertaken during parts of 1939 and 1942 to determine the tonnage and grade of chromite in the district that could be utilized as a war reserve for the steel industry. As a result of the Bureau&apos;s field work, which included construction of 9 miles of access road, 6,204 feet of diamond drilling, 195 channel samples, and 1,020 linear feet of trenching, an ore reserve of 208,000 tons of 22-percent chromic oxide was indicated in the 3 deposits. Less than 1,000 tons of this ore has been mined since the field work was completed because the 2 largest deposits are submarginal in grade and there is as yet no incentive to develop and mine the ore. Since the war, however, the Bureau has been seeking means of utilizing the ore. Two methods of utilization that show promise are direct smelting of the ore in an electric furnace and use of the chromite for making refractory brick.

Jan 1, 1956