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By James R. Craig

The Central and Southern Appalachians were the major sources of gold in the United States throughout the first half of the 19th century and have continued to yield gold to the present day. Small amounts of gold were probably extracted by the Indians and the Spaniards but the first documented report of gold in the region was made by Thomas Jefferson who found a four pound lump of gold ore, which yielded 0.85 troy oz., in the Rappahannock River of Virginia in 1782. Gold was subsequently discovered in North Carolina between 1793 and 1799, in Virginia in 1806, in South Carolina in 1827, in Georgia in 1829 and in Alabama about 1830 (Becker, 1894-5; Pardee and Park, 1948). The gold belts of the Central and Southern Appalachian Piedmont and Blue Ridge Provinces are shown in Figure 1. The superimposed circles indicate the mount of production from some of the more productive and well known areas. Although North Carolina produced far more gold than the other states, the most significant concentrated area of production is the Dahlonega District in Georgia which yielded more than 500,000 troy ounces. After discovery, gold production increased rapidly as shown in Figure 2. Production was at its maximum between 1830 and 1852 with combined totals generally exceeding 30,000 troy ounces per year. Production dropped sharply after the California gold rush in 1849 as experienced miners moved westward in search of bigger and easier stakes. After the Civil War briefly halted gold mining in the Appalachians, production rose to an average of about 8,000 ounces per year from 1865 until 1878 and to an average of about 13,000 ounces per year from 1881 until 1915 when it again fell to near nil (Pardee and Park, 1948). Minor resurgences occurred in the 1930's and 1940's. Although there has been no reported production in recent years, it is likely that "weekend panners" still remove hundreds of ounces from streams annually. The total reported production for the area through 1959 is in excess of 2.5 million troy ounces.

Jan 1, 1981

By James W. Cooksley

This report concerns a seismic geophysical exploration program which was conducted 3 miles southeast of the Carlin Mine, in Lander County, about 18 miles north of Carlin, Nevada. A twelve-fold reflection seismic line was executed over a one-mile traverse in section 32, Township 35 North, Range 51 East. This study is part of an exploration pro- gram directed toward finding Carlin-type gold deposits which are concealed under younger alluvium and volcanics. The exploration objectives of this program are as follows: 1) measure the thickness of the younger, sedimentary and volcanic deposits which overlie the "productive rock sequence", 2) delineate the Roberts Mountains thrust fault, 3) investigate the origin of the geochemical anomalies present in the western portion of section 32.

Jan 1, 1985

By Russell. A. Smith

This paper describes some recent work on the identification and development of new chemical reagents aimed at improving the industrial processing of phosphate ores by froth flotation. In particular, three chemical product families which will be discussed appear to offer enhanced flexibility by: 1) utilizing a small amount of a silica control reagent which can significantly reduce the amount of anionic (carboxylic) collector required for a given P2O5 recovery level; 2) utilizing a new anionic collector family which offers high P2O5 recovery and selectivity versus standard carboxylic collectors; and 3) utilizing another new anionic collector family which has, in some tests, allowed for selective removal of dolomite from apatite. Examples and use characteristics of each of these new chemical ideas will be presented.

Jan 1, 1993

By Alexander N. Winchell

The cities of St. Paul and Minneapolis are located side by side on a double loop in the Mississippi River near the eastern boundary of Minnesota. Both cities lie on both sides 'of the Mississippi River, which in this region describes an S-shaped curve. The two cities together have a population of over 600,000 people, gathered in an area which has grown to be a single urban district inasmuch as the two cities have expanded until they occupy all the territory formerly between them, though the business centers are ten miles apart. St. Paul is located at the head of navigation on the Mississippi River and Minneapolis, farther upstream, at the Falls of St. Anthony. A recent water¬power development below the Falls of St. Anthony, constructed by the Federal Government, has at the same time made possible navigation to the foot of St. Anthony Falls through a lock around the dam which replaces the former rapids. Minneapolis, in 1920, had a population of 380,000 people, and St. Paul, 235,000. The two cities occupy land at an elevation of 700 to 900 feet above sea level. The average elevation is slightly less at St. Paul. Minneapolis has nearly 4,000 acres of parks and park¬ways, while St. Paul has nearly 2,000.

Jan 1, 1920

By D. Spindler

Pursuant to the Federal Surface Mining Act of 1977 and the Illinois Surface Mining Act of 1980, Illinois has adopted revegetation success standard regulations that include the Agricultural Land Productivity Formula. The Formula establishes yield goals and standards to measure the success of meeting yield goals for reclaimed prime farmlands. The formula compares the quality of the pre-mining soils in the permit area and the county, to the crop production achieved on the reclaimed permit area and the county crop yield in a given crop year. The regulations also specify acceptable crops, erosion control requirements and time frames for demonstrating success.

Jan 1, 1986

By A. W. Khair

This paper presents an analysis of respirabie dust generation due to the action of a continuous miner. Underground coal cutting by a drum-type continuous miner was simulated in the laboratory using a specially designed unique automated rotary coal cutting simulator (ARCCS). An analysis of -400 mesh particles was done on gravity collected material. Samples of entrained dust were collected through the use of cascade impactors. Both samples were analyzed for size distribution and particle shape. Using the simulated coal cutter permitted variation of operating and in-situ parameters to provide information on the effects on generation of -400 mesh particles. In these tests coal blocks with an approximate dimension of 18 in. x 15 in. x 6 in. (45.7 cm x 38.1 cm x 15.2 cm) were first subjected to confining pressures, equivalent to in-situ conditions. Such blocks were then cut by the cutting head of the ARCCS, thus simulating the action of the continuous miner in underground coal mining. During the tests under a particular set of in-situ and operating parameters a number of other parameters such as 1) penetration of bit into coal, 2) penetration resistance (thrust and cutting pressures), 3) rotating velocity of cutting head, and 4) acoustic emission activity in the coal block were monitored. After each cutting cycle the fractured surfaces were photographed and a velocity survey was conducted by using a sonic technique. At the end of each experiment the cutting paths of the bits in coal were photographed using an optical microscope with an attached camera.

Jan 1, 1985

By Edward J. Harvey

Joplin, one of the most famous zinc mining camps of a bygone era, is today experiencing a healthy growth in manufacturing enterprises. Manufacturing requires water, and knowledge of its availability and quality often is the main factor in location of industry. For this reason in January 1964, on the suggestion of the former State Geologist, Dr. Thomas R. Beveridge, a study of the water resources of the Joplin District was undertaken as a cooperative effort of the Missouri Geological Survey and Water Resources now under the direction of Dr. William C. Hayes and the U. S. Geological Survey. The project area is in southwestern Missouri on the Springfield Plateau and is bordered on the west and north by the Osage Plains of Kansas and Western Missouri, (fig. l). Upland altitudes rise from 900 feet above sea level in the west to 1400 feet in the east. The countryside is rolling to moderately hilly and much is excellent farmland.

Jan 1, 1965

By J. D. Grace

[Screening by centrifugal force is an unique, subject, for with the exception of only one vibrating screen presently on the market, all vibrating screens depend upon, gravity to pass material through a sizing mesh or screen cloth. This one screen that sizes by centrifugal force and utilizes gravity only to convey materiel along the screen, is the SYMONS V-Screen. This screen was designed by Loren Symons, a member of the family that has contributed so much to the metallic and non-metallic mineral processing industries. Among Symons' other outstanding contribution to these industries are the original Cone Crusher which revolutionized reduction crushing practice, the first high-speed horizontal vibrating screen, the original Rod Deck Screen, and one of the earliest vibrating Bar Grizzlies.]

Jan 1, 1965

By V. K. Karra

An improvement in the present day screen sizing methods calls for knowledge on i) how material in the size range: 0.5 x 1.5 times the through-fall opening of the mesh on a deck, splits between the oversize and undersize streams of the deck, and ii) how near-mesh content of the feed affects the screening performance. In the throughput based sizing method given here, this is accomplished through the introduction of a generalized partition curve and a near-mesh factor. A newly developed efficiency factor is employed in addition to the traditional screen sizing factors.

Jan 1, 1979

By Viggo C. Bertelsen, David G. Hammond

LOCATION AND EXTENT OF BART TUNNELS The San Francisco Bay Area Rapid Transit District (BART) during the past six years has become the Owner of 23.5 miles of single-bore tunnels. The tunneling experience gained while working closely with our Engineer and Contractors in the design and construction of these major transit facilities provides a basis for our "Owners" viewpoint. The 23.5 miles of tunnels are divided into two categories. Fifteen and one-half (15-1/2) miles of tunnels were constructed in soft ground underlaying the downtown areas of San Francisco, Oakland and Berkeley. Eight (8) miles of tunnels were built in "hard ground" in the hills separating Oakland and Berkeley from Contra Costa County and in the San Francisco hills on the Mission Line. Location of tunnels within the BART system are shown on Figure 1. The tunnels comprise 15.7% of BART's 75-mile dual track system. Their 176 million dollar costs (excluding rail, electrification or ventilation features) are 12.4% of the system's total estimated cost of $1.4 billion. The tunnels constructed in soft ground were shield and boring machine driven with ground support provided by steel liner rings. The exterior diameter is 17 foot, 6 inches in the majority of tunnels; however, on two tunnels with a 500 foot radius of curvature, the diameter was 18 feet. BART awarded 14 contracts for soft ground tunneling. The work was accomplished under free air or compressed air depending upon the ground water and soil conditions, safety requirements, and considerations for protecting adjoining property from damage either from the de-watering operations or settlements due to excavation. The tunnel bores, except on curves, were normally parallel being spaced at 32 foot centers on the Mission

Jan 1, 1997

By Dan Nilsson

Open pit mining is the strong sector of the American mining industry. In the middle of the 60's. 17-18% of the ore in metal mines was mined with underground methods. From the middle of the 60's to 1980 the production in open pit metallic mines increased from about 400 to close to 600 million short tons while at the same time the underground mine production decreased a little, from about 90 to about 80 million tons. Less than 15% of the ore prodction now come from underground mines. Large amounts of waste rock were also handled in the open pits. In the middle of the 60's about 600 milion tons were handled, in 1980 1,200 million tons were moved. This means that the average stripping ratio increased from about 1.5 to over 2.0 tons of waste rock per ton of ore, figure 1.

Jan 1, 1983

By Bernie W. Martin, Jesus Schabib

The East Side Access (ESA) Project in New York will be the largest tunneling project ever undertaken by a US railroad. The objective of the ESA project is to connect the Long Island Rail Road (LIRR) Main Line and Port Washington Line in Queens to Grand Central Terminal in Manhattan. The Project is divided into two distinctive segments: Manhattan and Queens. The Queens segment is subdivided into two major components; cut and cover tunnel construction and bored tunnels. The bored tunnels in Queens consist of five tunnels driven from a launch shaft and traverse a railway storage yard, Sunnyside Yard and terminate under the multitrack mainlines of Amtrak and LIRR at portals in the heart of Harold Interlocking where1200 trains pass every day. The soil consists of remnants of glacial till moraines and of outwash and till deposits of inter layered gravel and fines, with the occasional boulders and cobbles and with a high ground water table. It is anticipated that a Pressurized Face Machine, either slurry or Earth Pressure Balance equipped with roller disks to mine the boulders encountered as well as the mixed face, will be used to mine the tunnels. One pass reinforced concrete gasket bolted liner will be used. The cut and cover construction consists of an approximately 21.3 m (70 feet) deep excavation supported by slurry walls and jet grout columns. The slurry walls, in combination with overlapping jet grouted columns, are installed to top of rock forming a closed bathtub to control external groundwater drawdown. Maintaining the groundwater level near its original elevation is of paramount importance in order to prevent undesirable settlements and migration of groundwater that could be contaminated. Mitigation measures to prevent the migration of nearby plums are contemplated for all types of tunneling and excavation work in this site of the ESA project.

Jan 1, 2001

By C. K. Jankousky

The midwestern area referred to is the Illinois basin. The coals presently worked are mainly the No. 5 and No. 6 coal seams which vary in thickness from five to eleven feet. Present average of the more important No. 6 id about nine feet. The coal can vary considerably in toughness within the same mine with some coal perhaps rashing very easily and other coal being extremely difficult to cut. Top is generally well laminated shales with some fortunate areas having limestone roof. There are local areas with troublesome top of poorly laminated shales, shale with slickensides and shale intermingled with small partings and traces of coal. The bottoms are generally one to three feet of clay which softens readily on exposure to moisture. The mines are dry although some water is released and collects from rapid penetration of the seam by continuous miners. However, there are locally wet areas. Most of this material refers to mines of the Freeman Coal Mining Corporation. The mining operations written about are underground mines in southern and central Illinois.

Jan 1, 1962

By Michael Ferrell

The primary reason pigments are used in plastics is to impart a desired color to the plastic. Color is one of the more important assign considerations associated with today's market oriented society. Secondary reasons for adding pigments to plastics include: 1. Improved UV stability 2. Enhancement to selected physical properties 3. Changes in optical properties Pigments may be used at loadings as high as 20% or as low as .001%. Generally the loading levels are between 0.2% and 2.0%. Pigments may be added to the plastic either by the manufacturer of the plastic, or by the user of the plastic. If the customer buys material that is already colored, it is referred to as "pre-colored". If the customer buys uncolored plastic and adds colorants, the process is referred to as "in-house" coloring.

Jan 1, 1985

By Nelson M. Solow

Raise boring of mine ventilation shafts in many cases offers a lower cost and higher speed method of construction in comparison to conventional shaft sinking. Where underground access is available for raise boring the potential savings indicate that raise boring should be considered as an alternative to other methods. Raise boring machines are currently in use which have the capability for reaming shafts up to twenty feet in diameter, depending on the strata and depth. These large capacity machines make it possible to consider raise bored shafts for moving large volumes of air. Although we will consider here only ventilation shafts, raise boring should also be considered for men and material shafts. When the mine planner has determined the volume of air required through a shaft at a particular location he is faced with the problem of selecting the shaft size. The principal factors in optimizing the shaft size are the construction costs for the shaft 'and the power cost to move the air through the shaft. The larger diameter the' shaft is the more it costs to construct, but for a given volume of air the power required (cost) becomes lower as the diameter increases. The construction cost is paid only once, when the shaft is constructed. The power costs, however, are paid throughout the life of the shaft. Methods of optimizing air shaft size found in the literature (References 1 and 2) amortize the construction cost and include it in the average annual cost of operating the airshaft. These methods derive a formula for the average annual cost vs. shaft size and de-rive the formula to compute the optimum size for a given air flow rate. It is, however, desirable to take into account tax considera-

Jan 1, 1977

By Thomas Camus

"STATE OF THE ART The current situation of ground prediction in TBM is of great concern for tunnelling contractors, and the subject has been quite widely addressed over recent years, for instance by the French Eupalinos 2000 programme, which tested a variety of technological approaches. A number of interesting projects were executed, such as the SOUND and OnSITE projects, part of the German Geotechnologien programme: these projects are focused on seismics, while other techniques such as radar are not considered. Little information and even less industrial applications have been released apart from lab simulations and numerical modelling. A number of field tests in different configurations have been carried out for compression waves, but the results were often not reliable or convincing, and therefore little has been reported in open literature. The advances seem somewhat promising as far as hard rock tunnels are concerned, but ignore the problem raised by concrete lined tunnels such as those bored by a TBM in soft ground. In such tunnels, sending and receiving seismic waves reliably through the lining (and the grouting behind) is quite illusory. A careful analysis of the seismic prediction research results show that the main problem is the source which is poorly controlled and poorly coupled (for instance in concrete lined tunnels, or in approaches that use the TBM cutter head vibrations as a source). Generating waves perpendicular to the tunnel axis is also a problem: aligning with the tunnel axis makes more sense. Radar (Ground Penetrating Radar - GPR) has been used in geotechnical surveys for decades, and also for tunnel inspection. Attempts have been made at using it on a TBM (for example in Japan by Taisei) but mainly using off-the-shelf GPRs, which are not adapted to work in the specific environment of a TBM (because of its huge mass of metal, to start with). Very few results have been published, probably due to the somewhat disappointing performance of such implementations. At present, no TBM has a GPR incorporated in its cutter head that is able to predict ground characteristics while drilling. Another characteristic and drawback of most current methods is that they require dedicated periods of time during which other tunnel construction activities must be stopped. Due to the duration of such operations this leads to performing ground prediction on a weekly basis only, and therefore to a requirement for an investigation range of 100 metres approximately (in order to cover the TBM advance over the coming week). This is not achievable with boreholes made from the TBM, even less if a reasonable accuracy is required, as is usually the case."

Jan 1, 2016

By G. Jim Cardwell

The question "what constituents should be determined?" is one that defies a simple answer, because earth scientist being what you are, the rock and mineral analyst will eventually be called upon to determine about three quarters of the elements in the periodic table. The concentrations of these analyses will range from as low as 1 ppb to 100% of the material being analyzed. The most important thing to remember about a quantitative analytical result is that it can only be an estimate of the concentration of the analyte present. A measure of the reliability of that estimate is given by statistically derived statements of the precision and accuracy of the measurement. When evaluating your data an understanding of precision and accuracy are of paramount importance. Precision is the measure of agreement between replicate values while the accuracy of a determination is the concordance between it and the true value. There is no quarantee, however, that a precise answer is an accurate one. The numerical difference between the two values is the error. When evaluating your data, the repeats analyzed with your samples will identify the precision and control standards of U.S.G.S. or Canadian Certified Materials quality will identify the accuracy. The main problem is this data is routinely withheld from the report, or was it ever included in the analysis of your samples?

Jan 1, 1983

By Evan Adams

The Ireland Mine is located some seven miles South of Moundsville West Virginia, along the bank of the Ohio River. We are mining the Pittsburgh #8 seam. This seam is approximately 60" in thickness, and is immediately overlain by some 10 feet of a conglommerate material. The roof is difficult to control, due to the fact that it frequently is composed of substances not hard enough to be held together with 6-foot roof bolts. In many cases, we must use 10-foot roof bolts, in order to get bolt anchorage in the limestone above the conglommerate. Due to the elasticity of the limestone and its tendency to bend rather than to break, we have been unable to maintain a pillar line. Thus, we have found it necessary to mine by the room and pillar system. Belt haulage is used on room entries to automatic loading stations, thence into 15-ton mine cars, controlled at the loading point by car spotters. The maximum belt length is 2,000 feet. Rail haulage to the slope-bottom dump is by 27- and 50-ton locomotives. The mine produces coal two shifts per day, with 7 production crews on each shift. Mine and machinery maintenance is performed on the Midnight shift. We handle an average of 660 tons per machine shift.

Jan 1, 1964

By David L. Durler

In-situ uranium mining is a relatively new and innovative method utilized for the commercial extraction of uranium. As with any mining method, however, significant environmental concerns will be evident and must be addressed in a rational and far-sighted manner. Experience has shown that radiological and non-radiological environmental problems may not manifest themselves until after the in-situ methodology has become established and matured to some degree. It is important, therefore, to recognize potential environmental concerns and incorporate them into an environmental program that spans the premining, mining, and post-mining phases of an in-situ operation.

Jan 1, 1982

By D. A. Dahlstrom

Since the initiation of continuous vacuum filtration over a half a century ago, control of the performance of these units has been largely in the hands of the plant operators, Obviously there has been the introduction of variable speed drives, adjustable speed feed slurry agitation, vacuum control, etc. However, control of , filtration rate, cake moisture content, dissolved solids recovery by cake washing and dryness of solids where thermal drying is practiced is primarily up to the operators judgment and the settings he imposes on the controls he regulates, - filter cycle time, submergence, vacuum level, filter medium condition, wash water- rate, and other such factors. While this may seem to indicate that good operators are a paramount necessity, and certainly always desirable, a considerably more vital factor is a properly designed filter and filter station for the particular application. With improper design, highly skilled operator control will still leave much to be desired in the way of process performance. On the other hand, with correct design and application, the operator can easily and quickly control normal plant surges and quality variations within the flow sheet. Due to the growing complexity and inter dependency between the various processing steps in the modern flow sheet as well as the rising costs of capital investment, labor, maintenance, and losses involved with off quality product or insufficient recovery, automatic or inherent performance control of many of the unit operations within the metallurgical mill must be achieved. Continuous filtration should and can be susceptible to such control. However, as every instrument engineer knows, before control and automation can be achieved, a basic understanding of the operation is mandatory. This is primarily due to three factors. First, as in so many control applications, it may not be possible or feasible to measure the factor that it is desired to control. Thus, secondary variables that influence the major factor are substituted for control purposes. Secondly, it is always desirable to take advantage of any ?self-regulation? within the operation being performed on the equipment. In so doing, not only will automatic control be facilitated, but instrumentation is minimized while experiencing most efficient operation. Finally, automatic control is not a cure-all for improper process and equipment design and application. Hanging instruments on such an operation can be compared to constructing a sizable building on sand, Results will be disappointing.

Jan 1, 1960