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At Namdeb, submerged beaches are earmarked for sampling and future mining and various sampling configurations are tested for optimality through the use of spatial simulations. For the creation of these virtual orebodies, basic statistics and variograms are needed, but in this specific instance no data exists from which the necessary parameters can be determined. The best that can be done is to use proxy data from onshore beaches, with adaptations where needed. The reworking of raised beaches during periods of rising and falling sea levels in some cases destroyed the internal beach structures, and it is very difficult to determine the variograms. A method is proposed whereby simulated annealing is used to adjust the sample locations to align the data pertaining to beach crests or cliff lines, thus improving the variogram structure along the shoreline in the direction of the highest geological continuity.

Jan 1, 2014

As part of the Phase I study activity, a questionnaire was sent to a representative sampling of mining companies to obtain information on the uses, use conditions, personnel policies and other user concerns associated with front-end loaders. On-site visits to several of the mining companies were also parried out and the questionnaire was used during these visits as well. Five major areas were dealt with in the user questionnaire. These included: 1) Front-End Loader Critique - An open-ended form was employed to permit the mining companies to describe the particular things they liked and disliked about front-end loaders, in general, and/ or specific models in particular. 2) Usage - A form indicating the functions performed by front-end loaders and the numbers, makes and models of front-end loaders being used by mining companies. 3) Environment - A form where the user indicated the various types of conditions encountered in their use of front-end loaders. 4) Personnel - A form for describing factors pertaining to the qualifications of front-end loader operators. 5) Miscellaneous and Comments - A form permitting the user to comment on his feelings toward standardization of front-end loader operator stations.

Jan 1, 1973

By J. Dean Warner

Alaska contains many critical and strategic minerals that are scarce in the conterminous United States. Among these are tin, tantalum, and columbium. This Bureau of Mines report summarizes available data on the production, reserves, and occurrences of these minerals in Alaska. Alaska produces about 200,000 lb of tin per year, with historical production since 1901 estimated to have totaled 5,830,600 lb. Measured, indicated, and inferred tin reserves total over 140,000,000 Ib. Much of the tin production has been from the placer mines of the western Seward Peninsula; however, most of the reserves are in that area's lode deposits. Alaskan tin occurrences are part of a belt of tin mineralization that extends along the western coast of North and South America. The Alaskan portion of this "tin belt" comprises placer occurrences and lode occurrences of five major types: greisen, vein, skarn, pegmatite, and volcanogenic massive sulfide. Greisen and vein occurrences are the most abundant, but skarn deposits have historically been the most economically important. Columbium and tantalum have not been produced in Alaska; however, they may be recoverable as byproducts of tin, tungsten, gold, or uranium mining. Approximately 135,000 Ib of columbium oxide (Cb205) are inferred within the Tofty placer deposits in the Manley Hot Springs district.

Jan 1, 1985

By Robert L. Sundeen, Richard V. Wenberg

INTRODUCTION Shotcrete can be defined as spray-applied concrete with a maximum size aggregate in excess of 9.5 mm (0.375 in.). The concept evolved from guniting, which uses smaller aggregate and generally produces concrete with poorer physical properties. The larger aggregate used in shotcrete requires less water in the mix, while offering larger bonding surfaces, thus imparting greater tensile and compressive strengths. TYPES OF MACHINES Two basic designs of shotcrete machines in general use are the wet or prehydrated zero slump and low slump type, and the dry or nozzle hydrated machines. Fig. 1 shows a typical zero-slump machine in a con¬figuration commonly used for small-volume require¬ments. The prehydrated zero-slump machine mixes exactly proportioned batches in a sealed pressurized chamber. "Slugs" of hydrated shotcrete mix and com¬pressed air are sent through a distribution hose to the nozzle where the wet mix emerges as a spray. The spray is directed onto the rock surface by the nozzle operator. The low-slump machine is similar, except that a thick slurry mix of aggregate is delivered throughout the distribution hose to the nozzle. Fig. 2 shows a typical low-slump shotcrete machine used in moderate-volume applications. The nozzle-hydrated shotcrete machine accepts a premixed "dry" (4 to 6% moisture) batch of aggregate and cement. A constant feed of this mix is directed by compressed air through the distribution hose to the nozzle. At the nozzle, water for hydration is introduced into the emerging spray. The hydrated mixture is di¬rected onto the rock surface by the nozzle operator. Fig. 3 shows a typical dry-mix machine. The major difference between the two basic machine designs is the consistency of the shotcrete quality. Pre¬hydrated machines have high degrees of consistency and produce high-strength concrete, resulting from their ability to produce exact mixtures of zero or low-slump concrete within the machine. Nozzle-hydrated machines tend to produce poorer quality concrete because of the difficulty in controlling the water content at the nozzle. Water input essentially is an art. As such it is not precise, and the shotcrete produced is of variable quality. MATERIALS HANDLING Materials handling presents a problem to either type of shotcrete machine. At times considerable quantities

Jan 1, 1982

A clear understanding of the meanings of terms is important when discussing a project. Whether it is a submission, an investment study, a feasibility study, an environmental impact statement, an estimate, a tender, a contract, or a close-out.report, the need for all parties involved to understand what is under discussion or what has been written is paramount. The clarity of definition and the level of understanding can affect the outcome of the project. It is vital that all parties know what is wanted, what is expected, and what it will cost. This paper draws attention to some of the problems that beset many projects, clients, project managers and contractors, and it is hoped that its presentation will encourage us to pay more attention to defining what it is that is required. Ultimately we should all be the richer for having defined and understood the requirements at the beginning rather than at the end.

Jan 1, 1990

Objective To develop safety training tools for mine health and safety trainers that fill gaps in currently available materials and help capture the wisdom and knowledge of “expert miners.” Background NIOSH began a series of stakeholder meetings in 1998 to determine what research was needed to improve miner health and safety. One of the more common concerns among stakeholders was a critical lack of appropriate training materials applicable to metal/nonmetal mining. Participants provided many insights into what effective training materials should include and how materials could best reach both new and experienced miners. The most important factors were that any materials be realistic and interesting and that some way must be found to capture the wisdom of expert miners before they retired. Approach NIOSH researchers chose videos as the best means of achieving these training goals. Over the past 3 years, NIOSH has produced three training videos that present information on safe work practices in underground mines: handling explosives, recognizing roof hazards and using proper scaling techniques, and installing ground supports. The last two videos, “Rock Falls—Preventing Rock Fall Injuries in Underground Mines” and “Miner Mike Saves the Day—or—Ground Support…It’s Important,” have won Alice Hamilton awards, NIOSH’s highest recognition of Excellence in Occupational Safety and Health, in the Educational Materials category. Two new videos are now being released. Both of these videos were shot completely in operating underground hard-rock mines and used expert miners to tell the story. Hazards In Motion The first, “Hazards in Motion,” deals with the dangers of working around mobile equipment in an underground mine. Ben, a new trainee, refuses to pay attention in his 40-hour New Miner Training class, and when the class takes its first trip underground, he wanders off and finds himself in many dangerous situations. He encounters many experienced miners who both chew him out for his unsafe attitude and give him advice and information on how to survive around mobile equipment. Many common pieces of equipment are shown, including haulage trucks, LHD=s, tracks and trains, slushers, skips and hoists, and air doors. The dangers of ignoring signals and of horseplay are also included. After nearly losing his life numerous times, Ben learns his lesson with the help of the Safety Angel, an experienced miner who looks suspiciously like his safety trainer. Ben’s Safety Angel saves his life repeatedly, teaches him how to work safely around these common conveyances, and introduces him to experts who have specific safety tips. Ben learns the error of his ways and vows to be the safest miner in the mine. “Hazards in Motion” is approximately 30 minutes long. Hidden Scars The second video is the first in the NIOSH “Expert Miner” series. “Hidden Scars” is a narrative interview with Don Capparelli, a miner and supervisor at the Sunshine Mine in north Idaho. This video captures the story of a fatal rock burst in May 1994, when Don was seriously injured and his long-time partner, Jimmy Findley, was killed. “Hidden Scars” is a very powerful story. Don Capparelli shares the physical and emotional pain he lives with daily as he relates the events leading up to the rock burst that took the life of his best friend and partner. This video is an excellent reminder of the human cost of uncontrolled accidents and the hidden scars that survivors must deal with for the rest of their lives. It runs approximately 25 minutes.

Jun 1, 2001

If an orebody has been drilled to achieve some level of regulatory compliance, then a number of associated geological databases will exist, representing 10 000 to 100 000 m plus of core intervals. The databases usually contain data about assays, lithology, mineralisation and geophysical attributes. They will also include location information such as collar positions and downhole surveys. Obviously this data is collected by geologists for, predominantly, geologists and mining engineers. However, from a process design viewpoint process engineers usually ignore the geology where possible and rely on a small number of metallurgical test samples. Typically these test samples are sourced from convenient and available cores or from a small number of specially drilled metallurgical holes. One of the worst instances known to the author was the design of a SAG mill using only two SAG specific test results (one for each of the major ore types) while, geologically, the orebody was defined by more than 30 000 m of drilling. This paper sets out a philosophy to maximise the use of the geological data, both for process design and in preparation for the commissioning phase of projects. Geological data is used in the identification of preferred locations for metallurgical test samples, for checking the metallurgical validity of the geological ore-type definitions, where necessary developing new ore-type definitions (geometallurgical domains) and developing mathematical relationships for the estimation of important metallurgical factors across the geological database. If the estimation of factors (for example ore competence) is considered reliable enough then there is also the possibility of feeding calculated data back into the block modelling process to allow the generation of metallurgically relevant outputs in the mine plans.

Jan 1, 2007

By J. E. Fox Jr., J. L. Lummus, J. P. Gallus

Fresh water or brine drilling fluids may be kept free of suspended drilled solids by the addition of a water soluble acrylamide-carboxylic acid copolymer at the flowline. Addition of from .01 to 0.2 lblbbl of the polymer solution to drilling fluids containing less than 5 per cent clay solids by weight causes the solids to flocculate and settle rapidly to the bottom of the pits. Solutions of the polymer injected at the pump suction reduce the loss of water to permeable formations without impairing the permeability to oil. The use of drill-itlg fluids clarified with the polymer has resulted in increased drilling rates, extended bit life, and lower drilling fluid costs. INTRODUCTION Field experience and the results of a number of investigations have established that the accumulation of solids in drilling fluid reduces drilling rate.'-' Drilling with water makes possible higher drilling rates than can be achieved with mud but in many areas drilling with water may not be feasible because of the possibility of encountering high formation pressures or by-dratable formations. To combat these conditions, the drilling fluid must possess certain physical properties such as viscosity, density, fluid loss, etc., which require the presence of solids. The current trend in drilling fluid treatment is to maintain as low a percentage of solids as is possible without harmfully affecting the mud properties needed for drilling. Mechanical separating devices such as wet cyclones and decanting-type centrifuges are proving to be an economical means of controlling the percentage of solids and thereby maintaining low solids muds. Also: special muds have been developed for the purpose of retarding the hydration of drilled solids so that they may be more easily removed by shale shakers or settling pits. In some areas, such as West Texas, the characteristics of some formations will permit drilling with water. However, because of the dispersion of drilled solids, it is usually not possible to maintain clear water even with the aid of mechanical separators, or by utilizing large settling pits. For this reason the commonly used term "water drilling" is a misnomer since the water usually contains some solids. Because of the improved drilling rates and other benefits which might be effected, a laboratory and field study was made of the use of flocculating agents for maintaining clear water for drilling. PROCEDURE Laboratory—Solids Settling Two techniques were employed to determine the effectiveness of flocculating agents in settling solids from drilling mud. First, the rate of fall of solids was measured in graduated beakers containing mud treated with various flocculating agents. Natural gum, oil-in-water emulsions prepared with ethoxylated nonyl phenols and diesel oil. and a powdered synthetic acrylamide-carboxylic acid copolymer* (hereinafter referred to as "polymer") were tested as flocculating agents in both fresh water and salt saturated muds containing 4 per cent solids. The polymer was not added in the powder form directly to the muds but was first dissolved in water in a concentration of 3.5 lb/bbl. The polymer solution was then added directly to the mud. The concentration of the flocculating agents, including the polymer, was varied. High rates of fall of the solids indicated high flocculating efficiency. A second technique consisted of measuring the time in minutes required to obtain clear water at the pump suction after addition of the various flocculating agents at the flowline. These tests were made using a model mud circulating system having a total volume of approximately 10 gal. The natural fresh water and brine muds used contained 4 per cent solids. A sketch of the circulating system appears in Fig. 1. The circulating rate

By T Walsh, S R. Mudnuru

The development of lithium-ion batteries, coupled with the global trend towards electrification of transportation, has led to a dramatic increase in the demand for lithium. The production of lithium from hard rock ores is increasing, and flotation has proved to be an effective means for the beneficiation of many pegmatitic lithium ores. Clariant Mining Solutions has developed a range of novel collectors for the flotation of spodumene and other lithium ores, and this paper presents examples of some of the most recent developments. Fatty acids are the typical collectors for lithium flotation, however the grade and recovery achieved with these collectors is often below the desired level. There are also some significant drawbacks associated with the use of fatty acid collectors, such as the formation of calcium soaps which give rise to filtration problems and the need for acid washing. Several FLOTINOR products have been developed as alternatives to fatty acids. These products offer equivalent or better metallurgical performance at significantly lower dosages than fatty acids. This offers benefits to the flotation circuit as well as potentially reducing the issues associated with downstream processing of the concentrate.

Aug 24, 2022

By E. D. Gardner

This paper is one of a series on mining methods and costs being published by the United States Bureau of Mines. In April 19.74 the St. Joseph Lead Co., at Atlanta, Elmore County, Idaho, was mining and milling about 225 tons of gold ore daily with a total force of 150 men. The mine, which comprises the old Boise-Rochester and Monarch properties, is at an elevation of about 6,000 feet. Snow lies on the ground about 5 months each year but does net interfere greatly with local operations. However, the road to Mountain Home, the shipping point 80 miles distant, passes over a high range and usually is closed by snow from about November 15 to June 15. Heavy supplies are brought in and concentrates trucked out during the summer. In winter the district is served by a biweekly mail plane and a passenger and express plane making 4 to 6 trips weekly. Mine timber is cut locally. A plentiful supply of water is obtained from a stream brought to the property through 7,500 feet of plume.

Jan 1, 1935

By J B. Gemmell, D R. Cooke

Recent mapping at the Kelian epithermal gold deposit in East Kalimantan, Indonesia has delineated intrusive and extrusive-phreatomagmatic breccias, their magmatic roots, and late-stage endogenous domes of a maar-diatreme complex. The Kelian epithermal system is characterised by a wide variety of mineralised and unmineralised breccias, which include tectonic, hydrothermal, phreatic and phreatomagmatic varieties. Phreatomagmatic breccias and associated igneous rocks post-date early stage alteration and mineralisation, and pre-date main stage precious and base-metal mineralisation. This study emphasises the spatial, temporal and genetic links that have been drawn between diatremes and both epithermal and porphyry systems in volcano-plutonic arcs.

Jan 1, 1999

By Arthur M. Hartstein

The Federal Bureau of Mines, under a contract with Ultrasystems, Inc., investigated the thermal oxidative degradation characteristics of conveyor belts used in underground mines. This included the determination of smoke evolution, glow characteristics, char yields, and the identification and quantification of all volatile decomposition products in the form of gram of specific product formed per gram of belt sample tested. In addition to these investigations, degradation studies were conducted on some pure ingredients used in conveyor-belt formulations. Three basic classes of belts were investigated: neoprene, polyvinyl chloride, and styrene-butadiene rubber compositions. The studies indicate that styrene-butadiene-based belts exhibit good flame resistance and are the least hazardous in regard to overall formation of toxic decomposition products. Under this program, thermogravimetric analysis was definitely established as a method of material differentiation.

Jan 1, 1976

With a growing concern over mine fires, prevention and suppression are hot topics. NIOSH researchers Michael Trevits, Alex Smith and Edward Thimons discuss their research in the area. The leading causes of US mine fires include flame cutting and, welding operations, frictional heating and ignitions, electrical shorts, mobile equipment malfunctions and spontaneous combustion. From 1990 through 2007, there were 1601 reportable fires that occurred in the US mining industry -an average of 89 fires per year. The fact that mine fires are occurring with alarming regularity reinforces the importance of recognizing and eliminating the potential hazards. These statistics also show the need for improved control and suppression technology to ensure worker health and safety if a mine fire does occur.

Jan 1, 2008

By T. R. Carter, A. C. Colvine

"Rocks of the Grenville Province in southeastern Ontario are currently largely dismissed by many geologists as having little or no potential for discovery of significant deposits of metallic minerals. The present study demonstrates that the area contains numerous deposit types which elsewhere are major metal producers. Therefore, there is significant unrealized potential, especially for gold, zinc, uranium, and possibly copper.The variety of deposits of metallic mineralization include stratiform zinc in marbles; stratabound base metal sulphides in volcanic and sedimentary hosts; gold-quartz veins; quartzmagnetite iron formation; copper-nickel and iron-titanium in intrusive rocks; magnetite skarns; molybdenum in skarns and pegmatites; uranium and thorium in pegmatites, veins, and calc-silicate gneisses; hematite veins; dolomite marbles (magnesium); and barite-jluorite-celestite-galena-calcite veins. There has been significant production of iron, lead, zinc, magnesium, gold, silver, and uranium.The vast majority of the metallic mineral deposits are confined to late Precambrian supracrustal and related intrusive rocks of the Grenville Supergroup. Many of the deposits are stratiform and/or stratabound and occur within units toward the top of major volcanic successions and in the lower portions of younger carbonate-clastic sedimentary successions.Processes responsible for mineral concentration in the area include: (I) syngenetic hydrothermal activity related to both volcanism and sedimentation; (2) epigenetic processes related to diagenesis, regional metamorphism, and igneous intrusive activity; (3) magmatic processes related to igneous intrusions; and (4) supergene concentration and enrichment. The genetic classification of the mineral deposits presented is based on observed geological relationships and these interpreted geneses. The deposit types have counterparts in volcanogenic and sedimentary exhalative, Mississippi Valley type, magmatic, contact metasomatic, and lode gold deposits. Many of the exploration criteria for deposits of these types may be applicable in the Grenville Province, despite the generally high metamorphic grades and complex deformation."

Jan 1, 1985

Controlled recirculation of nine ventila- tion air is becoming an acceptable practice world-wide. A brief review of operating and planned schemes is given which illustrates the various purposes for using controlled recircu- lation in different types of mines. A de- tailed description is given of the operating and proposed schemes on South African gold mines. This is followed by a description of some theoretical and experimental work which has recently been carried out into certain important aspects of controlled recircula- tion. This includes: safety systems, dust filtration, blast contaminant removal, radia- tion hazards and the development of an expert computer program for the design of controlled recirculation systems.

Jan 1, 1988

By R. H. Harrington

The definition of precipitation-hardening1 is well understood and its principles have been subjected to study for some time. However, the variation of properties with double aging, combined with strain-hardening, gives promise of new and useful phenomena. Properly to understand these distinctions, definitions of these terms are necessary. Precipitation-hardening1.—This reaction usually depends upon an alloy having such a composition that it consists only, or in major part, of but one phase, a solid solution, at a high temperature, so that, upon slow cooling, this solution breaks down into two phases, the solid solution and a compound. By heating the alloy to the temperature for maximum solution of the compound, quenching, and reheating to a suitable lower temperature for critical dispersion precipitation of the compound, useful properties of the alloy may be developed to a maximum. Double Aging.—Dougle aging in part is similar to the process for precipitation-hardening, consisting of heating a precipitation-hardening alloy to the solution temperature, quenching, reheating to the suitable dispersion precipitation temperature, strain-hardening, and again reheating to a suitable temperature to develop certain useful properties to a maximum. The strain-hardening may be induced by two methods: (I) a rate of cooling from the first reheat may suffice to strain the solid solution lattice of the alloy; or (2) the alloy may be cold-worked to a suitable degree between the two reheats. Pkecipitation-hardening of Copper-cobalt-beryllium Alloys1.2 The composition of principal interest is that of 2.6 per cent Co, 0.4 per cent Be, 97 per cent Cu. The alloy has been developed commercially and, with certain reasonable precautions, ordinary brass-foundry practice suffices to produce an alloy of high quality. Preliminary Precipitation-hardening Study.—Samples were cut from a I-in. round rod cast in a graphite mold. These samples were then

Jan 1, 1937

By Ian S. Lowndes, Adrian T. J. Moll

With the current trends towards the concentration of extraction to fewer but higher production units in deeper seams, often of higher coal rank, the role of methane drainage ranges has become critical. As mines exploit seams at greater depth and more remote locations there has been a need to extend the lengths of methane drainage ranges and to increase the capacity of the surface pumps. This trend has highlighted the need to effectively simulate the operation of a methane drainage range in order to produce the optimum design and operation of a safe and economic system. This paper describes the development of such an analytical tool. The application of this computer model is illustrated by the analysis of the operation of the drainage system of an extensive mine. The paper concludes by considering the development of a [Knowlege Based or Decision Support System] which will assist the ventilation engineer in assessing the current performance of an existing drainage range and will suggest possible remedial modifications or design strategies which may improve the system performance. INTRODUCTION In order to maintain the general body methane levels to below predetermined statutory threshold limit values (TLV's) on major longwall production units there are, for a given production rate, two major complementary control devices which may be employed by the ventilation engineer. These are the combined design and application of a competent mine ventilation and methane drainage system. The methane drainage system should be designed so as to maximise the capture of the methane (firedamp) from the seam being mined and the strata gas liberated in the vicinity of the extraction zone from gas bearing seams or other reservoirs of gas situated at above or below the mining horizon. The design fresh air quantity entering the face should ensure that under normal operating conditions the methane entering in the vicinity of the face is rapidly dispersed and dilute to well below statutory TLV's. The drainage system must therefore be designed to maximise the capture of the methane gas liberated to minimise the amount of gas which enters the ventilation airstream. GAS DRAINAGE The inherent dangers of methane emissions in mine workings have been a problem of concern to mining engineers for many years. To alleviate the risk, methane drainage has been employed for some years to capture the gas before it becomes a hazard to the operation of the mine. The method of drainage employed will be dependent on a number of factors which include the longwall mining method and production cycle employed, the characteristics of the coal seam being extracted and those of the adjacent gas bearing strata. The location of the gas bearing potential of the over and underlying coal measures must be determined. The gas bearing

Jan 1, 1993

By I. R. Kramer

The delay time for single crystals of iron, zinc, and pre-strained aluminum was measured under conditions of high-speed deformation. The delay time of aluminum was found to be affected by the orientation of the crystal. Under the dynamic conditions employed, tile calculated "activated volume" term appears to be very small for the three metals studied. IN a previous paper,1 it was shown that under dynamic testing conditions at 78° K, there was a delayed yield in single crystals of aluminum and copper which had been cold-worked prior to testing. The experimental results also indicated that the delay-time effect was not due to the interaction of dislocations with impurity atoms or vacancies, but rather to a dislocation-dislocation interaction since aluminum which has not been prestrained shows no delay-time phenomenon. In this paper, some data are reported on the effects of orientation on the delay time of aluminum single crystals; the delay time of zinc single crystals saturated with nitrogen and the delay time of iron single crystals also were measured. EXPERIMENTAL PROCEDURE Aluminum (99.997 pct) and zinc (99.999 pct) crystals, 1/2 in. in diam and 8 in. long were grown by the Bridgman technique. The iron single crystal was supplied by Dr. R. Maddin. The zinc crystals containing nitrogen were prepared by melting high-purity zinc in a graphite crucible and the nitrogen was introduced by additions of ammonium chloride. The liquid zinc was then drawn up into glass tubes of 1/2 in. diam and allowed to solidify. The rods were cooled to room temperature before the transfer to the mold for conversion into single crystals. The orientation of all specimens was determined by the Laue' back-reflection technique, Fig. 2 and Table I. To prepare for the delay-time measurements, the crystals were cut with a fine jewelers saw and the ends carefully machined. The specimens then were electrolytic ally polished to remove the cold-worked metal, mounted in a special fixture and hand-lapped. As a final step, the crystals were annealed in evacuated tubes. Specimens of aluminum crystals, Nos. 24 and 26, were compressed 0.5 and 2 pct, respectively, in the direction of the later impact. The zinc specimens were aged at 50°C for 15 min, In the case of iron, only two specimens could be obtained. To obtain sufficient data, it was necessary to resort to a reaging treatment. After each delay-time test, the specimens were aged at 65° C for 100 min. This treatment, according to Clark,2 is sufficient to restore the original delay time. It is believed that although the specimens were plastically deformed approximately 10-4 pct, after each test the delay-time values are reliable. The delay-time measurements were made in an apparatus similar to that described previously.' Single crystals approximately 1 in. long and having a diameter of 1/2 in. were placed in a pendulum which consisted of a bar 1/2 in. in diam and 8 ft long, designed with a crystal holder to accommodate the specimen at low temperatures. The crystal was held at a position 2 ft from the front part of the pendulum. This portion of the apparatus was supported on a fine molybdenum wire. A projectile bar of the same diameter and length comprised the other portion of the apparatus. This bar was supported on

Jan 1, 1962

The mmmg of alluvial gold involves many deposits of theMesozoic, Tertiary, and Quaternary Ages in processing. Majorfeatures of the composition of such alluvial deposits are the lowcontent of gold and the small size of the gold particles. Atpresent, the gold-miners treat alluvial deposits in which a portionof fme gold (0.25 mm) exceeds 45 per cent. It is expected that by2000 these resources will be the main deposits mined (Zamyatinet aI, 1991).Under real industrial conditions the losses of minus 0.25 mmmetal are 50 per cent and more. The low level of recovery of finegold is observed not only at concentrators equipped with sluices,but also at concentrators equipped with modern diaphragm andpistonless jigs (Table 1).

Jan 1, 1993

The Torington Lodes.This paper describes investigations into mineralogical, petrological and structural associations of cassiterite in occurrences of economic value. The work was carried out in three mines, during a number of years, in the hope that the, data collected might be helpfulin the search for occurrences of cassiterite in stanniferous zones and reduce unproductive exploratory work. Tin-bearing lodes at Torington, in the New England district, New South Wales, have been worked since 1880, and the locality is the most important centre of lode tin occurrence in the, State. The township of Torington is 18 miles westerly from Deepwater, a station on the Great Northern Railway, 446 miles from Sydney.The tinfield forms part of the Mole Tableland, which has an altitude between 3,000 ft. and 4,000 ft. above sea level. The country rock, in which the stanniferous lodes occur, is granite of Permian age, which has been intruded into Carboniferous claystone. An inlierof claystone is exposed to the west of the stanniferous area, 'and in it, close to' its contact with the enclosing granite, are occurrences of wolfram and bismuth. These minerals, together with chalcopyrite, pyrite, arsenopyrite, zinc blende, galena and molybdenite, in very small quantity, are associated with cassiterite in lodes traversing the granite, particularly near the claystone, but decrease in amount with distance from the contact. Their occurrence is sporadic and usually causes no trouble in dressing the cassiterite concentrate, the final product containing less than 1% of total penalisable impurity. In Curnow's mine, pyrite, galena and molybdenite have been observed at 700 ft. from surface.The granite is of the biotite type and its structure may be divided into four groups, or classifications, arising from segregation processes during cooling and consolidation. The four classes, in order of extent of distribution, are:1. Granite of normal type, in which the constituent quartz felspar and mica, have a particle size approximately 14, in.2. Porphyritic granite, in which the felspar particles are from % in. to lin. in size, that of the quartz and mica approximately % in.3. A fine-grained granite, in which the particles of all constituent minerals are % in. or less in size;4. A rock of highly siliceous ground mass containing very small particles of felspar and almost negligible biotite.Type 1 is the general type of granite in all mines of the field; types 2 and 3 may occur as large masses, or all three classes may merge rapidly one into the other, and all be disclosed in 20 ft. of driving. Usually, however, the segregations are massive, but are not associated with any special horizon. For instance, a mass of porphyiiticgranite extends from surface to a depth of 440 ft., for a distance of 350 ft. south from the New England main shaft. The upper levels of Curnow's mine, 14" mile south-east, are in normal granite, but a restricted mass 'of porphyritic granite occurred between Nos. 5 and 6 levels, or 400-500 ft. below the collar of the shaft...

Jan 1, 1950