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By C. H. Wayman, D. W. Fuerstenau

The effect of bubble size and concentration of certain reagents on the terminal velocity, shape, path, and drag coefficients of single air bubbles in distilled water has been investigated. Bubbles of a certain size range rise considerably faster than Reynolds number-drag coefficient relationships predict, whereas a small amount of frothing agent reduces their terminal velocity. The rapid velocity at which bubbles rise in distilled water appears to result from slip at the boundary and from circulation within the bubbles. Surface-active agents retard bubble motion through prevention of both circulation and slip at the boundary. A surface tension concentration gradient helps maintain bubble sphericity. HE gas phase is one of the indispensible in-gredients in flotation operations. Flotation depends on the collision of an air bubble and a mineral particle in a pulp and their ability to remain in contact long enough for adherence to take place. Before it is possible to understand the mechanics of air bubble-mineral particle encounter, it is necessary to learn more about the nature of bubbles themselves before collision with a mineral particle has taken place. To date, little work has been done on air bubbles in flotation systems. In 1945 Fahren-wald' presented a study of the role of frothers on air bubbles and on aeration in flotation, and recently Wark and Sutherland' discussed the work of Rosenberg- in relation to flotation. The research reported in this present article was undertaken to investigate systematically the effect of bubble size and the concentration of certain reagents on the terminal velocity, shape, path, and drag coefficient of single bubbles in distilled water. Most of the work is concerned with the effect of a-terpineol on bubble motion in water, but studies were made with potassium chloride, potassium hydroxide, potassium ethyl xanthate, and potassium amyl xanthate. Experimental Method and Materials: To obtain free bubble rise and reduce wall and surface effects, the investigators used a tank of 5½x5½x30-in. internal dimensions, filled with water to within 4 % in. of the top.' The tank was made of acrylic plastic so that the walls would have good optical properties. Distilled water, which was re-distilled in a block tin still and saturated with air before each test, was used in all the experiments. All solutions were made with reagent-grade chemicals. During each experiment the water was at room temperature, and during the course of an experiment the temperature did not fluctuate more than 0.5°C. Since the experiments were performed over a period of six months, the temperature varied between 25° and 27°C. The temperature at which each series of experiments was conducted is recorded with the data. The experimental apparatus is presented dia-grammatically in Fig. l. Individual air bubbles were generated from purified compressed air through a capillary of 0.003-cm internal diameter at a rate

Jan 1, 1959

By F. D. Ayhan

The aim of this study was to investigate the effects of various water mediums on desulfurization and deashing of a coal sample using flotation. For this purpose, experimental studies were conducted on a coal sample containing high ash and sulfur contents. The effects of pH, solid concentration, collector amount and frother amount on the flotation were investigated separately in Mediterranean Sea water, Çermik thermal spring water, snow water and tap water. Flotation results indicated that, when comparing the various water mediums, the following order for the ash content was obtained: snow water < Çermik thermal spring water < tap water < the Mediterranean Sea water. For the reduction of total sulfur, the following order was obtained: snow water > Çermik thermal spring water > Mediterranean Sea water > tap water. When snow water was used as a flotation medium, it was found that a concentrate containing 3.01% total sulfur and 27.64% ash with a total sulfur reduction of 57.06% was obtained from a feed containing 7.01% total sulfur and 41.17% ash.

Jan 1, 2009

Tougher physical mining and processing conditions as well as economic circumstances are causing many mining companies to re-evaluate the effectiveness of their mine planning. The recent wave of inexpensive computing power provides the engineer an opportunity to go beyond the simple one-off manual mine design and production schedule. The basis of a good mine plan is a good reserves model. Concepts of mine model development are explored. The only advanced computer methods that have found consistent success in optimising mine planning functions are economic pit limits determination and material scheduling. Three pit &apos;optimisation&apos; methods are examined; the moving cone, the Lerchs-Grossman 3-D graph algorithm, and the new network flow algorithm. A comparison between the methods in terms of total profits generated and computer time involved are made. The results show that both algorithms produced a higher profitability than the simple moving cone, but at much higher execution times. However, the profit increase never exceeded much more than 1 % of the base moving cone case. Finally, a method for the development of long range material production schedules with forward waste planning is presented.

Jan 1, 1989

Thallous chloride and cadmium metal were recovered from a thallium-cadmium concentrate by a method suited to the treatment of small batches. Differences in oxide solubility and control of pH were employed to separate the thallium and cadmium. The cadmium metal produced by zinc reduction analysed better than 99.95 per cent Cd and thallous chloride of high purity was precipitated from solution.

Jan 1, 1969

By A Webster, T Murphy

Block cave mining, in its broadest sense, has transitioned from an orebody/rock mass determined method of extraction, to a low-cost and high production mining method that may be applied to any large ore deposit. This inherently means that caving is now required in more complex rock mass conditions where assistive damage, through preconditioning, may be necessary. This requires comprehensive understanding of the geology, and its interwoven relationship with geotechnical parameters, and is made more challenging due to limited exposure in block cave mines. Limited mine development throughout the cave volume equates to a heavy reliance on drilling data in terms of observations, modelling of the mine geology, and collection of geotechnical data. This translates as increased uncertainty of geological and geotechnical models and has potential to impact significantly on the ability to make informed decisions in the design and operation of the cave mine.Modelling of cave propagation behaviour requires a complex, coupled system of draw of material, flow of material through the cave stocks, and propagation of the cave-back assisted by autogenic stress-related breakage of the rock mass, manifested as seismicity. The role of geological features in the process of cave propagation is not well understood and requires evaluation on a mine-specific basis, given the diversity of geological controls/settings of ore deposits and local variability of stress fields.Seismic monitoring systems can elucidate key geological features and domains, as heterogeneous seismogenic activity is observed ahead of the advancing cave-back. The observations made from analysis of seismic monitoring data may have potential to be used as a validation tool for numerical modelling of predicted cave behaviour in similar geological settings (eg next lift/panel).Understanding of the geological structure, at all scales, is critical to optimise the design and operating decisions made in a block cave operation. At present, intermediate-scale structure, anisotropy, mineralogy and model uncertainty may be neglected or under-represented despite their likely significant role in the mechanisms of cave propagation.Insights from an analysis of the Ridgeway Deeps block cave mine are discussed in this paper.CITATION:Murphy, T, Webster, A and Chitombo, G, 2016. Beyond rock mass characterisation – the impact of geology on block cave mining, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 861–872 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

The stratigraphy of the Western Coalfield is briefly reviewed and the important units of the Lithgow Coal Measures, particularly the coal seams, are defined. The possibility of coal measures of Tomago age ocurring near the edges of the Sydney Basin is discussed onpresent evidence.Using data obtained from unpublished drilling records, detailed structural, isopachous and lithofaeies maps have been drawn. These show that the structure of the coal basin has been influenced by the underlying basement in many ways.The prominent jointing in the overlying Triassic sandstones is discussed in relation to jointing in the coal measure sediments.It is concluded that in addition to the general knowledge obtained with respect to the coal basin, useful information regarding coal quality and quantity can be gained by the study of broader sedimentary and structural features.INTRODUCTIONThe term &quot;Western Coalfield&quot; covers approximately the area from Katoomba to Rylstone, together with the smaller, separate Ulan area (Fig. 1). The area studied is part of the great sedimentary Sydney basin named by Osborne (1948). The first discovery of coal in Sitlt in the area was made in 1824 by Andrew Brown, although George Bass noted the presence of coal float in the Grose River in 1797. Production is recorded from the Western Coalfield in 1838 but mining was intermittent until 1868 when mines in the Lithgowvalley (producing coal from the Lithgow Seam) came into production. In 1882 the Katoomba Seam was first worked at Katoomba.The work of J. E. Carne (1903, 1908) defined the limits of the Coal Measure sediments and also contributed a great amount of valuable detailed information about the region.

Jan 1, 1960

An effective electrowinning process in hydrometallurgical industry requires fluoride levels in the base metal solution to be less than 10 mg/l. Selective removal of the fluoride ions from base solution is thus desired, if fluoride was added to control calcium and magnesium in the circuit. Consequently, adsorption of fluoride onto activated alumina was studied in a batch and a column set-up. The effects of base metal solution pH, temperature, initial concentration and flow rate on activated alumina performance were investigated in either a batch or column configuration. A two-level factorial experimental design was implemented in studying column dynamics. Results demonstrate that activated alumina is an effective adsorbent for selective removal of fluoride from base solution. In the batch operation, fluoride was removed to values below the maximum allowable concentration (10 mg/[l]) when pH was = 8. In the column adsorption step at 55°C and 600mg/[l] initial concentration, up to 16 bed volumes were processed before breakthrough level was reached. Desorption step using 1% sodium hydroxide solution achieved an elution of 8 bed volumes. The activated alumina (AA) had a capacity of 8.65 gF/[l]AA at the 10mgF/[l] fluoride breakthrough level during the column adsorption test. Keywords: Fluoride; activated alumina; adsorption; recovery; regeneration.

Jan 1, 2009

By H. Pei

PZH (Pan Zhi Hua) Iron and Steel (Group) Corporation, the biggest steel company in southwest China, has been using titanium-vanadium-magnetite as the main raw materials for blast furnace iron making processing for over 30 years. One of the problems that has a negative affect on the blast furnace operation is slag foaming. Based on the chemical components of the blast furnace slag-bearing higher TiO2, the foaming properties were studied. The TiO2content, which is calculated according to the total titanium content in all the forms of titanium compound in the slag, in this research is 30% weight per cent. Different forms of titanium compounds have different actions on the slag foaming behaviour that depends on the reduction condition in the blast furnace. The relationships among slag foaming performance and the binary alkalinity of the slag, the content of CaF2, MnO in slag, and the amount of gas injected in slag are investigated. The results show CaF2 and MnO have a stronger anti-foaming affect on the slag, even in the lower percentage. The way to measure high TiO2slag foaming performance and how to eliminate foamy slag are also discussed. Keywords: blast furnace slag bearing TiO2, foamy slag, foaming performance

Jan 1, 2004

By John Lindsay

"Although diamond mining is a relative newcomer to the Canadian mining industry, with the first diamond mine coming on stream in 1998, Canada is already a significant producer of high quality diamonds. This paper will review diamond production trends and highlight some of the projects currently under development, which have the potential to enhance Canada’s role as a significant diamond producer.Diamond recovery plants generally incorporate well-established mineral processing and recovery techniques, with issues such as product security, cut-off sizes, and diamond preservation becoming important considerations when developing process flowsheets. A diamond processing plant must achieve three key objectives, namely:• Liberation of the diamonds from the host rock;• Separation of the heavy minerals, which include the diamonds, from the host rock;• Recovery of the diamonds from the heavy mineral concentrates.Processing technologies and equipment commonly utilized in diamond processing plants will be reviewed and some of the significant issues associated with each option briefly discussed.Typical process flowsheets will be presented.Finally, an overview of De Beers’ Victor diamond project, located in northern Ontario, will be provided. This potentially significant diamond producer is currently at a pre-feasibility stage of development.DIAMONDS IN CANADAWorld Diamond ProductionCommercial diamond mining commenced in earnest with the discovery of the Kimberley diamondfields in South Africa in the late 1800s, and this resulted in a dramatic increase in the supply of diamonds. As can be seen from figure 1, world diamond production, mainly from South Africa, Angola, Congo, and Namibia, remained relatively constant through the early 1900s until the development of the large Russian kimberlite pipes in the 1950s. Production increased again in the 1960s and 70s with the development of the Botswana mines, but the most significant increase in global production came from the Argyle mine in Australia, which came on stream in 1983 and produced a peak of almost 43 million carats in 1994, representing approximately 40% of the world market. Production from Argyle has since fallen-off as grades have declined and the strip ratio has increased with the deepening of the open pit."

Jan 1, 2003

By A. C. T. Bigg

"The mineral potential of the Nanisivik area was discovered as far back as 1910 when a prospector of the Geological Survey of Canada, on an expedition under Captain J. G.Bernier, recorded a deposit of pyrite with minor sphalerite and galena. An outcrop of the present orebody was discovered by Texas Gulf Company in 1957. Subsequent drilling outlined the orebody consisting of 6,000,000 tonnes of ore containing 13 % Zinc and 1.5 % Lead. The orebody appears to have been formed by the filling of a limestone cavern with sulphides. The sulphide minerals consist of pyrite, sphalerite and galena. The limestone bedrock is mostly dolomite with some calcite and magnesite. A cutoff grade of about 6% Zinc has been calculated.In 1972 Mineral Resources International Limited took an option on the property. Upon completion of the feasibility study by Watts, Griffiths and McOuat, the then new independent project management group of Strathcona Mineral Services Ltd. were engaged to develop the project through the financing, construction and operating phases. Strathcona Mineral Services still manage the project from their head office in Toronto and through the Mine Manager and Department Superintendents at the Mine site. The interest for the project is presently split five ways: Mineral Resources International Ltd. 53.5 %, Government of Canada 18 %, Metallgesellschaft A.G. of Germany 11.25 %, Billiton B. V. of Holland 11.25 % and Texas Gulf Co. 6 %."

Jan 1, 1980

By David Colloby, Darelle T. Janse van Rensburg

Premature coating failures of new and refurbished structural steelwork of clarifiers have been a common occurrence at power generation plant in recent years. Several of these failures have ended in disputes regarding which party was actually to blame for the early degradation of the coating system, i.e. quality of the power station?s water, poor application, substandard materials, outdated corrosion protection specifications, etc. Having investigated several of these premature failures, it is clear that the corrosion protection of clarifier steelwork is a highly complicated process and that the painting work needs to be closely monitored in order to ensure long-term protection by whichever product that is applied. The need for quality control inspections during the painting of the plant is often underrated during the project planning stage, also the importance of detailed corrosion protection specifications that consider not only the practical application of the materials, but also the quality control responsibilities of the Contractor, End User and Third Party Inspectorates that may be involved. This paper considers the application constraints of coatings to clarifier structural steelwork and importance of stringent quality control procedures in order to ensure the long-term performance of the corrosion protection systems.

Jan 1, 2006

In the Bendigo district, with its large number of comparitively small leases worked by separate companies, we might naturally expect to find many different arrangements of winding machinery and, as a matter of fact, there are steam winches, old portable engines, single and duplex geared engines, twin engines on the first motion, and in one instance a single engine on the first motion, all employed for hauling purposes from depths of 1000 feet and over.It would be impossible in the compass of this paper to discuss at all fully the various arrangements of winding gear employed on the field the writer can simply refer to some of the more prominent features, in the hope that the information may prove of interest and benefit to the mining community. In criticising our machinery it must be remembered that when many of the plants in use at the present time were erected, they were not intended to wind from more than one third of the depths now common on the field; but so long as the machine could be made to haul a tank of water from the bottom of the shaft it has remained, the greater power required being obtained by increasing the piston speed and altering the gear wheels to suit. The consequence is, of course, that in some of our mines the speed of winding is painfully slow this feature, however, though certainly not consistent with modern ideas of economical mining, does not so seriously affect Bendigo as it would other fields, for the comparatively small quantity of stone to be raised from a given reef by some...

Jan 1, 1902

By A. H. Bell

Continued low prices and restricted markets for crude oil discouraged drilling activity in Illinois oil fields during 1933. Only 36 wells were completed in the state, the smallest number since 1904, and of these the majority were scattered wildcat wells, only 10 having been drilled in producing fields (Table 2). Production was curtailed approximately 40 per cent for the first half of the year. During July, August, and the early part of September there was no restriction on production. On Sept. 8, under the "code of fair competition for the petroleum industry," the quota of allowable production for Illinois was fixed at 12,000 bbl. per day. The state&apos;s production in 1933 was 9 per cent less than in 1932. What it would have been had there been no curtailment of production and if economic conditions had permitted a normal amount of cleaning out and repairs to wells, it is not possible to estimate, but it would no doubt have been considerably more than the actual figure. No new pools or new producing horizons were discovered in 1933, but the deepening of a Robinson sand well in Crawford County to the McClosky "sand" horizon (St. Genevieve limestone of the Lower Mississippian) resulted in a production of 3 bbl. per day (Fred Patchel, Savilla Shipman No. 5, NE. 1/4, SW. 1/4, sec. 26, T.6N., R.l3W., deepened from 1122 to 1388 ft., to be tested to the McClosky horizon, and, owing to the rapid variations in porosity within short distances, as shown in the Lawrence County field to the south, one test may not be considered as proving or condemning any large area. The average price of Illinois crude oil in 1933, calculated from the posted prices as published in the Oil and Gas Journal and Oil Weekly, was $0.862 per barrel. This compares with a calculated average price of $1.032 in 1932 and 0.852 in 1931. The total value of Illinois crude oil produced in 1933 obtained by multiplying the average price (0.862) by the total production (4,227,000 bbl.) was $3,643,674. Of the 26 wildcat wells drilled in 1933, only one was drilled on known favorable structure. This was the Walmar Oil Company&apos;s William Pepple well No. 1, sec. 12, T.4N., R.12W., Hancock County, which tested

Jan 1, 1934

By R. S. Dean

The possibility of cheap electric power for a number of mining areas in this country has suggested to many the idea of electric smelting of nonferrous ores in small units at or near the mines. The electric smelting of nonferrous ores was tested fairly thoroughly 20 years ago by United States Bureau of Mines and by others, and the fact that it did not achieve continuing workable success in any instance is sufficient proof that it offered no advantages at that time.

Jan 1, 1937

The relationship between the maceral composition of coal and the strength of the coke produced from that coal has received a great deal of attention in recent years.Studies using two Bulli Seam coals, and blends of Bulli and Wongawilli Seam coals, from the IIIawarra Measures of the Southern Coalfield of New South Wales were carried out.The optimum range of vitrinite was found to lie between 45 per cent and 60 per cent (mineral matter free).Above and below this vitrinite range coke strength deteriorated. Coke strength indices increased with rank, and the optimum vitrinite content increased with an increase in rank. These changes require confirmation as trends by testing a third level of rank. It was noted that vitrinite content decreased with an increase in the specific gravity of separation of the coal.Use of petrographic analyses will increase confidence in choosing coals for coking, provided the coals are well known. Such analyses offer the possibility of greater flexibility in coal purchases and the possibility of producing a marketable blend from coals, which have limited market potential. Critical base coals for blends can be conserved.Significantly more work is required before coal reserves can be utilized to optimum advantage. This work would require extension of the studies discussed in this paper and, in particular, the testing of a wider range of rank.

Jan 1, 1971

By AIME AIME

EITHER the 2300 people who came to the Annual Meeting were in a better frame of mind or they were resigned to their fate, or it was a better meeting than usual. Whatever the reason, at the 1nstitute?s 148th meeting the attendance was better than ever before, things went more smoothly than in some previous years, and complaints appear to have been almost entirely absent. Patience was sometimes reauired but. almost without exception, it was forthcorning the well-known recession seems to have given many members enough leisure time to come to the meeting without depriving them of the tangible wherewithal to come.

Jan 1, 1938

By ARCH L. FOSTER

The rapid increase in the mmber of automobiles during the last 25 years has resulted in the insistent and growing demand for better roads of more permanent construction. Some form of State license for the operation of automobiles has been in effect almost from the time of the first "self-propelled" vehicle, and some part of the revenue derived from the sale of these licenses has been applied to the maintenance and construction of roads. However, to obtain funds with which to build their present highway systems, the individual States have resorted to the taxation of gasoline. The first State to adopt a gasoline tax was Oregon, the law becoming effective February 25, 1919. By 1928, all of the States except two had levied taxes on gasoline at rates varying from 2 to 5 cents per gallon. New York and Massachusetts passed gasoline tax laws which became effective in 1929. Regulations governing the quality and the methods of handling gasoline and other petroleum products sold in the States have also been adopted by 29 States; many of these laws antedate the adoption of a gasoline tax. The variations in motor fuel speci- fications and methods of test have been pronounced in the several States. The Bureau of Mines, in making certain technical studies of the rasolines marketed throughout the United States, the results of which are reported in its semiannual motor gasoline surveys and other reports, has had occasion to obtain and compile all of the present (April 1, 1931) tax and pection laws of the several States which relate to motor fuel and other petroleum products. To facilitate the use of this material and to obviate the need in most cases of reading the complete text of the laws as published by the States, the pertinent information was arranged in tabular form for cly reference. 3 Although digests of States gasoline tax laws' are available and copies of the complete laws can be obtained from the State agancies in charge of the enforcement of gasoline tax and inspection laws, it is believed that

Jan 1, 1932

By A J. Nick, I I. Townsend, J M. Schuler, J D. Smith, R P. Mueller, L Sibille, K Leucht, J J. Fox

The first steps for in situ resource utilisation (ISRU) on target bodies such as the Moon, Mars and near-Earth asteroids (NEA), and even comets, involve the same sequence of steps as in the terrestrial mining of resources. First exploration including prospecting must occur, and then the resource must be acquired through excavation methods if it is of value. Subsequently a load-haul-dump sequence of events occurs, followed by processing of the resource in an ISRU plant, to produce useful commodities.While these technologies and related supporting operations are mature in terrestrial applications, they will be different in space since the environment and indigenous materials are different than on Earth. In addition, the equipment must be highly automated, since for the majority of the production cycle time, there will be no humans present to assist or intervene. This space mining equipment must withstand a harsh environment which includes vacuum, radical temperature swing cycles, highly abrasive lofted dust, electrostatic effects, van der Waals forces effects, galactic cosmic radiation, solar particle events, high thermal gradients when spanning sunlight terminators, steep slopes into craters / lava tubes and cryogenic temperatures as low as 40 K in permanently shadowed regions. In addition the equipment must be tele-operated from Earth or a local base where the crew is sheltered. If the tele-operation occurs from Earth then significant communications latency effects mandate the use of autonomous control systems in the mining equipment. While this is an extremely challenging engineering design scenario, it is also an opportunity, since the technologies developed in this endeavour could be used in the next generations of terrestrial mining equipment, in order to mine deeper, safer, more economical and with a higher degree of flexibility. New space technologies could precipitate new mining solutions here on Earth.The NASA Kennedy Space Center (KSC) Swamp Works is an innovation environment and methodology, with associated laboratories that use lean development methods and creativity-enhancing processes to invent and develop new solutions for space exploration. This paper will discuss the Swamp Works approach to developing space mining and resource extraction systems and the vision of space development it serves. The ultimate goal of the Swamp Works is to expand human civilisation into the solar system via the use of local resources utilisation. By mining and using the local resources in situ, it is conceivable that one day the logistics supply train from Earth can be eliminated and Earth independence of a space-based community will be enabled.CITATION:Mueller, R P, Sibille, L, Leucht, K, Smith, J D, Townsend, I I, Nick, A J, Schuler, J M and Fox, J J, 2015. Swamp works – a new approach to develop space mining and resource extraction technologies at NASA’s Kennedy Space Center: prospecting, excavation, load, haul and dump for in situ resource utilisation, in Proceedings Third International Future Mining Conference, pp 297–304 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

By H. Aykul

The choice of which mining method to use at many large surface coal mines is often dicated by what machinery is available or what experience the mine management can offer. One of the most significant surface coal mines in Turkey is owned and operated by the Turkish National Coal Board, located to the west of the city of Kütahya. The Seyitömer Lignite Enterprise (SLE) extracts low quality coal, the majority of which is supplied to an adjacent power station. The coal seems at SLE contain bands of ash which under normal mining conditions are extracted with the coal. This increases the ash content of the run of mine coal and results in lower efficiency at the power station and financial penalties for SLE. In this paper, therefore, selection of the best possible equipment and production method was identified to achieve high selective mining at SLE. The research found that two different high selective mining methods were suitable for selective excavation of the B3 seam, which were hydraulic excavator and truck and surface miner and truck combinations. It was also found that high selective excavation could provide the desired coal quality at 52% lower costs when the whole process (excavation, transportation, processing, etc.) was considered. Keywords: coal mining, surface mining, selective mining.

Jan 1, 2007

The difficulty of accurately sampling cyanide gold bullion for valuation is well known, and nothing new or original is claimed in presenting this paper, but it was thought that a record of differences in the composition of bullion bars found here may be of interest to others, and perhaps helpful to those who have to do with theevaluation of cyanide bullion. This investigation was made after reading Mr. Sydney W. Smith&apos;s interesting paper on the Liquidation in Molten Alloys.*A method was in use of boring each ingot in two places and mixing the two borings for the sample. More accurate values were obtained, however, when the bullion was sampled in a molten condition immediately before casting into the ingot; the sample being so taken as to preclude oxidation of base metals before solidification of the sample.In all, samples from 32 ingots were assayed, and comparisons made between the existing boring sample and the proposed dip sample. Assays were also made of two other portions of the borings from each ingot, and the results show that in the majority of cases the borings sample assays higher in gold than the dip sample of the same ingot.The largest ingot cast weighs approximately 920 troy ounces, and has the dimensions shown in the attached sketch (Fig. 1). Ingots are cast in 0.1. moulds i in. thick, smoked and heated.METHOD OF TAKING BORING SAMPLES OF BULLION BARSThe bar is cleaned from adhering slag and drilled in two places only, to a depth of i-in., one hole on the top near one end and the other in the bottom at the opposite end of the bar.

Jan 1, 1931