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By R L. Brathwaite

As part of an investigation of the deep structure of the Waihi Basin, an extensive set of resistivity measurements was recently collected by DSIR Geology & Geophysics. The objective of this work is to map deep resistivity changes throughout the Waihi area in order to contribute to a better understanding of the regional geophysical structure. This research is also aimed at improving techniques for locating 'deposits of epithermal mineral resources, and helping to establish their origin and genetic relationship to fossil geothermal systems.   The results indicate that the basin south of Waihi is underlain by an extensive layer of low resistivity, modelled as a 5ohm-m layer several hundred metres thick. Lake sediments (mudstones), as exposed in the south western part of the basin, near Waitawheta, are the most likely source of this low resistivity layer, although hydrothermally altered clays and/or elevated temperatures are other possible causes. Strong northeast trending anisotropy is also observed, implying structural links from Waitawheta through to Golden Valley. The observed resistivity pattern is consistent with a æburied calderaÆ or æfaulted depressionÆ structural model for the basin, as inferred from gravity and magnetic data.

Jan 1, 1991

By Conny Postupack

The first principle one usually learns about blasting is that competence in this field is best gained by experience in making blasts rather than by reading a book or by listening to a lecture. The reason for this is that there are a large number of variables affecting blasting results and not all of these can be accounted for by a few rules or a few sets of equations. Even an experienced in a new area, may have co make one or two himself to the new conditions with which he blaster when operating shots just to acclimate is faced.

Jan 1, 1991

The need for legislative reform of health and safety legislation has been recognised in New Zealand for about a decade. Previous legislation did not cover all work places, many areas were excluded from coverage, and there were at least 14 different acts and dozens of sets of regulations dealing with various aspects of health and safety.

Jan 1, 1993

Because of its small interburden thickness, concentrated stress distributions, high coal seam metamorphism, and complex geological conditions, mining the five coal seams (Nos. 5, 7, 8, 9 and 12) of Kaiping coalfield is difficult. Kaiping coalfield is located within 80 m in the Kailuan Group. The overburden caving caused by mining the five coals seams was measured using ZTR12 geological penetration radar (GPR) survey combined with borehole observations. The development characteristics of full-cover rock fractures after mining were obtained from the GPR scan, which provides a measurement basis for the control of rock strata in close multiple-seam coal mining. For the first time, it was found that the overburden caving pattern shows a periodic triangular caved characteristic. Furthermore, it is proposed that an upright triangular collapsed rock pile and an inverted triangular area with larger fragments piled up alternately appear in the lower gob. The research results show that the roof structure formed in the gob area can support the key overlying strata, which is beneficial to ensure the integrity and stability of the upper coal seams in multiple-seam mining of close-coal seams.

Jan 7, 2020

By Kwong. Kyei-Sing

Gasification is a process that converts a carbon feedstock into synthesis gas (CO+H2). Slagging gasifiers operate at high temperature and pressure and in a corrosive-wear environment from the slag. Cr2O3-based refractory linings are used to protect the steel vessel that comprises the gasifier from the aggressive gasification environment. Increasing service life of the gasifier is one of the keys for wide spread development of this technology. In support of the goals, research on the gasifier atmosphere, the slag chemistry, the interaction of Cr2O3 refractory with different feedstock mixtures (e.g., coal and petcoke) were characterized by post mortem analysis of bricks from service in gasifiers and thermodynamics simulation of the environment. Examples demonstrating how thermodynamic calculations can explain the post mortem results and make predictions of material interactions will be given. Attention is placed on the possibility of Cr+6 in different feedstock mixtures and operating conditions.

Jan 1, 2010

By J. D. Appleton, J. Ridgway, K. B. Greally

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). The results suggest that meaningful geochemical maps can be produced from very low-density surveys, and that existing data sets could perhaps be incorporated into such a map series with the use of a system such as Uniras software. There are still many problems to be resolved, however, including the compatibility of data derived from different analytical methods, and the precise methods to be employed will necessarily require international agreement. Sampling densities should be chosen on the basis of the scale of the geochemical and geological features to be distinguished and will vary from region to region. Reanalysis of selected samples from archives to increase the range of elements determined or to unify analytical methods is only likely to be effective if the original survey was at quite a low density

Jul 1, 1991

By M. Nete

Qualitative analysis of three mineral samples from northern Mozambique was accomplished by X-ray diffraction (XRD), microscopy, scintillation, and magnetic determination. Chemical characterization was accomplished using ICP-OES and pressed powder XRF after dissolution using microwave-assisted digestion and flux fusion. The samples consisted of a mixture of minerals with tantalite as the major component, with minor amounts of microlite, quartz, mica, accessory garnet, and tourmaline. Incomplete dissolution was obtained using microwave digestion, with maximum recoveries of 90.25 ± 0.06% and 88.90 ± 0.04% for Nb2O5 and Ta2O5 respectively. Complete dissolution using Li2B4O7 resulted in recoveries of 98.5 ±0.2% Nb2O5 and 100.4 ± 0.3% Ta2O5.

Jan 1, 2012

By Walter Smith

Environmental Quality Committee ?EQC was created in 1995 to facilitate dialogue between industry and northern communities and help build the understanding of the industry in those communities. ?EQC is made up of representatives from 32 northern communities. ?Meet regularly with Cameco to discuss on going and new projects. ?Tour mine sites on a yearly basis.

Nov 1, 2011

By E. Pardo-Igúzquiza, R. A. Olea

The bootstrap is a computer-intensive resampling method for estimating the uncertainty of complex statistical models. We expand on an application of the bootstrap for inferring semivariogram parameters and their uncertainty. The model fitted to the median of the bootstrap distribution of the experimental semivariogram is proposed as an estimator of the semivariogram. The proposed application is not restricted to normal data and the estimator is resistant to outliers. Improvements are more significant for data-sets with less than 100 observations, which are those for which semivariogram model inference is the most difficult. The application is illustrated by using it to characterize a synthetic random field for which the true semivariogram type and parameters are known.

Jan 1, 2015

By Guillermo P. Selas

Perhaps this is the first time that an analysis of the industrial minerals panorama has been made in Mexico for that type of commodities. Because the non-metallic minerals lack the glamour of the metallic minerals and are usually of less unit value than metallics, a comparative study of these commodities has seldom been attempted. Sulphur, fluorite, barite and few others are an exception. Consequently, the statistics on the lowest per unit value industrial minerals, such as limestone, dolomite, gravels, sands, etc., are usually scarce and not always accurate. The following, then, will be an attempt to show a general status of the industrial minerals in Mexico with due reservations regarding volumes and values. According to Kruger (1971), this group of minerals surprisingly very little known, and called non-metallics because the lack of metallic luster, is the largest group of the mineral kingdom. It constitutes perhaps 75% of all the mineral varieties. For the most part, these minerals are compounds of common acids, sulphides, hydroxides and two elements carbon and sulphur. The list of non-metallic minerals is therefore very long. It includes the borates, carbonates, chlorides, fluorides, nitrates, phosphates, silicates, sulphates and less commonly arsenates, chromates, molybdates, sulphides, tungstates and vanadates. The latter group and many of the oxides are sought usually for their metal content.

Jan 1, 1974

By Martin Herrenknecht

The world?s growing population and rapidly proceeding urbanization are boosting an enormous demand for new and high-capacity infrastructures to secure the mobility of goods and people. Densely populated areas face the challenge to provide efficient traffic infrastructure, such as a modern public transportation system. At the same time, the maintenance and modernization of supply and disposal structures for water, sewage, energy and communication are also essential. Additionally, supra-regional transportation routes such as long distance water diversion schemes are the challenges for the future. All these projects are as demanding as they are characterized by a tight time schedule.

Jan 1, 2010

By B. T. Brady

Recent theoretical, experimental, and field studies conducted by the Bureau of Mines suggest that rock failures may be predicted and, in some instances, controlled. Theoretical studies that were later corroborated by laboratory and field studies predict that a seismic anomaly will precede rock bursts and/or roof falls in mines. The seismic anomaly is predicted to consist of an increase in the number of seismic events occurring in the immediate vicinity where the failure 1s nucleated. This increase will then be followed by a dramatic decrease of seismicity in a broad region that surrounds the location of the impending failure. The dimensions of this region allow a preliminary estimate of the time to failure (measured from the time the seismicity increase began) as well as an estimate of the energy that will be released at the instant of failure. Field observations indicating that this predicted behavior does precede rock bursts and a roof fall are presented in this report. Implications of results to the problem of failure control in mines that experience massive rock failures are discussed.

Jan 1, 1978

Lonmin, earlier than any other primary platinum producer, had to deal with the concentrating and smelting of UG2-rich ores and concentrates respectively. Smelting was performed at a fairly modest scale compared to the company's industry peers in the platinum group metals (PGMs) industry, and was focused on smelting concentrates obtained through low mass pulls while still maintaining high recoveries at its concentrators. Lonmin gradually smelted larger quantities of UG2 concentrates. Initially two 2.3 MW Infurnco furnaces were commissioned in 1982, followed by three 5 MW circular 3-electrode Pyromet furnaces in 1991. Deep electrode immersions and moderately high hearth power densities were used in all the designs. Lonmin decided to continue with circular furnace technology when it planned its new high-intensity No. 1 Furnace. Neither Lonmin nor the technology supplier and EPCM company foresaw the challenges that scale-up would bring when applied to the smelting of UG2-rich concentrate blends. Superimposed on the high chromite content, was the low base-metal loading, mineralogical difficulties, and fine particle size that resulted from milling of all concentrates (especially UG2 and recycle materials within the smelter). Through a process of fundamental diagnoses of furnace run-outs and wear patterns observed during repairs, the main challenges operating this high-intensity furnace were identified as sulphur vapour corrosion of the copper coolers, uneven and unpredicted movements of refractory bricks with associated copper cooler lift and matte tapblock movement, the formation of three-phase 'mushy' zones, high refractory and taphole wear rates, uncertainty in matte level and associated insufficient matte buffer height, and high furnace operating temperatures. These factors seldom worked in isolation and will be explored in more detail in the paper. The variability in furnace feed characteristics led Lonmin to redesign Furnace No. 1, to invest in backup furnace capacity, and to invest in improved monitoring and control. These improvements consisted of online and high-frequency off-line monitoring of feed chemistry and mineralogy, online pressure monitoring of water-cooled circuits, an alternative matte liquid level measurement in the furnace, and electrode immersion estimation. Improvements were also made at the converters by installing and utilizing optical spectral analysis of the converter flame to characterize converter behaviour and achieve the desired iron end-point for white matte. This paper also briefly discusses the current and future expansion plans, as well as ancillary operations at the smelter such as flue-gas handling and materials handling.

Jan 1, 2011

By J. S. Peterson, G. P. Cole

The National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Center (PRC), has conducted research to improve electrical fault detection on coal mine direct current (dc) trolley systems. Present circuit breaker protection systems are current-magnitude-based and cannot discern between normal traffic and high resistance electrical faults. Tests were conducted at cooperating mines to assist in developing a neural-network-based detection algorithm for distinguishing between electrical faults and normal operation. The Fast Fourier Transform of the trolley rectifier current signature served as baseline data for the neural network. During field tests, the algorithm performed with greater than 90% accuracy.

Feb 24, 1997

KIeeman (1968) described practice in the Mount Hebbard dump concentrator, Broken Hill, N.S.W. The purpose of this note is to give data on flotation pulp chemistry in the plant for comparison with results of Woodcock and Jones (1970a, 1970b).Ten chemical parameters were measured at ten points in the circuit using the techniques of Woodcock and Jones (1970a, 1970b). Fig. 1 shows a condensed time plot of some continuous measurements in conditioner overflow and rougher feed. Fig. 2 shows average values of selected parameters at the start and end of each of the three rougher flotation stages.DISCUSSIONpH and redox potentiaIsFig. 1 shows that pH and Eh were relatively constant at the start of sulphide lead flotation. There was a fairly steady increase in pH throughout the circuit (Fig. 2), but flotation was always conducted in a slightly acid pulp in spite of the large amount of alkaline reagents added. Eh values became more positive as the pulp progressed through the circuit (Fig. 2) in accord with results elsewhere.

Jan 1, 1973

By Koch D. F A

An electrochemical study of the dissolution of gold in aerated cyanide solution shows that the dissolution rate is determined by the nature of the surface. A passive film (probably a basic cyanide) formed at -0·6 V vs a saturated calomel electrode inhibits both the anodic dissolution of gold and the cathodic reduction of oxygen. Thallium has an "activating" effect on these reaction mechanisms.INTRODUCTIONIn general the dissolution rate of a solid in a liquid is studied by weight loss measurements or analysis of the solution at known time intervals. However, if the solid is a metallic conductor, on which a redox reaction can occur at the metal-solution interface, it can be studied by electrochemical techniques. Electrochemical measurements have the advantage that the overall reaction can be separated into its components, in some cases by electrical measurements alone, and in others by a combination of these with analytical determinations.The overall equation for the dissolution of gold in aerated cyanide solution may be written4Au + 02+ 8CN- + 2H20 = 4Au (CN)2- + 40H- ..... (1)which can be separated into the two electrochemical componentsrepresenting the oxidation of gold and the reductionof ogygen respectively.4Au + 8CN-,= 4Au(CN)2- + 4eand O2+ 2H20 + 4e = 40H- These two reactions occur at the gold-electrolyte interface and it is the purpose of this paper to discuss the mechanism...

Jan 1, 1964

By Dan Payne

The Crinum mine has recently completed workings in the southern area of the mine. Over the 10 years of longwall production 40 million tonnes have been extracted and the mine has experienced over 40 longwall face, 3 main gateend, and 2 tail gateend roof falls as well as 5 roadway roof falls away from the longwall. Weak roof (less than 10MPa (1450psi) in the bolted horizon) has been the principal roof control issue at the mine. However, weak, highly cleated coal, water inflow from overlying aquifers, some minor structure and a diatreme in the main headings have also contributed to the challenges at the mine. This paper describes the geotechnical experience over the 10 years, the mine?s approach to addressing the issues and the relative success of these approaches.

Jan 1, 2008

By Anna M. Ferrero

Stability condition of underground excavations have to be assessed to guarantee safe operations within the quarrying working areas. This objective requires a reliable assessment of the rock mass natural state of stress and of the stress redistribution induced by the excavations. This goal is often complicated by difficult geological conditions induced by tectonic stresses, complex topographies and large and irregular excavation geometries. Consequently, the acting state of stress needs to be measured by specific in situ measurement devices. This work refers on an in situ measurements campaign carried out by CSIRO tests in an underground quarry located in the Carrara marble basin. The difficult path carried out for interpretation of the measurements is described in this paper. In particular, the numerical modeling performed using the Boundary Element Method (BEM) first, to study the influence of both surface topography and excavation geometry and then the Distinct Element Method (DEM) to evaluate the influence of rock discontinuities in the measurement zone are illustrated in this work. Parametrical analysis of the rock mass mechanical features is also described in order to calibrate the numerical models and analyze the experimental results. The work has been carried out trough several phases, which are: characterization of the rock mass through geostructural surveys: this allowed us to classify the rock mass and determine the mechanical and physical parameters necessary for modeling; on-site measurement of stress levels through the application of over coring techniques; numerical analyses for the simulation of excavation phases, using the Examine3D (BEM) engineering analysis code. comparison between the measured stress levels and those numerically calculated and subsequent calibration of the BEM model; Numerical model of the forecasted excavation based on the calibrated (BEM) model.

May 1, 2009

The Development of a Non-Roasting Technology for Polymetallic Gold and Silver-Bearing Sulfide Concentrates Treatment

Sep 13, 2010

By M. Gous

Keywords: Pyrometallurgy, Namakwa Sands, ilmenite, DC arc furnace, titania slag, pig iron Namakwa Sands is a heavy minerals mining and beneficiation business in the Anglo Base Metals Division, and operates along the West Coast of South Africa. The business encompasses mining, mineral concentration, separation, and smelting operations. The smelting process comprises the carbonaceous reduction of ilmenite to produce titania slag with a TiO2 content of 86%, and iron with a carbon content of 2.5%. The Namakwa Sands smelter, situated near the Saldanha Bay harbour, commenced smelting operations in 1994, when a 25 MW DC arc furnace was commissioned. The smelting operations were expanded in 1999, with the commissioning of a second 35 MW DC arc furnace. Despite the fact that ilmenite smelting poses a technical challenge in terms of the high temperatures required, the physical characteristics of the slag, the constraints placed on the feedstock, and the tight product specifications, Namakwa Sands has continually increased slag production since 1995. High furnace feed-on utilisation and furnace stability, complemented by continuous improvement drives, will be the vehicle to drive performance in the short term, with longer-term performance enhancements due to strategic process development.

Jan 1, 2006