Richard Minnitt

University of the Witwatersrand | wits · School of Mining Engineering

The underground mining process typically results in some of the metal inventory remaining as a broken residue within mine workings. Up to 0.5 m of broken ore may be left on the floors of development drives and in stopes. It is possible that this broken ore contains 5% or more of the original metal in the ore reserve, which will have a material effe...

This paper investigates the implications for coal supply security for the domestic South African market when faced with weaker export demand. A model is proposed of domestic coal trade via a trading hub which links coal production to consumer markets. An application of the theory for equilibrium price discovery at the mine-trader and trader-consume...

In the development of mining projects, there is a period in between commitment of finance and production commencement. Risks are present in various aspects of development such that production start-up could be delayed, thereby affecting the value of the project. This paper demonstrates the application of convolution in the capital investment proble...

The management of outlier grades in positively skewed gold distributions is a contentious issue. Incorporating outliers in standard ordinary kriging (OK) estimation procedures in a way that honours the data without smearing extreme grades into surrounding areas has been problematic. Cutting or capping of outliers to mitigate their influence in esti...

A mathematical model of a multi-product coal mining project is proposed to characterise the economics governing coal production. The model accounts for mining cost variation due to varying production levels, changes in reserves available for extraction by means of a cut-off parameter, as well as lead-time delays between investment and when operatio...

South Africa's mineral commodities generate approximately R420 billion per annum from export earnings. Of that amount coal (28.1%), gold (15.2%), iron ore (14.5%), and platinum (21.7%) account for 80%, and together with chrome and manganese account for 88% of the earnings. Payment for these products is based on the metal content, and in the case of...

Grade control in underground mines aims to deliver quality tonnes to the process plant via the accurate definition of ore and waste. It comprises a decision-making process including data collection and interpretation; local estimation; development and mining supervision; ore and waste destination tracking; and stockpile management. The foundation o...

A modified version of the Cobb-Douglas production function is proposed for simulating production costs in resource extraction models. The resulting average cost function is U-shaped with a wide bottom, and as such should be more representative of the economies of scale associated with bulk operations. It also possesses a minimum which is obtainable...

Bulk commodities such as iron ore moving on a conveyor belt represent a one-dimensional lot providing an ideal opportunity for probabilistic cross-belt or cross-stream sampling at regular time intervals. The quality of such materials is measured by the mean, but the variability in the analyses arises from a variety of sources and is aggregated in a...

The grouping and segregation error is one of Gy's seven errors that cannot be measured in any qualitative manner because of its transient and changing characteristics each time the sample is handled mechanically. Attempts to calculate the mean and variance of the segregation error is considered by some as 'an exercise in futility' that would not he...

This study examines the problems faced by open pit mine superintendents who make choices about how to direct their materials, either to the waste dump or to the mill. The paper explores the effects of introducing a 10% sampling error and a 0.9-times to 1.1-times sampling bias on positively skewed distributions for precious and base metals, negative...

The two methods for calibrating the parameters K and α (alpha) for use in Gy's equation for the Fundamental Sampling Error (FSE)-, Duplicate Sampling Analysis (DSA) and Segregation Free Analysis (SFA)-, are described in detail. A case study using identical broken reef material from a Witwatersrand-type orebody was calibrated using the DSA and SFA m...

Mineral Resource estimation (MRE) and classification are highly dependent on the confidence in the model of the orebody geometry, known as the geological model, within which the estimates are constrained. An understanding of the geology of a deposit is thus fundamental to the Mineral Resource evaluation process. The geological model is a function o...

Rock properties have a material impact on mining processes, including drilling performance. An investigation using point loaded index (PLI) data converted to uniaxial compressive strength (UCS) has revealed that a direct relationship between grain size and UCS exists at Mogalakwena Mine. This correlation is best seen in unaltered rock, with lower c...

Application of Gy’s formula to the determination of the fundamental sampling error is critically based on the calibration of the parameters K and alpha ((Formula presented.)) in his equation. Typical calibration methods include the heterogeneity test (HT) and the duplicate sampling analysis (DSA). Concerns relating to these methods are that the HT...

The applicability of a stochastic approach to the simulation of gold distribution to assess the uncertainty of the associated mineralization is examined. A practical workflow for similar problems is proposed. Two different techniques are explored in this research: a Direct Sampling multi-point simulation algorithm is used for generating realization...

Cokriging uses a sparsely sampled, but accurate and precise primary dataset, together with a more abundant secondary data-set, for example grades in a polymetallic orebody, containing both error and bias, to provide improved results compared to estimation with the primary data alone, as well as filtering the error and mitigating the effects of cond...

Previously, the grade of ore at the shaft head was taken to be equivalent to the grade measured in the faces by means of chip sampling. The tonnage mined from the stopes is determined from survey volumetric measurements. Estimates of shaft head grade and tons include the grades and tons of waste, development ore, sweepings from old areas, and other...

With the advent of the First World Conference on Sampling and Blending (WCSB1) in Denmark in 2003 and the subsequent biannual meetings, together with other sampling conferences held on a regular basis, the central tenets of sound sampling practice and theory are spreading throughout the minerals industry. End-users and project houses, or groups who...

The status of sampling practices in the gold mining industry in Africa was determined as an initial step in a process to standardize sampling practices in the mining industry. Twenty-one gold mines, twenty metallurgical plants, and thirteen laboratories were rated for the potential influence of the relevant sampling errors on each component of the...

Although not fully accepted in South Africa, the Theory of Sampling originally proposed by Pierre Gy is fast becoming the cornerstone of sampling practice throughout the world. The growing acceptance of Gy's Theory of Sampling in South Africa can be attributed to a number of factors, chief amongst them being the development of a tradable mineral as...

A brief history of channel sampling in South African gold mines is followed by a chronicle of different sampling events and sampling methods that used the traditional 'hammer and chisel' approach as well as diamond core extraction of the sample. The problems associated with each method of sample collection are documented and the use of a laser scan...

Any company operating a fleet of trucks will be greatly advantaged if the associated fuel costs can be decreased. The optimal tonnage that trucks should be hauling to ensure minimum consumption of diesel fuel has been investigated. The fuel consumption in litres per ton for a fleet of trucks hauling different tonnages of iron ore was recorded in a...

For any gold deposit-based geometallurgical study, the collection and processing of representative samples for gold grade and recovery tests is critical. Sampling protocols should be designed to suit the style of orebody in question. The proportion and size of gold particles has a direct impact on the effectiveness of sampling protocols and metallu...

The Witwatersrand Supergroup is host to the world's largest gold deposits. The location, quantity, grade, continuity and other geological characteristics of a Mineral Resource are either known, estimated from specific geological evidence and knowledge, or interpreted from a well constrained and portrayed geological model. Establishing such a model...

Grade control programs aim to deliver economic tonnes to the mill via accurate definition of ore and waste. The foundation of a successful program is high quality sampling supported by geology and a suitable data management and modelling system. Underground sampling methods include chip, channel and panel samples; grab/muck pile samples; and drill-...

Grade control programmes aim to deliver economic tonnes to the mill via accurate definition of ore and waste. The foundation of successful grade control is high quality sampling supported by geology and a suitable data management and modelling system. For underground operations sampling methods include chip, channel and panel samples, grab/muck pil...

This article captures the intrinsic differences of thermal coal products, their utilization and their substitution characteristics. South Africa produces approximately 245 million tonnes of coal annually. Eskom consumes 46% (approximately 112 million tonnes), 26% (approximately 65 million tonnes) is exported, and SASOL Synthetic Fuels consumes 18%...

Mining is important to the economies of both Tanzania and Namibia. Recently, both nations revised their national mineral policies to ensure future economic benefit. The main difference in the mineral policy-formulation processes followed by the two countries is identified as the degree and timing of stakeholder involvement during the articulation p...

The demographics and the growing numbers of people provide a strong signal that the demand for electrical power in Southern Africa will grow considerably over the foreseeable future. Without a steady and increasing supply of electricity development of the continent is likely to be constrained. The inventory of solar, wind, hydrothermal, geothermal...

Until 2000, pricing involved profit taking and cost covering combined with limited global published information. Market information was mostly subjective in nature and large resource companies benefited exclusively from aggregated company information and data. The market constituted producers and consumers only. The nineties saw massive cost cuttin...

The compilation of the sampling nomogram is an essential tool in the optimization of a sampling protocol and allows the operator to track the change in relative variance of the sampling error (the Fundamental sampling error) during steps of comminution and mass reduction in the process of recovery of the aliquot for analysis. The data required for...

The use of a time series variogram as an aid in controlling the quality of a product was pioneered by Pierre M. Gy and is described. The ability to analyse and interpret covariance relationships time series data is possible using the variogram. The concept of stream heterogeneity allows sources of variability in process streams to be identified and...

The influence of Harold Hotelling's work in the field of mineral economics is both unusual and outstanding. In the 66 years since its development, theory surrounding the economics of exhaustible resources has only been significantly researched since the early 1970s. At that time a wave of research into the economics of exhaustible resources arose f...

The variety and sources of sampling errors have been studied since the late 1800s, but the pioneering work of Pierre Gy in the 1950s provided insights into sampling as an error generating process. Total sampling variance is a measure of the total sampling error, but disaggregating the variance into its component parts is problematical. Ten sources...

Application of Gy's formula is appropriate for calculation of the Fundamental Error (FE) prior to samples being collected at any stage of the minerals process, provided that sampling parameters K and α (alpha) have been determined by calibration of the ores. Two types of calibration procedure are well established in the industry, the Hetrogeneity t...

The simple act of taking a sample implies that someone will use the information contained in the analytical result to make a decision about a course of action. In the mining industry, the decisions may involve huge capital commitments for opening or closing a mine, or marginal tactical costs that involve deciding if a truckload of mineralized rock...

South Africa remains the largest global producer of gold, accounting for 11.3 per cent of total world mine production, which amounted to 2520.2 t in 2005. The benefits and disadvantages associated with hedging practices in general, and among South African gold producers is examined. The wide variety and unique nature of risks faced by the mining in...

An often overlooked factor in the analysis of mine layouts and schedules is technical operating flexibility, mainly due to its nebulous nature. If one glosses over technical operating flexibility the resultant mine layouts and schedules tend to be sub-optimal. The need to incorporate technical operating flexibility into the analysis and comparison...

Globalization creates investment opportunities for enterprises around the world. Attracting foreign investment has been a key challenge for economic growth in developing countries. Corruption, political instability, armed conflict, and other internal problems affect foreign direct investment (FDI) inflows negatively. A framework of criteria provide...

South Africa has developed niche competencies around the extraction and processing of mineral resources. Firms involved in the manufacture and supply of inputs to mining and mineral processing represent a key source of competitive advantage upon which future growth and development in the country can be planned. Drawing on a qualitative and quantita...

This paper explains how the well-accepted concept of improved stakeholder participation during mineral policy development leads to a national mineral policy that accommodates the diverging views and interests that allows wide acceptance of decisions, enhancing the success of implementation and, ultimately, national benefits. This process is based o...

Since 1994, South Africa has been the subject of international attention, especially in regard to its transformation initiatives, which aim to redress the post-apartheid imbalances. Mining, as a major employer and one of the major industries in South Africa, has been the focus of the government's Black Economic Empowerment initiative with the intro...

Work undertaken in the field of cut-off grade optimization has not advanced much beyond the work undertaken by Lane in 1988, His definitive work is based on the calculus of the Net Present Value criterion, which is the most widely understood, consistent, and appropriate method by which sequential cash flows arising from the extraction of mineral re...

Traditionally, mineral reserves management at most underground mines in Zimbabwe focus on maintaining large mineral reserves so that the time between development and production is as long as possible. Historical data at Shabanie mine, a Zimbabwean sub-level caving underground mining operation, confirms this practice. However, the high cost of under...

A number of countries have introduced codes governing the valuation of mineral assets and securities. The African continent will follow suit in due course considering the importance of the global minerals industry as it relates to the attraction of foreign investment. South africa is to introduce the Petroleum and Minerals Development Bill legislat...

Synopsis The definition of mineral rents has historically been somewhat unclear, but a growing understanding of the source and composition of the revenues that comprise these rents mean that they can be more easily identified and quantified. Furthermore the way in which the flow of the rents from mineral developments are captured and then distribut...

The new South African Mineral Policy has major implications on the way mineral rent will be collected and shared between the stakeholders in future. Although the policy does not supply details on how this will be done, drastic departures from practices under the previous dispensation require a new approach. For example, the reintroduction of the 'r...

This paper examines the consumption, production, and pricing patterns of the platinum-group metals (PGM) for the years 1980-2000. The aim is to better understand the happenings in the PGM market of recent years and to project the likely trends and economic impacts for the future. Hypotheses about the PGM market are generated and tested using correl...

This paper provides a survey on studies that analyze the macroeconomic effects of intellectual property rights (IPR). The first part of this paper introduces different patent policy instruments and reviews their effects on R&D and economic growth. This part also discusses the distortionary effects and distributional consequences of IPR protection a...

A new system for granting access to mineral rights is proposed in the recently released White Paper, 'A Minerals and Mining Policy for South Africa'. Official policy states that 'Government's long-term objective is for all mineral rights to vest in the State for the benefit of and on behalf of all the people of South Africa'. In order to achieve th...

Direct reduced iron (DRI), produced by the reaction between iron ore and reducing gasses, is used as a source of low-residual iron, in addition to ferrous scrap and pig iron, in the production of steel mainly through the electric arc furnace (EAF) route of steelmaking. The main DRI technologies in use are those of Midrex and HyI, but In recent year...

Inauguration of the new political dispensation in South Africa, Initiated a dynamic period in the historical development of its minerals policy. The process of substituting the current South African mineral policy framework with an acceptable 'post apartheid' system, started soon after the 1994 election of the African National Congress (ANC) govern...

Crescentic fractures resembling impact-produced shatter cones occur in stream-bed and palaeo-channel exposures on quartzites of the Klapperkop Member (Timeball Hill Formation, Transvaal Supergroup) in the Mpumalanga Province and the Orange Grove Quartzite Formation (Witwatersrand Supergroup) from the southeastern sector of the Vredefort Dome. They...

The structural history of the eastern portion of the Murchison greenstone belt can be explained in terms of three deformational events. Early high-angle faults, formed during gravity slumping of unstable ensimatic crust, provided a regional synformal framework for the preservation of linear homoclinal and synclinal greenstone belt assemblages. A se...

The paper will attempt to identify the threats, however obscure, that could confront the South African platinum industry. South Africa has the largest reserves of platinum group metals in the world, and is the largest producer of those metals. This situation is no different from that which existed in the gold sector fifty years ago. Since then Sout...