Ore processing

Ore processing or extractive metallurgy is an integral part of the mining industry. It is focused on extracting metals from their natural ores. Ore characterization using mineralogy is of crucial importance in all branches of mineral processing.
Different ore textures as well as different mineralogy of the ore can cause significant changes in the plant performance. Automated Mineralogy (AM) is a very important diagnostic tool in extractive metallurgy as it adds ore and particle mineralogical properties to traditional bulk mass, chemical and XRD data. AM is used in project development, for future ore studies and for diagnosing day-to day plant operations. These are industrial scale problems and the emphasis is on high productivity and fast retrieval and interpretation of results rather than on classical microscope mineralogical research.
  • Large numbers of samples and sampling statistics are required. This means that manual measurements would simply not be fast enough and representative enough. This industry-related work requires automation – Automated Mineralogy analysis. TESCAN brings its own solution. TIMA (TESCAN Integrated Mineralogical Analyzer) is a purpose-built system for automatic industrial use. An additional feature of the TIMA is the TESCAN AutoLoader that takes automation to an even higher level by using a robotic system to load the samples into the SEM chamber.
  • TIMA automatically evaluates relationships of the individual minerals using backscattered electron (BSE) imaging combined with X-ray mapping from the electron beam sample interaction. The BSE intensity is proportional to the average atomic number of the observed phase. Boundaries among different phases can thus be easily visualized.
  • The samples come directly from plant and laboratory tests and are particles ranging in size from a few micrometres to few millimetres. The powder is cast in an epoxy block which is sectioned, ground and polished to a flat smooth finish. The polished samples are coated with a thin conductive layer of carbon. The surface finish is needed to enable calibrated comparisons of the BSE intensities and the collection of representative X-rays.
  • The mineral particles are discriminated from the mounting epoxy based on the BSE contrast. The epoxy is considered as a low brightness background and excluded from the analysis.
  • To minimise measurement time, the characteristic x-ray spectra for the phase identification are collected only from areas above specified threshold of the BSE intensity. The BSE thresholding can also be used to exclude common rock-forming minerals or gangue and focus the analysis solely on particles containing high BSE intensity phases - typically gold particles or platinum group minerals.
  • Mineral identification is based on both the BSE level and the chemical composition of the phase. The minerals are identified automatically based on a set of predefined rules in a mineral classification scheme.
  • TIMA generates modal mineralogical composition of the sample. Each of the mineral grains (segments) is treated as a separate entity whose properties (size, neighbouring grains, extent of the free surface etc.) can be recalled and used to synthesize different outputs valid for the entire sample – association, liberation degree, grain size etc.
  • The measured modal volumetric composition of the sample can be converted to the weight of individual minerals using density values from the mineralogical database.
  • Based on the mineralogical database, the system can then calculate the average density and chemical composition of the entire sample and compare it to the results obtained by independent chemical analysis.
  • Automated mineralogy systems are most commonly used to track causes of low recoveries of metals in the concentrator and dilution of the concentrate. TIMA can provide many relevant answers about poorly liberated grains of the mineral of interest, the presence of gangue minerals influencing the process, the deportment of the valuable metal between minerals, and the occurrence of penalty elements. These are a few examples from many other possible diagnostic results, which can be reported in images, tables, and charts.
Ore processing
Tantalite grain complexly intergrown by muscovite

Related Application Notes

TIMA Modal Analysis - REE Mineralization in Silicate Rocks
Unusual rare-earth mineralization associated with primary silicates, carbonates and fluorite, and hosted by the silicate rocks, was discovered at alkaline complex and rare-earth deposit Lugiin Gol in South Mongolia. Whereas carbonatites as a primary REE source have been investigated in a fair amount of detail because of their economic potential, their associated silicate rocks are not as well understood. The predominant type of silicate rock at Lugiin Gol is leucocratic nepheline syenite. Representative syenite samples are composed of potassium feldspar, nepheline, sodalite, plagioclase, amphibole, biotite, cancrinite and minor quantities of calcite, titanite, magnetite, apatite and zircon. Primary carbonate phases usually occur close to drop-shaped fluorite clusters and contain both silicate glass and fluorite melt inclusions.
pdf – 5.2 MB
TIMA Study of Tantalum- Niobium-Tin Pegmatites and Its Residual Soil
Tantalum and niobium are rare and valuable metals which are needed for many high-technology applications. As the discovery of mineral resources becomes more difficult, more sensitive detection techniques are required. Microscope and electron microscope examination of heavy mineral grains is only occasionally used as an aid to geological interpretations. The high grade ore concentrates mineral composition should be also supervised before and during the ore metallurgical processing by electron microscope due to relatively cheap outlay and significant data profits. Samples of Tin-niobium-tantalum ore from Central Africa Great Lakes Region (Western Rwanda) have been studied.
pdf – 2.3 MB
Characterization of Platinum Group Minerals
The platinum-group metals (PGM) consists of six elements – platinum, palladium, rhodium, iridium, ruthenium and osmium. Chemical inertness, oxidation-resistance, biocompatibility, high melting temperature, good conductivity and electronic and catalytic properties are unique properties that make PGM irreplaceable starting material in many specific applications. The deposits in the Norilsk-Talnakh region of Northern Russia are the largest nickel-copper-palladium deposits in the world and, the intensive mining activity in this region, positions Russia as the world’s second global PGM supplier. In addition to PGM output, a by-product of this mining is nickel and copper extraction. In this application example the effectiveness of the separation process (gravity separation and hydro-separation) by comparison of PGM mineral content, both in concentrate and in tailings, is studied.
pdf – 2 MB