QEMSCAN

The QEMSCAN system is the third generation of automated mineral analysis systems that began with the QEM*SEM at CSIRO 30 years ago (Butcher et al. 2000). It has now become a successful commercial instrument with 39 instruments in operation around the world at companies such as Rio Tinto, BHP Billiton, Phelps Dodge, Falconbridge and Anglo Platinum (Pirrie et al. 2004).

The system is based on a Zeiss Evo 50 scanning electron microscope fitted with up to 4 light element x-ray detectors and pulse processor technology. It operates in a PC windows based environment, which allows for both online and offline interpretation of dat .

minassist - qemscanBack Scattered Electrons (BSE) and Energy Dispersive (EDS) X-Ray spectra are used to create digital mineral images with mineral identification occurring online. Low-count EDS spectra are used preferentially to BSE brightness, allowing minerals to be accurately identified by chemical composition. Individual minerals or groups of similar composition are identified by comparison to a comprehensive mineral database incorporated into the QEMSCAN software. The whole package allows for the identification of most ore and rock forming minerals in 10 milliseconds (Pirrie et al. 2004). A recent summary of the QEMSCAN system has been provided by (Gottlieb et al. 2000).

One of the advantages of the QEMSCAN system is its ability to cope with a wide variety of ore types by utilizing a number of different analysis modes. There are four separate analysis modes available with QEMSCAN, that allow for anything from bulk ore mineralogy to the identification of trace minerals within grains.

One of the advantages of the QEMSCAN system is its ability to cope with a wide variety of ore types by utilising a number of different analysis modes. There are four separate analysis modes available with QEMSCAN, that allow for anything from bulk ore mineralogy to the identification of trace minerals within grains.

Bulk Mineralogical Analysis (BMA)

Bulk Mineralogical Analysis (BMA) is a rapid line scan analysis method used to identify the number and length of intercepts with mineral species. The data can then be used to determine modal abundance, particle and mineral surface areas, mineral associations and mineral grain and particle sizes .

Particle Mineralogical Analysis (PMA)

Particle mineralogical analysis (PMA) is used for the detailed characterisation of particles typically up to 1mm in size. These particles are selected by BSE images, which are used to determine particle diameter, perimeter and whether it is touching other particles. Touching particles are discarded from analysis. Data from PMA is ideal for liberation analysis .

Specific Mineral Search (SMS)

Specific mineral search (SMS) operates the same way as PMA except that images are only taken of particles that contain a phase of specific BSE brightness. The number of particles analysed in this way is determined by the concentration of the mineral of interest and hence this method is usually only used for minerals present at about 0.5 vol % or less. This method is often used in conjunction with BMA .

Trace Mineral Search (TMS)

Trace mineralogical analysis (TMS) is very similar to SMS but is used when only trace amounts of the mineral of interest are present. TMS is a hardware function, which continuously monitors BSE brightness compared to a threshold value and immediately rejects any fields lacking bright phases. TMS is the mode most suitable for gold analysis because of the inherent trace nature of gold in most ores and as with SMS is most useful when combined with BMA .

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