ZEISS Mineralogic Mining is an automated particle analysis software solution tailored towards process mineralogy applications and allows for detailed acquisition of characteristics relevant to mineral processing, exploration, environmental mineralogy and tailings control (See Graham et al., 2015, Tonzetic, 2014; Graham et al., 2014a and references herein).
This is the first of several posts exploring the Zeiss Mineralogic software with subsequent posts looking at topics such as image processing and analysis tools; post-processing tools and typical end uses. First of all though the data needs to be collected and the first thing to be decided is which analysis mode to use – essentially how are data to be collected from each particle / phase.
Zeiss Mineralogic operates five different modes all of which are user configurable. Deciding between the different analysis modes depends on the complexity of the sample, how much information needs to be gathered and how much time is available. The following descriptions of the analysis modes are largely taken from Graham et al., 2015.
The mapping analysis allows the user to set an EDS pixel size (step size) and magnification for the analysis and the software draws the analysis grid over the sample. This method gives a full analysis of the sample, with the time taken to controlled by parameters such as step size, EDS dwell time, number of analysis points and the number of particles (sample surface area) to be measured. This is the longest of the analysis modes and the most detailed. It is usually used for sample with complex mineralogy, where easily separating phases by BSE intensity is not possible.
Spot centroid analysis segments the BSE image to find each individual mineral grains. The geometric centre of each grain is then calculated, from which a single EDS analysis is collected. The composition of this one analysis spot is then given to the grain. This is an extremely fast mode of measurement due to fewer individual EDS points being analysed, but is forced to rely on the minerals of interest having a discrete BSE value and will not report changes of elemental deportment within grains (as only one point on each grain is analysed rather than many).
Feature scan uses the same BSE function to identify mineral grains as spot centroid analysis. It then rasters the beam across the surface of the grain and sums the x-rays gathered together to give the average composition of the grain. Sitting between the spot centroid and full mapping modes in terms of analysis speed, this mode gives good average composition of mineral grains. Along with spot centroid analysis it offers the best opportunity to accurately reproduce the mineral morphology but is highly dependent on their being simple mineralogy with large differences in BSE threshold values (e.g. gold, pyrite and quartz).
Line scan, is an analysis mode designed to provide a fast and statistically valid bulk mineralogy analysis. EDS analysis are collected at pre-determined points across a single line through the centre of each particle. Line scan is another extremely fast measurement mode designed to very rapidly characterise samples for modal mineralogy and to provide an indication of relative texture (size, liberation, association) and is useful in instances where non-unique BSE values for minerals limit the use of spot-centroid.
The Back Scatter Electron (BSE) only mode uses the BSE electron grey scales (0-255) to classify the mineral phases present. BSE-only mode is the fastest mode of analysis as it does not use any EDS analysis. This mode relies on the unique BSE value of each mineral grain to identify the mineral present.
Once the analysis mode has been determined other factors need to be adjusted to minimise the time taken to collect the required information. This will include setting the “dwell time” for each analysis where typically a minimum count time of 2,500 cps is required to ensure the correct identification of mineral phases. Lastly, analysis modes can be combined with statistical stop criteria, which make use of the real-time mineral identification. Once the analysis mode has been decided upon the rest of the anaylsis routine can then be defined. This will be the topic of the next post.
References
Graham, S. D., Brough, C., Cropp, A. 2015. An introduction to Zeiss Mineralogic Mining and the correlation of light microscopy with automated mineralogy: a case study using BMS and PGM analysis of samples from a PGE-bearing chromitite deposit. Precious Metals Conference | pdf |
Graham, S. D., Hill, E., Dominy, S. C. and Spratt, J. 2014a. The Application of ZEISS Mineralogic Mining, an automated mineralogy solution for mineral exploration. Society of Economic Geology: Building Exploration Capability for the 21st Century.
Tonzetic, I. 2014. Applications of Mineralogic in the minerals industry. 21st General Meeting of the Internal Mineralogical Association.
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