5 common misconceptions about process mineralogy

Process mineralogy is a term that is used in a lot of contexts from process optimisation to Geometallurgy but it’s usefulness and application is often clouded by misconceptions that it is too hard or “our ore body is homogeneous and simple”.  For many of you the term has probably come up in conversations about ore types but have you ever stopped to think what getting a better understanding of mineralogy at could mean for your operation and whether it might actually make your job easier?

Traditionally mineralogy has been the domain of those geologists that enjoyed looking down a microscope all day and finding weird and wonderful rocks.  Today things are very different.  Automated mineralogy has made mineralogical information available to everyone and ruggedised systems such as Zeiss’ MinSCAN mean that even metallurgists can generate quality data very easily.  To highlight how far we have come with process mineralogy I wanted to highlight 5 common misconceptions that might be holding you back from using tools that could really help.

1. Process mineralogy is only for mineralogists in universities

This has never been further from the truth.  Advances in automated mineralogy and standardisation of the type of mineralogical reports we use means that any geologist or metallurgist can use the information.  Process mineralogy is more about identifying which minerals are important in the process and tracking their behaviour.  This provides just another tool to use when looking at process problems.  Often some simple mineralogy can provide the answer to why testwork results aren’t behaving as you expected or why recoveries are so low.  To highlight this, I was trained as a metallurgist and never even heard about mineralogy until investigating practical problems in my research.  Now I have used mineralogical information in hundreds of projects and see it as one of my principle tools in tackling metallurgical problems.

2. Why would I need mineralogical data when I have good chemical assays

Chemical assays give us a great general idea of what is going on in a process and will always be critical for things such as metallurgical accounting.  However, think about what we actually process.  The metals we are chasing are generally only present as metals right at the end of the process, up until this point what we are actually looking to recover is the minerals hosting these metals.  The minerals hosting those metals all behave very differently in any given process and understanding which minerals are there can give you a huge advantage when trying to understand what is going on.  Have you ever stopped to think why flotation concentrate grades vary so much?  It is because the minerals in these concentrates vary in the amount of metal they contain.  As an example, a copper concentrate containing only chalcopyrite can never have a grade above 34% Cu as this is the ratio of copper in chalcopyrite.   However, if the Feed ore hosts mainly chalcocite the copper concentrate grade could be as high as 70% Cu.

3. How can we get meaningful representation of our ore feed from looking at mineralogy on just a few particles?

This is an important question but no more so than it is for chemical assays.  We always rely on representing our processes based on tiny portions of material but we get around this by using good sampling methods and compiling results into daily, weekly or monthly composites.  This should be no different for mineralogy.  If we approach mineralogy with the same diligence as chemical assay then the results should be just as representative.  By using site based automated mineralogy systems, such as the MinSCAN, these issues can be further alleviated by analysing daily composites from key streams to produce data suitable for mineralogical trending.  While individually these data may produce higher errors once they are combined to evaluate trends the level of error drops dramatically and high quality data can be produced.

4. The turnaround time for mineralogy reports is too slow to make meaningful decisions.

The explosion in the number of automated mineralogy systems in analytical laboratories means that generation of mineralogical data is no longer a severe bottleneck.  Data can be readily generated in a matter of days and a number of operations are already using routine services from groups such as ALS, SGS and Bureau Veritas to generate general monthly analysis reports.  The real restriction on achieving consistently fast turn around time from laboratories is the lack of sufficient expertise in analysis and reporting of results.  This is where specialist groups, such as MinAssist, can really help by utilising data produced by commercial facilities to provide fast targeted reporting.

In addition, the advancements in on site mineralogy solutions mean that results can be generated in almost the same time frame as many chemical assays.  On one project we are working on currently the site is capable of producing mineralogical data within 48 hours of the sample be taken.  This opens up a huge range of possibilities for short range decision making utilising mineralogical tools that have previously only been available weeks or months after the sample was taken.

5. Mineralogy is just too expensive.

Mineralogical analysis can be expensive if programs are poorly thought out and have ill defined goals.  The cost is still much higher than chemical assays but as analyses become more routine these costs are coming down.  What should be considered when budgeting for a mineralogy program is what the goals are and what the incremental value of achieving those goals are.  Good process mineralogist can help you build programs using a combination of chemical and mineralogical analysis that are well targeted at your specific goals and highly value adding.

For example we recently completed a project with an ongoing value to the operation of over US$1M per month in revenue, simply by targeting the behaviour of key minerals and whether they were being directed to the appropriate part of the circuit.  Costs can be reduced even further when site based mineralogy is considered.  While there is a capital investment requirement the ‘all in’ cost per sample can be greatly reduced even when considering the expert help that may be required.  If you are serious about developing a serious capability in ore body and process knowledge through mineralogy then site based solutions is definitely the most efficient way to go.

So we hope that we have answered some of your questions about process mineralogy.  It is clear that advances in the technology for mineralogical analysis over the past decade have made it much ore accessible to everyone and a tool that can be used in day to day decision making, not just for major projects.

If you have any questions feel free to contact us directly.  Also if you are interested in finding out more about process mineralogy make sure you download our digital book, which gives some more details on how to build mineralogical capability and start getting real value for your investment.