What’s in my tailings? Mineralogy as a diagnostic tool for process performance

Tailings evaluation using mineralogy is an area that I believe can define the actual losses in a plant, while simultaneously providing the first step in defining why they occur.  There is massive scope to use an understanding of tailings to see what is and what isn’t working in your process.

Of course, working with tailings is never easy.  Minor or trace concentrations of valuable elements or minerals means that sample collection and integrity become one of the major concerns in any project relating to tailings.  My expertise lies specifically in gold analysis and often the process of selecting and preparing an appropriate sample is more work than undertaking the analysis.

The rewards for getting sampling right can be significant.  Using your process tailings as a diagnostic tool gives insights into everything from what is being lost to why it is being lost and whether it will cause problems in the tailings dam.

Some examples of what a well designed tailings evaluation study can provide using systems such as QEMSCAN include:

1. The distribution of valuable elements with host minerals.  Identifying the major mineral host/s for unrecovered value.
2. The grain size of key minerals.  Can be used as a diagnostic tool in identifying inefficient process areas.
3. The locking/liberation characteristics of key minerals.  Can be used as a diagnostic tool to define root cause for losses.
4. The presence and nature of environmentally sensitive minerals such as sulphides or heavy metals.

As a diagnostic tool a well designed mineralogical study of your tailings can act as a fast and efficient means of first stage process auditing or ongoing process monitoring.  This is even more powerful when combined with mineralogical investigation of the feed (ore characterization).  This analysis of input and output streams can immediately show core inefficiencies in the process that can be targeted by more focused stream or unit operation audits.

Overall, I believe that mineralogical tailings evaluation should be the first step for anyone wanting to get a handle on the fundamentals in their process.  The use of automated systems like QEMSCAN or MLA makes this practical now.  While good sampling is still the key, these systems allow good statistics to be achieved and reliable data to be generated.

If you haven’t looked hard at what is in your tailings before I encourage you to think about the benefits a single study can bring.  Over and over you see historic tailings dumps with recoverable value still there.  It is much better to get the process right first time and make sure that you are getting maximum recovery from your process.