HIGH PROFILE the distribution of waste in ore , ore in ore , and ore in marginal material in mining block models , the test results reflecting these conditions can be populated into those same models for mine planning ,” McCarthy explains .
Typical mine planning steps of pit / stope optimisation , mine design and scheduling can proceed on the assumption of one or more preconcentration strategies , with different versions of mine schedules , reflecting different preconcentration strategies , evaluated .
This type of analysis typically works for a project in pre-feasibility study stage , where engineers can go into the existing block model , bringing the results from the heterogeneity and lab tests into the mine optimisation , design and scheduling process that takes place .
“ The challenge is that the scheduling needs to assume a certain strategy – maybe you have determined what that strategy is close enough with the ‘ size the prize ’, but there are always a few elements you may want to tweak ,” McCarthy says . “ This could be the mass pull , or waste rejection targets , for instance .”
As a result , sensitivity analyses – mostly numerical tweaks – are embedded in the process . When not dealing with a pre-feasibility-level project , the SRK team typically rely on an existing schedule that has been run during a scoping study or preliminary economic assessment . This model is modified and tested with different
Example of drill core intervals showing waste in ore percentages of up to 80 %
schedule scenarios and pre-concentration strategies based on the heterogeneity measures ( step 1 ) integrated with the lab test results ( step 3 ).
Out of the mine planning step comes a schedule that would go onto the next step : mine economics modelling .
“ The model is configured to take in the heterogeneity measures , recovery curves , etc to change the amount of metal reporting to revenue and so forth ,” McCarthy says . “ Once I get schedules – based on the upgraded block models or it may be a pre-existing schedule – I would then put them into an economic model that has all the levers to pull for different pre-concentration strategies .”
Such a stepwise approach is indicative of where the mining industry is at the moment with vendor-agnostic pre-concentration analysis , enabling companies to get comfortable with the data and assessments as their understanding of their deposit ’ s heterogeneity grows . There are potential refinements and fine-tuning opportunities too .
For example , if SRK was gifted with drill core or assay data that was more granular than the 1-2 m intervals typically taken at the exploration stage , it could indicate with greater certainty how particle sorting – typically analysing grades at intervals around a few centimetres – could benefit the deposit in question .
Also , if mine modelling software had matured to the point where block models could be tailored specifically to these waste-in-ore and ore-in-waste characteristics , SRK could segregate the areas in question , instead of applying the type of dilution factors they currently have in place to account for the grade-based realities . This would more clearly communicate the deposit ’ s heterogeneity to all stakeholders .
Yet , McCarthy and Dance know this will come in time , and are happy to work within the current confines to continue the industry ’ s education process and identify where the pre-concentration opportunities are . IM
Further discussion on this and what SRK ’ s preconcentration analysis evaluation – with that embedded pre-concentration screening test – means within the broader mining industry context will follow in the final article in this three-part series later this year .