I’ve mentioned numerous times that the reason the partial extraction results are coming in way under the much higher true grades I’m expecting from the assays is that it’s testwork using a partial extraction method (how many times have I said that).
It’s never going to be 100% but anywhere in above 90%in the commercial facility would be fantastic.Basically,you’ve got a bunch of factors influencing the extraction or recovery during smelting (e.g. temp, flux, chemistry, viscosity, time, etc) that affect the extraction efficiency and the resulting grade. The more factors there are,the more difficult it becomes to get a results that reflects the true grade.
I’ve knocked up and extraction efficiency matrix to illustrate my point.
The total recovery the solution from a simple multiplication matrix If you’ve got 4 factors you can represent it like this. If one factor is off the mark by90% the recovery is 90%.
…but it’s more likely to be about 9 factors and since it forms a neat cube I’m going with 9 cells.
As you can see it only takes one or two misses from a couple of parameters and the extraction efficiency and the resulting recovered grade drops off bigtime.
The most realistic scenario during testwork might be #8, with a fair few misses like #5, 6, 7, but as the BBX team perfect the process it will hopefully approach something like #3 or better.
So if you want to get a feel for what grades we might expect from the assay method measuring the true grades, look at the best results, maybe the top decile because they are much more representative that the lower grade extraction results.
I've taken the results generated above and applied them on an assumed true grade of 5oz/t as an example of a grade in the top decile.
Those grades look familiar huh? They closely resemble the drilling extraction results to date.
If I vary the grades to allow for natural grade variation the output still resembles the extraction results we're getting …
The important takeaway from this is that the highest grade results are much more representative of the true grade than the lower grade extraction results, keeping in mind that the mineralisation is disseminated, widespread and pervasive, independent of the host rock lithology.
