Making the best use of extraordinary drilling results Content370x298“It’s essential to make the best possible use of extraordinary drillhole results and give them the attention they deserve.

What would it mean to your project if you could ensure maximum validation of your high grade drillhole results?"

High sample values should be properly treated

Companies spend a lot of money and effort to obtain high quality sample information - and are justifiably happy when outstanding analytical results are encountered. It’s therefore essential to make the best possible use of extraordinary data values, and not ‘cap’ them if it can be avoided.
Drilling results can make or break the economic assessment of a mineral deposit and the best possible data should receive the attention they deserve. They should be used in an intelligent and responsible way, necessitating the use of technically advanced estimation methods such as those specifically developed to include extreme drillhole results and treat highly skewed data distributions.

The solution

The solid mathematical foundation that supports the use of estimation methods that are based on ‘spatial statics’ or ‘geostatistics’, in turn allows the formulation of non-linear estimation methods. Over the years, these methods have proven reliable in incorporating all drillhole results, including ones with very high analytical values.

There are many different methods available for treating highly skewed data distributions, and the geological characteristics of the deposit will determine which is selected. In addition, geologists intuitively know that low grades are usually more continuous than high grades, and employing non-linear methods will ensure the highest results are weighted appropriately to add value.

Established techniques include Multiple Indicator Kriging (MIK) and Uniform Conditioning (UC) methods. These allow different spatial models to be used for different value classes, and also provide estimates of smaller Selective Mining Units. The astute engineer knows these smaller volumes are a critical contribution to mine planning and scheduling studies. New variant MIK and UC methods have been tried and proven which also allow local estimation of selective units. With the new methods, the most likely location of high grades can be predicted from the available drillhole data.

How we can help

Over a number of years we have perfected the use of non-linear methods like MIK and UC for the estimation of ‘recoverable’ or ‘mineable’ resources. Our approach incorporates a proven change-of-support method that predicts grades and tonnages above a series of realistic mining cut-offs, even in the early stages of drilling. Assessing project viability can be decided before closer infill drilling has been completed, and the process therefore supports early investment decisions.

We’ve also automated a large portion of the estimation routines to allow rapid turn-around of resource models. In this way, realistic ‘what-if’ project validation scenarios are generated.

We apply Local UC methods and use established in-house practices to allow the estimation of Local MIK models. These predict the most likely location of high grade mineralised zones. As a result non-linear estimation methods can be completed quickly and at the lowest possible cost.

If you have any questions about how you can maximise your extraordinary results, please contact Louis Voortman on +61 8 9269 6200 or via email at aloysius.voortman@coffey.com

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