Multiple-indicator kriging

Multiple-indicator kriging (MIK) is a more recent advance on other mineral deposit modeling and resource block model estimation techniques such as ordinary kriging. Initially, MIK showed considerable promise as a new method that could more accurately estimate overall global mineral deposit concentrations or grades.

Unfortunately, the technique has not lived up to the promised benefits. Many experimental reviews over a range of actual mineral deposits has demonstrated that the technique will frequently be responsible for the over estimation of reported resources. Typically observed with the technique is an inflated reported total tonnage of mineralized deposit material along with sometimes a coincident non-proportional reported deposit grade. This problem has been reported for a range of different deposit types including most typical precious metals and base metals deposits.

The primary reason for the failure of the MIK technique have been demonstrated to be in part or totally due to each of the following deficiencies:


 * The use of inherently large block sizes (required for adequate spatially distributed drill-hole and block sample support) does not allow for adequate resolution of geologic geometry;
 * The considerable level of difficulty in generating indicator cut-off variograms for all indicator cut-off grade levels;
 * The failure of being able to determine the appropriate levels of post interpolation "uniform conditioning" support or adjustment for reported block grades;
 * The allocating of probability block proportions for each indicator cut-off levels is difficult to apply;
 * The accuracy of reported block grades often cannot be verified without the use of localized high density sampling.

Conditional simulation is another new interpolation technique that will probably largely replace MIK for the purposes of global estimations and it is showing great promise as preferred deposit modeling method.