The PGM, gold, nickel and copper mineralisation occurs as a narrow ore zone straddling the base of the MSZ. The MSZ contains 1-6% sulphides and persists laterally on both a regional- and mine-scale.
The MSZ dips gently eastward at Hartley, the strike averaging 17 [degrees] and the dip 18 [degrees], flattening slightly and thickening with depth.
The distribution of mineralisation within the MSZ is such that the sulphide content builds up towards the visual base of the MSZ, reaching a maximum of 3-5% S.
Thus, the optimum mining width is a 900 mm section above and below the visual base of the MSZ which has a value of some $60/t.
Effective grade control is essential to the viability of this mine, including both the ability to stay within the 'sweetest' part of the MSZ and to control over-break, so metallurgical accounting starts at the face.
The quality control team logs and marks the visually identifiable position of the peak platinum value (PPV) within the MSZ. Further confirmation of the PPV position is provided by the use of a hand-held X-ray diffractometer measuring nickel sulphide abundance.
Anglo had drilled 21 test holes in the late 1960s and early 1970s and Delta completed a 23-hole diamond drilling programme which, using wedges, gave 46 new intersections of the MSZ over an area of some 100 [km.sup.2].