24-MMP-A4 Mine Valuation and Mineral Resource Estimation · May 2013
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Mining and Mineral Processing Engineering, 09-Mmp-A4 Mine Valuation and Mineral Resource Estimation, 2013-May. 3 hours duration; one handwritten 8.5×11 in reference sheet permitted (not an open-book exam); only approved Sharp or Casio calculators allowed. Question 1 is compulsory (40 marks, parts 1.1–1.7); candidates then select FOUR of the six optional Questions 2–7 (15 marks each) to complete the paper.
Reference texts: Isaaks & Srivastava, An Introduction to Applied Geostatistics (variogram modelling, kriging estimators, volume–variance relations); Hustrulid, Kuchta & Martin, Open Pit Mine Planning and Design (mine valuation, NPV and cut-off grade methodology, mineable reserves, selective mining units); Gentry & O'Neil, Mine Investment Analysis (Canadian mining taxation, smelter/refining contract terms, net smelter return); SME Mining Engineering Handbook, 3rd ed. (mineral exploration and evaluation stages, ore reserve classification).
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
Blebs are, by definition, smaller-scale and more irregular than the main ore body, so a drilling grid designed and spaced for the main body's continuity will systematically mis-estimate them – sparse holes that happen to hit the bleb core overestimate its volume (the polygon/block assigned to that hole is far larger than the bleb actually is), while holes that miss the bleb entirely underestimate it (or drop it from the model altogether). The fix has three parts. (1) Orient the drilling along the preferred direction of bleb development, established from the first few holes and from structural/lithological controls, rather than drilling on a direction-blind orthogonal grid – fence sections and fan drilling from a single set-up cut across the bleb train instead of parallel to it. (2) Tighten the spacing locally once a bleb is identified – infill holes at a fraction of the main-body spacing (e.g. one-quarter to one-half) specifically around each bleb's margins so the boundary is bracketed by holes that hit it and holes that clearly do not, rather than being interpolated across a wide gap. (3) Model blebs as discrete wireframed domains in 3-D rather than folding their assays into the main-body grade envelope on a single 2-D section – because bleb size decays in a preferred direction, a 3-D wireframe lets the estimator honour that decay trend explicitly (e.g. via a locally-rotated search ellipsoid in kriging) instead of assuming isotropic continuity, which is the single biggest source of over/under-call on this kind of feature.
