24-MMP-A4 Mine Valuation and Mineral Resource Estimation · December 2014
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, 2014-Dec. 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); Gentry & O'Neil, Mine Investment Analysis (Canadian mining taxation, smelter/refining contract terms, net smelter return); SME Mining Engineering Handbook, 3rd ed. (mineral exploration/evaluation stages, ore reserve classification); CIM Best Practice Guidelines and NI 43-101 (Canadian Securities Administrators).
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.
Open pit porphyry copper. Porphyry deposits are large, low-grade, broadly disseminated bodies with gradational (not sharp) grade boundaries, so grade control is a statistical, bulk-tonnage exercise. Blast-hole cuttings on a regular grid (commonly 5–8 m spacing on production benches) are sampled and assayed, and the results are kriged or inverse-distance-interpolated onto a block model to generate ore/waste polygons for each bench before loading. Because the deposit is voluminous and grade varies smoothly, a modest mis-classification of any single block has limited economic consequence, and grade control tolerates a coarser sampling density relative to deposit size. Selectivity is set by the mining unit (SMU), which for a large-shovel/haul-truck operation is typically 10–15 m × 10–15 m × bench height — far larger than the sample spacing, so dilution and ore-loss are managed statistically through the block model rather than by tracing individual structures.
Underground steeply dipping vein. Vein deposits are narrow (often <3 m true width), high-grade, and structurally controlled, with sharp, sometimes erratic grade boundaries at the vein/wallrock contact. Grade control here is a geological, structural exercise: face mapping and channel/chip sampling at each round advance, supplemented by close-spaced underground diamond drilling from drifts, are used to trace the vein visually and geologically rather than statistically. Because the mining width is usually constrained to a narrow stope envelope hugging the vein, small positioning errors translate directly into severe dilution (waste rock mined alongside the vein) or ore loss (vein left in the wall), so sample spacing must be tight (often every 1–2 m of advance) and interpretation leans heavily on structural geology – strike/dip continuity, faulting offsets, and vein pinch-and-swell – rather than on kriged block grades.
Contrast. The core difference is one of scale and continuity: porphyry grade control is bulk, statistical and tolerant of local error because the mining unit is much larger than the sample spacing; vein grade control is selective, geological and intolerant of positioning error because the mining unit approaches the deposit's own width. Both ultimately feed the same purpose – separating ore from waste at the point of extraction – but porphyry relies on geostatistics (variograms, kriging, block models) while vein mining relies on real-time geological mapping and narrow-vein survey control.
