24-MMP-A4 Mine Valuation and Mineral Resource Estimation · Undated paper
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, undated sitting. 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 (parts 1.1–1.5); candidates then select THREE of the five optional Questions 2–6 (20 marks each) to complete the paper.
Reference texts: Isaaks & Srivastava, An Introduction to Applied Geostatistics (variogram modelling, anisotropy, volume–variance relations); Hustrulid, Kuchta & Martin, Open Pit Mine Planning and Design (mine scheduling, NPV/valuation methods, stripping-ratio economics); Gentry & O'Neil, Mine Investment Analysis (Canadian mining taxation, CCA classes, smelter/refining contract terms, net smelter return); SME Mining Engineering Handbook, 3rd ed. (mineral exploration/evaluation stages, ore reserve classification); Guilbert & Park, The Geology of Ore Deposits (volcanogenic massive sulphide genesis); 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.
4.1.1–4.2.1 — The North-West-Corner scheduling method. The North-West-Corner rule is a systematic way to allocate a fixed annual production quota (7 Mt ore/yr here) across a grid of mining blocks ordered by mining sequence (rows) and available production years (columns): starting at the highest-priority block in the earliest available year (the grid's "north-west corner"), allocate as much of that block's tonnage as the year's remaining quota allows; if the block still has tonnage left, move down to the next block in the same year; if the year's quota is exhausted first, move right to the same block's continuation in the next year. Repeating this down/right stepping until every block's tonnage is exhausted produces a schedule that (a) always honours the fixed annual quota, (b) always mines blocks in their required priority order, and (c) never leaves a year under-quota while an available block still has ore, because the very next block in sequence absorbs any remainder. Applied here, the schedule works through the highest (shallowest) benches of Phase 1 first, filling each year's 7 Mt quota bench by bench, and only begins drawing from Phase 2 once Phase 1's benches (or the immediately available portion of them) are exhausted — consistent with the source's own statement that "Phase 1 ore will normally be mined out before moving to Phase 2."
4.1.2 — Grade trend with depth. In a porphyry/epithermal deposit mined from surface downward and inward toward the pit core, the earliest-mined benches are typically lower-grade, near-surface, often partially oxidized/leached material, while grade generally rises with depth as the pit converges toward the higher-grade hypogene core of the mineralized system — though many porphyry systems also show a near-surface secondary (supergene) enrichment blanket that can locally spike grade before it drops again through a lower-grade leached cap, so the trend is not always perfectly monotonic. The sketch (grade $y$ vs. life-of-mine time $x$) accordingly rises through early-to-mid life as mining descends toward the deposit core, illustrating why average mill feed grade commonly improves over a mine's life even as the pit gets deeper and stripping costs rise — a trend mine planners exploit deliberately by sequencing lower-grade near-surface material early (when it is cheapest to access) and reserving higher-grade core material for when cumulative stripping cost has already been sunk.
