24-MMP-A4 Mine Valuation and Mineral Resource Estimation · December 2018
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, 2018-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 1.1–1.8); 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, kriging, anisotropy); Hustrulid, Kuchta & Martin, Open Pit Mine Planning and Design (mine valuation, NPV/IRR and cut-off grade methodology); Gentry & O'Neil, Mine Investment Analysis (smelter/refining contract terms, net smelter return, taxation and risk); Guilbert & Park, The Geology of Ore Deposits, and Evans, Ore Geology and Industrial Minerals (VMS/SEDEX and porphyry deposit models); 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.
A deep, narrow structurally-controlled vein (e.g. a mesothermal gold or Sn-Cu vein filling a fault/shear) is geometrically thin (often <2 m), steeply dipping, and its grade is strongly influenced by nugget-scale coarse-gold or cassiterite distribution — the grade population is typically highly skewed (lognormal) with a large nugget effect on the variogram. Continuity along strike and plunge can be good, but continuity ACROSS the vein is essentially non-existent past the vein margin, so the estimation domain must be defined by hard geological boundaries (the vein contacts) rather than a statistical search. Because of the high nugget/erratic grade, resource estimation for a vein relies on close-spaced underground channel sampling and face mapping, sectional (polygonal) methods honouring the vein geometry, and often a top-cut or indicator approach to tame outlier assays; block kriging on a coarse surface drill grid is unreliable because drill intersections are widely spaced relative to the vein's own short-range variability, and intersection angle/true-width corrections are critical.
An extensive porphyry copper (or epithermal gold) deposit is the opposite case: large volume (hundreds of metres to kilometres), gradational disseminated/stockwork mineralization with comparatively low nugget effect and long-range spatial continuity tied to the intrusion's alteration zonation. Grade varies smoothly from the potassic core outward, so ordinary or indicator kriging on a regular block model, using a wide (50–100 m) diamond or RC drill grid, gives statistically robust, low-variance block estimates suitable for early Measured/Indicated classification. The controlling geological framework here is alteration/vein-density zoning rather than a hard structural boundary, so domaining is done by an alteration envelope or grade contour rather than a sharp contact.
