Built by a geologist
Sampling & Quality Control
Proper sampling is essential for accurate grade estimation. Poor sampling practices can lead to incorrect resource estimates and costly mine planning errors. Sampling Fundamentals Why Sampling Matters - Core represents a tiny fraction of the deposit - Sample quality directly affects resource estimates - Errors compound through the estimation process - Financial decisions depend on reliable data Sampling Principles 1. Representative : Samples must represent the volume of interest 2. Unbiased : No systematic over- or under-representation 3. Precise : Reproducible results 4. Documented : Complete chain of custody Sample Interval Selection Approaches - Regular intervals : Fixed lengths e.g., every 1m or 2m - Geological intervals : Based on lithology/alteration changes - Composite approach : Geological intervals with maximum length Guidelines - Respect lithological contacts - Minimum sample length typically 0.3m - Maximum sample length typically 1.5-2m - Don't dilute high-grade with low-grade Core Cutting Half Core vs. Whole Core - Half core : Standard practice - preserve half for reference - Whole core : Used for low-grade deposits or when more sample needed - Always sample the same half typically right-hand side looking downhole Cutting Protocol 1. Mark sample intervals clearly 2. Place sample tags at both ends 3. Cut along core axis 4. Bag the sample half 5. Return reference half to box 6. Document in log Quality Assurance/Quality Control QA/QC Standard Reference Materials SRMs - Certified grade materials inserted regularly - Verify laboratory accuracy - Typically 1 in 20 samples 5% Blanks - Barren material e.g., clean limestone - Detect contamination - Typically 1 in 20 samples 5% Duplicates - Field duplicates : Quarter core or same interval - Coarse rejects : Re-split at lab - Pulp duplicates : Re-analyze prepared material - Assess precision at each stage Insertion Rates | Type | Rate | Purpose | |------|------|---------| | Standards | 5% | Accuracy | | Blanks | 5% | Contamination | | Duplicates | 5% | Precision | | Total QC | 15% | | Chain of Custody Document every step: 1. Sample collection and numbering 2. Bagging and sealing 3. Secure storage 4. Transport to laboratory 5. Sample receipt confirmation 6. Results delivery