Grade Reconciliation Workflow Standard (PDF)

Grade reconciliation is a cornerstone of Mine Metallurgical Process Integration, bridging geology, mining, and processing disciplines. The workflow standard establishes a repeatable, auditable sequence—starting from data acquisition (e.g., drill core assays, in-pit mapping, mill head assays) through statistical comparison, variance attribution (e.g., sampling error, geological uncertainty, blending effects), and root-cause analysis—to quantify and explain discrepancies between predicted and actual grades. Central to the standard is the concept of 'reconciliation tiers': short-term (shift/daily), medium-term (monthly/quarterly), and long-term (annual/reserve-level), each with defined tolerance thresholds, reporting formats, and escalation pathways. The standard mandates metadata governance—including sample IDs, assay methods, detection limits, QA/QC flags—and requires version-controlled digital workflows to support real-time dashboards and automated alerts when reconciliation variances exceed predefined control limits. Crucially, it integrates feedback loops: reconciliation outcomes directly inform updates to geological models, mine planning assumptions, and metallurgical recovery predictions—enabling closed-loop process optimization and improved forecast reliability.