Core recovery is a measure of the proportion of intact drill core successfully retrieved from a borehole relative to the total length of the interval drilled, expressed as a percentage. It is a fundamental quality indicator in mineral exploration drilling programs conducted in bauxite, gold, iron ore, and diamond mining operations. A core recovery of 100% means that all of the rock drilled in a given interval was recovered as intact core, while a lower percentage indicates that some material was lost, either because it was too fractured, weak, or soft to survive the drilling process without disintegrating, or because of drilling-related factors such as excessive water flow, poor drilling technique, inappropriate drill bit selection, or inadequate penetration rate control. Core recovery is calculated as: Core Recovery (%) = (Length of Core Recovered / Length of Interval Drilled) × 100. Low core recovery has serious implications for resource estimation because missing core represents missing data; if the lost material happens to be high-grade mineralised zones, the resource model will underestimate the true grade and tonnage of the deposit. In gold mining exploration, zones of intense silicification or soft, clay-altered mineralisation are prone to poor core recovery. In bauxite drilling, the highly weathered and friable nature of pisolitic bauxite often results in reduced core recovery if drilling parameters are not carefully managed. In iron ore drilling through banded iron formations, fractured zones are common sources of core loss. In kimberlite drilling for diamonds, the soft and fractured nature of kimberlite can result in poor recovery unless specialised triple-tube core barrels are used. Core recovery data is recorded by the geologist during core logging and is an essential data field in any compliant geological database.
