Infill resource drilling is a focused exploration and resource definition drilling campaign specifically designed to improve the classification and confidence level of mineral resources within an existing resource envelope, primarily for the purpose of advancing a project toward a definitive feasibility study, mine plan, or production decision. In the mining of bauxite, gold, iron ore, and diamonds, infill resource drilling is a specialized subset of infill drilling that is formally documented within resource estimation workflows and subject to the oversight of a competent or qualified person under the applicable mineral reporting code. The term distinguishes this activity from general infill drilling, which may also serve purposes such as geotechnical investigations, hydrological characterization, or grade control. Infill resource drilling programs are typically preceded by a review of the existing resource model to identify areas of low confidence or high estimation variance, a statistical analysis of required drill hole spacing to achieve target classification thresholds, and a cost-benefit assessment to prioritize drilling effort against potential resource classification upgrades. In iron ore mining, infill resource drilling may involve hundreds of vertical holes on a regular grid pattern across large tabular BIF deposits. In diamond mining operations, reverse circulation (RC) or core drilling is used to intersect kimberlite pipes at depth, improving understanding of vertical grade variations. Gold operations use infill resource drilling to refine high-grade structural interpretations. The results of infill resource drilling are incorporated into updated geological models and resource estimates, which form the foundation for mine scheduling, production forecasting, and financial modeling.
