Orebody delineation drilling is a specialized drilling program conducted to accurately define the boundaries, geometry, and grade distribution of a mineral deposit after its initial discovery. The primary purpose of this drilling phase is to collect detailed geological and assay information that confirms the extent and continuity of mineralization, enabling more accurate resource estimation and mine planning.
In mining projects, delineation drilling typically follows exploration drilling. Exploration drilling identifies the presence of mineralization, while delineation drilling uses closer-spaced drill holes to provide higher-resolution information. Depending on the deposit type, methods may include reverse circulation (RC), diamond core drilling, auger drilling, or air-core drilling. In bauxite mining, closely spaced auger drilling is commonly used to define ore thickness and quality. Gold and iron ore projects often rely on diamond drilling to obtain detailed geological information, while diamond exploration uses drilling to characterize kimberlite bodies and ore grades.
Data collected from delineation drilling include lithology, mineral content, structural characteristics, ore thickness, and laboratory assay results. These data are integrated into geological models to calculate mineral resources and reserves. Accurate delineation drilling reduces geological uncertainty, supports investment decisions, and helps optimize mine layouts. It also assists in identifying variations in ore quality that may affect processing performance. Because mining projects involve substantial capital investment, orebody delineation drilling plays a crucial role in ensuring that mine development is based on reliable geological information and realistic economic assumptions.