The first stage involves locating prospective deposits. To do this geologists use their knowledge of ore genesis and occurrence. Geologic environments that are associated with the wanted type of mineral deposit are target of investigation. Methods such as geological surface mapping and sampling, geophysical measurements and geochemical analysis is often applied at an early stage to pin out potential deposits. After a deposit has been located, the next stage is to map the deposit in more detail to evaluate grade and tonnage of the mineral occurrence. The deposit is then drilled to investigate and sample the mineralization in depth. The density of the drilling is determined by the wanted level of geologic confidence and project economics.