Exploring near a known deposit or an existing mine, where infrastructure already exists.
Exploration conducted near existing mines or known mineral deposits to find additional resources or extensions. Brownfield exploration has lower geological risk than greenfield work because the geological setting is already understood.
Ounces found beside a mill are worth more than ounces found in isolation, because they can be processed without new capital. This is why historic mining camps stay actively explored for decades after their original discovery.