Drilling provides most of the information for the final evaluation of a prospect and will determine if the prospect is mineable. Prospecting and exploration is the first phase in the life cycle of a mine, followed by development, extraction and finally closure and reclamation. These activities, which often occur simultaneously, involve searching for mineral deposits using a variety of geological methods.
Drilling is used to search for mineral occurrences or clues in the rocks that may lead to mineral deposits. The information gathered during this stage may or may not lead to a discovery of valuable minerals. Drilling penetrates deep into the ground and brings up samples of whatever it finds at a specified depth. If there is any mineralization at given points far beneath the surface, drilling can give a straightforward answer and can quantify its presence at a particular depth.
There are two main methods of exploration drilling - core drilling and reverse circulation drilling (usually referred to as RC). Core drilling, yields a solid, cylinder shaped sample of the ground at an exact depth. Reverse circulation (RC) drilling, yields a crushed sample, comprising cuttings from a fairly well determined depth in the hole. Beyond that, the drill hole itself can provide a complementary amount of information, particularly by logging using devices to detect physical anomalies, similar to the geophysical surveys mentioned above.
To quantify the mineralization, and to define the shape, size and metal content of the deposit, a step by step procedure in exploration activities is required. Geologists examine the information at hand and then recommend whether further drilling is required or not.
In the majority of cases, mining will start with open-pit excavation, gradually turning into underground mining once the waste to ore ratio becomes too excessive.
While exploration has never been as challenging as it is today, advances in technology have meant that the most arduous and repetitive tasks of drilling can be confidently overcome – largely thanks to the rapid progress of advanced control systems and automation. Safety is always a priority too. Features such as guards, built-in interlocks and increased automation to eliminate dangerous tasks has lead to a significant increase in safety for operators.