Geologists search for surface minerals through visual examination, whereas geophysicists identify underground mineral deposits by detecting rock alterations beneath the surface. Geochemistry is also used to analyze samples of soil, rock, and water. These methods are supplemented by aerial or satellite photography and combined with historical maps and literature to develop detailed maps of surface and underground rock formations.
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 on its way. If there is any mineralization at given points far beneath the surface, drilling can give a straightforward answer and can quantify its presence at that particular point.
There are two main methods of exploratory drilling. Core drilling, yields a solid cylinder shaped sample of the ground at an exact depth. Percussion drilling, or 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.
The core is an intact sample of the underground geology, which can be examined thoroughly by the geologist to determine the exact nature of the rock and any mineralization. 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. At every step of this procedure, the geologists examine the information at hand, to recommend continuing the exploration efforts or not.
The objective is to be fairly certain that the deposit is economically viable by providing detailed knowledge of the geology for a clear financial picture. Ore is an economic concept, defined as a concentration of minerals, which can be economically exploited and turned into a saleable product.
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 at deeper depths..
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.
Gone are the days when operators had to pay close attention to every aspect of drilling at every second of each shift, which often required immense physical and psychological stamina. Automation is now one of the reasons why exploration projects are perfectly viable at sites that are exposed to severe weather events and extreme temperatures.
In addition, automated functions play a critical role when it comes to living up to modern safety standards for operators on site and are also viewed as an important way of maximizing efficiency and the predictability of drilling performance.
More about RC drilling →
Exploration drilling requires drilling deep holes to locate reserves of energy and important minerals. This can be on-shore and off-shore.
By its very nature, mineral exploration involves drilling to discover what is below the surface. Drilling is used to obtain detailed information about rock types, mineral content, rock fabric and the relationship between the rock layers close to the surface and at depth.
The most important minerals are Iron ore, Silver, Gold, Cobalt, Bauxite, Lithium, Zinc and Potash.
Today, reverse circulation is the preferred method for initial exploration, ore body development and in-pit grade control. The technology has gained ground for its speed, efficiency and ability to provide accurate samples for evaluation by geologists. We, at Epiroc, continue to drive the development of new and improved technologies.
As competition gets tougher and tougher, it all comes down to the bottom line. Meaning; total cost vs productivity. To make the right operational decisions, you need all the information you can get.