Drilling

If the grab sample gave interesting results, a drilling program must be planed in order to have a better knowledge on the deposit. The drilling program can involve one or more types of drilling, conditioned by the material to be sampled, rock environment, and the reason of the sampling. Basically, there are two types of drilling, one involves core drilling and the other one is reversed circulation.

The core drilling is employed for most the mining companies. The main disadvantages are the cost and the time required to complete the programs, however the information to be obtained is excellent. Essentially, provides accurate samples of a mineral deposit, the rock types, mineral types, and rock structures. By employing this method, the core is removed from the hole. There are some variations of this technique than improve the time required to extract the core. This greatly accelerates the drilling process and improves core recovery. However, it yields a smaller diameter core. Some drilling techniques often produce poor core recovery, but with improved core barrels, a good design, the total core recovery can be improved. Disadvantages of diamond core drilling are its high cost, small size of sample and slow penetration rate. Bulk sampling for metallurgical testing or placer deposit testing are generally obtained by the drilling of large diameter holes (plus 6-inches in diameter), or by sinking winzes.

                                                                                           It necessary to get the right material according to hole to be drilled

During the drilling program the core has to be stored and extracted for geological and metallurgical purposes, which reduces cost and time. There are five main sizes of diamond core employed for mining projects,

The cost is influenced by rock type, terrain conditions, environmental conditions, and time required to complete the program. The time depends on ore body size, diamond core diameter required, geology department and the previous information obtained at the beginning of the project. For instance, if the objective is to have complete information on mineralization and perform metallurgical tests (e.g. comminution, concentration, leaching), the time required is around eight weeks. Obviously, there are several activities involved such as mobilisation of the drill team on site, drilling, geological mapping, core splitting, core logging, and core packing. Finally, the samples are delivered to different laboratories.

Performing a drilling program