diamond drilling history
Early diamond drilling opened up many new locations for mineral mining, and was associated with a boom in mineral exploration in remote places. Before the invention of the portable diamond drill, most mineral prospecting was limited to discovering outcrops at the surface and hand digging.
Exploration diamond drilling differs from other geological drilling (see Drilling rig) in that a solid core is extracted from depth, for examination around the surface. The true secret technologies of the diamond drill is the real diamond bit itself. It’s composed of industrial diamonds set into a soft metallic matrix. As shown within the figure, the diamonds are scattered throughout the matrix, and also the action relies on the matrix to gradually wear throughout the drilling, so as to expose more diamonds. The bit is mounted onto a drill stem, that is linked to a rotary drill. H2o is injected into the drill pipe, so as to wash out the rock cuttings produced by the bit. An actual diamond bit is really a complicated affair, generally created for a specific rock type, with numerous channels for washing.
The drill makes use of a diamond encrusted drill bit (pictured around the right) to drill through the rock. The drill produces a “core” which is photographed and split longitudinally. Half with the split core is assayed whilst the other fifty percent is permanently stored for future use and re-assaying if essential. Although a larger diameter core will be the most favored it is the most costly. Probably the most common diameter dimensions of core are NQ and CHD 76.
 Core extraction
Extraction of core using triple-tube
Simply advancing the drill by rotary action (and washing) leads to a core to become extracted within the barrel as shown. However, at a depth of maybe 300 m, there should be a way to retrieve the core and take it to the surface. Continuously withdrawing the entire heavy drill pipe is impractical, so methods were developed to pull up the core inside the barrel. If the rock would usually be solid granite, and the core would usually break at the drill bit, then it would be a simple matter to stop the drilling, and decrease a straightforward grabbing gadget by a wire and pull up the core. Regrettably, numerous programs require an undisturbed core in fractured rock, which calls for elaborate wire-line devices.