Sculpin Knows!

Here's a piece from a link Sculpin posted a while ago.

Diamond drills:

Designed specifically for the resource exploration industry, diamond drilling is the most versatile of all drilling methods and the only method that generates core. A core sample is a cylindrical section rock – usually 10 to 15 centimetres in diameter – and generates reliable samples for accurate geochemical assaying along the depth of the drill hole.

Diamond drilling consists of a ring-like bit studded with small, industrial grade diamonds mounted to the end of hallow doubled-walled shaft. The bit rotates and cuts out a cylindrical core of rock, which is stored in the inner shaft of the drill rod, known as the core barrel. Water or mud is pumped down between the inner and outer rods to lubricate and cool the cutting surface, while sludge and rock chips comes up on the outside between the shaft and casing.

In optimum conditions, drilling can advance at a rate of 10m per hour, but in exceptionally hard ground the rate is far slower. Costs vary with the length of the hole, but on average holes up to 300m cost approximately $50 - $80 US per meter.