The core purpose of carrying out sample drilling is to get furnished with information with which you can estimate the quantity and grade of ore. Nonetheless, the accuracy of the estimates will largely depend on the care taken when obtaining the samples, the judgment on sample intervals, and assaying accuracy. Nevertheless, quality sample drilling has to be carried out with expertise and excellent judgment, and above all, using viable techniques. Here is an overview of the the standard methods employed in procuring quality samples from prospective sites.
1. Churn Drilling
Churn drilling involves the use of cable or ropes to raise the drill which is allowed to pulverize the rock after several blows. The stone cutting from each unit length of a hole is brought to the surface and constitutes the sample of the rock formation at the corresponding depth. The cuttings are examined regularly, often using the panning method to separate the minerals. Moreover, samples are taken in intervals, and special care is taken to prevent contamination. Churn drilling samples are used in various mining sites to estimate the grade and tonnage of ore before the actual mining process.
2. Core Drilling
The dominant type of core drilling technique used in sampling is diamond drilling. Diamond drilling involves the use of carbons as the cutting media. Besides cutting through hard rocks, diamond mining can be carried out at any angle, whether vertically or horizontally. Drilling mud is circulated down the drilling rods to cool the cutting bits and help in raising the rock cuttings to the surface. Before drilling out a sample, you must ensure that the hole is clear of cuttings. Reliable assaying of diamond drilling samples requires an ore to be reasonably uniform in grade, which leads to high core recovery and equal core diameters.
3. Use of Hammer Drills
The employment of hammer drills to obtain samples is gradually gaining popularity. The technique creates short holes and is used where the ground conditions disqualify the use of diamond drilling. Additionally, you can drill at any angles utilizing a hammer drill. The conventional practice in this technique is to obtain a separate sample for each change in ore or formation. You must take proper care when collecting the cuttings to enhance the reliability of the assaying. Conventionally, the samples are trapped in a canvas bag attached to the collar of the hole with the drill steel passing through an opening in the bag’s side.
Sampling help surveyors and geologists to determine the grade and the tonnage of an ore in a potential mining site. Quality sample drilling involves the use of appropriate techniques as well as taking extra care when collecting samples. Additionally, different drilling techniques are used to obtain the samples, and they include core drilling, churn drilling, and hammer drilling.
