The type of drilling they are doing is not the elaborate type one might think. It is nothing like core drilling which can drill very deep holes depending on the size of the core drill. It is small-scale drilling using a jackleg drill with 4 foot sectional drill steel. It is messy and unpleasant work. Miners call it “long-holing” and consider it kind-of a hassle relative to normal jackleg drilling for blasting or bolting. It is basically probing for a target.
If I were drilling for a channel target the scenario would be like this:
Geologist would paint some holes in the “back” (ceiling) where he wants the holes drilled.
Set-up drill, air and water hoses. The upward drilling would be at a slight angle usually about 55-70 degrees. Long hole steels for jacklegs usually use button bits approx. 1-3/4 to 2 inches diameter. I would start by drilling one short hole at an angle a few degrees off from the main hole. Then I would start the main probe hole, intersecting the short hole at about a foot or so into the rock. The first short hole will then act as a “spout” to collect the cuttings. In this spout hole I usually install what is called a “Mickey”, or a short 12 inch hollow rock-bolt. This acts as a liner for the hole, and the flange of the Mickey is used to tie on sample bags.
Assuming we are drilling in slate bedrock all the way, and say for example the target channel is believed to be 50 feet above the tunnel, I would probably not collect samples for the first 20 to thirty feet. After that depth, I may begin tying bags to the Mickey spout and then continue the drilling, screwing on another drill steel every 4 feet, and adding grease to each coupler to aid in disconnecting when pulling back out. I would be drilling by “feel”, that is a driller can feel the different resistance of different rock and mineral structures. After drilling a few feet, both myself and my helper are now covered in slate black drill spray water/gunk as we are standing under the drill hole. As each sample bag is filled, we remove it, tie it closed and mark it with the depth, such as from “32’ to 35’.” The drill string becomes progressively heavier as we add drill steels. Each time we remove the drill string from the drill-chuck, we grab the drill steel with a large pipe wrench and may support the pipe wrench on a ladder wrung or something similar as we add another steel, since the weight is almost becoming unbearable.
I have drilled for channels and lode deposits this way many times. In channel exploration, it usually provides only limited success. Let’ say for this example that there actually is a channel near the 50 foot mark. I would notice a sudden change in the feel of the drill and the resistance would usually change. The drill may suddenly surge up faster as the channel matrix is softer than the slate bedrock. If I happen to hit a large boulder of quartz though, the drill would indicate more resistance since quartz is very hard. Whatever we hit, my hand would be on the drill handle, and as soon as I feel a break-through into a different type of rock, I would quickly stop the drill, then resume, as I don’t want the sudden change at the contact to cause the steel to “hang”, or get stuck. Hanging the steels can happen often in this type of rock when you hit a clay seam or break into a channel. It takes some effort to “unstick” a hung drill-string, and once in a while you may even lose all or part of the drill steels. I would note the depth of any perceived break-through. If I break into a channel, I would try to drill into it a couple feet to confirm it may be a channel, though drilling in the actual channel becomes difficult since there are rocks, boulders, and matrix of different densities that tend to grab the drill bit.
This is not going to be an easy “just punch a bunch of holes” into a channel proposition. The drilling will probably interfere with the moving of material from the Black Channel Raise, as the drilling may be blocking the haulage drift. Many of the targets are probably out of range, for a jackleg, and there will be other difficulties I don’t have time to explain now, as I am out-the-door for the day. Not sure, but I think I may have explained some aspects of this in previous posts a few months ago. GLTA
PS - If the drilling program is critical, and you're drilling relatively short holes then the geologist is usually there supervising the entire process, otherwise he will just look at the cuttings in the sample bags, paying close attention to, and panning the sample from the point of channel contact. Usually gold won't be found, as the diameter of the hole is too small for a very indicative sample.
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