Monday, March 4, 2013

Gold Sampling: a 3-Phase Plan of Attack (Part 5)

(Trust me, the "Chicken Little" approach doesn't work well.)

As you can tell, I'm pretty much a believer in sampling first, then mining for gold after. This is true no matter the scale of mining and regardless whether you're a lode (hard-rock) gold miner or, like me, a placer miner first and foremost.

PHASE II: SAMPLING (continued)

There are any number of gold (or mineral/metal) sampling approaches. Drilling is one of those:

Drilling: This approach is both underestimated and under appreciated by many small-scale miners and no small amount of larger-scale commercial mining operations (including a few of those TV reality "star" types). Granted, drilling can be expensive at times and is not for everyone, but it can be one of the most effective ways to determine what lays beneath your feet in dry placers and gold-bearing gravels like benches or old stream gravels where running water isn't an issue.

Motorized drilling rigs are much like those used for drilling wells. Sections of pipe (often combined with high-pressure water or solutions) are used to penetrate layers of overburden or gold-bearing gravels all the way to bedrock. Samples can be analyzed at any given level or layer to determine the gold values present. Once a spot has been tested or sampled, the rig can be moved to a new spot or location and the process begins anew. Needless to say, this sort of drilling/sampling is most often used in commercial operations due to the costs involved.

Getting a Line on Gold Values Present

I've seen a few occasions where small-scale placer miners have used the drilling approach with hand tools like gas-powered augers. This approach seems to work best where the gravels are loosely consolidated and not bound or locked up tightly. Hand drilling like this won't get you to depth nor will it work well in many mining contexts, but it does enable a small-scale miner to "see" underground to some extent and to get a line on the gold values present.

Yes, there are occasions where drilling rigs are mounted on floats or barges to sample underwater, but you won't see that here in the United States much, if at all. In gold-bearing locations in Africa, Asia, and South America this sort of approach has been used in the past and is probably still being used on occasion.

Core sampling is a form of drilling for samples that's widely used in many commercial lode gold operations (and some placers as well). Again, the expense associated with this sort of sampling typically exceeds the cash flow most of us little guys and gals operate with the majority of the time, so it's probably not going to apply to most of us. Just thought I'd mention it.

Be Systematic, Be Logical

Let me stress this point again: it really doesn't matter what sort of sampling approach you decide to take as long as you approach your sampling in a consistent and logical fashion. The more samples that are taken over a larger area at various depths per location equals better "data" in terms of gold values present, including the width and depth of potential paystreaks.

 (Visible gold in a lode gold sample.)

In other words, be systematic and logical in all your sampling efforts and make absolutely certain that your samples are numbered and recorded for future reference. If you can't remember where you took your samples then how do you expect to know where the gold is? In this case you just wasted the time (and money?) spent on your sampling efforts for the most part and are right back at first base using the "Chicken Little" approach again.

In my next post I'll start out by discussing trenching. Until then, be safe and keep the faith.

If you liked this post, you may want to read: "Failing to Sample: the Biggest Mistake in Gold Mining"

(c)  Jim Rocha (J.R.)  2013

Questions? E-mail me at jr872vt90@yahoo.com

2 comments:

  1. I know this is really general and hard to answer, but for a guy with a shovel and stream sluice digging in random (but likely) places in the stream bed, how deep do I need to go? I usualy dig at least knee deep, and then move to anouther spot. Tearing down the sluice to check samples is slow, I might only get two or three a day. Is there a better,quicker way? Thanks JR, Gary

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  2. Test panning is probably the quickest means. Samples should always be taken in a systematic way and recorded or noted..location and colors per pan. Best, J.R.

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