Thursday, November 21, 2013

A Short Course on Hard Rock Gold (Part 6)


Since I didn't cover "strike" or "dip" earlier, let me do so now. The first refers to the compass direction a gold-bearing vein or ledge travels in along its length and the second term refers to the angle of a vein as it declines. Now let's move on to mine development functions and concepts.

Mine Development Functions

There are some basic mine development functions that should be addressed in small-scale hard rock operations:

Exposing areas of minable gold. This may sound like a no brainer but your first order of operations is to expose as much as you can of any and all gold-bearing material or ore. The rule of thumb here is simply, "You can't mine it if it's not exposed and accessible." Ideally, you want to expose your high-grade material first but veins and ore bodies tend to vary considerably in richness, even within a few feet at times. My advice here is this: you wouldn't be developing a hard rock venture if there wasn't something there to begin with. You're not a multi-million dollar mining operation but a guy or gal (or a small group) swinging picks and shovels or maybe using pneumatic drilling tools. Go for getting as much gold-bearing material as you can safely and efficiently and let the the gold average out later in terms of total value. Once again, it's all about how much material you move...rich or not so rich.

Opening up access. To get at that hard rock gold of yours, access is a fundamental premise that you'll have to consider. Often in small-scale vein or lode operations, opening an access point (or points) can be a very crude affair. Most, if not all, the work done is by hand at great physical effort and without the benefit of fancy machinery that makes everything systematic and "pretty." You really shouldn't care about how nice and neat things are but should focus instead on laying out and digging pits, portals, tunnels, and shafts that best serve your main purpose, getting the gold out. This access should also allow you to easily move yourself, your gear, supplies, or fellow miners around and through the workings. That's the ideal image you should have your mind, anyway. Most of the small-scale hard rock operations I've seen or been peripherally involved with dealt with this aspect in pretty much a hit or miss fashion.

 (The vein material here in Greenland's first hard rock gold mine shows very little dip.)

Movement of air. In many instances, you don't have to burrow very far underground or into the side of a hill or mountain before the air starts going bad on you. I'm no safety engineer but I can tell you right here and now THIS IS A POTENTIALLY LIFE THREATENING MINE DEVELOPMENT FUNCTION. Every hard rock mine is different and some require more immediate attention in this regard than others, but sooner or later (hopefully sooner) you'll need to deal with it. Back in the day the old timers used candles and canaries as a means of determining when the air was too foul or dangerous to work in. Thankfully, these days there are any number of reasonably priced air monitors or "sniffers" that are much more reliable and accurate for reading air quality.

Putting it bluntly, without good air to work in you and your pards are gambling your very lives to get at that hard rock gold. So listen up. It ain't worth it brothers and sisters. Dying for gold makes no sense whatsoever (although I know many people do it just the same). Make sure you establish a main flow-through ventilation system beefed up by auxiliary air flow raises, channels or ducting, fans, and/or whatever else gets the job done. A  well thought out and properly configured hard rock mine air system will also provide a certain amount of cooling...something that'll prove very useful the farther down you dig and begin knocking on the devil's door.

(There's some coarse gold in this vein material.)

Water drainage.  Unless your hard rock vein is striking consistently north, west, south, or east minus any downward dipping at all, sooner or later you'll be faced with a water problem as you dig deeper underground. We're not talking water shortage here either. Constantly dripping walls and faces are quite common in small-scale hard rock mining operations and so is water beneath you. It doesn't take very long at all for some shafts and tunnels to start flooding so an efficient pumping system will be necessary unless you want your workings flooded out. Now don't get me wrong here...groundwater is not a problem in EVERY hard rock mine but typically it is in most. This is a small-scale mine development problem you'll have to address at some point if you're serious about being a hard rock miner.

Amazing how complex hard rock mining can be, isn't it? And we've just scratched the surface here...

(c) Jim Rocha (J.R.) 2013

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

2 comments:

  1. JR, the term "dip" makes perfect sense, but where did the term "strike" come from? Seems like "streak" or "run" would make more sense. There is a mine here above my house that is boarded up, half full of water. It still has the iron tracks in it and looks to go in quite a ways. There is no way I would try to go in there, but I wish I could know how far it go's. It is also a timbered mine....I don't like those much. If there are no timbers,and no water, I might go in, but not this one! I have traps up that way I need to check tomorrow, I'll take a picture and send it to you if I remember. Thanks, Gary

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  2. Gary I think the term "strike" came from the old timers because a common expression of the day for heading a certain direction was "striking off." I'm only assuming here though. By all means, send a pic or two of that old mine. Best, J.R.

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