Saturday, April 2, 2016

Developing a Small-Scale Hard-Rock Mine (Part 6)

 (In hard-rock jargon, mine entrances are known as adits.)

Some small-scale lode mines can be developed with minimal cost if the gold ore is rich enough and you want to keep things as simple as possible without resorting to shoring or pillaring or other labor-intensive and costly approaches. But if you're following vein material underground it's a different story altogether.


The old timers used some pretty colorful adjectives to describe various aspects of their hard-rock (and placer) activities. "Gophering" was the term they used for mining out ledges, veins, and blow outs with a high gold content. Remember, just like you and I, most of the time the old timers were working as individual miners or small groups or "companies" ranging from two or three individuals to six or seven people. Additionally, they used the same sorts of hand tools and approaches that many of us are familiar with. They typically didn't have the financial or labor resources to develop a small mine by the book, nor do many of us I suspect. "Gophering" is not really a mining method or approach per se, but an attempt to mine stringers or veins of richer ore by digging or gouging out the ore in the simplest and most direct way possible. Much like the critter it's named for, "gophering" involved shallow digging over various areas of ground and rarely involved tunneling or sinking shafts. More often than not "gophering" was an above-ground effort to get at the richer parts of the gold carrier. "Gophering" was not a systematic mining development effort for the most simply went for the best gold in the quickest, and arguably, safest way possible. If extensive but lesser (in terms of richnesss) ore bodies were discovered as the "gophering" process went on, then the claim or mine could be sold to those entities possessing the financial resources to do so. Then they would do the hard and costly development while the discoverer(s) went on their merry way searching for another ore body to "gopher." In all honesty, most of us small-scale guys and gal would probably want to head in this direction all things considered equal. I know I'm a claustrophobic sort who wouldn't want to be tunneling or shafting deep underground unless I'd found the U.S. version of King Solomon's mines. Even then I'd be very wary. But hey, that's me. Perhaps some of you bolder types out there would have no qualms about working beneath the earth's surface. In any event, the thing to take away here about "gophering" is that it's best applied to richer, more uniform ore bodies where a limited, low-cost approach or application works best.

 (One form of "gophering." Notice that the quartz veins head straight down.)

Drifts, Stopes, and Raises

On the flip side, if you're dead (probably a poor choice of words) serious about developing a small-scale hard-rock mine and determined to go by the book, then the next push forward may be a little something called drifting. What's a drift? It's simply the channel or tunnel you dig to follow the ore body. Many old timers drifted on their stomachs or hands and knees in tunnels barely large or open enough to contain them. But this sort of approach makes a drift extremely hard to work and sometimes it's nearly impossible to get the ore out and to the surface. That's where stoping (stow-ping) comes in. A pure stoping approach is best used if the country or host rock containing the crystalline vein carrier is consolidated enough and strong enough to support itself without lots of additional shoring or pillaring. Stoping involves creating larger open areas at one or more ends of the stope to provide ventilation as well as access. These open areas are known as raises. In more-developed mines, the entire stope is "raised" from foot to ceiling providing easier access and greater ventilation potential. Needless to say, cutting stopes and raises is time consuming, labor-intensive work. So is drifting, for that matter. If you're having trouble visualizing the drift, stope, and raise concept try this approach: Imagine the drift as a very narrow length of PVC pipe. Right behind the drift is a bigger section of PVC pipe and right behind that is an even larger section of PVC if the stope is fully raised. Otherwise that second section of PVC might only be wider or larger (raised) in certain areas. I know this is crude, but it may help some of you understand the drift, stope, and raise sequence more easily. You first drift, then stope, and then raise a mining shaft or tunnel. A well-developed stope is necessary for laying ore cart track, lighting, ventilation, storage, and just about any other task you can imagine.

(Miner taking a break in a shored stope. The drift is ahead in the darkness.)

(A fairly well-developed stope with the drift ahead.)
Feel Free to Kick In

Some of the information I'm presenting to you about developing a small-scale lode mine is based on personal knowledge and experience, but I probably know less about it overall than some of you. So if you're expertise is in hard-rock mining, please feel free to kick in and share your knowledge and experience, and correct me if I'm in error on any aspect of this topic. I sure as hell don't know everything about this particular subject and I am always willing to learn more. All this said, I think we can all stand to learn more about every aspect of small-scale gold mining. After all, that's why we're here. We love gold!

There's more to come. Take care out there and keep smiling.

(c) Jim Rocha (J.R.) 2016

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