(These old timers are just getting started.)
I apologize to one and all for the delay in posting. I had a bit of minor surgery done this past Wednesday and have been out of the loop for the past few days. Anyway, let's move forward and talk more about developing a small-scale lode mine.
There are four major physical factors governing how you'll approach developing your small-scale hard-rock venture. That is, once you've made the fateful decision to give things a go:
Again, we're assuming you're dealing with free-milling gold ore in this context. Some ore bodies and their carriers are decomposed or "friable," meaning they are fairly easy to break loose from their host rock and crush to extract the gold. Other others can be quite hard or compact and can be a bitch to deal with, to put things simply. Another aspect of this physical ore issue is whether or not the rock walls you're dealing with in terms of pitting or tunneling are strong enough to support themselves or require extensive shoring. The overall physical characteristics of your mine and the ore it contains will dictate (to a great degree, anyway) how you'll approach your mining activities and what sorts of specialized gear or equipment you'll need to get the gold out.
In some respects this is a no-brainer. The richer your gold ore the more your mining efforts and expenses are validated. Some gold ores can be very rich but not extensive in nature while others can contain low-to-moderate amounts of the yellow metal but be widespread in terms of area. Then again, you can have just about any mixture of these two poles. Richer ores provide the funds for faster development while poorer ores require a slow and steady approach over time. It's always been my personal viewpoint that any mining you do should be planned out well and done carefully, regardless of the ore values you're dealing with. I just don't think there's any value added to rushing around and pushing the limits, but sometimes greed rears its ugly head and folks get carried away.
(Ore values like this are ALWAYS a go.)
Gold veins rarely continue in length indefinitely. When they narrow down to nothing the old timers called this "pinching out." In an ideal situation, your main gold-producing vein would continue on for some distance before pinching out but ideal situations are a rare commodity in hard-rock gold mining (or mining in general). All this said, the length of a given vein is a prime factor that governs your mining approach as well as the overall economics of your small-scale efforts. There's no magic wand to wave that will tell you exactly how long a given vein is. You typically find out by following it as you dig, tunnel, or excavate. One thing is certain in this regard, however. The longer and richer the vein(s), the more worthwhile small-scale mine development becomes.
Width is coincidental with vein length. Mine development is tied to this factor as tightly as it is to the other characteristics already mentioned. Veins often fluctuate in length and width (as well as richness) so what you're looking to assess here is the average gold value you can expect to recover over a set distance (length and width). I've rarely seen large vein widths in small-scale lode mines myself. Some of the hard-rock miners I've known over the years were working veins that were quite narrow and some were so narrow I'd classify them as stringers, not veins. It really doesn't matter to most folks like us, though. Any gold is good and if we're getting it consistently from a narrow vein or stringer, then I suspect most of us would have a smile on our faces.
(Decent width here but what about length?)
This characteristic has caused more trouble and frustration for small-scale hard-rock gold miners than any other. Dip is the angle at which the gold-bearing vein moves upward or downward as Ma Nature has laid it out. Some dip angles can be quite severe with the vein plunging down steeply toward the earth's core below. Working a dip like this can be likened to digging straight down to excavate a water well. Other dips move upward slightly and some can go up and down like a roller coaster. Dips that are consistently moving at a slight angle in the same direction are the most reliable to work while those that rise and lower with no apparent rhyme or reason can drive a sane man or woman into a form of mining madness where you're ready to tear your hair out by the roots or toss all your gear into the back of your pick up and say "bye-bye" to the entire enterprise.
(The dip here is heading ever downward.)
Speaking plainly, most small-scale miners with little or no hard-rock mining experience are going to have great difficulty getting a solid line on these physical characteristics. Highly experienced lode miners, on the other hand, have seen this all before and often have a sixth sense when it comes to the value, length, width, and dip of the vein material they're working. Still, even the most experienced miners will struggle to get a handle on things in the beginning. One of the best ways to help yourself out in determining some of these physical factors is to do your research up front. Although each mine is different (has a unique "personality") other mine workings in the immediate area can tell you quite a bit about the nature of the veins you're tackling.The historical literature and production records of the area your mine is in will tell you a great deal and perhaps help simplify the physical characteristics of your own claim. Good research on the front end can save you a ton of time, effort, and yes...money when it comes to working your own diggings. So can a well-trained and highly schooled geologist, if you have one of those hanging around the house. Good information and data is key in this regard. Remember that, OK?
There's still more to come so stay tuned.
(c) Jim Rocha (J.R.) 2016
Questions? E-mail me at firstname.lastname@example.org