Thursday, August 8, 2013

Interpreting Visual Prospecting Clues: a Dying Art? (Part 1)


As I've said before in Bedrock Dreams, I believe that gold prospecting is a dying art in the small-scale mining community. Moreover, many "weekender" type gold prospecting and mining enthusiasts don't even possess the most rudimentary ability to interpret the visual clues Mother Nature provides to the potential presence of gold and other precious metals.

This is in direct contrast to the old time prospectors and miners. I don't say this this as a put down or to humiliate or denigrate anyone...it's just a statement of fact. Additionally, I also understand that comparing the mining situation in past history to ours today is somewhat of an apples versus oranges thing. Yet, knowledge is knowledge, just the same.

Gold Concentrators

The old timers may not have been highly educated or able to fully understand the science of gold prospecting, but they did have the ability to "read" the terrain around them and pick up on the visual clues Ma Nature provided. In fact, some of the richest gold and silver discoveries in the American West were a result of this innate ability to interpret visual prospecting clues.

Visual Clues

With a tip of the hat to the old timers, there are any number of visual clues or tip offs that may lead you to precious metal. These include the following:

1) Sudden or abrupt changes in country rock

This sort of radical change in local geology is often a sign post to mineralization. As some of you already know, potential gold locales typically contain a prevalent or dominant host rock known in geology and mining circles as country rock. When the country rock drastically changes from one type or form into another, the specific boundary (or contact zone) where this change occurs often delineates significant geological change on a much broader scale, including possible precious metals mineralization.

This sort of country rock change or abrupt transition is most easily seen in desert or dry environments, but a sharp eye can discern its presence anywhere. The old timers may not have understood the science behind country rock shifts (geological contact zones), but they knew this could be an important visual clue to the presence of gold, copper, silver, and so on.

2) Sudden or abrupt changes in vegetation

Many aspiring gold prospectors and miners today have a hard time understanding this visual clue, although the physical principles involved are quite basic. The main thing to remember is that dramatic shifts in vegetation types in a localized area are not always the result of changes in altitude or the result of common environmental factors like rainfall, cold and heat, and the like. Sudden chemical changes in the soil itself can have a significant impact on vegetation, stunting or killing it, or denying purchase to weaker species of plants or trees while providing the same to hardier species. Where are these chemicals coming from that are impacting plant life so dramatically? Take a guess...

If you said sulfides or any other type of chemical reaction taking place in host rocks from the oxidation of irons, iron pyrites, or other constituents you are absolutely correct. So how do these chemicals adversely impact vegetation to the point that it becomes a visual clue to the possibility of precious metals mineralization.? Here's a simple test. Try soaking a bucket of rusty nails in water and then using that rusty water on a given plant. Next, use pure, untainted water on an identical plant. Would you expect to see differences between the two at some point? If we take this a step further the iron oxides in the tainted water might also prevent certain plants from growing while other, tougher species might fight their way through or even thrive.

 (There's gold in this area...could you find it?)

The old timers kept an eye out for just these sorts of vegetation changes, particularly if those changes were sudden or abrupt. Along with other visual clues these sorts of changes could mean that mineralized (and potentially gold-bearing) rock was leaching oxides or sulfides into the soil of the immediate area.

Art of "Visual" Prospecting

The old timers may not have been very "sophisticated" in the snobbish sense of the term, but one thing I can guarantee you is this: they weren't stupid people. Their ability to discern even slight amounts of precious metal over broad swaths of terrain was based partly on trial-and-error, a good deal on hard-won experience, and the rest on an intuitive understanding of just what Mother Nature was telling them through her visual clues.

This ability, this "art" that the old timers were able to use freely and effectively in the past is now on the decline. There are numerous reasons why this is so and I won't bother to go into them here. Hopefully, the art of "visual" prospecting won't be lost forever at some point as I often suspect it will be.

Believe it or not, you have a choice in the matter...

(c)  Jim Rocha (J.R.)  2013

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


14 comments:

  1. JR, now this is what I've been looking for! The books I have found, have whole chapters on useing a gold pan, but very little on just what to look for in the rock itself. Most tell you the inside bends of the river, and behind big rocks, but nothing on the actual rock itself. Your picture "could you find it", I would look in the bottom end of the "V", just right of center. Am I close????? I know very little about hard rock mining.....not a heck of a lot about placer mining either really! I've managed to find a little, but I know there is much more to find, and to learn. THANKS! Gary PS: What's on that guy's hat? It looks almost like a plastic rain cover, but the picture looks too old to be that.

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  2. Jim, You are so right! One of my worst habits is constantly watching the vegetation...and the geology of areas we were driving through. Don't get me wrong...I do it while prospecting as well...but driving through the Mojave areas of Palmdale, Lancaster, I constantly stop to investigate the rocky out cropings. If you told me the above photo was from that area....I would believe it! This makes the old lady mad...but she induldges my bad habits. (Prospecting)

    Since she has made out from my finds...she is now looking as well. Stopped many times near the San Andreas fault lines along the back roads...and have found mining remenants at many of those places.

    As for vegetation....your rusty nail example is a great one. Funny how some clues are seen from afar...and others up close. The problem in the Palmdale desert area is accurately estimating the distance to the geological formation. I have become much better now...but have hiked for miles....with the mistress (hope) in my pack...and found it was just to far. So....great info...and eye opening for those looking for other methods of location the precious metal we all love! Thanks again...be safe out there!

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  3. I don't know what's on that old timer's hat. I do know the photo is of an old time prospector in Arizona back in the day. Best, J.R.

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  4. My friend you and I are on the same wavelength! I too eyeball terrain all the time...looking for clues, changes in coloration, vegetation, rock formations...you name it. I'm at the point now where I can pretty much tell what's mineralized and what's not. But put me up next to an old timer who REALLY had prospecting down and I'd soon be put in my place! Best, J.R.

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  5. As for the pic of the terrain, I would say the brownish red areas may be where some gold is hiding, but just a guess since I have no knowledge of how to spot the visual hints. The area I live in has mountains galore with lots of dry washes. I have tested a few and some are loaded with black sand but no gold, others have fine gold. Have not found any nuggets yet. And sadly I wouldn`t know a gem in the raw if it bit me.

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    1. Well, at least you're checking the low laying areas for signs of color. That's a good start! Best, J.R.

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  6. So after inspecting that "old timer" photo....I think it was his "hooch" bottle. Did not want to break it. Would have to go back into civilization...to get another. Who knows?
    Maybe his mining map!

    My other thought....Lord knows what went to the grave with this old grizzled miner....both knowledge wise and "stash" wise. So much that's kept as a closely guarded secret...has been lost..or never passed on. So sad.....and frustrating. That's why working with the old "pards" could be a treasure trove....once they know and trust you for many years....they may share their knowledge "treasure".

    You know, as the body ages...our brain still thinks we are young...and could still do all those things we did in our younger days. Denial....still wishing to get back to that spot....who knows...but that mistress "HOPE".... fools us all..then and now! Wish more of those old timers were literate enough to write it down for future generations. Some left clues....possible topic for another day. Ask the Spanish...right? Thanks Jim!

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  7. These old timers were, quite often, literal vaults of valuable info. As far as treasures go, many small placer gold or gold ore caches were left behind by them and are still waiting to be found. As for the Spanish? Well, that's a whole different story! Best, J.R.

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  8. Great article JR. At the young age of 38 I'm still trying to learn the signs to watch out for on where to look for gold. Thanks!

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  9. You're most welcome...glad it helped! J.R.

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  10. soooo.... much , Hombre ! .... I'm headin' up-north to the Trinitys- pronto . / private land , probly not worked since 1940 /( + o - ) / ... so here we go > .... hada drink 'r -some this 'eve , coz I'm juglin' balls -in-the-ethos ina 7,000 mi. radius ,here , costa rica , alasksa,N.Y./ England ,Canaries , etc... + time to go 'quiet' ' n "digg-down" whilst tryin' to keep evereh-one 'con calma' .... wtf - gas ... >
    Thanx for all efforts & consistance .... manana en manana , gracias , Richard

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    1. Rich, I envy you heading for the Trinitys my man! Good gold up that way. You hang tough and get lots of gold. Thanks for the good words and don't let the bastards grind ya down! J.R.

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  11. J.R. would you haul a drywasher the first time up there or nugget shoot it first? My perception of the photo leads me to think it was taken from 300-400 yards away. Or is it 2-3 miles away? The right side of the mountains look like they were there before the stuff on the left side of the picture. I do see the faultline- intrusion area in the upper left. It looks like someone started prospecting right above that (upper left}. I'd check that first and if nothing is left I'd go lower some and start working towards the right. Sounds good doesn't it? Here's the real truth though- after being in awe of everything surrounding me, I'm from Kansas} I would start at the bottom where the gray colored path/washout looking area is. Question is which method should one start with? A metal detector or a drywasher.

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  12. To answer your question I'd dry a dry washer...a portable hand-crank or sampling dry washer. You could make your own small, back-pack variety "sampler" dry washer or have someone make one for you if you're not the best DIY guy (like me!). What you want to find is color, first and foremost. Nuggets and coarse pieces are not that common and a detector isn't going to do much good where very small gold is concerned. Once you're on to something, then you can try the "big guns!" Make sense? J.R.

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