Thursday, June 2, 2016

"The Heavies Drop Out First" (Conclusion)


 (This is the heavy we're all looking for.)

I'm going to wrap up this series on heavies in this post and make a few suggestions on how your new-found knowledge of stream and wash hydrology can help you find the gold. So venture inward and see what transpires.

By now most of you readers out there have gained a better understanding of heavies (including gold) deposition in wet and dry placers. You old timers and mining vets already know this stuff but one thing I've learned over time is that you can never know enough about small-scale gold mining. I may know a lot but I surely don't know everything and I'm constantly learning as I go. That same sort of intent on your part will, with time, give you the mining and gold recovery edge you're looking for. Never stop studying and learning. This is just as true in gold mining as it is in life in general.

Suggestion #1:Try Searching for Non-Gold Heavies First

Some of you are probably wondering what the hell I'm talking about here so let me explain. Nowadays when I'm out and about placer mining I forego my initial search for gold by focusing my efforts on finding heavies like oxidized iron or lead. This approach requires a good gold machine, however. I use my Gold Bug Pro gold detector in all iron mode with the small 5-inch double DD waterproof coil attached and it has proven quite effective in locating non-gold heavies which, in turn, have led me to the gold. This is especially true in the area (wet placer) I started working last year and which I will be returning to tomorrow (June 3rd) after having been stymied by the long winter and a wet, cold spring. Nearly all the gold in this location is quite small and a good part of it is undetectable even with the Gold Bug Pro (which is super-sensitive to very small gold, by the way). However, there's a lot of exposed or shallow bedrock available riddled with small troughs and crevices. Packed into many of these troughs and crevices are dirt, rocks, and heavies like lead and oxidized iron.

 (Yours truly using my Gold Bug Pro to flush out non-gold heavies.)

Oftentimes, a decent amount of fine gold and small flakes are snuggled into those crevices along with the lead and rusty metal. This is not true in every case but it is in most instances at this location. Last season my mining pard Ernie M. pulled a small but very nice nugget from one of these bedrock locations after I had swung my machine over a section of ground and told him to check things out. That nugget registered on the Gold Bug Pro but as I said, most of the gold at this spot is sparse, spotty, and very small. The idea here is to allow the non-gold heavies to lead you to the gold since you're more likely to find these things first than the yellow metal itself. I realize that there is an overlap between searching for placer gold and the incidental non-gold heavies that are often found with it. What I'm doing is not an exact science but it has paid off at the current location I'm working and at others in the past. However, if  the site you're working is littered with lots of big or coarse gold and you already know where that gold is, then you can forego my suggestion. However, I do believe this approach could help quite a few of you out there.

Suggestion #2: Examine Any Oxidized Concretions Carefully

It won't happen very often but once in a while you'll turn up an oxidized mass or concretion of ferrous metal infused with grit, dirt, black sand, and at times, placer gold. This is true in both wet and dry placers. If you come across something like this in your detecting, shoveling, sluicing, panning, or dry washing stop what you're doing and give that concretion a very close look. Better yet, break it up and then crush that rusty mass of iron odds and ends. Then carefully pan it out. You may be very surprised by what it contains. In my mining career (36+ years now) I've found placer fines, flakes, and even small nuggets in just such concretions or jumbled masses of oxidized iron. This won't happen in every case but it'll happen enough of the time to warrant the little bit of extra effort you'll expend checking things out.


 (I know I keep going back to this photo again and again but it tells the oxidized clump or concretion story the best.)

Suggestion #3: Keep Your Eyes Open for Unnatural Oxide Staining 

OK, what's the difference between natural and unnatural oxide staining? The first is a result of natural geological forces or chemical reactions in host or country rock...iron-stained quartz for example. Any significant amount of natural oxidation should always be given a closer look, but what I'm talking about here is keying your eyes to the presence of man-made or unnatural iron staining (oxidation). Any localized areas of oxidized ferrous metal leaching out and discoloring the surrounding rock and gravel are blinking neon lights that you should investigate thoroughly at each and every opportunity in which they arise. Where those ferrous heavies exist, so may gold. Got that? Good. Now don't expect to come across wide swaths of ground stained rusty red or orange. In most cases this sort of unnatural staining will be highly localized and often only a few inches in length or diameter. Many bedrock crevices I've come across over the years have displayed this sort of unnatural staining. Right away I zoom in on those visual clues. Why? Because oxidation is occurring in that crevice due to the chemical breakdown of man-made ferrous heavies that tend to end up close to or with gold. It's simple logic and nothing mysterious or fancy. I've also found highly localized areas of unnatural iron staining in bench gravels as well. Those are also worth your prospecting efforts.

 (Natural or unnatural staining?)

Suggestion #4: Make Sure it's Lead and Not Gold 

Another heavy frequently found with placer gold is lead in the form of buckshot, expended bullets, fishing weights of all sizes and shapes, and a wide assortment of flattened or twisted pieces. Most lead that shows up in your test pans or sluice boxes is exactly that, but you better make damn sure that's what it is and not the yellow precious metal masquerading as something else. Let me give you an example. I had a dredging pard ("Johnnie") very briefly back in the 1980s who wasn't very well-versed in all things mining. He was an eager student but still green around the gills. But Johnnie was a good guy who pulled his weight and I needed the help (dredging underwater is a no-no for a solitary individual if you're truly safety conscious).

One day during a break in dredging activities Johnnie and I decided to do a bit of crevicing nearby just for shits and giggles. Crevicing was good in that location and small nuggets were fairly common recoveries there in bedrock cracks and behind larger obstructions. I always found crevicing like this a relaxing break compared to running a suction dredge all day long. Anyhoo, I ambled over to where Johnnie was crevicing away on exposed bedrock and asked how he was doing. "Shitty," he replied. "All I'm getting are big, flat pieces of lead and flour gold...maybe a small flake or two once in a while." I peered over his shoulder to see what he was talking about and sure enough there was some lead shot in his pan along with lots of coarse black sand but what caught my eye were some larger pieces of gray material resting in the bottom of the pan. "Let me see that," I said. Right away I knew those larger grey "lead" pieces in Johnnie's gold pan weren't lead at all but mercury covered gold. How did I know this? Through experience and the fact that the section of the North Yuba we were working had a decent amount of mercury left in it from the old mining days. I looked up at Johnnie. "That's gold coated in mercury bro'." I told him. "Really?" he asked with a pained expression etching his face "Yep," I replied. "Aw shit!" he exclaimed. "I been throwing all that away!" Back at our campsite I got a ceramic bowl and had Johnnie watch as those pieces turned bright yellow after I dropped nitric acid on them. (By the way if you use nitric to burn off mercury make sure to do so in a well-ventilated location or better yet...in the outside air. The fumes are toxic, don't ya know? Also, NEVER try to burn off mercury in a metal gold pan! If you're wondering why see my return comments to "Muskrat" in the comments section at the end of this post.)

(Pan containing pieces of mercury coated placer gold.)

So the moral of this little story? Know what the hell you have in that pan of yours. Especially in  areas where mercury was used to amalgamate fine placer gold. Also be aware of the fact that under conditions of heavy iron oxidation (natural or unnatural), placer gold can assume a thin coating of oxidation itself and appear to the untrained eye to be bits and pieces of rust-colored metal. This happens more frequently in dry placers than wet, but I've seen it rear it's head in both types of environments more times than I care to count.

There it is my friends...

(P.S. Johnnie, if you're still out there I hope all is well. You weren't much of a miner but you were a damn good guy!)

(c) Jim Rocha (J.R.) 2016
  
Questions? E-mail me at jr872vt90@yahoo.com

3 comments:

  1. JR, OK, now you have me stumped! "Never try to burn of mercury in a metal gold pan". That's how I've been doing it, with a a half potato hollowed out over the gold coated mercury. Propane torch under the pan....why is this bad? I know the fumes are very toxic and stand upwind from them.
    Nitric acid....where do I get that? What is the advantage to the acid versus heating it under a potato?
    Downstream from my best spot, a few years back, we were finding what looked like copper shavings. Well, it wasn't gold so we threw them back. Now, after learning more, I think it was "rose gold"....gold with a high percentage of copper mixed into it. Live and learn I guess.....

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  2. Gary, chromium, aluminum, and iron can be readily dissolved by concentrated nitric acid so it's typically not a good move if the acid hits the bottom of a metal pan. However, I doubt if a few drops of nitric will cause much reaction. However, to play it safe I wouldn't suggest doing it. Be careful with the potato routine...cyanide fumes can be given off so you want that out in the open when you do it. Also, don't do like some of the old timers and fry or boil the potato to eat after! Some died this way.

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  3. OK, thanks. I've only done this a few times, but the potato go's either into my burn barrel or under a big rock afterwards so nothing eats it. I misunderstood when you said "burn off in a metal gold pan". I thought you meant burn as in heat, not burn with acid. Anyway, makes sense now! Thanks.

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