On Dry Washers, Desert Gold, and Working Dry Ground (Part 8)
(This old timer wasn't screwing around.)
I hope I'm not beating a dead horse by continuing on at length with this series, but your votes in the poll at the left indicate you'd rather have the info regardless. So here we go...
8) Keep that gold-bearing material dry: As you readily know by now, operating a dry washer at peak efficiency means the gold-bearing (auriferous) material you run through that "puffer" or electrostatic unit has to be completely dry. If by some weird sense of fate the planets align themselves perfectly and you find yourself in a dry or desert placer location where the dirt is always drier than a bone and no clumping is evident, consider yourself blessed. If, on the other hand, moisture is present in that material you need to hold up a minute pard. Try staking out a tarp in the direct sunlight and then shoveling that gold-bearing material onto it like the old timers used to do. Spread the material out evenly across the tarp using your shovel, or better yet...the tine-free or upper end of a sturdy metal rake. Let the desert sun do its thing for a bit and voila! You'll have dry material ready to run through your dry washer.
I've seen a few miners (novices and otherwise) over the years who would cover their still-to-be-processed material at the end of the day with a tarp...I assume to protect it from overnight moisture (??) or from blowing away in high-wind events. This approach is a two-edged sword of sorts and a judgment call on your part. I can tell you this...I've never done this and here's why. Once the sun's up in the desert things can get hot very quickly. By the time you finish your coffee and breakfast and amble on over to start work for the day you'll find that tarp you left on overnight has generated "dew" on its inside surfaces and has dampened that material you piled up or spread the day before. This is especially true if you use a plastic tarp. Now this isn't a major issue, but it is something I thought I'd throw out there for you to digest just the same.
9) Screen or classify your material before running it: Most dry washers are pretty sturdy little pieces of gear and can take quite a bit of punishment out in the field. However, they're not invincible so don't treat them as such, especially that "puffer" you carefully and lovingly designed and constructed out of wood. You want to screen or classify your auriferous material before running it for two reasons: 1) to increase feed efficiency and 2) to avoid damaging your unit. How large or how small you want to classify your feed material down to is up to you...I typically screen down to around one half or one quarter inch or so. Either way, shoveling large and often sharply angular desert rocks directly onto your hopper screen is one sure way to damage (gouge or splinter) the wooden frame of your "puffer" or dent up that model manufactured from lightweight metal or aluminum.
(Classifiers can be your best buddy in dry placer mining.)
I know it's tempting to set your dry washer up right next to where you're digging and then shoveling unclassified material directly onto the hopper screen (hell, I've done it myself on occasion) but I don't recommend you make a habit of this approach. One last thing in this regard...I wouldn't worry too much about multi-ounce gold nuggets getting tossed away along with the detritus from classifying or via your hopper screen. Anything's possible, but nuggets are few and far between in most dry washing venues if the truth be told. However, if you're a bit paranoid about these sorts of things you can sit on a 5-gallon bucket and spend a little time sorting through your large tailings or flatten them out and take your metal detector and make periodic passes over them to make sure nothing BIG has escaped the preliminary screening.
10) If it ain't happening down low, go higher up: Due to its inherent weight, density, and specific gravity, gold will always move downward as long as there are sufficient natural forces (rain, erosion, snow, etc.) present to create this cause and effect pattern. However, dry placers tend to throw a monkey wrench into this nice, neat package because the environmental factors that are so consistent in helping gold move downward and accumulate in paystreaks and pockets in wet placers are, at best, intermittent in desert or dry gold regions and often come in the form of heavy thunderstorm rains and flash flooding. The upshot? Desert placer gold tends to be intermittent and spotty (what I call "hit or miss" mining) and often remains entrained in place until it is forced to move onward and downward again.
So here's my tip of the day for you: If gold is scarce in the usual "suspect" spots down low in those washes and gullies, start moving upward to sample. Go from the wash bottom to any bench gravels, from bench gravels to any terraces, from terraces to hillsides, and so on. That gold you so desperately seek may be hiding higher up...not down low as you were always taught "by the book." This is the essential difference between wet and dry placers and although certain consistencies do apply between the two, more often than not there are enough essential dissimilarities between wet and dry gold deposition to force you to think outside the usual box.
I saw a 1/4-1/3 quarter troy ounce nugget plus a bunch of smaller ones turn up this way in one desert location because an astute miner decided to try higher up along an adjoining hillside and ended up finding a nice elluvial deposit. This doesn't mean that's going to happen every time, but if you're getting skunked down below why not give it a try? It's worked for me in a number of dry placer locations over the years. Also, keep an eye out for visual clues from the old timers like test pits or tailings on terraces, slopes, and hillsides.
Hang tough out there.
(c) Jim Rocha (J.R.) 2013
Questions? E-mail me at firstname.lastname@example.org