Placer Gold and Bedrock Potholes: Much Ado About Nothing?
(A good example of rounded potholes on water-worn bedrock.)
The question whether bedrock potholes are viable gold producers has about as many answers as there are gold prospectors and miners out there. No, this question isn't earth-shattering in nature, but it's a topic that seems to rear its head again and again in the small-scale mining community. That being the case, I thought I'd give you my take on the subject.
Nature of the Beast
Although I'm doing my damnedest these days to be optimistic and an overall positive thinker, I tend to view bedrock potholes with suspicion when it comes to getting the gold. Most small-scale placer miners with a modicum of experience under their belts probably feel the same way. The issue at hand here is very basic: smooth water-worn bedrock is not as reliable a gold grabber as highly fractured or "bookshelf" bedrock and it's no small coincidence that bedrock potholes (those rounded, smoothed-out depressions we often find on bedrock surfaces) are invariably tied into bedrocks that are highly water-worn. So the general rule of thumb is that you shouldn't waste much, if any, of your field time cleaning out bedrock potholes for whatever small amount of placer gold they may (or may not) contain.
The reasoning here is that when flooding or strong water flows of one sort or another scour smooth, water-worn bedrock a goodly amount of the gold-bearing gravels on that bedrock get carried away, including the material found in shallow to medium-depth potholes that are part of bedrock configuration. Even deeper potholes can have most of the material they contain washed away in these sorts of situations. Experienced placer miners know this and in the majority of cases will bypass these sorts of potholes, no matter how jam-packed they are with river gravel. Old salts and sourdoughs might spend a bit more time and energy with dry wash depressions or potholes (yes, you can find these in certain dry placer locations) because of the intermittent nature of stream hydraulics in desert placer environments, but they usually aren't going to view those situations as their best gold-producing opportunities. It's just the nature of the beast, you see?
(The nature of some beasts shouldn't be messed with.)
Sure, when old material gets scoured out of water-worn bedrock potholes new gravels will often be dropped into place in that very same pothole. Sometimes (but not always) small amounts of placer gold or even a small nugget or two will be deposited in that mini-bank belonging to Ma Nature, but based on my own experience out there I wouldn't be holding my breath on that one if I were you. Interestingly enough, it's the novices or greenhorns out there who really get to salivating when they're stumbling along some bedrock-exposed stream with juicy looking potholes filled with mostly barren gravels. Hell, I used to do the same thing when I was a newbie. I'd clean those potholes out with a fine-tooth comb, screen that material into a five-gallon bucket, and then pan away like any other poor SOB thinking he was about to hit the "big one." The end result? Usually nothing to very little. That's the sad fact of the matter, truth be told.
Now that you novices out there are eagerly eating all this up and you crusty old veteran miners like me are nodding your heads sagely in agreement, I'm going to throw a big monkey wrench into the works here. I've found good gold and even nuggets tucked away in the bottom of water-worn bedrock potholes that were less than a foot in depth! Go figure, huh? A classic example of this took place for me in southwestern New Mexico some years back. From one small bedrock pothole lying a short distance away from a drop off I pulled two perfectly matched nuggets about the size of pencil erasers and boo-coo fines and flakes. There have been a few other instances during my checkered mining career when I've had similar experiences with bedrock potholes. But here's the clarifying point, so listen and listen well. In every one of the bedrock potholes where I found good gold I also found at least two of the following:
1) Gravels with varying sizes, shapes, and types including smooth rocks and pebbles mixed in with rougher, angular pieces of rock and gravel.
2) Bits of rusty (oxidized) iron such as old nails, bits of wire, lead weights, bullets, buckshot, or better yet...clumps of oxidized, fused iron (always check the latter for gold, by the way).
3) Moderate-to-large amounts of coarser black sands (forget potholes containing nothing but silt or blonde "blow" sands mixed in with the gravel).
These items in any combination are tip offs that something good may be hiding in that bedrock pothole.
(Would you bother with this? I wouldn't despite the presence of angular rock.)
Should you avoid bedrock potholes that don't fit the above description? Probably, because I'm telling you again that I've never come across anything good gold-wise where at least a couple of these descriptors weren't present. In fact, you'll probably be batting a thousand if all three are present in that pothole you're looking over. With this in mind, you newbies out there should be able to save yourselves some time and hassle by tempering your lust for bedrock potholes with these qualifiers in mind.
One Last Tip
Now sure as shit, after saying all this someone out there is going to come back at me with something along these lines: "Well J.R., just so you know, I pulled an ounce and a half out of one tiny pothole filled with gravel all the same size, no iron or lead, and filled to the brim with blow sand!" To add insult to injury they'll probably also add, "And this pothole was sitting on top of bedrock so slick you could use it for a water slide!" What the hell am I going to say to that, I ask you? Here's what I'm going to say. "Good for you." What that tells me is something I've suggested to each and every one of you all along here in Bedrock Dreams, and that is that Ma Nature doesn't always conform to hard and fast rules when it comes to where she drops her gold. Moreover, I'll bet you dollars to donuts that the bulk of the potholes you clean out that don't fit my profile are going to end up more barren than the Kalahari Desert in midsummer.
Here's one last tip for you about water-worn bedrock potholes. If (and it's a BIG "if") you ever come across a bedrock pothole ensconced underneath a large obstruction like a large rock or boulder, then you better take the time to check that puppy out. There's a good chance you might get some decent gold out of it (then again, who knows?). Do you know how many times I've come across a pothole situation like this in my three and half decades prospecting and mining? Zero. Nada. Not once. Never. But hey...it could happen and probably will to one of you (if it hasn't already).
Last but not least, an entire placer gold mining district was named after the bedrock potholes gold it once contained. Yep, I'm talking about the "Potholes" District near the Colorado River in southwestern Arizona and southeastern California. Long ago placer gold was carried along and deposited here in numerous bedrock potholes (thus the District's name) where it remained until the Spanish came on to the scene (with the Anglos hard on their heels) and started cleaning the gold out of those bedrock depressions. Oh, one last thing in this regard. The "Potholes" District is hard-core desert terrain with the Colorado River providing visual (and actual) relief to an otherwise arid region and you don't find gold in bedrock potholes there. You have to work for it!
Quite a topic isn't it? Bedrock potholes. It sort of reminds me of Shakespeare's comedic play, "Much Ado About Nothing." Then again, if you've learned something here maybe we can call this post "Much Ado About Something!"
Have fun out there.
(c) Jim Rocha (J.R.) 2015
Questions? E-mail me at firstname.lastname@example.org