Monday, April 18, 2016

Additional Thoughts on the Straight-Line Theory

In this post I'll be musing a bit about the straight-line theory of placer gold deposition. This is an oft-repeated theory in placer gold mining so I think it deserves a closer look. Read on to find out more.

Theoretical Concerns

The straight-line theory of placer deposition basically states that stream (or wash) borne gold will tend to follow straight lines as it's laid down by the stream flow. Additionally, the theory postulates that those straight lines will cross the stream's path back and forth, usually on inside bends or in other significant low-pressure hydraulic areas. I know from my suction dredging days (back in the 1980s, primarily) that this straight-line theory was fairly accurate for the most part, especially where pockets and paystreaks were concerned. But like any theory, the straight-line formula is based partly on science and experience, and partly on supposition. If theories were solid, concrete entities then they wouldn't be theories, right? So when you're dealing with theories in small-scale gold mining it's best to take things with a grain of salt. Sometimes they're proven out and other times they'll leave you standing there shaking your head in disappointment. Those are what are known as "theoretical concerns."

(You find decent gold in the bedrock at the lower left center. Trace a straight line from there to the bedrock at the inside bend at the upper left center of the photo. That's the straight-line theory in action.)

Part of the Game

You know, Ma Nature is very fickle in terms of how she dispenses her wealth. Sometimes she sides with the scientists and theorists out there but more often than not she'll throw a curve ball your way to see how well you hit a breaking pitch. It's all part of the game. I think it's a fine idea to approach your placer mining with the straight-line theory in mind because it does apply in many (if not most) wet placer situations. Again, I'll reach back in time to the heyday of my suction dredging days. When we (myself and my pards) hit something good we'd typically try to keep moving upstream along a straight line, repositioning the dredge along that line as we did so. This seemed to work well for us, for the most part. But looking back now with an additional 25-30 years of mining experience under my belt, I think we might have missed the boat in certain instances. Why do I say this? Simply because I know a hell of a lot more now about gold deposition than I did back then when I was barely out of my greenhorn stage. In those days I tended to place more emphasis on the science of gold deposition than I did the intangibles that are part and parcel of small-scale placer mining. So I guess what I'm saying here is that placing your faith strictly on the science of gold deposition may not always be your best move. Sometimes yes...sometimes no. Remaining flexible and adaptable in your mining endeavors is much more valuable in the long run than any theory ever postulated. Remember that.

 (I miss my days suction dredging. It's the best means for recovering gold from wet placers.)

Few and Far Between

Another thing to remember is that what happens in wet placer locations is not always going to happen in dry or desert placers. I honestly believe you can throw away the straight-line theory when your heart's set on working dry placer areas. Yes, there are exceptions, but trust me...they are few and far between. How do I know this? I spent the first few years of my small-scale mining career working dry or desert gold placers and continued to do so for many years after those early days, usually in the "off" season for wet placer mining. I won't be timid here. I'm damn good at dry placer mining and know just about all of the ins and outs of that particular endeavor. The problem with the straight-line theory in dry placers is very easy to grasp, even for the rawest mining recruit out there. Dry placer gold can follow the theoretical rules at times, but in the majority of instances in my dry placering experience the basic rules of hydrology and in particular, the straight-line theory, don't hold water (pun intended!). I'm being perfectly honest here, just so's you know. The intermittent water flow in dry placer areas and the intensity of that flow tend to make mockery of even the most data-driven scientific theories out there. Don't believe me? Get out there and see for yourself.

Never Accept Things at Face Value

I'm a very emotional guy on one end of the spectrum and on the other I'm very rational and analytical. The bulk of my working career has been in science and engineering, both of which emphasize math, logic, and data acquisition to support theoretical concerns. That said, I've always had a good inner "sense" or intuition, if you will. The straight-line deposition theory falls into the category of logic which is a good thing, as long as the theory is balanced out by your miner's nose. Getting my drift here? Never accept anything in small-scale gold mining at face value. That's the worst mistake any of you can make, especially you newcomers to mining and prospecting.

(We're all green at one point.)

Am I telling you to totally discount hydrological or depositional theories as you approach your small-scale mining activites? Of course not. In fact, I think that following the straight-line theory is a good starting point for finding and recovering placer gold in wet areas (and in certain dry areas). It gives you a solid framework to go at things and should be employed as a general rule. On the other hand, if you fail to recognize the straight-line theory's limitations, then you're liable to turn into a robot of sorts, slavishly following the rules of logic at the detriment of your gold-recovery potential. Balance, brothers and sisters. It's all about balance.

Be good to one another, OK?

(c) Jim Rocha (J.R.) 2016

Questions? E-mail me at


  1. Jim. your honest and open-minded thinking out-of-the-box is a fresh breath of air. Now I admit that I'm guilty of trying what others say won't work at times. Mostly I prove them right. LOL But, the straight line theory is only correct if specific conditions are met for a long period of time. One thing that can muddy the water (pardon the phrase) is flash flooding, especially in arroyos in the desert, where the water is usually not running except under flash flood conditions. That water isn't following the rules of a sluggish river that has the occasional spring flood. During a rapid flash, water might decide to jump out of the bed over a bank and spread out before returning to the bed again. Narrow sections of a river might be swept clean to the bedrock and then covered with sand or pebbles. There is no end the possible scenarios. It's true, we should not get hung up on theories.