Tuesday, March 23, 2010

Bedrock Gold Recovery Tips: Processing Overburden



Tip 1: If the overburden covering a section of bedrock is fairly shallow, try processing it.

Let’s take a minute to redefine overburden for those newcomers to placer mining out there. Overburden layers are the various-sized stream (or drywash) gravel and rock layers covering existing bedrock (or “false” bedrock) in a given locale.

Gold Panning Kits
Metal Detectors

I would consider shallow overburden to be anything a solitary individual could shovel away or remove by hand methods without assistance or unreasonable effort. For me this means overburden running 3-4 feet in depth typically. But you need to understand right here and now that removing overburden of any depth by hand anywhere, anytime is a laborious and time-consuming effort.

First School of Thought

There are two schools of thought on just how to deal with overburden. The first says that you should consider the upper layers of overburden as “waste” and just remove them and dump them aside without processing them.

The overall idea here is to reach bedrock as quickly and as efficiently as possible since your best gold values will likely be found on and/or slightly above bedrock. Again, that bedrock can be true bedrock or, in some instances, “false” bedrock composed of clay or caliche ("desert cement").

Second School of Thought
The second school of thought on overburden is the one I tend to subscribe to. That is, if you have the time and the equipment (i.e., highbanker, sluice box, trommel, etc.) available, it may pay to process that shallow overburden as you dig your way down to bedrock.

If you are on the ball and working a likely gold deposition point, chances are gold values will be dispersed (to some degree or another) throughout those upper layers of gravel. In dry placer areas this gold dispersion in overburden gravels can become quite problematic at times (due to intermittent water flow) and will present itself in the form of highly erratic gold disposition tendencies.

Sampling as You Go

The idea here is to capture and recover any and all gold values that may be dispersed through those overburden layers as you work your way down to bedrock itself. Additionally, by running the overburden through your equipment you are, in a sense, continually “sampling” the material as you go.

By periodically clearing your equipment and examining the header box or riffles, you’ll be able to get an idea as to what sort of gold values are in the overburden and secondly, extrapolate a bit about how good (or bad) gold values may be once you’ve hit bedrock. Granted, in some isolated instances you may find that the overburden is barren…if so, you must make a decision as to whether you want to continue processing it or not.

Dredges are Automatic Overburden Processors

Finally, it should come as no surprise to you here that if you’re running a suction dredge underwater you’ll be processing any overburden automatically and that’s probably a good thing. Once again, if you’re a California placer miner you cannot use a suction dredge until the current moratorium prohibiting dredging ends or is overturned.

By the way, thanks “greenies,” avaricious Indian casino interests, spineless politicians, and various and sundry other whack jobs…way to go. All the same, if you’re a California miner keep smiling and don’t let the bastards grind ya down.

Treasure Hunting

Good luck out there.

If you liked this post, you may want to read: “The Miner as Dreamer: Musings on Being Born Too Late"

http://goldbedrockgold.blogspot.com/2010/03/miner-as-dreamer-musings-on-being-born.html

© J.R. 2010

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

2 comments:

  1. Hi JR
    Still visit your site - still enjoy and get so much out of it. Got to get another $5.00 donation in to keep it going since I have learned more here, than I have anywhere else. Getting the fever to go try a few weekends of panning in N. Ca if I can find a relatively easy location still open to the public that this ole gal can hike down to with a little gear to spend the day. Anyway PLEASE keep this site going, all the best.
    Lou
    Reno, NV

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  2. Thanks for the good words Lou! Nice to hear from you...no worries. Your previous donation is greatly appreciated and gives you a chance at winning one of the 3 Donation Drive raffle prizes on June 16, 2010. Keep safe out there and get lots of gold in the process. Best to you, J.R.

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