Tips on "Seeing" Where the Gold Is (Part 6)
(A section of California's N. Yuba River. [Note the true bedrock extending from the left side of the ravine and re-emerging just below the white water.])
Here is the 6th installment in my series on "seeing" where the gold is:
Tip Number 6: Not All Bedrocks are Created Equal
One fundamental truth in placer gold mining is that true bedrock will invariably contain the very best gold values on any stretch of flowing water (and in most dry placers as well). Again, the high density and weight of gold makes it nearly 19 times heavier than the water surrounding it and it will always move deeper down in a flowing stream until it can move no further.
What do I mean by true bedrock? The basic underlying solid rock or "country" rock structure underneath a given stream. True bedrock is not to be confused with false bedrocks like clay layers that can often be laid down in multiple layers resting at various depths above true bedrock.
It goes without saying that decent gold values can be recovered from false bedrocks because they act as impermeable layers that prevent gold from continuing it's downward journey to true bedrock. However, no matter how good a gold trap false bedrock may be it will never be as productive as true bedrock (providing each type of bedrock hasn't already been "worked out").
So not all bedrocks are created equal. To take this premise a step further I want to qualify this statement here and now by stating: "not all TRUE bedrocks are created equal."
What do I mean by this? Simply that true bedrock sections that are smooth and heavily water worn will not be good gold traps, nor will true bedrock sections resting in the high-pressure areas of a streambed.
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The reason is simple. On smooth-surfaced bedrock (or in rounded potholes) most gold gets washed over, out, and away downstream on its way to better resting places. Ditto for bedrock in areas of high water flow and other poor deposition points.
As a placer gold miner you should focus your sampling and mining efforts on those sections of true bedrock composed of highly fractured rock with lots of cracks, crevices, irregular depressions, and vertical rock "shelving." Why? Because this sort of bedrock provides the best sort of gold trap for everything from fines and flakes to "chunkers" and nuggets.
This isn't rocket science of course. But you'd be surprised how many placer mining "newbies" overlook these very simple but important facts about stream bedrock. Don't you be one of those.
That's it for now. Be safe out there and keep smiling.
If you liked this post, you may want to read: "A Positive Sign? (More on the California Dredging Moratorium)"
(c) J.R. 2009
Questions? E-mail me at firstname.lastname@example.org