The Finer Points of Crevicing and Underwater Gold Sniping (Part 2)
In this post I'll be offering more tips on the finer points of crevicing and underwater gold sniping. Again, finding bedrock crevices that offer a better chance for you to recover gold isn't just a spin of the roulette wheel...there are certain indicators that can lead you to the good stuff. Read on to learn more.
2) Know where the gold goes. Having a basic understanding of stream or wash hydrology and gold deposition factors is a must when you're hunting good bedrock crevices. This is especially true when dealing with wet placer locations with running water. In dry or desert placer this still holds true but there are wider variables at work with both hydrology and deposition that can work in your favor or against it, depending on the locale. In general:
- The smallest particles or pieces of gold ("flood" gold, tiny flakes, microdots, etc.) will be found in crevices in low-pressure areas near the flood stage levels of that stream or wash. In other words, crevices higher up the banks of washes and running streams tend to collect the lighter gold that's easily moved by high-water flows. I call these "high" bedrock zones.
- "Chunkers," small coarser gold pieces, medium and large flakes, and occasional small nuggets will typically be found in bedrock crevices that are in the "middle zones" of that stream or wash. That is, those areas of bedrock that lie between flood stage and the main stream or wash flow. These are the medium or "mid" bedrock zones.
- Nuggets and heavier pieces of placer gold tend to remain in crevices within the boundaries of the actual stream flow in normal or flood stages (although heavy flooding can carry some of these heavier pieces higher up.) In most instances in wet placers you'll have to wait for low-water months (mid-Summer to the Fall) to have any chance at accessing these crevices that are normally underwater. However, if your thing is underwater sniping this restriction may only apply to bedrock crevices located under very swift or deep water. These are what I call the "low" zones...they are either underwater or very near current water flow.
3) In general, crevices on angular or broken bedrock are better gold traps but not always. A good case in point here is the Northern California Motherlode region where I used to spend a lot of time mining back in the 1980s. Most of the bedrock there (North Yuba River, South Yuba River, etc.) is smooth or highly water worn. Yet many crevices in this area are packed with gold both above and underneath the existing stream flow. This becomes even more true if those crevices run perpendicular (or nearly so) to the stream flow. So don't automatically assume that water worn bedrock is a bust when it comes to crevicing. If other bedrock crevice factors that I've talked about (or will talk about) are in play so are you. Remember this point.
4) Look for crevices in areas that have secondary channels with larger obstructions near them. This isn't an absolute, but in my experience (which is pretty extensive) I've found that when working bedrock areas above the stream itself it's a good practice to focus your attention on what I call secondary channels. I don't mean stream channels like when a river or creek splits. Here IS what I mean. If you use your eyes you'll often spot boulders and larger rocks lining bedrock that indicate the boundaries of possible water flow from upstream moving downstream. These secondary channels will have lots of rocks, cobble, gravel, and dirt packed inside them. Any crevices that can be seen in these channels or uncovered by removing shallow overburden should be investigated or sampled. When high water or flooding conditions occur water typically rushes through these channels carrying gold. You can look for these sorts of channels (however small or large they may be) in the high, medium, and low zones I spoke of in Tip 3. This tip is also valid for dry placer bedrock.
(Here's an example of a "secondary" bedrock channel...lower center of this pic where the rocks are discolored by water flow. However, this channel is on the outside of the bend...not the inside. I'd probably have a look at it anyway.)
(There's another secondary on the left side and upper left side of this photo. If you look closely you can see rocks packed into it. If crevices are here you should take a look. In midsummer at spots like this on the South Yuba River in the Northern California Motherlode you'll encounter low water conditions and probably a nude sunbather or two!)
Take good care out there.
(c) Jim Rocha 2018
Questions? E-mail me at firstname.lastname@example.org