Picking Pay Layer
In the third video the guy is dredging a few feet below the bottom of the layer with larger rocks. It doesn't look like he's down to bedrock. I'm wondering why he picked that layer as pay. There's 2 or more layers of larger rocks so it looks to me that that river came and went several times. If you can't get to bedrock, wouldn't the areas just under and above the larger rocks have the better chance for pay?
Stan's response: Thank you for a most excellent question Jeff. In a modern, live river situation where gold is currently being eroded and deposited in real time, you would normally expect to dredge down through larger and larger rocks until hitting a solid, hard bedrock. That is where you normally find the better and larger gold. It is fairly simple and straight forward.
When it comes to ancient river channel gold deposits, you often need to put on your detective hat and work hard at solving unique mysteries. As you said Jeff, in this case it looks like the old river came and went a few times.
We will get into this subject deeper in Modules 5 and 6. For now I will say that many of these deposits were laid down for millions of years... millions of years ago. That means that conditions of erosion changed, weather conditions changed, tectonic activity raised and lowered some areas many times, lava flowed off and on in some places, and, well, you probably catch my drift that all of these changing conditions over such a period of time, created some really complex looking deposits to us in modern times.
I have seen some pretty weird looking deposits in the field where currents flowed in different directions, one nearly right on top of another, and sometimes the big nuggets are in the top layer.
So, here is what I do... I first try to get a geological map and understand the basic geology.
I try to find a local geologist who is familiar with the deposit and can explain it to me in greater detail.
I look for any mining history to see where the older guys dug and had the best luck.
I look at current erosion and gold deposition to try to figure out where the ancient channel is being eroded. I pay a ton of attention to road cuts and landslides.
I do pebble counts, separating the various types of rocks into groups because each individual ancient river gravel is unique. This helps me discover channel continuations over large distances, especially where there is more than one ancient channel involved.
If there isn't a lot of information available such as in newly discovered ancient channels, it boils down to tedious test work. Every layer/level of every channel possible, needs to be tested in some sort of a grid pattern.
Of course, you're not going to want to go to so much work if no gold has ever been discovered in the area. Many ancient river channels are completely devoid of any gold at all. In fact, most of them are sterile throughout the world.
The exposed ancient channel material I found last week called out to me because it lies within a very large and rich ancient channel area.
So, to finally finish off this tirade (apologies for the long response), ancient gold nuggets, or highly concentrated small gold, can be found where you least expect it. Sometimes it is found in smaller gravels many feet above the big, water worn boulders and sometimes it is found well beneath the ancient clay bedrock.
But, when you find it, the payday can be huge!
More to come soon...