HOW NATURE CLASSIFIES GOLD
Nature is amazing, especially during spring thaws that create predictable flood-stage water events, and how it not only moves gold but does a pretty darn good job in classifying gold as it goes.
This edition of Where’s the Gold? focuses on good prospecting techniques and making sure that as a prospector you have not gotten onto good gold and ended up leaving higher (better gold) values behind. This is in fact where sampling and trending your area pays off.
Looking at this photo and thinking about a compass with the top of the photo being north, this inside bend on a famous California river is prospected every year when the water goes down after the spring thaw of snow. During the thaw, the scrub bushes to the northwest are completely underwater and the bar that you see in the photo is nowhere to be seen. In all actuality the water is so high and fast through here that there is not even a ripple in the water that would hint of the bar below. But as a prospector, you know it’s there; you just have to wait it out until you can get on it and get the gold. I almost forgot to give you this one: the water flow is from the north (top of photo) to the south.
Let’s take a really close look at the area starting in the north. This is the top section of the beginning of the inside bend in the river. You can see the large rock and gravel deposit that follows the water flow from the north to the west and how the bar has a number of different levels, dips rise and flow patterns, right? I hope so, because they are all clues as to where to start your prospecting.
In the photo look at everything — the rocks, the gravels and how they are laid out — before making your decision on the high vs. low values on this bar. Imagine what is happening to the bar during the high water and think about how gold is affected. Think about where smaller values would drop in comparison to larger pieces of gold with more surface area. The big hint here is this: the rocks and the gravels tell the story along with the arrows I included. (Another hint: this site was the subject of a recent On the Gold Podcast.)
Nature did an amazing job in not only laying out the gold in this site but in classifying the gold into different sizes and values.
Starting at the north, take a good look at the water-created rock and gravel sidewall. Anytime I see this type of layout of rock I get excited. To me, it means that gold was trapped inside of the wall, making a huge inside bend a whole lot smaller and tamer during the flood stage.
From this point on we are looking at the way the water laid everything out. The row of larger rock and gravel to the east between the red and blue lines was a divider. Inside the blue east lines was fine gold down to 200 mesh and a great amount of it from top to bottom of the photo. The slowest water of the bend churned the fine gold and dropped it over a much larger area leaving good values of gold. Working this area took a great deal of time and required running a lot of material. Good gold but not dollars per yard.
The area between the red lines carried no appreciable values of gold. Look closely at the photo and you can see where the split took place by looking at the channel wall of rock and gravel. Notice that there are two different levels and lines of rock in the northern end?
The most telling of all the clues are the larger rocks laid out in the yellow circle. Notice how all the other rocks are stacked by the water and in this area they were laid out flat and pointing in one direction leading into a depression. This depression was created by three factors: the scrub bushes to the west acting to create an eddy and channeling water toward the bank; the larger rocks laying out because of the eddy and water circulation in the area; and lastly, all of it working together to slow that larger gold and dropping it at the edge where the circulation settled it quickly.
The values of each of the blue areas were basically the same, with the greatest difference being the amount of material required to run to recover these values.
That leaves us with the age-old question of, “Would you only work the high-grade material and leave the rest for a later time and go off to find another high-grade deposit?”
For me, I tend to leave the low-grade and prospect for dollars per yard over specks in the pan. But just like money in the savings account, I know where it is and I can go back and dip into it anytime I want.
Kevin Hoagland is the Executive Director of Development at the Gold Prospectors Association of America and the Lost Dutchman’s Mining Association of America. He can be reached at firstname.lastname@example.org