OUR STORY & PHILOSOPHY
how black sand effects gold movement in waterways
Besides being an exciting title, knowing how gold behaves in a waterway will help you recover more.
What prompted me to write this article was the almost complete misunderstanding of “why some miners get more gold while others don’t”.
The easy answer is because some miners understand gold better. To that I say, well, sort of. Others call those placer miners lucky or that they have better claims or bigger sluice boxes. Well, no, no and maybe.
Being “on the gold” or in a pay channel can help a lot but there are two primary ways that gold accumulates.
On bedrock (A time honored favorite). This one is my first choice above all other mining methods, however having shallow bedrock anywhere near a road means competition. The cottonwood river North of Quesnel, BC is like that. Bedrock is only 18 inches deep in select locations and in spots the flake gold is heavy (Please remember that the whole river is staked and is not for public gold mining).
High benches. This is where most miners are going now, up on the banks. With rivers being so wide there is often upper benches rich in flake gold. The thing to watch for here is when the river cuts through solid rock creating great hiding places for gold, both coarse and flake. Also look for discolored horizontal bands that will mark mineralization layers and gold.
What’s common about all these spots is Black Sand.
This heavy sand puts the brakes on gold movement, something like trying to run underwater. Only time and prolonged water movement will cause gold to settle right on bedrock otherwise you find heavily mineralized bands of magnetite mixed with gold. Typically what happens is erosion over thousands of years takes place wearing away gold, iron ore and other less common minerals. Due to iron pyrites being so common in the earth’s crust it accumulates in greater quantities in streams and waterways forming magnetite. Depending on the age of the washed iron deposit, pieces of lesser oxidized material can accumulate in suspended payers in almost any waterway. If this happens it typically forms “conglomerate” or “hardpan” trapping slowly descending gold in its matrix, however even black sand can slowly cement together given the time and pressure.
The results of compacted, black, mineralized sand in descending layer excites most miners. That is where your pay is. Gold would drop right to the center of the earth if it had its choice. These mineralized bands mark a stopping point for gold as it’s headed to bedrock.
Every gold deposit is different. I’m talking about how it is formed in placer deposits. In other words, which happened first? The black sand or the gold? Possibly both at the same time!
If the black sand is there first, gold will wash over top of it and settle between the rocks based on flow rate and heaviness of each gold particle or nugget. Then depending on the amount of agitation and weight of the gold pieces one of two things will happen.
Nuggets will quickly work their way down through the magnetite and stop on bedrock. The speed that this happens again depends on the agitation and nugget weight.
Flake and micro-nugget gold can be picked up by the next flood surge and washed further downstream. This simplistic view depends on how much of the stream bottom is eroded by nature’s fire hose during seasonal floods.
Also gold trapped between rocks on the bottom of a water way that is still stick in the surface black sand is a sitting duck for flow surges. The way rocks get moved around when the current increases is by rapidly eroding the surrounding sand and gravel surrounding them first and then the water flow can push them down stream. The effective flow is actually magnified between the rocks as this whole process starts, just like the wind between buildings in any city.
Another tip that may help you is when there is a real down pour. I’m talking about Apocalypse buckets of rain. You can see evidence of this by washed out hill sides and newly exposed sections of gravel. If you’re in gold country some of the ancient stream beds will temporarily reactivate, washing down a fresh shot of gold. When gold enters an existing stream or river it will quickly start to settle and will stop in the surface layers of black sand. Look for sleepy almost non-existent little streams that have way too much open gravel on either side. Freshly downed trees is another way of spotting earth moving events. An abundance of elevated root balls sitting high and dry in a log jam tell the same story.
I look for these signs and then pick out a likely side stream feeding the main water way. Trace the side stream down until it opens onto the main water way channel. Now look just slightly downstream of that point. What you’re looking for is a mound of sand and gravel. This mound is a cumulative build-up of the small side stream’s discharge at or near maximum discharge. Remember this build-up will be well above the current water levels position.
If you find a good one there will be graded (sized) sand, gravel and black sand in a comet like tail tapering away from the small side stream. Nuggets will be in the front part of the compacted gravel section. Flake gold will be interspersed throughout the black sand.
One more thing I need to mention. If you find nuggets, even small nuggets in the side streams mound, back track up the center of the side stream water course. I learned that lesson while gold panning North West of Cassier, B.C.
The great thing about this type of find is that most of the freshly washed down gold will be in the top inch or so of the stream bed gravels.