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Author Topic: Gold ní Clay  (Read 57299 times)

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Offline GollyMrScience

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Re: Gold ní Clay
« Reply #30 on: February 11, 2010, 07:33:40 AM »
The gold will only move down if the material it is liquified or opened up through motion. Generally this means movement towards the bottom of a moving slurry or scoured zone but can be dry as in a slide of dry material. There has to be some mechanism to cause sorting by specific gravity.  In an area that has not been sorted by motion or washing, gold will essentially stay where it is in the strata. When sorting does occur gold will move towards the bottom of the material being sorted. That may not be bedrock but rather the first layer below the one being sorted. That layer is generally more resistant to the sorting action. It could be a layer of larger rock, a layer of clay, bedrock or cemented gravel. In the case of the reclaimed area the bulldozed tailings had gold in them and it sounds like the reclamation spread these tailings all over the place but unless a sorting agent attacks the material the gold will remain homogenized throught the gravel layers.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline cloudwalker

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Re: Gold ní Clay
« Reply #31 on: February 11, 2010, 02:08:44 PM »
This thread inspired me to try an experiment at the reclaimed area today.  I found some bluish-gray clay a few weeks ago that was so sticky I broke a fiberglass shovel handle trying to pry it loose.  My idea was that the really thick clay was some that didn't get broke up during the hydraulic mining.  Today I pried/chopped out about three gallons of the stuff.  I put it in a bucket of water and stirred it with my shovel until it was broke up.  It turned into a thin soup not much thicker that chocolate milk with virtually no sand or gravel.  I literally poured this through my grub-steak sluice and the results were the best pan I have had to date.  ;D It was a lot of work but worth it.


The gold will only move down if the material it is liquified or opened up through motion. Generally this means movement towards the bottom of a moving slurry or scoured zone but can be dry as in a slide of dry material. There has to be some mechanism to cause sorting by specific gravity.  In an area that has not been sorted by motion or washing, gold will essentially stay where it is in the strata. When sorting does occur gold will move towards the bottom of the material being sorted. That may not be bedrock but rather the first layer below the one being sorted. That layer is generally more resistant to the sorting action. It could be a layer of larger rock, a layer of clay, bedrock or cemented gravel. In the case of the reclaimed area the bulldozed tailings had gold in them and it sounds like the reclamation spread these tailings all over the place but unless a sorting agent attacks the material the gold will remain homogenized throught the gravel layers.

Offline Blister

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Re: Gold ní Clay
« Reply #32 on: February 11, 2010, 03:41:30 PM »
 If you had spread out tailings as in the area stated above, could it be possible for rain to wash the fine/micro gold down deeper ? At least for the first season of two, I would think the ground hasn't become packed down and would have some small spaces where rain water could get in and trickle down. But would this be enough to move small gold?

Offline GollyMrScience

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Re: Gold ní Clay
« Reply #33 on: February 11, 2010, 04:41:50 PM »
If the gold was small enough to fall through between the unimpacted mineral grains but there would be minimal movement I think. Settling and compactionn certainly but not really any concentration action. Runoff areas are a different thing. They will have a placer character and those areas should be looked for as potential concentration zones
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline kerbyjackson

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Re: Gold ní Clay
« Reply #34 on: February 11, 2010, 08:25:48 PM »
In my experience (some of which is farming), the rain will only futher compact the clay material when it's exposed to the elements. To force the gold to drop or concentrate, the clay would need to be liquified into a slurry to break the bonded particles apart enough for the gold to drop. With farming/gardening, it's been found that the only way to break up the clay is to work organic matter (ie. compost) into the clay as thoroughly as possible. As the organic matter breaks down, the clay particles become separated and allow for better drainage and aeration. That can take years.

So needless to say, on an old operation, if vegetation has had a chance to grow and die off/shed leaves, etc. it's possible that enough organic material has broken down to work its way down into the clay and to break it up. That might take 100 years. Any gold could concentrate downward in that scenario, but then again maybe not.

I say maybe not, because I live less than 1/4 of a mile from the Rogue River on land that my great grandparents homesteaded 100+ years ago. Some time in the past, this area was either a flood plain or part of the Rogue's old channel. Round river rock (including a lot of quartz and agate) ranging from the size of a quarter on up to the size of a man's head was a bane to farming operations in this vicinity stretching across this area for a distance of several miles on the south side of the Rogue. On some ocassions, when people dug ditches, cellars and ponds, small well worn nuggets were often recovered and it was also known that the advent of irrigation had a habit of concentrating fine gold in the ditches and canals.

Recently, having grown sick of all those rocks, I undertook a project to begin ridding our property of all those rocks one 10 X 10 foot square at a time. And I figured, if I was going to dig and sift the rocks and other debris out, I also decided that it might be worthwhile to work some of that material and see what happens. Needless to say, I'm currently running all this material through a highbanker. What surprised me is that I am recovering some flour gold and a hell of a lot of black sand within inches of the surface. This is topsoil which would have been worked almost annually by plows to a depth of at least a foot. Some gold is coming out of this depth (you would think it would have all dropped through ages ago), but what is surprising is that just below this depth, I'm uncovering bands of gray-blue, as well as bright red clay (probably river sediment) that is literally sitting on top of a heavily compacted layer of larger water washed rocks. These bands are giving up a fair amount of gold - enough to hold my interest at least.

Now the point is, we are talking about an area that for one, is virgin from the point of view of mining and two, the river material was deposited HUNDREDS, if not THOUSANDS of years ago. Despite that, there is gold very close to the surface and at two feet, bands of clay are trapping it in a greater quantity. Keep in mind though, this gold is very small and I've seen no pickers or nuggets and I don't think I'm going much deeper. It's worthy to mention that at one time, raspberries were being grown on this parcel and annually, a lot of shed leaves and dead canes were allowed to lie on the top of the soil and have added a lot of organic matter to the soil. Despite this, there is still gold at a shallow depth, so lots of organic matter doesn't necessarily expand the soil particles enough to work the small gold downward.

So in my opinion, it's very difficult for the small gold to travel through clays and I would say that if you are working in an area where clay tailings have been spread over an area, any gold, PGMs, etc. captured in that material are probably still locked up in those clays, even if it's an older operation. On an old operation like that, anything substantial may have dropped all the way through the clay, but the small stuff will remain. Nuggets are nice, but as anyone who has done this for any real length of time will tell you - the fines are your payday.

Were it me, I'd be in there seriously sampling that material. Mark off a mental grid and start running pans. When you locate some hotspots, start working downward a little at a time and take notes based on depth. You'll eventually establish a pattern that shows where the gold is petering out and you can use this as a guide. The layer you're working might be three foot thick, but if samples are showing that 95% of the gold is trapped in the first 18 inches, there's not much point working the lower half for that extra 5% unless its a small area, is there?

Offline Chuxgold

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Re: Gold ní Clay
« Reply #35 on: February 12, 2010, 05:47:00 AM »
Good post kerbyjackson. I like to see well observed and self taught thinking. Every were is difrent. And if you aproch it with a bumch of pre conceved notions. Born from other conditions. You will miss something. Have you tryed a rocker to see the volume of the unpanables. Also you mite concider puting traps in your ditches where gold is showing.
And I bet if you just sampled deeper on the corners of 40 foot squares. You mite find that pryor to the top soils being deposited a volume of courser gold mite have deposited here and there. You must have some deeper exsposed places to test. A well or were a road cuts into a hill.
And to add a little to what you already said. Before agiculture turned the soil the gold would have had curtain places of greater concentration. But plowing and discing has spread it out.
Chuck.
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Offline GollyMrScience

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Re: Gold ní Clay
« Reply #36 on: February 12, 2010, 07:37:50 AM »
As a follow-up on the observations made by kerby the conditions reported confirm the fact that gold cannot dig holes for itself. The gold will try to mve to the bottom of an open layer of material created through movement or liquifaction but once the conditions for that stop so does the gold. If you have a field and a flood causes a wash of alluvial material across it there is only so much scour associated with it. The material that is mobilized in the flood will create the conditions for gold movement both along and down but the field under that that does not move will be the barrier that the gold that reached the bottom of the liquified layer will stop against.
You can see this when you get a good cross section on an old stream bed. There are layers in the bed of fine sand and gravel that represent different energy pulses in the stream. Quite often a stream will have the energy to scour only so far down into the exisiting stream bed. Only the portion that gets scoured will offer the conditions for gold mobilization and I have seen old streambeds with several pay layers one above the other with fine sand and gravel between them and a long way down to bedrock with no gold on bedrock at all.
As an experiment to prove the point. Take a large gold pan and put some dirt in it. A mix of gravel and sand. Cover that mix with water. Let it sit a bit just to let it set up and then put a nugget on top of the material in the pan. Dollars to donuts that nugget will still be laying on top of the wet material a week from now. Pick up the pan and start swirling the water around it gently so that the upper layers start to move and that nugget will disappear. Now stop all motion. If you dig down you will find the nugget sitting right on top of the material that was not moving at the bottom of the layer that was. Take it one step further and start the swirling and really go at it with some shaking to boot and in no time you will hear gravel scraping on the bottom of the pan which is the bedrock in your pan. The nugget will be down there now.
This illustrates the need to really examine an area as you prospect it and test each layer as you dig down watching along the way for evidence of scour and concentration.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline willthedancer

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Re: Gold ní Clay
« Reply #37 on: February 12, 2010, 08:02:39 AM »
Another example is the fact that even with the shaking of a vehicle going down the road,  the bucket of wet aggregate that you got to pan at home will have gold on top. Probably more, as the material on the top of the bucket is the last you put in there (from the best part of the deposit). That movement is not enough to cause sorting. The gold only settles down far enough to reach a locked area in the matrix.  Quoted from Tom: "Gold can't dig a hole for itself".

 I think clay is a great help to us as prospectors, in that when the aggregate pile moves down stream, the gold finds it's way to the clay layer (if there is one), and stays there due to the lack of openings in the layer. The clay is much easier to remove from the stream than discreet gold from the bedrock.
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Offline kerbyjackson

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Re: Gold ní Clay
« Reply #38 on: February 12, 2010, 09:33:19 AM »
Chuck: I hadn't planned on punching down much deeper (keep in mind, my main interest was eliminating rocks for soil improvement), but I think it's safe to say that there could be bigger gold at greater depths. "Neighborhood" history indicates its a possibility. I do have one spot that seems to have a much higher concentration of river material (practically an exposed gravel bar in that corner), so I may very well try to push that corner down deeper and see what happens. At worst, I get rid of the rocks, but maybe I'll get lucky.

GollyMrScience hit the nail right on the head: Gold doesn't dig its own hole. And as Will said, I think the clay is a big boost to us, even if it's hard to work.

That said, talking about scours ...

If we are talking about an existing active stream (or even an ancient channel) and we wanted to be on the lookout for a scour and the subsequent pay layer (s) created by the mobilization of the material, visually, what exactly should we be looking for in the layers? Also, in your experience, would they differ visually between an active stream and an ancient  (dry) one?

Offline SeloamLakeGoldMiner

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Re: Gold ní Clay
« Reply #39 on: February 14, 2010, 10:22:58 AM »
As being the avid reader that I am, and especially on the subject of gold prospecting, I have found several interesting things in my reading on the subject of clays and gold. one of the more interesting things that have come to light are few statements made by the old fellers who put in the work back in the day. keeping in mind that the first man who found the gold at Rabbit creek renamed bonanza was not the first , second or even the third man to have prospected this area and run his pan thru the gravels it goes to show that even the "biggest thing ever" can be passed by before revealing the secrets she keeps.
                      I have found several repeats of the story but it runs like this, after finding small amounts of pay and working out an  area, most of the prospectors left once they hit the clay and a particular color of clay had been passed thru into another, thinking the area now worked out and the streak depleted they packed up and moved on to the next  stampede hoping their fortunes would hit it. but there is always one man who seems to be more driven than the others who kept on digging, all about him laughed and told him he was a fool wasting his labour. but he persists. and after digging that few more feet of clay he hits another, older, thicker channel which bears the richest pay yet.
             I have always thought about this when ever I encounter clay. we all know it can act as a 'false bedrock and trap gold in great quantity on its surface and even a foot or two in, and then it peters out. Yes it could be nothing more than a story, like the "lost dutchman" and I'm sure that it dosent happen every time. but the next time you hit that clay that does not pay.
think about mother natures sense of humor and how many fortunes might have been missed all for the sake of a few shovel loads more.

 


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