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dogbone

getting black sand using a cement mixer

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Thanks for having this great forum. Here is what I am trying to do. I sampled some streaks of black sand on the beach awhile ago and a pan full of this black sand/regular sand mixture had alot of tiny flour gold sitting in the bottom crease of the pan. I realize this is a small amount but it was still more than I expected. Panning the sand has been helping my mental state while I am in between gold prospecting outings. Since I use alot of washed sand in my concrete operations I figured I might as well collect what gold I can while I am washing/collecting the sand that I use in my concrete mixture. The problem I am having is consolidating the black sand out of the regular sand by aggitating a container. I can get a good part of it down but alot of the gold and black sand doesn't seem to be settling out. Is this because the gold is like 1/4 of a sand grain? It seems like aggitating the sand is packing the fine sand so much that it is acting like a dense barrier that the fine gold doesn't easily penetrate. I even used a concrete vibrator on a bucket of the sand mixture figuring all the heavies would shoot to the bottom. It only sort of works. The sand is darker but not black. My other idea was to use my cement mixer thinking all the heavy stuff would drop to the bottom. It only sort of works too. Why is this? I wish I could just fill up the mixer, turn it on for awhile and then just pan the bottom stuff. Do I need to get a sluice box to recover the black sand? I know...my girlfriend says I am crazy too. The other day she laughed at me and said, "why don't you look up how much an atom of gold is worth on the internet?" I did and after some brain calculations...one atom of gold is .06 x 10 to the negative 16th of one penny.

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Just today I was looking at some black sand under high magnification and I was amazed at how much tiny gold it contained. I would suggest that you try adding a surfactant (like Jet Dry) to the water. An idea that I have that is similar to yours is to use something shaped like a large funnel with an aquarium aerating stone at the bottom to keep the black sand in a state of liquefaction, along with a small vibratory motor (from a cell phone or pager) against the side of the funnel. Black sand would feed into the middle, water would be fed in from the outside edge to swirl the light stuff over the side. (Like a reverse Blue Bowl but fed into the middle, and with aeration and vibration.) The heaviest material should settle down to the very bottom at the aeration stone. It should work.

I've been looking for a plastic carboy to make this.

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I have been thinking along the same lines Rick. I have a large plastic funnel that feeds sand into my sandblasting unit so I first tried vibrating the funnel full of sand and then releasing the sand out the bottom but it only sort of worked. I also used some tubing to blow air in the bottom while I swirled the funnel but it only sort of worked...I should add that the looks my girlfriend gave me while I was doing this were classic. A surficant may help like you said. I hadn't thought about continuously adding sand/water while vibrating or adding air and letting the lighter sand flow over the top. Good idea. Maybe I can just keep adding sand the the cement mixture while vibrating it and let the lighter sand flow out the tilted end. I'll check it out and let you know. Thanks for the input.

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I have been thinking along the same lines Rick. I have a large plastic funnel that feeds sand into my sandblasting unit so I first tried vibrating the funnel full of sand and then releasing the sand out the bottom but it only sort of worked. I also used some tubing to blow air in the bottom while I swirled the funnel but it only sort of worked...I should add that the looks my girlfriend gave me while I was doing this were classic. A surficant may help like you said. I hadn't thought about continuously adding sand/water while vibrating or adding air and letting the lighter sand flow over the top. Good idea. Maybe I can just keep adding sand the the cement mixture while vibrating it and let the lighter sand flow out the tilted end. I'll check it out and let you know. Thanks for the input.

I think that the key to making this work is to have enough water flow coming in to get a whirlpool action going, and then to find the right rate of feed of the black sand to allow it to stratify by density down in the the neck of the funnel, while at the same time letting the lighter stuff go over the edge. The advantage that this would have over a Blue Bowl is having the low area of the funnel neck for the gold to hide. Also, slinging the lighter stuff out for disposal should be more efficient than trying concentrate it the center, where logic would dictate the denser stuff wants to be. In my mind the Blue Bowl has it backwards, but I may be mistaken on this. I won't know until I get a prototype built. In the meantime, I'm going to start saving my black sand to experiment with.

For what it's worth, my wife thinks that this whole prospecting thing is a waste of time. (Not like her opinion will influence what I do in the least though.)

Rick

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Good thoughts Rick. I have gotten a good whirlpool action with a sheetrock mud mixing blade in a five gallon bucket of sand and water with my power drill. Tomorrow I will try a steady addition of water and sand along with the mud mixing blade and see what happens in both a bucket and the big funnel I have. I am hoping to process alot of sand quickly down to black sand, which is probably asking for too much. It will be interesting to see if your idea works. As to our wives...I bet their tune would change if they were to try panning and saw their first flake of gold lit up in the sun against the black sand.

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I should mention Rick that in all my experimentation I did find one very good method for extracting very fine gold from beach sand. I cut a four foot length of black abs pipe along its length on a table saw creating two halves. Using one of these halves as a sluice box, sluice circle?, I scruffed up the slick inside with 60 grit sandpaper trasversly. Using a very slow water feed and a slight angle to the pipe the light sand and black sand will slowly disperse down the pipe leaving the fine gold behind. One thing I found important was that the sand feeding into the sluice had to be almost a trickle so that there were always stretches of pipe exposed for the traveling gold to stick to. I did this by suspending a large funnel of sand/water mixture above the sluice and controled the flow with a valve. If I didn't do this and I let the sand build up into a continuous pathway then some of the gold would skip away on the surface of the sand and out into the catch bucket. The only drawback to this method is the time spent making sure the sand is not piling onto the sluice. I may try this again in the summer when the sand will be dry and I can control the flow easier as it comes out of the funnel. The other reason I am trying to find a different method is I have all this construction equipment laying around. I should be able to come up with something quicker so I don't have to babysit the operation all day.

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I've done it!

Set the mixer at full Zenith. That straight Up. LOL

keeping a hose of water slow flow running into it, Fill it half full of material.

Let it run for a 1/2 hour.

Dump off the top half.

Repeat this process until your pooped out.

I'd end up with 1/4 of the bucket full of black sands and goodies.

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Good Homefire, I like that. I have tried the mixer in every configuration but never left it on more than five or ten minutes. I guess I have been to impatient. I will try a half hour with constant water flow. Thanks.

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Good Homefire, I like that. I have tried the mixer in every configuration but never left it on more than five or ten minutes. I guess I have been to impatient. I will try a half hour with constant water flow. Thanks.

Just have the water going enough to barely flush the Tub out. You will loose the powder if you have it going to strong.

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A mixer takes what is on the bottom and delivers it to the top. Just the opposite of what you would want unless it was pointed straight up. Even then it lacks the action to stratify materials well.

A cone bottom tank with a "jig pump" stratifies materials as well as any other configuration and is a lot like the cement mixer. Water is forced up from the bottom of the cone bottom tank and allows complete seperation. It is how material is accurately stratified in many processes. Any tall decanting container with a flow from bottom to top will stratify your sands completely in a big hurry. If you add a low frequency vibration to the slurry it will do it a lot faster.

Use your concrete vibrator for the "shake" and set a round sprinkler in the bottom of the mixer pointing straight up. Fill the drum with water and shovel the material in as the water runs over the lip of the drum while using the vibrator. Dont turn on the mixer at all. You have made a crude "cone bottom jig" that will probably concentrate material as well as anything. It just wont seperate the gold from the black sands.

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The one I used only had Spoons/Blades on the middle section and worked quite well. A hell of a lot better then panning in a tub.

Never tried to do it dry but I bet it would work . Not Good but would work.

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Thanks bedrock bob and homefire. I am going to try both of your ideas today. It seems though like I would need a good amount of water flow to get the lighter sands up and over the mixer rim?

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Thanks bedrock bob and homefire. I am going to try both of your ideas today. It seems though like I would need a good amount of water flow to get the lighter sands up and over the mixer rim?

You arent going to wash any sand out. Just stratify the material. So it is not really concentrating....just sinking the heavy stuff to the bottom.

A much better idea would be a recirculating sluice that actually got rid of the waste and kept the gold. Just my two cents.

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It was my thought that a cement mixer is configured to fold the contents back on it's self thus mixing all together. Now on a cement truck they reverse the rotation to expel the cement. So what would happen if you reversed the rotation of your mixer with it at 90° and turning slowly. Shovel in your dirt, sand whatever and have a stream of water running into the mixer, would not the gold seek the lowest level while the lighter sands and such would be run up and out. This is assuming the the vanes in the mixer don't go all the way to the bottom of the mixer bowl. What thinks ye?

Gramps

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Good idea Gramps. My blades go all the way to the bottom though. I tried the mixer straight up for a half hour and that worked pretty good. I got more gold than I had in the past and this was with sand I had already processed before. I am going to try and concentrate a bucket of sand/water with the concrete vibrator for a half hour and see what happens. Also make some kind of bubble maker with my air compressor. You are right Bedrock, I could probably go get a suice box and quit trying to re-invent the wheel.

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The way I did it, I ended up with 1/4 bucket (Mixer) of black sands and better then expected gold.

The blades on the machine I was using did NOT go to the bottom.

I borrowed that one. I'm going to buy one if I find it cheap enough. If the Blades go to the bottom, I'm cutting the bottom section out.

I'll Try running it Back Wards too.

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Here is my new technique. I have the five gallon buckets full of sand/water sitting in the back of my flatbed truck. Perhaps after a few weeks of driving over all the potholes around here, the black sand will be concentrated at the bottom.

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Here is my new technique. I have the five gallon buckets full of sand/water sitting in the back of my flatbed truck. Perhaps after a few weeks of driving over all the potholes around here, the black sand will be concentrated at the bottom.

Redneck prospecting at it's finest! beer.gif

Mike

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You are right Mike. I got tired of my girlfriend/wife telling me I was using more electricity $$ than I was recovering in my beach sands. This is a brilliant solution.

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