Magnetic sluice question

[wildminer]

I want to experiment with a magnetic sluice to extract fine beach gold. I have a 12"x48" box with stock for a slick plate and deep V mat. I know that's a little narrow for a beach box, but trying to hold the costs down. I have found magnetic tape online and wonder if any one has tried such a thing in making a section of the sluice magnetic. I was thinking of attaching strips on the underside of a plate downstream from the V mat. Appreciate any input.

 

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[Capt Nemo]

If you want tons of magnetite it's the way to go. I generally magnetize the middle and bottom of my sluice to catch it. It will pull 90% of the magnetite on the first pass. Be ready to clean out your sluice often as it will clog fast. You'll go home with a 150-175 lb 6 gal pail of cons. See if you have a blacksmith that makes his own steel in your area. If you do, he'll want the magnetite. Magnets will cause high grade magnetite to semi-permanently magnetize and clump together and float on lighter sands, so remove it and clean it out before panning down the non-magnetics.

As far as gold, magnets aren't a bad idea. As gold (conductor) passes through the magnetic field, eddy currents will form in it, and these currents will cause opposition to the direction of motion of the gold. This is known as Lenz's Law of Counter Electro-Motive Force (CEMF). The magnetic field will stop the gold in short order and gravity will drop it to the mat. It's the same law that allows electric motors and roller coaster brakes to function.

Put the magnets under part of the V mat.

 

[wildminer]

You have increased my fever. Your last statement is what has my curiosity. What, in your opinion, would be the location and arrangement of the magnets? I'm an old blue collar kind of guy and just want a starting point. The tape I am looking at has 1/2 " width, but I am thinking I may want to trim it more narrow. I am also concerened about the spacing.

 

[Oregon Viking]

Clean gold beach sluice.

 

[Goldwasher]

A magnet across the flow at water surface level is best. It lifts the magnetic sands up and away from the bottom allowing fine gold to settle better. Also creates less build up of black sand. A really strong magnet out of the water helps too. Imho magnets on the bottom are counter productive.

 

[goldenIrishman]

I've been toying with this idea for some time but have yet to really give it a try so keep in mind that the following is pure theory. This would only work on a sluice with no magnetic parts to it at all! Any bolts used should be nylon or some other non-magnetic material. I've been toying with it because of the high iron content of the soil in my area. At times my highbankers mat would be filled after only a half buckets worth of materials had been fed into the system.

If you're going to try removing magnetic materials from your slice while it's running, a door security electromagnet would give you all the lift you'd need and then some. These are much stronger than the majority of permanent super magnets and have the advantage of being able to turn them on and off. A simple rod mounting system that would allow you to lift and swing it away from the sluice for cleaning/dumping would be simple to make. The mounting system should also allow you to adjust the height of the magnet. These electromagnets can be had in several different strengths ranging from 600 to over 1200 pounds of holding force when powered and if one designed for an outdoor gate is used, it's already waterproof. A simple normally closed button switch that momentarily cuts power is all that's needed for quick cleaning the unit. I see it working something like this.

1. Power up your sluice and swing the magnet over the flow.
2. Run your materials until the magnet is in need of cleaning.
3. Pause the material feed for a moment and then lift and swing the magnet over a catch bucket and hit the cleaning button. Magnetic materials drop into the catch bucket.
4. Swing the magnet back into position and go back to feeding your materials. Repeat as needed.

If you're serious about getting as much gold out of your materials as possible, do not throw away your magnetic sands. Grind them down and you can get more gold out of them. There are several ways to do this. Rod mill, Ball mill and even the "Shake & Bake" method can be used to free up more gold. Yes... It's there but it can be a lot of work to get that super tiny stuff out.

 

[Capt Nemo]

Rereading the OP, I think that magnetic tape will be too weak to do anything. I use strong ceramics.

I've gone from sluicing to fluid bedding beach sands. It's a lot faster and more compact especially when I have to drive 5 hours to a great beach. If there were a lot of black sulfide gold present, then I'd go back to the magnetic sluice and keep as much black sand as possible. It's local conditions that should dictate capture methods.

 

[arizau]

I want to experiment with a magnetic sluice to extract fine beach gold. I have a 12"x48" box with stock for a slick plate and deep V mat. I know that's a little narrow for a beach box, but trying to hold the costs down. I have found magnetic tape online and wonder if any one has tried such a thing in making a section of the sluice magnetic. I was thinking of attaching strips on the underside of a plate downstream from the V mat. Appreciate any input.

I have made a couple of these using magnetic tape and have used it on the beaches there in Oregon. The magnet tape must be on the surface of the sluice. Mine works but I am not sure how it compares to the Cleangold sluice or to the Fossikers sluice that also uses the Cleangold magnet as part of the sluice. Here is the main thing you need to be sure of and how Cleangold is configured: The magnetization must be in parallel lines with the pole orientation such that each line opposes the next so that it forms little valleys between the magnetized lines of black sand accumulation. When in operation the loosely bedded but still held in place by the magnets magnetic black sand looks like corduroy (miniature riffles) and is about an 1/8" thick. What happens is that the gold buries deep into the black sand matrix and stays put/is protected while at the same time the black sand and other nonmagnetic materials are constantly exchanging and the bed never grows in thickness. Strong magnets will form a dense mat that the tiny pieces of beach gold will mostly not be able to penetrate, displace black sand and bury so the effect when they are used is akin to flatboarding in a conventional sluice.

There is a great deal of discussion about Cleangold over on the GPEX gold forum. Read them and sort out the wheat from the chaff since there is a lot of chaff/negative comments.

Good luck.

PS: If you shop around you can find magnet sheet stock that is configured the same way/parallel lines of magnification. If I make another one that is what I will use.

 

[wildminer]

The cleangold principle is what I want to try and I'm trying to locate a piece of sheet stock. Cleangold tells me they won't sell components and a complete sluice through Fossiker is out of my budget at this time.

 

[mike(swWash)]

I agree with goldwasher.
The black sand on the beach is so plentiful that the magnetic areas pulling down the magnetite will be full on the 1st shovel full. I suppose it would work like a riffle made of carpet somewhat but I prefer to place the magnets above the mat to give the magnetic sands a little more lift so the faster water flow the on the surface can wash it down and let the tiny gold settle out in the slower water near the mat surface.
I would suggest placing 2 or 3 narrow strips about 6" apart beginning 6" from the start of the matting just above the surface, far enough above so the sand can't stick but you can still see it react as it passes under.

 

[wildminer]

I may give this a try first as could do it with no cash outlay and it sounds reasonable. I assume you are talking about deep V matting? btw, I am a native of the Harbor and both sides of my family immigrated there late in the 19th century. We have all moved away or passed on, however. Thanks to all for the input on this.

 

[mike(swWash)]

I use Vortex matting but the results are the same. I tried various V mats and they all worked to some extent depending on the angle, water gph and feed rate, but I finally tried the vortex type and haven't looked back. Remember that the old saying is true, longer is better when it comes to super fine beach gold recovery.

I have a Gold Cube that I started with at the beach and it really works as advertised but feeding it is slow and have since made my own sluice using the same type of matting. Started with a 2' wide 3' long box and since changed to a 12" wide and 6' long with a 1500gph pump at 15 degrees angle. I get a bit more cons to bring home but it's more forgiving on feed rate and get's more gold.
If you can design an adjustable feed rate hopper then you could just throw a few shovel fulls in and sit back for a while

Here's my 1st trip to the beach .......