Introduction: Gold Prospecting - Backpack Sluice From Found Materials

About: In my free time, I like building and repairing almost anything especially with found or recycled materials.

I like the great outdoors, but I get tired of just looking at it.  In New Zealand, there are several rivers & creeks in the South Island that are set aside for amateur Gold Prospecting.  They are called Public Gold Fossicking Areas but I thought the word fossick might send most of you to the dictionary.  Anyone can prospect in these reserves, but you are limited to hand-held, non-motorized methods only. 

As with just about every hobby or obsession, you start out with the basics and before long you have acquired or made a toolbox or a car full of "specialised" tools and equipment.  I started with a gold pan and a small shovel and had a few very nice prospecting holidays with them.  They are easy to carry and like most outdoor activities, to get to the best "spots" you need to do a fair bit of hiking and carrying.  If you find a spot with gold, a sluice can work more gravel in a minute that you could pan in an hour.

What I needed was a sluice that I could easily carry in and out of the bush.  A couple weeks before the last prospecting holiday, I looked around for things I could make a sluice from.  I've got a video of the finished product in action in step 5.

On that trip we mostly found tiny garnets but a few bits of gold....certainly enough to go back again!

Good luck with your sluicemaking.
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Step 1: List of Materials

 Here is a list of what I used, but in the spirit of found materials, you might be able to make improvements.

Sluice Frame:  I found a couple of rectangular sections of flue from a kitchen extractor fan (vent-a-hood?).  Luckily, they were slightly different so one fit inside the other.  Also, one was galvanized so it will last a bit longer.  I have some more so if anyone around Christchurch wants any, they are welcome to take them.

Shoulder Strap:  I used car seat belting.  There is a place in town that does seat belt repairs and they have a bin full of old seatbelts they have taken out and offcuts of new seat belting.

Ribbed Rubber Matting:  This was the end of a roll at Para Rubber.  I think it was NZ$3.  They were selling it by the meter for making door mats.  It is excellent for catching any tiny specs of gold because they show up clearly against the black.

Ribs:  I used angle bracing.  It is a galvanized strap full of holes that is bent into a right angle.  It is usually used when framing a house to keep the walls square.  I had kept all of the off-cuts from when we were building, but I'm sure you could find some being thrown out at any building site.

Gold-Catching Carpet:  These were three different outdoor/marine carpet samples.  You can see in the pics that they are slightly different shades.  I'm pretty sure someone was throwing them out because I don't remember buying them.  I was looking for the 3M Nomad scraper door mat material that looks like lots of random plastic loops but couldn't find any.  Some people also call it "Miners Moss" because it catches the gold so well.

Fasteners: I did have to buy some little wing nuts but I had everything else.

Step 2: Making the Sluice Frame

I decided the best way to make the U-shaped sluice frame was to cut a strip from the middle of the wide side (with the join on it) and fold the remaining parts flat to the sides.  You need to measure the height of the sides and measure and mark a line that distance from the corner.  This gives extra strength to the sides and neatly eliminates any sharp edges.

I found the easiest way to cut the strip out of the flue section was to use two tin snips; one right-hand and one left-hand.  This way, you can bend the strip you are going to remove as you make the parallel cuts (see pic).

Next, work out which side will "fit" inside the other.  The "inner" side should be where the water is going in, and the "outer" side is where the water will go out.  If you do it the other way around, you might lose any gold where they join.

 I went to the trouble of bending over any single edges of metal to avoid any sharp edges

You'll need to glue the rubber mat to the "inner"side and you can cut the carpet or miner's moss to fit the slightly wider "outer" side.  Don't glue the carpet down because  While I was bending over sides, I bent the leading edge over the rubber mat to keep the water from getting under it.

Once you have made everything safe, and you have glued in the mat and placed the carpet where it is going to go, you can put the two pieces together and mark where you want the hinges.  I wanted the two sides to fold "into themselves" so I put the bolt as close to the middle of the "walls" as possible.  You also want to put the pivot point as close to the edge of the inner piece as possible.  If the pivot is not near the edge, the inner part will hit the outer part instead of sliding past.

You can drill and bolt the hinges now but I think it would be safer to do it after you build and install the ribs.

Step 3: Making the Ribs

I could try and convince you that the distance between the ribs was a result of hours of detailed research, but actually I decided best place for them was so they could hold down the edges of the carpet pieces.  I put in the sides first, then placed the cross pieces in the 4 spots.  I wanted them to create a "pool" in front of them and a bit of turbulence behind them so I opened them up to past their original 90 degrees.

After marking their positions, I mig welded the cross pieces onto the side rails. It's not a great idea to weld galvanized metal but I did these little tack welds at arms length in the open air so it's not too bad.

Once the welds cool, you can put the ribs back in place.  I wanted to be able to lift the carpet out so I attache the end the Ribs to the side of the frame to act as hinges and the beginning of the ribs to the bottom to keep the water from getting under the carpet.

I find that after a day of sluicing, even if I have thoroughly rinsed everything, I take each piece of carpet out and rinse it in my gold pan.  If I've found any gold that day, I always seem to get a bit more dust out of the carpet that night.

Step 4: Attaching the Straps

You want to situate the straps so the hinge is at the top (so the thing doesn't flop open when you are walking) and I left a loop at the top to hang things on.  I used the screws that I held the ribs in place to hold the strap and it works fine.

You could get fancy and make them adjustable and/or padded, but unless you make them removable too, they are going to be pretty wet having been in the water all day. I found the seatbelt straps to be very comfortable and they don't mind getting wet.

Step 5: Sluice in Action!

Here's a corny video of me folding up the sluice and putting it on my back.

The next video is sluicing on the Brittania Track, West Coast of the South Island.

Once the sluice fills up with gold (or gravel), you rinse it into a pan and see what you have found.

Where we were sluicing, we found mostly tiny garnets and a bit of gold.

Good Luck and don't forget to rate this instructable if you like it.