Another Drop riffle sluice ? for AstroBouncer (or whoever)

[Caminochaos]

As I said before I will have a 6' wood drop riffle sluice.

- No riffles in the 1st 12"
- then 6" of 1/8"Wx5/16"D @ 1/2" apart.
- 3" gap
- 1/4"Wx1/2D @ 1" apart
- 3" gap
- Then....my question.

Should I do 1/2"Wx1/2"D @ 3" apart
OR
3/4"Wx1/2D @ 3" - 4" apart.

The only reason I'm asking is because I think since the riffles are going to be square cut (for now) that the sluice may clear out faster with a wider drop riffle. What width worked for you the best. I am dealing with all sizes of gold.

Thanks in advance!

 

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[Astrobouncer]

I would do both as well as a couple wider ones even towards the end. You want to change up the current as much as possible and give gold lots of places to drop out if it somehow manages to get past the smaller riffles. Even a very wide riffle wont clear out faster it will just catch more stuff. If you want it to clear out faster you cut with a sloped angle on the backside of the drop, like the Angus Mckirk/ Le Trap sluices have.

Some things I noticed when testing:

If your drop riffles don't clear at all then you have not enough slope or flow.

If your drop riffles wont hold black sand (or other heavy gangue) then you have too much slope or flow.

Initially as you feed material you should retain the blond sands but as the heavies enter the sluice they should start replacing the blond sands. And the riffles should continually upgrade with heavier material the longer you run it. The first riffle should hold most of the zircon/gold/lead/monazite if the gold/zircon/lead/monazite is settling in further back then you have too much flow or slope.

If you feed it too slow, scouring can occur and you will lose most of the material in the riffles (but coarse gold should still stay). If you feed it too fast, the material wont have a chance to settle into the riffle and will slide on out.