Fine Gold And Abundant Iron Sand

[1864hatter]

Hi there, 

Has anyone had any experience with suction dredging in rivers with fine gold and a lot of iron sand / black sand (say up to 10% of gravel which passes through the sluice). I'm considering the use of hydraulic riffles but can't find any data in regards to relative gain in recovery versus a standard keene triple type sluice box. I realise this is a very complex issue as a lot of factors affect the recovery of gold but it would be good to hear from someone who's had some practical experience. Pictures of the gold at the location. 

[Valens Legacy]

Very nice haul on the black sand looks to be close to almost a half ounce.

I also see that you found some yellow stuff there also and it could be about 3-4 grams at least.

Kidding aside nice haul for all that work.

I set up a sluice that falls into another sluice like a waterfall, and about an inch from the water I have a magnet placed to catch the black sand and iron. Sometimes it gets more than what I would like to see and have to clean it off during the sluicing process.

Next time I have it assembled I will post a picture on the forum.

[1864hatter]

While magnets might work for a slight amount of ironsand they won't work where we will be dredging. We have tens of kilos of the stuff to deal with. 

[geof_junk]

Sorry but most of my suction dredging was done on the far side of major river that was feed by a very rich creek during major floods.  Most of the gold was picker that a 4" coil could pick up. I used a home made suction dredging of 3" suction and the sluice box on it was less than a foot long. Pan testing the spot yield no fines or dust. If you go the sluice box way the main thing is how you set it up ie: flow rate, angle and screening the larger material.

 

[phrunt]

I haven't found a solution, even with my little Keene A52S sluice in the Arrow I can fill a large coffee jar in an hour with black sand.  It clogs up the sluice in no time.  I've tried magnets up the front, they're useless with the amount of black sand. 

My daughter liked to keep it so I bag it up for her.

With the gold being small I just have to do a lot of clean outs.  Your pan resembles my issue except you've got more gold in it than I get and if I try suck the sand out of the pan with one of the magnet clean up tools plenty of gold goes with it as it seems to get stuck in the black sand.

[geof_junk]

To separate the two, I used to pan it first and reduce the amount then dry it. With a magnet above bit of cardboard or plastic sheet the dry concentrate was separated out with a couple of repeats. I also found the magnet method was more effective if the sample  was heated to a high temp. without melting the gold first, then when cooled using the magnet method. The remaining black sand can be further removed by blowing it with straw