Natural concentrators

Years ago,when I used to practice the dark arts of panning and sluicing,I came across this novel idea at letting nature do the dirty work for me.
There was a large set of diggings that were a raised Alluvial terrace along the Turon river in NSW. The old diggers had done well here and the ground was very rich in both Nuggets and Fines,supplied from multiple sources.
They had surfaced the entire area down to the slate bedrock,which was very decomposed and had a crumbly nature. Sitting ontop of that bedrock must have been several gravel layers,which consitsted mainly of larger,smooth river stones and a white powdery dirt that was most likely slate based.
Anyway,the old diggers removed everything but the big rocks,that were stacked in neat piles. They didnt remove all of the decomposed slate as far as I thought they should have,as they didnt reach the harder stone below.
You can take a pan full of this crumbly slate and get 5-10 colours from anywhere on this surfaced area,but it was at least 100 mtrs above the river and too far to wheelbarrow the pay dirt for washing. Fair dinkum these blokes must have been keen or the ground was super rich!
Thinking outside the square about rock bars I sparked this bright idea well it could have been the Port around the Campfire that did it
Mother Nature had done Her best to errode small water courses through this decomposed slate surfaced area,and in the 150 odd years since it was worked, she had done quite well. In some spots she had exposed the harder slate beneath,forming beautiful funnels running off the diggings.
So all I had to do was build a series of riffles that consisted of rock piles in my chosen spots and let the rain and gravity do the rest.
The last time I cleaned it out all that was required was 4 x 20 ltr buckets,1 fine sieve and a small shovel. I put the whole lot through my homemade battey opperated sluice and came up with 13.2 grms after the clean-up.
Its been a long time since I been up there and many thunderstorms have done there work since.
Maybe its time for a return trip.........

 

Rock piles Ay

Been pretty much doing the same thing too, only in the water though!
gottu couple of nice inside bends, where a big old well placed boulder and a few smaller ones works wonders until a tree falls down and changes the flow