Hey folks, looking to start some discussions around why people are so keen to sieve gravel prior to running it through a sluice?
Personally I would pick out any rocks that are too large for the water to push through the sluice and leave it at that. More time spent shovelling, more material through the sluice, more gold recovered.
That said there are situations where sufficient flow is not available to allow for this and sieving is essentially.
Dredges run any material thats gone up the hose, 4inch, 6inch, 8inch and even 10inches. And the recovery is just fine.
I redesigned my home built boxes with raised expanded steel mesh so as to run a faster flow which clears away those larger stones and saved the sieve operation, as you say speeds up the amount of paydirt washed and for us old fellows means less bending for more gold.
However for those with small narrow boxes I expect you are stuck with classifying.
i sieve when lack of water is an issue which is most times. even then i still throw out the big stuff before sieving. sometimes the bigger stones take some shifting even when theres a good flow. i think the time you save with quicker sluicing makes up for the extra time sieving. thats only my opinion. others will possibly disagree.
I have never used a sieve. I aggressively dump the shovel full into the box and help rocks through with a three pronged garden hand rake. The aim of the sluice box is to use the water to do the sorting and make less work, using a sieve adds an extra step to the process, you tube is to thank for that and shallower mass produced sluice box designs. You tube is also to thank for this one handed panning business at the final clean up of the concentrates!
If there is a lack of water to run the sluice in the normal fasion, in flow in the river, then a wing dam is constructed and angles adjusted, for fine gold areas, dont even bother with riffles but I still use my 25 year old asto turf I bought from Ried Farmers Dunedin! This material just runs slower through and you spend more time picking out rocks, but at that point I would just go into production panning mode or use a bilge pump highbanker. General rule of thumb is to have one inch of laminar flow in a sluice on any where between 10 and 15 degrees angle. My sluice I hade made up when I was 14yo. I had an engineer in town make my box up to the specifications in the book byJudy and Sandy fairservice. Gold In Your Bottle. L 1m, W 20cm, H 16cm. It was made with an added flume which the carpet tucked under.
This photo is that summer using it in the Hog Burn, Naseby. With my dad test panning with the shovel. Often he would spot it on his gum boot.The next summer there I spent 6 days with mininal flow courtesy of the Mt Ida water race, methodically clearing the creek gravel to a clay layer, shoveling the gravel like a viking longboat warrior. 14 grams of fine flat gold and an anomalous piece of point two of a gram. Brassy and honeycomb. A young lass would come everyday and sit there talking to me while I dug.
Some good feedback for new fellas here. I have used a sive only once in a tiny creek where the entire flow of the creek was barely sufficient to shift the 15mm gravels. But the gold was good there so it was worth it!
I always sieve as i only have a ezy sluice which is small and to quicken the process i got a 60L bucket from the warehouse and about 15L metal wire laundry basket and put some wire mesh on it works a treat and frys through the gravels
Never use a seive and if l had l would have lost a lot of gold over the years.
As for riffle boxes l just love these modern contrivances and the claims made for them as expounded by the experts - give me Lepreseans any day.
When, if or naybe when l get aroubd to it l might shiw some photos that are a nessage to all - throw away the seive otherwise its the best gold you might theow away.
It is said you cannot help fall over gold in Naseby. I dont know why but I was the only person at that campground July 1995…toilet bowl cracked, knives and forks frozen solid in the sink, fridges worked backwards, boots froze to the floor. I had to defrost firewood. Went for an epic 8 hour walk in very deep snow. Somehow panned gold. Fell and fractured my arm and hit my head. I lost my vision completely for about half an hour. The next morning when I woke with a headache, all I could see when I closed my eyes was blue and not stop watering. A couple of days later when dad came to pick me up…somewhere on the way back to Dunedin, not immediately, said to him sheepishly “could you drop me off at the hospital and pick me up later, and not to tell mum”. Greenbone fracture of the ulna in my right forearm, first stage snow blindness and concussion…loved it.
One other reason I never use the sieve…when panning that is, from observation and little experience, is that people tend to overfill the sieve with dry paydirt, a percentage of which billows over the edge when placed in the river…this is crucial when all the gold could have been in it. And because you are not manually reducing the size of the rocks, it is not kept as agitated, causing the clay to form a layer on the bottom of the pan, which the gold can sit on top of and easily lost especially when one handed panning. Best to fill it while submerged.
I also do sieve all my gravels, tend to think that if you place just shovel loads at the front of your sluice box, a certain amount of gold and gravels travel a way down the sluice before it might be stopped by the riffles, and once sieved, it also means anything stuck to rocks has been washed off into your bucket. Cheers.
