5/1/2023 0 Comments Sluice box riffle angleSo we went over to the coast on sunday found the best spot ive been to yet, lots of colour screened my stones down to 4mm then ran through keene sluice box getting colour nearly every scoop now ive been panning out my black sand doesnt seem to b much gold in it ?i am wondering can water flow be too fast? or too much Now pan this material and if you find gold then you know your sluice is not working efficiently. Even better half bury your pan and have the end of the sluice resting on it (so the material going through the sluice also passes through the submerged pan trapping any escaped heavy's). This reminds me if your worried about the angle and still cant figure it out then after sluicing for 5-10 minutes pan some of the tailing's taken from just below the end of your sluice box. I try and have a good amount of water flowing through my sluice i have had around 5-10 cm and upon panning the tailing's at the bottom of the sluice to check for lost gold i have not discovered any so the sluice was doing its job. If they don't clear at all then your angle is too shallow and if they don't even form then your angle is too steep. So i think the most important aspect is getting that magic angle.īasically i set mine up so i have approx a 10-15 cm drop from one end to the other (at a guess) and i put some material through it, now what i am looking for is are the beaches* that the material forms behind the riffles clearing at a good time frame e.g only takes a matter of several seconds to clear the majority of the material from behind the sluice (you can see if slowly throwing out the lighter material). Look at how fast the water flow is in dredging sluice boxes its very fast and they still catch the gold. Too steep of an angle and the gold washes right out of the sluice boxĪs for water flow if there is way to much then i am guessing gold would get washed out. Too shallow of angle and beaches" form and clog up behind your riffles in your sluice stopping gold getting trapped in the miners moss. The fine screen systems with recommended sluice box designs recovered 99% of their placer gold.I am no expert on sluice boxes and mine is home made and different to yours but yes angle does matter The article concludes with, “The fine screened sluice boxes had the lowest loss of all… one of the triple run boxes and a single run box lost more gold than they recovered. Use of expanded metal or angle iron is stated to, “severely reduces the opportunity for gravels and anything but very coarse gold and nuggets to enter the riffles.”įor those of you wanting to build your own sluice box, a 15 degree upstream angle is needed on riffles, and a slope of 12-15 degrees of your sluice box in the creek. This will not only dislodge accumulated gold but also float gold across overloaded riffles right back into the stream! We’ve joked about re-running the tailings of someone we know is overloading the sluice box or has too much water flow… but content ourselves with testing our own tailings periodically by pan to adjust for possible loss of gold. Many times a tired prospector starts feeding too much material to the sluice. the increased flow of the stream might clean it out for us!įeed rates, as mentioned above, are also critical. We try to remove our sluice box if an afternoon rain occurs. They are amazed that we even watch the ebb and flow of the stream during the day, adjusting for increased water flow. We’ve run into this situation many times with our guests… more is better! A high water flow will float finer gold right out of the sluice box. “Expanded metal riffles are shallow riffles which are sensitive to scouring and the resulting (which results in) coarse gold losses when they are subjected to surging or excessive water flows and/or steep sluice box gradients.” Packing and extreme gold loss were often observed when any of the following conditions occurred: Shallow slopes, narrow gaps between riffles, excessive feed rates, insufficient water flow, and riffles larger than 25mm. gap and be tilted at 15 degrees upstream of the sluice box‘s vertical in a sluice run, with a slope of 12-15 degrees. “Regular or modified angle iron riffles should have a 40-60mm. “The vortex is launched up to the top of a turbulent slurry column instead of onto the next riffle,” meaning the force of the water (vortex) carries the gold into turbulence rather than onto the next riffle, floating it right out of the sluice box due to bubbling and irregularity of gold particles. In a comparison of expanded metal versus angle iron, the report states, “Flat bar riffles are not recommended for fine gold recovery.” An example of this would be homemade angle iron riffles.
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