Saturday, July 02 2016
Although there are many variables that go into catching gold in a sluice, perhaps properly “tuning” your sluice is the most critical. A few months ago, Steven “Doc” Vetter, owner of Gold Hog brand mats, wrote an interesting article for Gold Prospector Magazine that focused on a few key factors that all miners should pay attention to. The following ideas from his article are all about achieving the proper tuning exchange, meaning letting the junk flow out, or be worked out by exchange zones, and holding the stuff you do want—gold. A well-tuned sluice will have heavy gold concentrations up top, medium gold in the middle, and trace gold near the end Hydraulic Equivalence: By definition, “hydraulically equivalent” (HE) refers to particles of varying size, shape and density that fall out of a water flow and deposit in the same area. While quartz rock and gold vary greatly in specific density, you can make them collect in the same place by making the quartz rock bigger and rounder. A 2 inch quartz rock and a 1 mm sphere of gold will fall through water and deposit in about the same place— making them hydraulically equivalent (HE). An opposite example is a .25 inch round piece of gold and a .25 inch round piece of quartz. The gold will sink through the water and likely land straight down. The quartz rock, however, will not fall as fast and will be pushed several feet away before it settles. These two items are not HE. The shape of the gold has a big influence on its HE. Flat things move more easily than spheres when either moving water or air is introduced. HE is a huge factor in gold mining and is often the main reason for classifying material to a certain size— the theory being if everything is about the same size, the heaviest material will stay in the sluice. When you slow down a sluice, you start to have a traffic jam. Things that are HE all want to gather in the same deposit zone and you start to gather/open the window for more non-gold particles to pile up and that’s not good. Incremental Processing: A great analogy of how this principle works is to picture a city bus. Imagine a rule where all passengers must enter through the front and must exit through the back. As they enter, passengers must fill the seats in the front of the bus first. Every time the bus makes a stop (you shoveling dirt into the hopper of your highbanker or sluice), the first few rows fill up quickly and remain full for a short period of time. As a new passenger (each new shovel full of material) gets on and finds the front seats taken, he must move further down the bus (sluice). The result is a bunch of folks all competing for the same seats up front and when there are no seats up front, they must take the next available one. If all the seats get full, a passenger (your paydirt) never even gets to sit down and exits the bus (sluice) without ever sitting (collecting in the riffles). As the working zones in your sluice fill up, slurry material will move down to the next zone before it settles there. During times of heavy loading, the first percentage of your sluice will load up heavy and take some time to exchange out. That means gold will keep traveling until it finds an “empty seat.” If you load too heavy or have too short of a sluice, you’ll have gold flowing over holding zones that are busy working and exchanging. It may take an exchange center (vortex) 3 or 5 seconds to fully process down material and exchange out non-gold and heavies. Fine Tuning: Because of the principles of Hydraulic Equivalence and Incremental Processing, you may have realized that slowing down a sluice can really cause problems and loss of gold. How do you know if your sluice is running too fast or too slow? Experiment! Of course doing so is a little scary because the #1 fear of most gold miners is losing gold, and quite honestly, until your sluice is fine tuned, that just might happen. To avoid losing gold, most miners start running their sluice at the “normal” or widely accepted pitch of 1 inch per foot. But this is just a starting point. If you see gold in your tailings, your first thought is probably to slow it down so you aren’t blowing gold out of the sluice. But perhaps that’s not the cause at all. Perhaps it’s because gold doesn’t have a place to sink down into and hide in your sluice. Experiment by running way too fast, say at a 15-degree pitch. Then take it to 13 degrees, then go down to 12.5. Keep adjusting until you find an acceptable capture rate for the size of gold you want to hold. Lose your fear of losing gold through testing and experimentation. Not only will you fine tune your sluice, but you’ll also get a great education. Good luck!     Comments:
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