The amount of black sand and other heavy minerals, found associated with placer Gold, varies a lot: there is not a simple direct correlation. There are places that are loaded with black sand but have no gold. Conversely, there are also places that have good quantities of gold but very little black sand.
Flour gold or flood plain gold is defined as ultra-fine gold found in low micron size fractions, often smaller than 74 microns or 200 mesh.
You might have heard the term “flood plain gold” and are wondering what it really means. A very simple definition is “fine-sized gold flakes carried or redistributed by flood waters and deposited on gravel bars as the flood waters recede.” When this “redistribution” occurs, it is usually after heavy winter storms that churned up rivers enough to turn part of the bedload over and move the river bar gravels from one place to another. Within these gravels is fine gold that was previously deposited there. When waterways flow way up and above their normal banks, they generally drop the heavier gold in the front of the bar, and as pressure decreases, the finer gold starts dropping into the mixed gravel. Over time, some of this finer gold will work its way down to bedrock, but generally it stays on the move.
Never throw away your black sand concentrates. It takes extremely good panning techniques to capture fine or flour gold in a pan, and a high energy sluice will generally wash the micron gold out with the tailings, maybe even easier than washing out the fine black sand. If you suspect you have micron gold, the first step is to look for it with a good 20X or 30X magnifier, looking for discrete, small particles.
Fine Gold Recovery Equipment
Fine Gold Recovery Equipment is specifically designed to reduce the amount of raw gold bearing material to a manageable amount for further processing and/or aid directly in the separation of finer grains of gold from heavy black sand.
