We are now going to dig into all of the various methods of actually recovering gold from the earth. There are many ways of doing this and much of it depends on where you are looking for the gold. In this case, we will discuss placer deposits. So what is a placer deposit? Let’s check it out.
In geological terms, placer deposits are areas where very valuable minerals are accumulated and collected. This is done by gravity, which separates the minerals, hopefully gold in our case, from the rest of the soil during the sedimentary processes that occur while the water in a stream is rushing about. This term is derived from the Spanish language word placer, which has the definition of “alluvial sand.” Alluvial sand is basically loose soil that has been removed, reshaped, and redeposited somewhere, in this case it is deposited in placer deposits where we can easily sift through it and find out precious gold nuggets.
Gold Rush Placer Deposits
Back in the day of the forty-niners in the gold rush, placer deposits were the leading source of gold for the individual who couldn’t afford the large equipment that the big companies could. Placer mining, or gold panning, was the main technique used to recover this gold for the forty-niners.
The materials that ultimately end up in placer deposits are the most dense, because they have to be heavier to not be washed away. Specifically they have to be more dense than quartz. They can’t collect in the placer deposits if they keep washing down stream. They are also the most resistant to weathering or they will become too small, too light, or busted apart and washed down stream. So what gets left in there? Among the leftovers is gold!
Black Sand in Placer Deposits
Placer deposits contain what is typically called black sand. It is obvious why it is called this once you see it. It is literally black sand, which is composed of a black mixture of shiny iron oxides. Among these other dark materials are valuable minerals such as monazite, zircon, wolframite, chromite, rutile, and cassiterite. Others are gold (duh!) and platinums, tin, diamonds, thorium, titanium, and in really old placer deposits you may even come across uranium (which is radioactive, so don’t pick it up and keep it!).
Formation of Placer Deposits
These placer deposits are usually formed in stream and rivers, typically around the inside bends, natural hollows, and the break of a vertical slope. You can also find them at the bottom of waterfalls and smaller barriers. It happens in these locations specifically because the velocity of the water stream becomes too low to move the dense materials.
This is the place you want to start your gold panning. Gold panning is something you must master, even if you get into the bigger equipment work, because you have to sort out even the last part of the heavy machinery systems. Head over to the black sand placer deposits in the rivers and streams near the popular gold finding areas and get panning!