The Geology of Placer Deposits
There are various sorts of placer deposits that are classified as the most common placers:
- There are eolian placers or local concentrations caused due the wind that has removed the lighter minerals.
- There are also glacier stream placers that in most cases do not have a lot of gold in them.
- There are bajada placers and these are located in a peculiar type of desert or dry placers.
- Hillside placers or elovial placers that represent transitional creep from residual deposits to stream gravel.
- There is also what is known as seam diggings or residual placers.
Stream placers
Stream placers have been the greatest source of almost all the placer gold mined. Stream placers have sand and gravel that takes place by the action of the water that is running. If there has been different times of wearing down which has then gone back to normal, there will be more of a heavier concentration of minerals in that area. Stream deposits have been around for an extensive amount of time and there are still a good number of them. There are well-defined channels whereas there are others that are just benches. All the bench placers were in the beginning stream placers comparable to the present stream deposits you see these days. If these were not worked on again by wearing down they stay as benches or terraces on the sides of the valley cut the by the present stream. These deposits are what are known as bench gravels. To be able to comprehend stream placers, it is essential to learn and study about streams and learn about their history, character and habits.
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