Residual Gold Placers

Residual placers come about when the gold is freed from it’s starting place and the material that encases breaks down. This occurs when there is continual surface weathering. Disintegration occurs when there is constant and strong geologic conditions that cause the mechanical break down of the rock and the chemical decay of the minerals. The top of the ore that bears gold is augmented while the rock disintegrates, due to the fact that some of the softer and more soluble parts of the rocks get taken and carried away due to wearing away. 

After the gold has been freed from the bedrock encasement and rock decay due to the weather, it starts to travel down the hill side and sometimes washed down to the rivulets and gullies and then into the stream beds. While it is travelling down the gold sometimes concentrates itself in a quantity that merits mining. These types of deposits are called Elovial Deposits.

There are some prospectors that point to the forming of some placer deposits to the action of glaciers and this is actually not the case. While it is true that glaciers scrape off loose soil and debris, they do not sort it and ice is not effective in the concentration of metals. The streams that come from ice that has melted might sometimes be effective enough in sorting to cause deposit to be formed though.

Bajada means slope in Spanish and it is used to classify a confluent alluvial fan down the base of a mountain range. The amount of gold that is produced from bajada placers is not much in comparison to other placer workings because of the lack of efficient dry washing methods used in the past.

The forming of a Bajada placer is pretty much the same as a stream placer only that it is conditioned by the climate and topography of the dry region it occurs in. the amount of the gold that has been released from its environment as it works down from the lode outcrop to the Bajada is deposited on the slope near the mountain range. The gold falls along the line, which is the contact of the central fill with the bedrock.

Even though the most amount of concentration of gold will be on the bedrock, bulk concentration does not happen the way it does in a stream deposit. Due to the fact that some percentage of the gold is still imbedded in its matrix, it is possible that less gold will get to the bedrock and more of it might be scattered throughout the deposit than in the case of the stream gravels.

A good number of beach placers have been found along the Pacific Coast and many of them have been worked on. Beach placers also occur because of shore currents and the action of the waves on the materials that are then broken down from the sea cliffs and washed into the sea by the streams.

There are two types of beach placers; ancient beaches and the current ones. A large number of the beaches that have gold are located in California but they have not produced a lot of gold. Most of the gold comes about from the rocks that are being battered by the waves.

Almost all of the Eolian placers that are in the desert occur because of the bajada being augmented by on the surface due to the action of the wind on the materials that blow off.