Beach Placers

A lot of beach placers have been discovered along the Pacific Coast and a lot of them have been worked on. Beach placers also take place 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.

Two types of beach placers exist; ancient beaches and the current ones. A big number of the beaches that have gold are situated in California except they have not produced a lot of gold. The majority of the gold comes about from the rocks that are being worn out by the waves.

Nearly all of the Eolian placers that are in the desert take place because of the bajada being increased by on the surface as a result of the action of the wind on the materials that waft off.

There are a several different things that happen in order for a placer deposit to be preserved. Because of the fact that streams are constantly altering their positions, leftovers of their deposits are left sheltered such as in the case of the terraces and beaches that are left at different periods when a stream is cutting into a channel that is deeper. The deposits that stay behind will sooner or later be worn away except if something is shielding them, that is. One way that a placer is conserved is when it is buried. For the most part this happens when a stream has been covered by mudflows, lava, ash falls and so forth. Other ways this could take place are when:

• When there is a covering with gravel when the stream is obstructed.

• When there is a covering with lake deposits.

• When there is a covering with gravel.

• When there is a covering by the material of a landslide.

• When there is a covering with gravel when the course of the stream goes down under the normal base level of wearing down.

• When there is a covering of an older stream course with alluvial fan matter as conditions that favor the stream to exist do not succeed.

• When there is covering with glacial till.

• When there is a covering of beach placers with sediments from the sea as the coast is flooded and elevated.

The rocky content of a placer may develop into tightly cemented stuff when it is saturated with by mineral material such as silica, lime and iron carbonate. This is more likely to take place as the placer becomes more mature.

It is at times awfully tricky to break down these older cemented gravels and because of this some of the tailings in the old mines are profitable to work in. The gravels that are cemented were at times never broken down as they travelled through the sluice boxes, and the gold was simply put back into the existing streambed.

The gold that can be seen in placers appears initially from veins and other mineralised areas in bedrock when the gold was set free from its rock by the weather and disintegration. Many times the starting place of gold in a placer was not in a deposit that could be mined effectively but the richer deposits in general take place when there is another concentration from older gravel that has gold. In most cases the original source of gold is not far from the place it was first stuck after having been carried by the water.

The minerals that are especially heavy and resistant to chemical and mechanical damage can be found with the gold in placer deposits. This is more commonly known as black sand. Black sand is on the most part made up of magnetite; nevertheless some of the other minerals that can be found in sluice boxes are tungsten minerals, cinnabar, platinum, chromite, pyrite (which is also and more commonly known as Fool’s Gold), hemitite, zircon, and garnet.

There are in addition a number of other things that can be found such as amalgam, metallic copper, quicksilver, nails, and loads of other things. When the cross section of a river has gone through down faulting on the upstream side it generates a pouch that catches the gold, gravel, silt and sand as well as titanium minerals, and in some occasions diamonds have been discovered.

Gold has a high gravity and is approximately six or seven times higher than quartz and increases up to nine times in the water and this is what makes the gold work its way to the bedrock or move until it becomes caught. After it has been caught in the bedrock it is not easy for the stream to raise it again. The specific gravity of gold is of nineteen and this means that it is nineteen times as much as an equal amount of water to its mass.