Placer Geology

Thorndike/Barnhart´s Customs Dictionary defines “placer” as “a deposit of sand, pebble or ground on a streambed that contains gold particles or some other kind of valuable minerals.”

In that same dictionary, the word “geology” is defined as “the traits of the external layer of land in a place or region, rock or rock formations in a particular area.” That is to say that if we put these two words together, we will get “placer geology” to identify the nature and traits of the formation of gold deposits and other valuable minerals in the streambed.

The main factor for gold to deposit in the locations it is found is due to the larger weight it has over the rest of minerals that also end at the bottom of the streambed. For larger weight we are trying to say that gold is heavier than any other material with the same space or volume as gold. For example, a big stone will weigh half an ounce of nugget gold; the nuggets will weigh more than six times than a chip of rock.

While gold is eroded from its original lode, gravity, wind and water apart from other natural forces can push it to the streambed. There are many kinds of gold deposits that the gold seeker should know about because they have different features and its exploitation varies along with each one of them

The different types are the following:

• Lode
  Any deposit of valuable mineral, in form of rock yet, that covers the cracks and crevasses expanding through the common country rock is called lode. Lodes are the source of origin of the placer deposits.  

• Residual Deposits
  A “residual deposit” consists of those pieces of lode that have loosened from the flourishing of the seam due to chemical and physical deterioration, but have not been removed or pushed towards the lode area. A residual deposit generally lies beside a lode.

• Eluvial Deposits
  An eluvia deposit is formed by those pieces of iron and gold that have been eroded from the lode and have not still been moved by natural forces to the streambeds. Eluvia deposits are usually spread along the mountains under their original lodes. Generally, the different forces of nature can cause an eluvia deposit to spread; more even when the segments are pushed beyond its lode deposit.
  The individual pieces of an eluvia deposit are commonly called “float.”