Types of Gold Placers
The natural processes of erosion result in a variety of different ways that gold will concentrate in the natural environment. Depending on how they were formed, placer deposits are given different classifications. Below are some common placers commonly associated with gold deposition.
Alluvial Placers- these gold deposits are the most commonly found throughout the Western U.S. and were typically the first deposits that were exploited by the early day gold miners. They are gold concentrated by streams and rivers, typically consisting of paystreaks on the inside bends of flowing waterways. For the most part, in the United States these deposits have been worked out on a commercial scale, with the exception of Alaska and a few other remote locations. Alluvial deposits are rejuvenated constantly to a small extent, and are some of the most popularly mined areas worked by recreational prospectors.
Eluvial Placers- these placers are generally consistent of deposits that form downhill of the original lode source. The forces of gravity and downhill creep move material downslope, generally concentrating heavier and larger concentrates toward to base of the exposure. The extent and spread of eluvial placers can vary greatly. The main lode source can commonly be located, but in some instances the entire lode deposits has weathered away, leaving behind only the eluvial deposition.
Bench Deposits- these are generally remnants of other ancient placers. These were typically alluvial placers at one time, but they were left “high and dry” by the down-cutting of a river system or the raising of mountains over millions of years. In California and other areas, these deposits were commonly processed using hydraulic mining.
Residual Placers- the continuous erosional effect on a gold outcrop will result in the deposition of gold in the nearby vicinity. Lighter materials will be taken away by wind and rain, leaving the heavy mineral concentration. Although these placers are generally not extensive enough to attract commercial mining endeavors, they can be a very productive for the individual prospector using a metal detector to find gold.
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Beach Placers- fine gold deposits can be found along the beach sands in many locations throughout the world. Two well-known areas in the United States include the rich deposits of Nome, Alaska and the beaches of Southern Oregon. Gold is either carried to the ocean by rivers and creeks from nearby sources, or eroded directly from wave action along the beaches. These deposits can often be found directly along the shoreline and along ancient shores well above current sea level. These deposits generally contain fine gold. (Also read about gold in the ocean).
Glacial Deposits- these placer deposits are formed by glacial movement, transporting gold bearing gravel from different sources and depositing them elsewhere. Glacial gold deposits are very well known throughout the Midwest and Northeastern U.S. They are almost always characteristic of very fine gold that has been pulverized by glacial action. Although widespread, these deposits are generally small and not economically viable for commercial mining endeavors.
Eolian Placers- typically found in arid regions, natural erosive processes (wind) cause sand and other light materials to blow away, exposing heavier minerals, essentially exposing the vein by eroding lighter material from around them. Although these can be rich sources, the spotty distribution of gold is generally not workable on a commercial scale. Patch hunters using metal detectors can often work eolian placers very efficiently.
Flood Gold- Very fine gold can be transported considerable distances by high water flows. Although some small amounts of concentration can occur, flood gold is almost without exception extremely fine textured, and do not concentrate in any payable quantities. Even to a recreational prospector, flood gold is very difficult to retain and does not attract much attention do to its small size and limited abundance.
There are many sub-classifications of various placer types. Different environment have various impacts on gold deposition. Understanding the characteristics of these different placer deposits are critically important in understanding how and where to find gold.
Alluvial Placers- these gold deposits are the most commonly found throughout the Western U.S. and were typically the first deposits that were exploited by the early day gold miners. They are gold concentrated by streams and rivers, typically consisting of paystreaks on the inside bends of flowing waterways. For the most part, in the United States these deposits have been worked out on a commercial scale, with the exception of Alaska and a few other remote locations. Alluvial deposits are rejuvenated constantly to a small extent, and are some of the most popularly mined areas worked by recreational prospectors.
Eluvial Placers- these placers are generally consistent of deposits that form downhill of the original lode source. The forces of gravity and downhill creep move material downslope, generally concentrating heavier and larger concentrates toward to base of the exposure. The extent and spread of eluvial placers can vary greatly. The main lode source can commonly be located, but in some instances the entire lode deposits has weathered away, leaving behind only the eluvial deposition.
Bench Deposits- these are generally remnants of other ancient placers. These were typically alluvial placers at one time, but they were left “high and dry” by the down-cutting of a river system or the raising of mountains over millions of years. In California and other areas, these deposits were commonly processed using hydraulic mining.
Residual Placers- the continuous erosional effect on a gold outcrop will result in the deposition of gold in the nearby vicinity. Lighter materials will be taken away by wind and rain, leaving the heavy mineral concentration. Although these placers are generally not extensive enough to attract commercial mining endeavors, they can be a very productive for the individual prospector using a metal detector to find gold.
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Beach Placers- fine gold deposits can be found along the beach sands in many locations throughout the world. Two well-known areas in the United States include the rich deposits of Nome, Alaska and the beaches of Southern Oregon. Gold is either carried to the ocean by rivers and creeks from nearby sources, or eroded directly from wave action along the beaches. These deposits can often be found directly along the shoreline and along ancient shores well above current sea level. These deposits generally contain fine gold. (Also read about gold in the ocean).
Glacial Deposits- these placer deposits are formed by glacial movement, transporting gold bearing gravel from different sources and depositing them elsewhere. Glacial gold deposits are very well known throughout the Midwest and Northeastern U.S. They are almost always characteristic of very fine gold that has been pulverized by glacial action. Although widespread, these deposits are generally small and not economically viable for commercial mining endeavors.
Eolian Placers- typically found in arid regions, natural erosive processes (wind) cause sand and other light materials to blow away, exposing heavier minerals, essentially exposing the vein by eroding lighter material from around them. Although these can be rich sources, the spotty distribution of gold is generally not workable on a commercial scale. Patch hunters using metal detectors can often work eolian placers very efficiently.
Flood Gold- Very fine gold can be transported considerable distances by high water flows. Although some small amounts of concentration can occur, flood gold is almost without exception extremely fine textured, and do not concentrate in any payable quantities. Even to a recreational prospector, flood gold is very difficult to retain and does not attract much attention do to its small size and limited abundance.
There are many sub-classifications of various placer types. Different environment have various impacts on gold deposition. Understanding the characteristics of these different placer deposits are critically important in understanding how and where to find gold.
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