The evidence of historic mining activity is probably the easiest way to identify a place that is gold-bearing. Mining activity that took place even back in the mid-1800s is often very noticeable today, and these indicators are excellent proof that gold can be found there. Even in areas that have been mined hard, the gold is never “mined out.”
Careful searching will almost always produce more gold for a patient and determined prospector, so seeking out these previously mined areas is a great way to find gold.
One of the types of historic mining that is easiest to identify is tailing piles left behind from dredging operations.
I am not talking about a modern suction dredge; rather we are talking about the huge bucket-line dredges, drag-line dredges, and smaller “doodlebug” dredges that were so commonly used in the rich gold bearing areas mainly during the early to mid-1900s.
These dredges churned up the valley bottoms in many of the gold districts throughout the world, and were very common throughout the western United States. The tailing piles left behind are very evident today; large, uniform piles of rocks and gravel, often for many miles along the valley floor.
Dredge tailing are very attractive to prospectors using metal detector. They still hold good potential for gold.
Each dredge was different. Some of them were set up rather well, and did not leave too much gold behind, however they often did miss quite a bit of gold that was lost out of the back of the dredge. Considering the huge amounts of material that they processed, it is not hard to believe that they occasionally got overloaded with material that would get missed in the sluices.
Hand Stacked Rocks
Another fun fact about dredges was how they would screen out the larger material, gravels, rocks, etc. to be discharged. This was the most efficient way to run them, so that only the richest material was processed, but in the process an occasional large nugget and specimen did get lost. There is some BIG gold laying in some of the old dredge tailings out there, it’s just a matter of finding it.
The dredges were generally used in the main river bottoms and in drainages that had sufficient water for them to operate. They required a decent amount of water year-round in order to run one profitably, so they couldn’t be used everywhere.
Hand stacked rock piles are another excellent indicator of historic mining activity. While mechanical mining methods could often be used in the major drainages, the smaller creeks and gulches that had limited water generally needed to be worked by hand. A miner had to manually dig down to bedrock to get down to the gold. Any rocks that were encountered in their digging needed to be moved out of the way and set to the side.
There are miles and miles of creeks and gulches that were worked by early-day placer miners. And the evidence of hand stacked rocks is one of the most notable indicators that they were there. These rock piles are generally still undisturbed.
Sometimes prospectors have a difficult time distinguishing between hand stacked rock piles and dredge tailings.
The most notable difference between the two is usually in the uniformity of the piles. Dredge tailings will be more uniform and generally larger, while hand stacking can be more subtle. Regardless of how the piles were made, they are both good indicators that gold has been found there in the past.
In more arid regions, it was impossible to use standard placer mining methods like dredging and sluicing due to the lack of water. This is an extremely common problem throughout many areas including the southwestern United States, Australia, and countless other mining regions throughout the world.
Where water was limited or nonexistent, drywashers were (and still are) the primary search tool for gold prospectors. Rather than sorting out the gold using water, a combination of air pressure and vibration is used to separate the gold out from the lighter materials, and although they do work quite well, they are much less efficient than other mining methods and because of this much gold is lost and left behind in the waste piles.
Scanning old drywasher piles with a metal detector is a great way to pick up a gold nugget or two that may have been missed. Finding these piles is also a great general indicator of where gold has been found, and you can explore the surrounding hillsides with your detector to seek out undiscovered gold deposits.