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 detectors. They still hold good potential for gold, particularly large gold in quartz specimens that were rejected by the classifier of the dredges.
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.
Small, rather insignificant pocket diggings can be found in just about every mining district in the world. These are small prospects that a miner made into the hillside in search of gold. It is not always apparent why the miner decided to start digging here, but for whatever reason they did, and sometimes these pockets diggings have gold in them.
Many prospectors often question why the old-timers would abandon these small diggings if there was gold in them. You can never know for sure, but there were a few reasons.
One important thing to remember is just how much gold a miner needed to find during the early days in order to live. It wasn’t like today where you might be happy to find a few grams of gold in a day. Back then, miners needed to be finding a lot of gold just to feed themselves.
Costs in the remote mining camps were extremely high, and if an areas wasn’t extremely rich a miner would often move on to look for a better gold deposit. Areas that were nothing special back in the 1800s might be considered extremely rich today. So don’t overlook these small, seemingly insignificant pocket diggings.
Lode Mines, Ore Dumps, and Tailings
When a miner discovered a rich gold outcrop and found that the more gold continued into the mountain, a lode mine would be developed. The size and scale of each mine varied, but many mines tunneled hundreds and even thousands of feet into the hillside following a gold vein. The ore would then be taken out of the mountain and processed.
If the ore was free-milling, it would be crushed and the gold would be extracted. This was a very expensive process, and often the ore needed to be very high-grade to be considered worthy of processing. For this reason there can often be ore found near old lode mines that was never processed and sometimes it contains gold.
Scanning old ore dumps with a metal detector can be productive. Just remember, there were no “rules” on how to it was done a back then, and not all of the mines were operated the same way. Some lode mines were very efficiently run and you may have a hard time finding a piece of ore with detectable gold. Other times, the miners were sloppy. They discarded pieces of high-grade ore with visible gold, and it can still be found in the waste rock piles. You never know what you will find until you look.
This is a good time to mention that it is never a good idea to enter an old mine shaft. Be careful when detecting around old mines. There may be hidden shafts that are hidden in the brush or other dangers. People die every year from entering old mine shafts. They can collapse. They often contain hazardous gasses. There may be snakes, bats, spiders, and all kinds of nasty stuff in them.
Unless you have the appropriate training and experience, NEVER enter an abandoned mine shaft.
Hydraulic mining was a practice that was used in many of the mining districts throughout the world. It used high pressure water to break up material and release the gold that was contained within. The practice was eventually banned in most of the United States due to environmental concerns, but it is still used in many places throughout the world.
The hydraulic mining operations found in the U.S. varied widely in size. Some of them were rather small and crude operations that were used in combination with standard placer mining in many creeks and rivers. Other hydraulic operations were massive, and they literally washed away mountains. Some of the largest and most famous can be found in the Mother Lode country of California.
Due to the size of some of these operations, many of them were quite sloppy and missed a lot of gold. These hydraulic pits can be prospected with a metal detector and still produce some nice gold.
A more modern indicator of gold mining activity is bulldozer scrapes. These are area where a bulldozer has been used to remove layers of earth to expose new gold bearing ground. It is common to see these in the desert, and the practice is used in combination with metal detectors. I’ve run across quite a few of these in Northern Nevada.
Once an area has been detected and all of the easily detectable gold is found, a bulldozer scrapes off a foot or two of material, exposing new ground that can be detected. The processes can be continued as long as there is still gold being found.
These can be excellent areas to find gold, but be aware that there are permitting processes required to do this sort of thing, and basically all areas that are actively being mined like this are on private lands or claimed land. Still, you can find older bulldozer scrapes on unclaimed land that were done years ago that still may produce a gold nugget or two.
Finding Historic Mining Activity
If you are a gold prospector, there is no better way to make sure that you are in a gold-bearing area than to find indicators of past mining activity. These are direct evidence that gold has been found somewhere before. With a bit of effort you will be able to find more gold there.
Some of the most obvious indicators of earlier mining activity are old dredge tailings and hydraulic mining pits. These can be seen from aerial photos and sometimes cover many miles. You shouldn’t have any trouble locating these areas.
Some man-made indicators will be smaller though. Drywasher tailings, pocket diggings, and smaller hand-placers will be less obvious. To find them it will often require “boots on the ground” and some research.
The old-timers didn’t find all the gold. If you can locate historic mining areas then you are close to gold.