Using a metal detector to find gold involves a series of swing movements at a constant height off the ground. Once a target is detected, the signal is re-checked over the area as it is being dug, getting closer to the anomaly, until the object is found.
Gold Detecting Techniques
To use a metal detector to find gold, the detector should be held in front of the operator and swept from side to side at a constant height above ground. This technique is known as “Swing 1“:
Depending on the gold detector model being used, the optimum height that the coil should be kept from the ground will vary. However, the most important part is to make sure that the coil is not raised on the end of each sweep because sensitivity will be reduced.
When a target is located during a side to side sweep, the exact location can be determined by passing the coil in a forward and back sweep direction, out from the feet and away from the body. This technique is known as “Swing 2“:
Useful Tips
Some gold detectors can be considerably heavy. Many professional prospectors operate a hip-mounted model to save energy, reduce arm fatigue, and ultimately maximise the working time and efficiency.
Control boxes are attached to a belt around the wais and connected via leads to a junction box on the handle of the tube. Some detectors however can be quickly converted from hand-held to hip-mounted or sling units.
The advantage of hip-mounted devices is that they can be tuned while the head is still scanning, thus enablilng a more efficient and accurate tuning to the particular ground the operator is working on.
To overcome the arm fatigue and reduce the chance of lifting the coil too far off the ground at the end of each sweep, some prospectors use elastic clips attached from a shoulder harness to the pistol grip on the hip mount.
Modern commercial harnesses are commonly used in the field. They help with the task of efficient transport of metal detector and other related tools such as GPS, maps, etc.
Pin-pointing a Target
It is important to not ignore the barely noticeable signals detected and immediately swing back over the area where a signal is heard to pin-point the exact location.
The first signal is normally detected with the swing 1 (side to side sweep). The movement after a target is detected should be changed to the swing 2 (backwards and forwards).
An alternative technique involves lifting the search coil approximately 6 inches above ground while continue scanning with an even motion. The signal becomes weaker, however the exact position of a target will be detected at the centre of the search coil.
Once an object is positively detected via a first scan, it is important to clear the patch of loose surface and objects by a quick scrape with your boot. If the signal disappears, it might indicate that the target was in fact small fragments of a metallic object such as scrap metal, wire, etc.
If the signal persists, a small depression approximately 1 inch deep by 2x the diameter of the coil is dug. The detector is set again over the target. If the signal is stronger/louder, it means that things are getting interesting and is time to start digging up the target.
Digging up a Target
In some areas such as Victoria (Australia), good sized nuggets can be recovered just below the surface. However, recovering a gold nugget in deeply weathered terrain such as Western Australia can be a hard task.
For this reason, is best to be prepared prior to heading out bush for gold detecting. The two tools that are needed at a minimum to dig up a target is a geologist pick or similar, and a digging tool with a small blade.
Holes should always be scooped so that the detector coil can be passed at a constant height down to the base and out again. Avoid digging steep-sided holes because the vertical walls interfere with the device’s ability to accurately detect targets.
A geologist pick or tiler’s hammer is a great tool to dig a gently sloping hole right below the signal area. It is also useful to break through consolidated soil, which can be hard to break.
Once you start digging over the area where an anomalous signal is heard, if no object is located in the first few inches, the detector is used for a second scan.
Don’t forget to remove the hammer away from the detector prior to doing so. Also remember to pile up any soil removed over the same area, as this will be scanned again at the end.
Digging tools with a small blade are more useful at this point for making disc-shaped holes wide enough to fit the detector. However, it is important to maintain gently sloping walls, as straight-sided holes will interfere with the signal produced by the detector.
A third scan is used to confirm if the signal is still positive and louder. At this point, it is imperative to proceed digging with care because many valuable nuggets or other treasured objects may be damaged with the digging tool.
Remember that gold nuggets with unusual shape may be sold at a premium price to museums and individual collectors around the world.
Sometimes, after the third scan the signal may disappear. This is very common and suggest that the gold nugget is in the soil that thas been removed. It is now time for a fourth scan over the soil that has been removed.
If no object is found in the pile of soil removed, try to carefully scan handful of soil under the detector. Alternatively, the soil can be slowly sprinkled on the upper side of the coil to isolate the substance creating the noise.
Often, small rusted nail heads or minuscule pieces of wire require a lot of searching before they can be isolated. However, sometimes the signal comes from a piece of rock – gold nuggets could be embedded within pieces of conglomerate (rock composed of other rounded rocks, generally “river stones”), quartz, slate, ironstone, etc:
Ground Noise
In heavily weathered terrains such as the Goldfields of Western Australia, ground noise is often a problem, because the soil is so rich in iron and other metals.
“Hot rocks” and “hot nodules” are pieces of rocks with very high concentration of iron, and when a gold detector scans over them, the patch will emit a signal similar to that produced by a nugget.
Some detectors are better than other at cancelling this “ground noise”. However, most detectors are designed for ground low in iron, hence it is important to use the right detector for the right location.
Most modern detectors however can be tuned to specific ground conditions to reduce the ground noise (“ground exclusion”)
Experienced prospectors can tell the difference between signals given off by hot rocks or mineralised soil, and the sound produced by a metal object. It takes a bit of time to learn to distinguish these.
Advice to Overcome Ground Noise
The key to overcome ground noise is practice. Nevertheless, these four tricks will help you differentiate between “noise” and real targets:
- Advice 1: One trick to overcome this confusing ground noise is the following: when a noise emitted from the speaker indicates a metal, repeat the coil sweep, but this time from a different direction. If the signal is only heard through sweeping from a single particular direction, then the object is almost certainly not a gold nugget or other valuable metal.
- Advice 2: Another way to identify ground noise is to carefully listen to the noise. Then elevate the coil approximately 2 inches and scan back over the patch. If the signal dies away rapidly, then it is almost certainly a non-metallic object. A gold nugget would still cause a weaker signal as the coil is raised above it.
- Advice 3: If the detector is picking up too many false signals and slowing you down, operate the coil at a higher position above the ground. In mineralised ground, this higher scanning position barely affects the penetration depth.
- Advice 4: Ideally, the discriminator mode should be avoided because some depth of penetration may be diminished. The key is to familiarise yourself with your detector and practice until you can distinguish the noise produced by gold nuggets and rubbish items. This training can be done at home, digging objects and scanning over them. The best gold for practice is natural nuggets, avoid using unnatural shapes such as gold rings.
Alluvials
Being able to recognise alluvial patches worked by early prospectors in the late 1800s is perhaps one of the most powerful skills you can master. This represents highly prospective ground for metal detectors as many nuggets were left behind.
With the high cost of fuel, a motorbike is a very handy prospecting tool. This allows the modern prospector to be based at a certain location and use the motor bike to cover more ground that would be possible in a 4WD vehicle. Additionally, the chances of staking a tyre on the main vehicle are greatly reduced.
Finding evidence of an old “dry blower” area is a key to finding alluvial gold in arid areas such as the Eastern Goldfields of Western australia. A lot of ground can be covered relatively easy on a motorbike, increasing the chances of success.