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 Thursday, November 5, 2020

Ask Kevin (GPM November/December 2020)


Ask Kevin (GPM November/December 2020)
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From the November/December 2020 Gold Prospectors Magazine



Dave R. asked:

I am a new member, new to detecting and do not understand many of the settings, especially sensitivity.

Can you help?



This is a recurring topic and one that I think I should get a video up on pretty quick explaining sensitivity and how it can help and hurt you detecting.

My trusted Gold Bug 2 in the factory preset. (7-7-7)


First, sensitivity is not a process of TX (transmit), it is a process of RX (receive), so no matter what you cannot turn it up and put more power into the ground. What you can do, however, is turn your sensitivity up high enough that it will mask a signal.

Think of it in the easiest of terms as an amplifier — each step up not only enhances the return of the target signal, it enhances the ground noise around the target. Given that the there is a lot more ground than there is target ratio, what you can end up doing is making the ground really loud and the target really soft — in some cases nonexistent.


After turning the Sensitivity down I will turn the Ground Reject main back up knowing that after the sensitivity is set to the ground, it will ground balance faster and be smoother.


This process holds for all detectors from Pulse Induction to VLF with the exception of the Minelab Gold Monster 1000.

You should always set your sensitivity to the ground you are working, not a factory preset. It’s a simple procedure; here is how to set sensitivity to the ground:

When you’re first setting your detector to the ground you are working, follow the entire process. After you get used to setting up to the ground, start wherever you are when you turn on the detector.


Over the years I have tried this many different ways and found that the coil just off the ground works the best.

PRO TIP: Carry a small piece of lumber (1x1 or 1x anything) with you. It offers you a good, stable platform for setting your sensitivity.

I.Turn on your detector and set it to the factory presets for sensitivity and threshold. Ground balance your detector until you have the same sound moving the coil up and down just a couple of inches off the ground.

After ground balancing, the Ground Reject is just above 4. Number does not matter, but it gives me an idea of the ground mineralization.


II. Once your detector is balanced and you have set your threshold to the sound of a mosquito buzzing by your ear, turn the sensitivity way down. Reground balance again and reset the threshold if needed.

III. Toss your piece of wood on the ground and set your coil flat on it. Your coil needs to remain stable and not moving around for this to work its best.


I drop my chunk of wood onto a flat ground so I can set the coil on the wood. I do not want the coil directly on the ground.


IV. With the coil stable on the wood and your headphones on, slowly begin to increase your sensitivity until your threshold starts to become unstable.

V. When the threshold becomes unstable, stop and back off of the sensitivity just until it smooths out. That’s it; you have now set your sensitivity to the ground you are working and not some number that is an average of the detectors testing before it was release to the public.


Adjusting the sensitivity up until it becomes unstable then backing off a bit until stable again. Now your sensitivity is set to the ground it is working on.


By matching the sensitivity to the ground, you are equalizing out as much ground noise as possible while still keeping targets in the mix. I have trained thousands of detectorists on this process over the last few decades and have had nothing but great responses from them on how it improved their ability to clearly hear targets in the worst ground. Good luck, and let me know how you do.



Rob T. asked:

All this talk about mercury in the streams in California — isn’t mercury naturally formed as well?





Great question and one that sparks a great deal of debate. And frankly there is more than one answer and more than just one type of mercury that is in the spotlight these days.

Let’s ask, is elemental (liquid metal) mercury (Hg) naturally forming right this second? Yes and no. The reason, and better question to ask is, does mercury randomly leach out of its major host, mercury sulfide (HgS) or as most of us know it, cinnabar? And to that I will say yes, given the right conditions that include events like volcanic events, subterranean heated fluid contact, heat creating friction from earthquakes and other geological events that create friction that may or may not have fluids involved. And yes, it can and does occur through material weathering of the host but in very minute amounts.

Cinnabar is not the only host to mercury. Some of the other ores include corderoite, montroydite and calomel, to name just a few. All of these ores are formed underground in heated mineral solutions that push upward to the surface mostly because of volcanic events. Coal-burning plants also release mercury vapor into the air.

Mercury has a very low boiling point of 675 degrees F and in processing/refining, once the temperature is reached, the HgS releases the mercury as a vapor. As the vapor cools, it forms into the liquid metal we know as elemental mercury.

Refining HgS into Hg is a very straightforward process:



• Cinnabar is mined, crushed to a fine powder in a series of mills, then roasted.

• The roasting process heats the HgS, which has a reaction with the introduction of oxygen and creates sulfur dioxide (SO2), and all goes into a vapor.

• From here the mercury vapor, sulfur dioxide, H2O vapor and anything else that is trapped in the vapor is forced into a condenser area with pipes constantly circulating cold water.

• As the vapor passes through these condensers, the mercury vapor cools and drops out as liquid or elemental mercury. After that it is collected and filtered to its highest level of purity.


So how does this relate to naturally forming mercury? Let me introduce one of many hypothetical situations. If you have ever traveled through Beatty, Nevada, then you have seen the hot springs resorts that align with the Amargosa River, which through this part of Nevada is for the most part completely underground.


Now let’s add a number of fissures that feed the surface hot springs and say that the geothermal waters pass through an area that has cinnabar deposits. The mercury sulfide would release mercury as a vapor and pushed up in the steam. Say one of these fissures breaks off the main and goes into the underground river. Where the vapor entered the river, elemental mercury would form. The remaining mercury vapor cools as it travels upward and will drop back due to specific gravity, and the process starts all over again. A seemingly never-ending cycle until the vapor finally makes it out of the system.


Don’t worry, though, in that area the chance of a cinnabar deposit that would have enough mercury to equal the amount of methylmercury you would get from eating a lot, and I mean a lot, of fish is nonexistent. According to the National Center for Biotechnology Information (NCBI), mercury deposition is as much a function of rainfall as it is of the actual point sources (


The debate over mercury will not end, and I agree that mercury mishandled can be dangerous. But any more than eating a predatory fish? It doesn’t seem so according to the leading experts around the world. Most importantly to me is understanding the facts and not misinformation or an interpretation of the facts.


I invite you to study and understand the three basic forms of mercury: elemental (metallic) mercury, inorganic mercury, and methylmercury.


Read about these from reliable sites such as the one listed above along with the USGS, WHO, CDC and others that state facts, not speculation. I think you will be surprised that the truths surrounding mercury differ from what you may be hearing.





YOUTUBE: goldrailstv


Total Comments (1)


1 comments on article "Ask Kevin (GPM November/December 2020)"

Brian Larson

11/20/2020 8:01 AM

Ive learned so many new tips on Detecting correctly and it has improved my skills meeting and reading Kevins teaching!

Thanks Kevin for all you do!

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