What Separates Gold Nugget Detectors From Other Types Of Metal Detectors?

[MikePfeiffer]

As you know I have been metal detecting for 30 years. I still consider myself a newbie. However, it is with the same old machine. Back when I purchased my machine we were told it will detect everything, it's a do all machine. I new of prospecting machines, but never knew the difference or seen the demand until I came to this forum. So if you have time, please answer these question. I am going to throw these out as I don't really know how to ask the correct question. What if the difference in a gold machine vs a regular machine? What makes them stand out? I know there is a frequency difference, but what make them stand on when looking for gold? Are they just not tuned for gold?

[mn90403]

Mike,

Steve has made a guide to gold detectors which he updated in May of this year.  That would be a good place to start.

https://www.detectorprospector.com/magazine/steves-guides/steve-guide-gold-nugget-detectors/

 

[Steve Herschbach]

Metal detectors for prospecting originally were just coin detectors with a different label. My first metal detector in 1972 was a White's Coinmaster 4. My next was a "prospecting detector", the old White's blue box Goldmaster. Even then I was curious about what made them tick, and my first lesson in detector marketing was that the Goldmaster had the same circuit board in it as the Coinmaster! White's just put the same board in a larger box and called it by another name.

Those old machines were very poor since they could not ground balance, but even then prospectors found a large nugget now and then using them. It was not until around 1976 when White's unveiled ground balancing technology in the form of the White's Coinmaster V Supreme, probably the most significant breakthrough to affect detecting up to this day. The CM5 though was a very low frequency machine running at 1.8 kHz and not sensitive to small items. True story though is I owned one myself, and sold it to a prospector who promptly went out and found a nugget weighing several ounces with it.

It was Garrett who really launched the modern prospecting metal detector era around 1980 with the 15 kHz Garrett Groundhog. The 15 kHz frequency choice was far higher than the 3 - 8 kHz standard of the day. This enhanced the sensitivity of the machine to smaller targets and combined with the ground canceling capability the Groundhog series was one of the first detectors to stand out in the fledging electronic prospecting rush just underway in Australia. The skyrocketing price of gold fueled detector sales, and soon reports of massive gold nugget finds appeared. All of the sudden all the other manufacturers wanted in on this new business opportunity.

Photo - Garrett 15 kHz ADS Groundhog in 1980, later rebranded as the Garrett Gold Hunter (click for larger version). Garrett employed the same basic circuit in several models all the way up to and including the 15 kHz Garrett Gold Stinger, only retired a few years ago.

Still, many of the new machines of the day were just repackaged coin detectors. The next big advance was what in my opinion was one of the earliest prospecting detectors designed from the ground up for that purpose. It was even part of the marketing pitch "the metal detector engineered for one job". The 19 kHz Fisher Gold Bug introduced in the late 1980's timeframe. By 1990 Gold Bugs were everywhere, and the new lightweight design with compact removable control box mounted on an ergonomic (for the times) S rod was truly revolutionary. The dual stacked ground balance control and 19 kHz low gain design was excellent at ground handling and had good sensitivity to gold nuggets.

In highly variable ground the manual ground balance machines left something to be desired, and this was most apparent in the Australian goldfields. In 1987 an upstart company in Australia introduced automatic ground tracking in the form of the Minelab GT16000. This was a real aid for prospectors in extreme ground and helped propel Minelab into view as an option for U.S. prospectors.

For me personally in Alaska, with low mineral ground and small gold, the next big event was the introduction of the 50 kHz White's Goldmaster II in 1992. This large jump in frequency made the machine shine on small gold in low mineral ground, and it was the GM2 that really caused metal detecting for gold to take off in Alaska. I could not get them fast enough initially to meet the overwhelming demand, which I personally stoked locally with my own success in using the unit.

By 1995 Fisher returned fire with the 71 kHz Fisher Gold Bug 2, which represents a high water mark of sorts in single frequency nugget detector designs. Still in production to this day, it is the detector of choice for many prospectors who choose to use a single frequency detector.

However, increasing metal detector sensitivity to small gold by boosting frequency was not helping get large nuggets deeper in extremely mineralized ground. Engineer Bruce Candy shopped a pulse induction design around to a few manufacturers but U.S. companies were not impressed with its poor sensitivity to small gold and they thought nobody would pay the money required to purchase such a device. The Minelab SD2000 was introduced in 1995. I tried one on my ground in Alaska and could run circles around it with a Goldmaster 2 or Gold Bug 2. The SD2000 simply could not detector gold much smaller than a gram in size even if the nugget was touching the coil. I could not see why people would spend thousands of dollars for such a device.

The answer of course was Australia. Large nuggets buried deep in highly mineralized ground, out of reach of the induction balance detectors. Massive amounts of gold were found with the SD in Australia, and savvy operators in the western U.S. took note. Soon SD machines were also being used in the worst soils in the western U.S. and pulse induction technology proved itself with its amazing ground handling capability.

And the rest, as they say, is history. The big failing of the pulse induction machines initially was in small gold capability, but with each generation Minelab improved on this, to the point that now a Minelab SDC 2300 is very close to the best induction balance detectors for small gold sensitivity while having superior ground handling capability. Minelab developed such a large lead in pulse induction that nobody else was able to seriously challenge Minelab in this area. To this day they are the undisputed leader in gold prospecting detectors, this reputation built largely on the back of their pulse induction machines, culminating in the GPX 5000 and SDC 2300.

This history points out two main areas where nugget detectors differ from other detectors. Higher frequencies to enhance sensitivity to small items, and advanced ground handling capability. The two things fight each other because making detectors more sensitive to small gold also makes them more reactive to the ground.

Along the way though a funny thing happened. In the quest to make better coin and relic detectors, manufacturers started boosting the frequency and gain on single frequency detectors. In my mind the 14 kHz White's MXT was the first real crossover model, designed first for coins and relics, but quite capable of finding gold nuggets in moderate soils. It's superb ferrous handling made it the machine of choice in Alaska in tailing piles, where moderate ground and massive amounts of junk were hiding some larger gold nuggets. Pulse induction machines are by and large "dig it all" units and their power worked against them in the tailing piles by finding too much deep junk. The MXT while not as deep was better at pulling the nuggets out of the tailing piles while ignoring most of the junk, and for some time the White's MXT was the number one nugget producer in Alaska.

Companies copy success, and soon everyone was producing detectors running in the 13 - 15 kHz range that were designed to "do it all". We are now buried in these type detectors from virtually every manufacturer. In the process the line between the dedicated VLF prospecting detectors and general purpose machines has blurred considerably. The 13 kHz Teknetics T2/Fisher F75 is another good example of this type of machine. The T2 really took of in Africa with its ability to hit gold nuggets well in moderate ground while dealing with hundreds of years of surface trash accumulation.

Where we are now worldwide is a nugget detector market split into three major segments:

1. The dedicated single frequency, LF induction balance prospecting detector. These detectors run at 30 kHz and higher and are marketed as gold prospecting detectors. The best examples are the 71 kHz Fisher Gold Bug 2, 48 kHz White's GMT, 45 kHz Minelab Gold Monster 1000, and to a lesser extent, the 56 kHz Makro Gold Racer. Main features - extreme sensitivity to very small gold, affordability. Main weakness - ground and hot rock handling. 

2. General purpose single frequency, VLF induction balance cross-over detectors. These detectors run from 13 kHz to 29 kHz and are marketed as do-it-all detectors. The best example is the First Texas 19 kHz Gold Bug/F19/G2 variants and to a lesser extent machines like the Teknetics T2, 14 kHz White's MXT, 18.75 kHz Minelab X-Terra 705, etc. Main features - general purpose capability and trash handling characteristics, affordability, slightly better depth on large gold than units in #1 above. Main weakness - ground and hot rock handling, slightly less sensitive to small gold than units in #1 above.

3. High power ground balancing pulse induction (GBPI) detectors. This area is dominated by the Minelab SD/GP/GPX series of detectors. Main feature - superb ground and hot rock handling capability resulting in near maximum depth on most gold nuggets. Weakness - affordability, weight, trash handling, and a lack of sensitivity to certain classes of small and dispersed gold.

Disputes arise often when Australian prospectors mix with others from around the world due to a fundamental misunderstanding. In low mineral ground common around the world, particularly when dealing with small gold and lots of ferrous trash, VLF and LF induction balance metal detectors are still the machines of choice for many people. They are lightweight, affordable, handle trash well, and in low mineral ground they find the gold. This is hard for people who only detect in the worst soils to comprehend.

In locations where ground mineralization and hot rocks impede the performance of the single frequency detectors, ground balancing pulse induction machines are dominant, with operators of LF and VLF detectors being at a severe disadvantage.

The truth is both types of detectors have their place, and many if not most serious prospectors own both a pulse induction and a LF/VLF detector. They complement each other well.

The Minelab GPZ 7000 really is something new. It in reality bears a closer resemblance in some ways to a super VLF as far as its operational characteristics than it does a pulse induction machine. It blurs the line between the two, and promises to do so even more in the future because in theory at least full discrimination can be added to the underlying technology. I look at the GPZ as being a crude first generation device that will undergo enhancement over the next decade or more. Other hybrid technologies loom on the horizon and eventually we will have detectors that combine most of the features currently available in separate classes of machines into single detectors, while advances in battery technology promise to bring the weight down.

To summarize, what sets dedicated prospecting detectors apart is either extreme sensitivity to small targets (less than 1 grain or 1/480th Troy ounce sensitivity is now common) and/or the ability to handle the very worst mineralized soils and hot rocks. Yet due to technological convergence there are many crossover detectors available that can serve well for those who may only go nugget detecting once a year while spending the vast majority of their time hunting for coins and relics.

For details you can always check out my Nugget Detector Review, which I update regularly.

[Steve Herschbach]

Here is a personal perspective. I use a GPZ 7000 for nearly all my nugget detecting. However, I do have uses for a VLF type detector. The first is when I get into some really trashy area, like an old camp. The old miners often put the camp right on top of the best ground so they could just walk out the door and get to work. Old hydraulic pits and tailing piles are often thick with deep nails that will have a GPZ owner digging two feet or deeper holes for as long as the back holds out.

A really hot model running at 30 kHz or higher can aid in sniping tiny gold in low mineral ground and gold in quartz specimens. Checking quartz on a mine dump is a good example.

These machines can also make good scouting detectors in very rough terrain, especially when ferrous trash is present. A good example is in logging areas in the Sierra Mountains, where steep terrain and tiny ferrous trash from old logging operations is the norm.

The big problem is in trying to find the machine that handles bad ground and hot rocks in some fashion while still retaining some sort of decent ferrous discrimination. Hot VLF detectors do not like bad ground and hot rocks, and ferrous discrimination gets less reliable as the ground conditions decline.

It is hard to find one detector that balances it all well. For me the Gold Bug 2 is the standard benchmark for performance and the only detector I have used consistently for over 20 years. A couple years ago I started using the Makro Gold Racer more than my Gold Bug 2, but that was really more about my being able to use it around town also because it does have a more extensive feature set making it more useful for general purpose detecting. I would be the first to say that a dedicated unit like the Gold Bug 2 has a slight edge over detectors aimed at more general use. The differences are small but in practice single minded focus on one task does help a detector engineer in the final goal.

Now I have tossed the Gold Monster and Deus V4 elliptical into the mix. The Deus on paper looks great but again it struggles a little due to it really being a coin and relic detector that is trying hard to be a gold nugget detector. It hits targets well enough but so far I am struggling to get clean ferrous/non-ferrous identification on really tiny bits of gold, an area where the Gold Bug 2, Gold Monster, and even Gold Racer seem to have the edge over the Deus. Jury still out there. The Gold Monster is winning some points versus my Gold Bug 2 for handling variable ground efficiently. Jury still out there.

What I will do is continue to use all these detectors for the rest of the year. In the end it is lots of things like feel on my arm, sound to my ear, and even types of batteries used that all come together. Sooner or later I look at the same set of detectors, and since I can only use one at a time, I will get to where there is one I would rather grab then the others. Certain detectors just click and some do not, and it is not always about splitting hairs over performance. They all will find gold. The question comes down to which one I personally like best, and the fun part is somebody else doing exactly the same thing with the same machines could come to a different conclusion. Think of it like you and I both go to Cabelas looking for a good pair of hiking boots. We have the same foot size and general build. Turns out though I like high tops and you like low tops. Both are valid choices. Such is the world of detectors.

The good news for me is that is all a sideshow. Day in and day out under normal circumstances my main gold getter is the GPZ 7000 with 14" coil.

[MikePfeiffer]

I can always rely on you Steve. I really did not know what to ask, and you know me well enough to give the educated answer.  Loved the history lesson on detectors. Thank you!

[frozen_north]

Thanks for the tremendously helpful explanation, Steve!

[MikePfeiffer]

I never prospected before. I can just imagine, just finding your first glimmer of gold. The excitement, the rush of adrenaline and the hook that grabs you to keep you looking for more.