Pulse Inductions vs Specimen Gold

[Lead Detector]

Recently I  had an opportunity to test both an axiom, and a 6000 on a piece of specimen gold that contains 5-6 grams of gold. Neither of these detectors would hear it unless the coil was touching the specimen.    The test was done on the large specimen on the left in the picture.  It's just an observation that may be of interest to some.

 

[Sgtfda]

I have some pieces of California gold. Tiny specks. No response at all with my 4500. My Troy Shadow x5 goes nuts. Very strong response at 4" with 6" coil. I set it up as a pinpointer.  Quite a surprise. I used it as a coin detector in Pennsylvania. Did not suspect it would be so hot on gold specks. 

[Steve Herschbach]

This is what used to be called "invisible gold" by users of earlier Minelab PI detectors. Specimen gold can be discontinuous in the rock, meaning it is more like detecting a gold chain than a gold nugget.

People are generally aware that gold is fairly low conductive compared to silver, which is extremely conductive. What most do not know is that adding silver to gold results in alloys that are far lower in conductivity than either pure gold or pure silver. What you found is low purity specimen gold with a high silver content. The resultant gold/silver alloy dispersed in rock, rock that often carries some sulphide content, has target id responses that actually run down into the ground and hot rock range. This means that the ground cancellation inherent in PI detectors, the very reason for using a PI, can actually tune out these gold specimens as if they are hot rocks.

I have a pretty good collection of specimen gold that a GPX 5000 and earlier models cannot detect physically touching the coil no matter what coil or setting is used. This is also Nevada low purity gold finely dispersed in the rock, invisible to almost any PI detector.

Delicate Nevada gold specimen found by Steve with White's GMT

The Axiom, GPX 6000, AlgoForce, and GPZ excel on gold other PI detectors will miss, but come nowhere close to matching a good induction balance detector. I do not say VLF because that means Very Low Frequency (3 kHz - 30 kHz) and many good nugget detectors are higher than 30kHz, technically LF detectors.

The Shadow X5 is very capable on small gold, unfortunately I had severe problems getting it to work in bad hot rock locations.

 

[GotAU?]

I called Gerry once saying that the SDC2300 I bought from him couldn’t pick up the gold nuggets that my Gold Monster could, even when they were all dumped in the same bottle. Poor guy, another call from a newby who didn’t know PI’s couldn’t pick up a little bottle of fly poop sized gold, even if they are together in a little clump!

I know better now, it’s interesting how a IB detector (induction balance) is the best choice to use for finding gold like that, hence I also picked up a 24k after selling the GM a while back for just that reason.  

[Wild Bill]

Steve, help me out here because I’m a bit puzzled and I want to understand this and what you are saying.  So here’s an example of a detector that the manufacturer says is a VLF induction Balanced detector.  
https://www.nexusdetectors.com/nexusstandardmpv3.html

You can change frequencies with different coils.  The highest is 24Kh.  I consider even the GB2 a VLF even though it’s much higher than your traditional 5-20Kh electronics.   Like some use the term HF-VLF.  I thought about starting a thread on the Garrett AT Max’s ability to detect tiny gold and the fact it’s the wrong detector at the wrong frequency doing what it shouldn’t be able to do.  But I figured no body wants to hear or talk about a 7 year old detector, they’ve moved on.  However it fascinates me that it can do this.  Warren NQExplorers YouTube, you’ve met, did a video nugget hunting and like I found, detected gold down to .05 gram.  I never tested it in depth and compared it to my Gold Kruzer or my friends GB2 but did find a similar response as the Kruzer at 61Kh.  Now I want to test the Max to find its limits.  It’s with the Garrett 5x8” DD just like Warren used in Australia.  Maybe you can explain it?  If it’s just another VLF, why does it work?  What are its limitations compared to other Induction Balanced and HF-VLF detectors?  Honestly I am curious. 

[Wild Bill]

Steve, you could just say “ read my post on the Troy Shadow X5” as I’ve never even considered detecting gold sub grain.  I use the Kruzer for searching high grade float specimens in areas it has been found in the past.  Thanks for posting that. 

[Aureous]

49 minutes ago, GotAU? said:

hence I also picked up a 24k after selling the GM a while back for just that reason.  

Good call 

[Steve Herschbach]

1 hour ago, Wild Bill said:

Steve, help me out here because I’m a bit puzzled and I want to understand this and what you are saying.  So here’s an example of a detector that the manufacturer says is a VLF induction Balanced detector.  
https://www.nexusdetectors.com/nexusstandardmpv3.html

You can change frequencies with different coils.  The highest is 24Kh.  I consider even the GB2 a VLF even though it’s much higher than your traditional 5-20Kh electronics.   Like some use the term HF-VLF.  I thought about starting a thread on the Garrett AT Max’s ability to detect tiny gold and the fact it’s the wrong detector at the wrong frequency doing what it shouldn’t be able to do.  But I figured no body wants to hear or talk about a 7 year old detector, they’ve moved on.  However it fascinates me that it can do this.  Warren NQExplorers YouTube, you’ve met, did a video nugget hunting and like I found, detected gold down to .05 gram.  I never tested it in depth and compared it to my Gold Kruzer or my friends GB2 but did find a similar response as the Kruzer at 61Kh.  Now I want to test the Max to find its limits.  It’s with the Garrett 5x8” DD just like Warren used in Australia.  Maybe you can explain it?  If it’s just another VLF, why does it work?  What are its limitations compared to other Induction Balanced and HF-VLF detectors?  Honestly I am curious. 

There are pulse induction detectors and there are induction balance detectors. Back in the 1970s when TR style induction balance detectors were running at 100 kHz the new breed of ground balancing detectors came out running at much lower frequencies, like 3 kHz to 7 kHz. They were running in the 3 KHz to 30 kHz range that is the Very Low Frequency or VLF range and manufacturers seized on VLF in their marketing material. VLF became the new magic catchword like hybrid is now. Eventually people started calling induction balance detectors VLF detectors just like people call tissue paper Kleenex. So yes, all kinds of people call detectors that are not running in the VLF range VLF detectors. Does not mean it’s technically accurate, it’s just become common usage. Think about it, what does high frequency VLF really mean? 

Frequency is only one component of how a detector performs and saying the AT Max is doing something it should not be doing - who says? You can find gold nuggets with any detector, all that differs is size and depth. 15 kHz used to be the standard for nugget detectors. There is nothing surprising at all about the AT Max being able to find gold nuggets.

https://www.detectorprospector.com/magazine/steves-reviews/metal-detector-technical-specification-notes/

https://www.detectorprospector.com/topic/8752-any-familiar-with-induction-balance/#findComment-87203

Back in the day Fisher even had a VLF series, and get this, the VLF Mother Lode 660 running at 4.5 kHz. Best nugget hunter ever! Not!!! Long story short company marketers have long played fast and loose with terminology.

 

 

[Wild Bill]

Thanks Steve, that definitely helps explain things.  I appreciate it.  I’ve been considering sub gram gold little!  You’ve schooled me on that.  I know the Gold Kruzer can handle super tiny gold.  The area I’ve been focusing on, old timers found rich float and there’s placers there but no mining records for placer production and no mention of nuggets.  Just lode records.   So I’ve been after the specimen.