Jump to content

Why Won't My Detector Find A Bottle Full Of Small Nuggets? Or A Gold Chain?


Recommended Posts

This subject comes up so often it is time to get it into its own thread so I can just link to it in the future.

It is best to think of metal detectors made for prospecting as "nugget detectors" as that is the truth of the matter. Nuggets have some size to them.

Metal detectors are electromagnetic devices, and as such can detect items that are conductive and non-magnetic, like gold, or non-conductive but magnetic, like magnetite. Or both, like metallic iron.

When dealing with gold you are dealing only with conductivity. The more conductive the mass, the easier it is to detect. In general what this means is bigger is better. Any detector has a limit to how small an item it can detect.

Here is the kicker. Multiple undetectable targets do not add up to create a detectable target. I do not know how many times I've seen or been told of people throwing a vial of small gold on the ground and running a detector over it and declaring the detector will not find gold because it does not pick up the vial of gold. Or people thinking the detector has a problem.

Let us say that on a scale of 0 - 10 zero represents an undetectable piece of gold, and 10 one that really beeps. 0 + 0 + 0 + 0 + 0 still equals zero. So lots of tiny gold is just as undetectable as a single piece of tiny gold. You need a single conductive mass.

Fine gold usually has a coating, and putting a bunch of fine gold in a vial still results in little or no signal. If the gold is super clean and packed tightly you will get a weak signal. Melt it all together, and now it goes beep.

Another way to look at it is take some fine gold and pour it in a pile. Get a multimeter and test your little pile of gold for conductivity. It is hard to get much current if any through a loose pile of gold.

So bottom line is you might have 5 ounces of fine gold right under your feet, and you will walk right over it with your metal detector. Rich gold ore where the gold is finely dispersed in the rock will be hard to detect or undetectable. Wiry or spongy masses of gold are hard to detect.

Jewelry hunters run into this when trying to detect lost necklaces. A fine chain is very hard to detect as each link is undetectable and the connection between the links is poor enough the signals does not add up to much. Often all you can detect is the clasp. Rings even display this issue if the weld breaks. A complete ring really gives a great signal. Break the ring, it will be very hard to detect.

Now once an item is detectable, it does add up. 10 + 10 = 20 so two large nuggets in the same spot are easier to detect than each by itself. If each link in the gold chain can be detected, then it will add up into a more detectable target. A fun trick with target id detectors is to tape 5 nickels together and run them under the coil. They will read as 25 cents!

  • Like 5
Link to comment
Share on other sites


Great response!

I like how you described how nuggets bedding down in the same spot will produce a stronger signal.

Last summer, I hit two spots with the Gold Bug Pro where I got a very broad signal in packed dirt, shallow on bedrock. I had never experienced this before, and I didn't know what to make of it. I almost thought it was some kind of ground mineralization effect or something, but as I'd been finding nuggets consistently in that area, I dug all of the dirt anyway.

In the process of scraping and gathering, I uncovered a crevice that ran about ten inches deep, cleaned it out as well, and threw everything in the gold pan. The signal in the ground was gone, but now there was a strong signal in the pan!

I panned down the dirt a bit and quickly saw the flash of gold. I spread the dirt out with the water and it was full of small nuggets, any of which, individually, the detector easily saw. There was also a 4 gram nugget keeping them company that I eyeballed as I cleaned out the crevice. As all of those nuggets had bedded down in that pocket/crevice together, that was what produced the broad signal in the dirt, but when they were concentrated in the smaller area of the pan, the signal was stronger.

Thanks, as you may have solved a bit of a mystery for me. 

That was a fun day, and unbelievably, I repeated it a couple of weeks later on another section of bedrock! I doubt it will ever happen again as it's never happened before. I mean, I've hit concentrations of small nuggets before, but they rang individually as I swept the coil over them because they were more spread out in their patch's area. They did not give out the broad signal I received on the nuggets that were much closer together. 

All the best,

Lanny

  • Like 2
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Similar Content

    • By Tony
      From what I can gather, higher frequency VLF detectors are more suited for smaller gold but ground mineralisation may be something to factor in. Would there be a “better” frequency for nuggets 1 gram and above in heavy ground?
      I’m not too concerned if I miss sub gram nuggets if there is a better suited frequency.
      The old Garrett Groundhog circuitry was legendary in this country…..I think it was around the 15 kHz mark. Is this frequency range a good starting point or do I need to consider other things such as better ground balancing capabilities or Garrett’s extra coil voltage. 
      My Minelab PI units will be mainstay detectors but as mentioned in another post, I have ground littered in man made iron junk and the ground mineralisation is severe. There are plenty of nuggets in the 1 gram to 5 gram range (maybe bigger) but the iron signals are as dense as 5 per square metre 🤬
       Thanks for any ideas.
       
    • By water spider
      maybe we could have a multi frequency coil, that recieves a single frequency or selectable single frequency and effectively distorts and amplifies the single frequency resulting in frequency variants up and down, mimicking or creating smf
    • By Skullgolddiver
      After the good new I realized when tested a few days ago my machine after It drowned and I've succesfully reanimated It....
      Now the horrible gasket Is fighting to stay out of the housing against any kind of attempt😒.
      So I'm in the middle of a headache manutention session with scarce results.
      That's the Mood guys😑
       

    • By Tnsharpshooter
      See NASA-Tom’s comments
      https://www.dankowskidetectors.com/discussions/read.php?2,181189
    • By Tnsharpshooter
      Don’t know any other better subforum to place this.
      When manufacturers design make sure platform can allow at least 2 software versions or at the very least allow what I call both newer version update (whole) and a older subset (portion of older version) to be used.  
      Why?
      Makes testing easier if and when a newer version is designed and requires pre release testing in the field for validation.   Would allow users after version release to use different versions and gain first hand feedback of the benefits or lack thereof of different versions or version subset(s).  Case in point.  Notice Minelab left old iron bias to be user selected when they released newer version with iron bias F2 option.  
      So in a nutshell this allows the detector versions ( or version subset) to be compared to the themselves in the field by the user.
      Xp should have done this too.  They should have designed Deus imo where at least  2 complete version allowed to be uploaded to unit.
      Notice the later released Ace Apex.  Garrett should have allowed on it too.  
      Don’t know what added production cost this would cause.  Hopefully not much.
       
    • By Northeast
      This was mentioned by geof_junk in another thread and had a little Google.  
       
      Found this  https://www.phys.k-state.edu/reu2011/nnorvell/Metal_Detector_Research.html
      I don’t really understand the technical side of metal detectors.  Does this have any application to current day detectors?  Will it help cancel out ground noise more?  Will the current crossing/not crossing the ‘bridge’ tell you something about what is under one of the receive coils.  
       
      Although I don’t understand it, I am amazed and a little in awe of those that do  👍
×
×
  • Create New...