GPX 6000 Halo Effect On Small Nuggets

[brogansown]

Yesterday while detecting in mostly dirt, I got at least 5 good repeatable signals and just couldn't find the nuggets.  My brother was with me with his GB 2, so I had him go over one of the signals and sure enough it was a small pellet sized nugget.  I'm pretty sure now, that I was experiencing the well-known "Halo Effect" and after disturbing the soil, the nugget was just too small for me to pinpoint it.  My Garrett Pro-Pointer wouldn't pick it up either.  This is good to know and another way to keep getting those nuggets.

The 6000 is amazing and despite its "turn on and go" reputation, I'm learning a lot with each outing.  Will be interested in seeing any new coils that are coming down the pike.

[phrunt]

I think we've all experienced this with PI/ZVT detectors, and why it's handy to have a VLF nearby to recover the little guys.

In my case it's often they're buried in my dig out pile deeper than they were in the ground due to the aggressive nature of how I use my pick so I've learnt to flatten out my dig out piles to get the tiniest nuggets.

You got a nice collection of nuggets there.

 

[MSC]

 I use a similar method, if I dig say 3 '' of soil out of the hole and no signal in the pile, I push the pile further away from the hole and dig the next amount of dirt and put it in front of the last pile, keep using  that method until I come up with the target. 

[geof_junk]

The well-known "Halo Effect" is it true or not. Hard to simulate unless you have a few thousand years to come back and see if it worked. For nuggets I believe it true due to the leaching of silver or copper from the nugget as the gold is inert. The lower the quality of the gold the more likely it would be detected. Some times the loss of signal is due to it not having the same surface and area that the Eddie were first acting on, as the target has be moved and rotated due to digging.

[Aureous]

If any metal detected isn't bondable with oxygen, carbon or chlorine, it will never create a 'halo' within the surrounding soil. Gold is not one of these and a piece of it will never affect the soil its contained within. But, because PI detectors actually detect the eddy currents surrounding a metal object and not the object itself, the surrounding soil has an affect on the signal quality, depending on the depth, size and shape of the detected metal object. Once the soil is disturbed by digging, the whole original, static situation at which the signal was obtained, is now dissimilar and altered. This is the actual issue on why apparently 'good' signals can disappear once dug. There are so many potential  'detection holes' in a PI's pulse train/code that this type of difficulty with signal 'vagueness' is a distinct possibility with small or flat gold shapes also.

[GB_Amateur]

9 hours ago, Aureous said:

...Because PI detectors actually detect the eddy currents surrounding a metal object and not the object itself, the surrounding soil has an affect on the signal quality, depending on the depth, size and shape of the detected metal object.

Will you go a bit more into detail about this?  I don't recall hearing it described this way, but maybe it was and I just didn't understand it.  Also, you specify 'PI detectors' -- does that imply the surrounding soil affects an IB/VLF signal differently?

[brogansown]

Although gold is the nobliest of the nine noble metals, it does form compounds and in fact, my friend Mike found a quite large piece of calaverite near where we were detecting the other day.  Gold forms compounds with the halogens and cyanide, of course, which is used in some extraction processes.  But if, (and it's a big if) there is an "halo effect," its more likely to be associated with the other metals in the alloys such as, copper, tin, silver, lead and even iron leaching out. The halo effect is very real and noticeable when we find heavily corroded nails, pennies, lead bullets & pieces of copper and tin.  I don't understand the PI detection process as well as the rest of you, but I'm sure Aureus is correct when he said each pulse creates an eddy currents around the nugget and it is influenced by the shape, size, density of the metal and the makeup of the surrounding soil as well.  I don't how this will help us find more nuggets, but it sure is an interesting topic.

Phrunt is correct in saying I probably moved the nuggets somewhere in the pile and it got even deeper.  But, I've left at least a dozen good original and repeatable signals because I'm impatience and just couldn't find the darn things.  So, I'm going to make a GB 2 pin-pointer with my extra detector, like Steve's old example and pack it around for awhile.  It not fair to my younger brother to have to follow his older brother around and rescue him.

[MSC]

I think a pin pointer has a a place in prospecting. I have saved much digging in areas that have some or a lot of metal trash by scanning the surface and finding the trash without having to dig. Some areas are covered with grass and weeds so side sweeping with your foot to try and push the surface trash out of the way does not work. A quick sweep with  pin pointer easley finds the trash. Some times when a small target is detected in the ground it may have a favorable flat exposure giving a good signal, when removed from the hole, if flat it may be in a vertical position making it harder to detect. Moving the pile around as phrunt suggested could expose it again with a clear signal. 

[Aureous]

7 hours ago, GB_Amateur said:

Will you go a bit more into detail about this?  I don't recall hearing it described this way, but maybe it was and I just didn't understand it.  Also, you specify 'PI detectors' -- does that imply the surrounding soil affects an IB/VLF signal differently?

PI detectors find metal by energizing the target with a pulsed magnetic field and the counter-magnetic field is then detected via remnant eddy currents. The mineralization contained within the surrounding soil will deflect or hinder the eddy currents to a varying degree, depending on the amount/type of mineralization present. Because the pulse train of Transmit (Tx) and receive (Rx) pulses and sampling use 'time' as the primary means of sampling, this allows the mineralization portion of the signal to dissipate, leaving the ACTUAL counter magnetic field (remnant eddy currents) remaining. This is where all the minute details matter....the way the code for the pulse train is written (distances between pulses, voltages, sampling speed etc etc) all have an affect on how the mineralization affects the end, audible result. In IB/VLF, there is no time parameter for the ground signal to dissipate because its 'constant wave', only relying on the  frequency of the oscillator to reduce mineralization and sensitivity. Hope that helps a little....a lot of it is beyond me as well as my level of electronics isn't within the engineering spectrum, only technical.

[Gold Catcher]

I have several times observed disapearance of fast timing gold after disturbance. Either you treck it out (wish the 6k had a manual GB option like the 7k), or the timing constants change in relation to the ground mineralization as the small nugget gets moved and change position in the soil. This happens less likely with the SDC due to MPF.

GC