Vito
Elite Member
Sorry about this question, but want to be sure in my thoughts...
What is a HALO??
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sectshun8
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In my understanding, i think of it as a rust halo. Many times digging, I get a signal that covers a large area for the actual find. When I dig down I notice rust colored soil around where the find was. That halo can still trigger the 'tector. Newly buried items tend to not having this halo, and can be harder to find.
Here's a link I found regarding it, great explanation: HERE
Here's a link I found regarding it, great explanation: HERE
DFX-Gregg
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WHAT IS HALO EFFECT?
Halo effect makes targets that have been in the ground a long time appear much larger than they actually are. Imagine an iron nail that has been in the ground for a number of years. As moisture in the ground slowly rusts the nail, forming iron oxides and iron salts, these oxides and salts migrate from the surface and tend to form a “halo“ around the nail. This, of course, makes it a lot “easier“ for a metal detector to detect. This effect is basically the same for most metals. When the target is dug, this halo effect (which takes years to form) is destroyed. So if you find a target due to the halo effect, and, for instance, it was a very weak signal, you will find that if you rebury it at the same depth, you will probably not now detect it (unless you leave it for five years!). For you beach-hunters, halo effect rarely has time to build up and will be destroyed if the ground moves. Relics are often found at greater depths due to these effects.
Gold can be very hard to find due to the odd shapes that are often formed. Halo effect really helps us liberate a lot of gold, as most gold hasn’t moved in a long time! But gold doesn’t rust or corrode I hear you say. Correct. Often where you find gold there are also salts and chemicals (like cyanide) and these will leach out the gold into the surrounding minerals, causing a halo effect
Halo effect makes targets that have been in the ground a long time appear much larger than they actually are. Imagine an iron nail that has been in the ground for a number of years. As moisture in the ground slowly rusts the nail, forming iron oxides and iron salts, these oxides and salts migrate from the surface and tend to form a “halo“ around the nail. This, of course, makes it a lot “easier“ for a metal detector to detect. This effect is basically the same for most metals. When the target is dug, this halo effect (which takes years to form) is destroyed. So if you find a target due to the halo effect, and, for instance, it was a very weak signal, you will find that if you rebury it at the same depth, you will probably not now detect it (unless you leave it for five years!). For you beach-hunters, halo effect rarely has time to build up and will be destroyed if the ground moves. Relics are often found at greater depths due to these effects.
Gold can be very hard to find due to the odd shapes that are often formed. Halo effect really helps us liberate a lot of gold, as most gold hasn’t moved in a long time! But gold doesn’t rust or corrode I hear you say. Correct. Often where you find gold there are also salts and chemicals (like cyanide) and these will leach out the gold into the surrounding minerals, causing a halo effect
Rudy
Admin
Hi Vito,
Strictly speaking, a halo can be found over the head of angels, as in these examples.
There is also a belief that halos form around buried targets made of less than noble metals. Although scientifically unproven, the assertion is that some of the metal oxides from the target diffuse into the adjacent ground, forming a cloud (ie. halo) of conductive oxides around the targets. The belief is that this halo allows the detector to detect the target (actually the halo), at a depth deeper than would otherwise be possible.
Many examples are given, to support this belief. The most common one being that the target can no longer be detected after the ground above it is disturbed (ie. the halo has been destroyed by the act of digging). Of course, digging also disturbs the ground matrix and can by itself be responsible for the loss of the target, without recourse to any halo effect.
One of the difficulties with the halo theory is that metal detectors work by detecting the magnetic field generated by the eddy currents in the target in response to the changing magnetic field transmitted by the transmit loop in the coil. The lower the electrical resistance of the target, the larger the eddy currents and therefore the stronger the signal. The oxide cloud of a halo is not as good a conductor as the metal target itself and thus the signal it would generate is not as strong although it would be distributed over a larger volume. Which is the easier signal for the detector to pick up? It is not clear.
Ground moisture is also reputed to enhance the halo effect, but it also modifies (shifts) the ground phase (ground VDI) itself, by enhancing the effect of the conductive salts, over the magnetic components present in the ground matrix.
To put it in the White's VDI scale, conductive salts have VDI readings in the low negative number range (e.g. -10). The magnetic ground components have a VDI in the high negative range (e.g. -95). The ground matrix VDI is an average of these two numbers based on their proportional effect. Thus, the more conductive the ground, the closer the ground phase is to -10.
Since best detection happens when the target VDI is far different from the ground VDI (if the target VDI was the same as the ground, it would be an undetectable target
). Keep in mind that the VDI scale is really a circle with +95 adjacent to -95, and silver targets are typically in the +80 range.
So, if grounds with a high amount of conductive salts get wet, the ground VDI shifts far away from the target (assuming silver or other high conductivity targets are being sought) and makes it easier for the detector to detect it at a greater than normal depth. Again, some attribute this to the halo effect, though high purity silver does not leach out a large amount of oxides.
So, is the halo effect real? Some people believe it is, but it has not been scientifically proven. Other things are happening at the same time making the contribution of any halo hard to isolate.
Strictly speaking, a halo can be found over the head of angels, as in these examples.
There is also a belief that halos form around buried targets made of less than noble metals. Although scientifically unproven, the assertion is that some of the metal oxides from the target diffuse into the adjacent ground, forming a cloud (ie. halo) of conductive oxides around the targets. The belief is that this halo allows the detector to detect the target (actually the halo), at a depth deeper than would otherwise be possible.
Many examples are given, to support this belief. The most common one being that the target can no longer be detected after the ground above it is disturbed (ie. the halo has been destroyed by the act of digging). Of course, digging also disturbs the ground matrix and can by itself be responsible for the loss of the target, without recourse to any halo effect.
One of the difficulties with the halo theory is that metal detectors work by detecting the magnetic field generated by the eddy currents in the target in response to the changing magnetic field transmitted by the transmit loop in the coil. The lower the electrical resistance of the target, the larger the eddy currents and therefore the stronger the signal. The oxide cloud of a halo is not as good a conductor as the metal target itself and thus the signal it would generate is not as strong although it would be distributed over a larger volume. Which is the easier signal for the detector to pick up? It is not clear.
Ground moisture is also reputed to enhance the halo effect, but it also modifies (shifts) the ground phase (ground VDI) itself, by enhancing the effect of the conductive salts, over the magnetic components present in the ground matrix.
To put it in the White's VDI scale, conductive salts have VDI readings in the low negative number range (e.g. -10). The magnetic ground components have a VDI in the high negative range (e.g. -95). The ground matrix VDI is an average of these two numbers based on their proportional effect. Thus, the more conductive the ground, the closer the ground phase is to -10.
Since best detection happens when the target VDI is far different from the ground VDI (if the target VDI was the same as the ground, it would be an undetectable target
). Keep in mind that the VDI scale is really a circle with +95 adjacent to -95, and silver targets are typically in the +80 range.So, if grounds with a high amount of conductive salts get wet, the ground VDI shifts far away from the target (assuming silver or other high conductivity targets are being sought) and makes it easier for the detector to detect it at a greater than normal depth. Again, some attribute this to the halo effect, though high purity silver does not leach out a large amount of oxides.
So, is the halo effect real? Some people believe it is, but it has not been scientifically proven. Other things are happening at the same time making the contribution of any halo hard to isolate.
~Alan~
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RelicHound
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its a game on xbox
sectshun8
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RickO
"In Memory of"
Super explanation Rudy.... often, when digging iron, this 'halo' can be seen as a 'rust' color in the dirt surrounding the item. As stated, this takes time to form (unless the ground is acidic). RickO
Rudy
Admin
Thanks RickO
Honestly Rudy.... are those the best examples of angels you could find???
Vito, I have dug up targets and there was nothing there but rust mixed in the dirt. I guess the target dissolved into the dirt. This happens in beach hunting too. When you dig a target and nothing is there but rusty sand.
Vito
Elite Member
Thank you very much for all your replies !
So what I understand from the answers is, a halo is created by time in undisturbed ground around a metal item.
Metals which are more sensitive to oxygen and acid will build out more halo than metals which will be less sensitive.
More - iron, brass, bronze | Less - silver, gold, lead.
Halo building items can be found deeper and the halo can fool your 'tector (disc and VID).
Carol - yes, same thing happend to me, too.
RelicHound - It's also available for PC now. (Good one 
)
Rudy - Nice collection of angels...and superb explanation.
DFX-Gregg - Said nothing but some good points there.
sectshun8 - nice explanation and very helpful link. TNX
There are detectors out there which will detect a fresh buried and now empty hole if researched. (Yes, empty.)
Is this because the ground "matrix" is destroyed? And is a detector, which will find deep targets without this halo not the real better one than one that will detect only "deep" targets if they were buried for a long time?
Wouldn't you also prefer a detector which is detecting deep targets fresh buried? I'm thinking about hunting a fresh plowed field...
So what I understand from the answers is, a halo is created by time in undisturbed ground around a metal item.
Metals which are more sensitive to oxygen and acid will build out more halo than metals which will be less sensitive.
More - iron, brass, bronze | Less - silver, gold, lead.
Halo building items can be found deeper and the halo can fool your 'tector (disc and VID).
Carol - yes, same thing happend to me, too.
RelicHound - It's also available for PC now.
(Good one )Rudy - Nice collection of angels...and superb explanation.
DFX-Gregg - Said nothing
but some good points there.sectshun8 - nice explanation and very helpful link.
TNXThere are detectors out there which will detect a fresh buried and now empty hole if researched. (Yes, empty.)
Is this because the ground "matrix" is destroyed? And is a detector, which will find deep targets without this halo not the real better one than one that will detect only "deep" targets if they were buried for a long time?
Wouldn't you also prefer a detector which is detecting deep targets fresh buried? I'm thinking about hunting a fresh plowed field...
