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Little Gold In Big Iron


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Now have three beach sites with one thing in common. They are on old human activity sites with a long history of use for many different things, and they have a lot of iron trash from old buildings torn down there. The Makro GR sounds off nearly continuously in AM mode yet still finds coins, a surprising number of them, and some junk jewelry as well as pulltabs/larger foil, etc.

These are popular beaches in continuous use by a lot of people for a very long time. They are hunted to death by the best machines in common use. That I was able to find coins in them was surprising, also surprising is that micro jewelry is conspicuously absent from the take. Most places I can find small gold no matter who hunts there, but not coins to any extent. These are the other way around. It has to be the sheer amount of iron trash.

Prospectors are familiar with the problem and use vlf when they can, discrimination if they must, and various tricks to pull gold, but this is a slightly different problem. Here the sensitivity to desired target appears to be lost by the presence of so many cut nails and spikes and iron flakes that lie in and below the sand. The reason I think this is the case is because of the size of the foil I am finding. The reason I think it is not because someone else with a better skill set has pulled them out, is because I am finding pulltabs and all denomination of coins. Including quarters, which even the most diehard cherry pickers find hard to leave, along with pulltabs/nickels which should mean that at least medium size gold should still be there.

In an experiment to see if high frequency was the problem, I ran the Compadre over one site today. Set to just reject some iron, what I found was...iron. And not much else, a few pennies. The machine ran nice and quiet and only the good sounding signals of proper shape/size were dug. Cut nails, spikes, bolts. Lots of them. The GR seems to have done a good job of taking out most available targets, targets that should not have been there at all and was able to leave the larger iron. But, it is not finding the tiny gold that should be there based on what was dug. Also, very small foil seems to be lost with it which is what leads me to believe the iron masking is strong at these particular sites and sensitivity to desired targets is lost.

Tried so far is the small coils, high gain and low gain, discrimination, and the Compadre with a 5" coil. For the GR, the stock coil seems to work better, and medium high gain in AM mode. It just will not go small enough on gold to get the job done. It is of course entirely possible that this just is not doable in practical terms. It is looking for gold stud earrings in a relic site essentially, and that is a lot to ask. So the question really is, is it possible at all? 

 

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2 hours ago, SLGuin said:

So the question really is, is it possible at all? 

If it is possible I'm sure you will figure it out.  

I can imagine that the places you detect are a soup of objects, much of it iron.  It does seem very possible that the sensitivity that you require to find the tiny objects you seek is taking a beating with all the iron and other often larger objects in close proximity to your tiny targets.   Good luck SL

 

 

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Thanks Terry,

It is a challenge to be sure.

It is assumed that the reason clad and tabs are still on these sites is because of the masking. Not exactly to the extent of appearing like virgin ground of course, but here in good ground nickels and pull tabs are not common finds so it might also be assumed that gold remains to be found as well. Larger foil/thick foil/balled foil is recovered but the usual tiny pieces are not, so it stands to reason that small gold is also there. If those assumptions are correct, though easy targets can be unmasked but smaller low conductors as yet are not. Large heavy gold hits well with a good clean signal on most detectors and is expected to be absent.

The big challenge in unmasking small low conductors in the presence of so much iron is confounded by the very gain and frequency required to get good signals on the desired target. What is needed to hit small gold is precisely what makes it worse. Of course it looks like a foolish concept to explore, perhaps even a total waste of time, but it is an enjoyable thing to think on.

Low and mid frequency detectors with small coils can push through iron on large (relatively) coin size targets and run much quieter, but are not sensitive enough to reliably recover small gold as a decent percentage. It follows then that high frequency will have to be adapted somehow to make it work if indeed it can be made to at all.

A very noisy business in any case. In disc mode, it is quieter but also more difficult to tell what the ground is doing and all but impossible to size and shape signal targets. Some version of disc may be the only real way to get it done though, AM gets really noisy and pulling good tone from some areas is it's own challenge because the noise gets old after a while.

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SLG;

during occasional moments of insanity I will try detecting in old dumps. That means an area littered with cans, lids, bottle caps etc...it is a trial to be sure. I do find small brass bits, small lead and other small stuff and the occasional coin. The only way I have found to work is in discriminate and very slow swing....

Of course you could rake a small area with magnets and then see if there are any of the goodies you want...

just shooting in the dark

fred

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Fred,

Insanity is precisely the right word, but sometimes that is what it takes. Doing what others are not crazy enough to try can pay off once in a while. Or at least that is the notion I am going with. Thanks for the idea!

S

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Target masking is target masking, and smaller targets are easier to mask. Fast machines do a better job of separating closely spaced targets and the smaller the coil the better. No matter how you cut it however detectors average all the targets under the coil at the same time, and shallow targets override deep targets. Ferrous targets, even small ones, produce very strong signals, which easily swamp the much weaker gold signals.

If you want to have fun take a typical micro jewelry target like an ear ring (or small gold nugget). Now take a couple common trash items like a hair pin or small rusty nail or wire, and bury next to the small gold item and see just how easy it is to mask the item. Most tests like this assume a flat plane but real world is items at different levels. So try deeper gold next to shallower ferrous item.

The reality is with the best detector and best operators a large percentage and possibly even a majority of the good targets are completely masked and cannot be found. People do not know what they are missing because they can't find it. The only solution - dig everything.

In nugget detecting it goes like this. Dig everything unless in very trashy locations. Then use a good VLF to cherry pick. If cherry picking turns up a nugget, switch back to digging everything where the nugget was found. Also, lower gain may be better as making the coil footprint smaller means fewer items in the target matrix at the same time.

You may want to try and sanitize (dig everything) in a 10' x 20' area just to experiment and verify your thoughts as to what may or may not be lurking.

Beneath The Mask by Thomas Dankowski

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Steve,

Thanks for the excellent response and the link. 

The idea of digging everything in a small area just to see seems a very good one. At least just to see.

38 minutes ago, Steve Herschbach said:

Ferrous targets, even small ones, produce very strong signals, which easily swamp the much weaker gold signals.

This, in one sentence, sums up the entire idea of masking that many have spent pages on.

 

41 minutes ago, Steve Herschbach said:

The reality is with the best detector and best operators a large percentage and possibly even a majority of the good targets are completely masked and cannot be found.

This, in one sentence sums up why digging everything is worth a try. I am already digging bobby pin fragments because they are so close to sounding like stud earrings. Just a little further might be just the ticket.

49 minutes ago, Steve Herschbach said:

Dig everything unless in very trashy locations. Then use a good VLF to cherry pick. If cherry picking turns up a nugget, switch back to digging everything where the nugget was found.

This is exactly how I am going to try it tomorrow morning.

Thanks Steve.

 

 

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Steve,

Could you expand a little on this?

4 hours ago, Steve Herschbach said:

Also, lower gain may be better as making the coil footprint smaller means fewer items in the target matrix at the same time.

I do not understand how lower gain makes the coil footprint smaller when transmit signal strength remains the same. Is it because lower gain evaluates less of the return signal by taking only the stronger portion which would create a net smaller field evaluated? Further, what might low gain on a Gold Racer be? I have had some places where sensitivity of less than 60 was required to get a decent threshold but was concerned that such low gain would cost the small gold. Does gain actually have a relationship with the size gold one is able to recover?

Every answer brings more questions. Sorry.

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Metal detectors only process the received signal. The transmit part lights it up but it is the sensitivity of the receive circuit and how the signal gets processed that determines what happens. Both transmit and receive gain can be changed on some detectors. On most just the receive gain is changed when you manipulate the control. It is not impossible that both may change via a single control. In general increasing gain adds depth and enables better signals on weaker targets. it can also pull in more interference from outside sources, increase saturation effects in bad ground and hot rock signals.

The reality as far as you are concerned however is that gain expands and contracts the size of the search matrix. This can be confirmed via simple air testing. Use low gain and observe the area under the coil where a signal is initiated. Increasing the gain will increase the volume of the area where the same target signal is acquired.

By using lower gain you light up a smaller volume of material and reduce the chance of two or more targets being detected at the same time, increasing the quality of the target VDI on the remaining targets.

It is also possible for higher gain to pull good targets out of a mix, because it enhances the desired signal more than the signal from undesirable targets.

There are no black and white answers, because everything depends on the ground mineralization, the exact mix of targets under the coil, how those targets are positioned exactly in relation to one another, the machine itself, and the coil used. Again, try the same tests with buried adjacent ferrous and non-ferrous targets, both at high and lower gain levels.

Lower gain is just lower than whatever you are already using. This is no magic bullet stuff, just something I bring up because it is counter-intuitive for most people. Yet it can help in some situations and so is worth trying.

Long story short lowering gain is a bit like running a smaller coil. Raising the coil an inch or two can have a similar effect.

metal-detector-gain-sensitivity-matrix-search-area.jpg

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4 hours ago, SLGuin said:

Steve,

Thanks for the excellent response and the link. 

The idea of digging everything in a small area just to see seems a very good one. At least just to see.

This, in one sentence, sums up the entire idea of masking that many have spent pages on.

 

This, in one sentence sums up why digging everything is worth a try. I am already digging bobby pin fragments because they are so close to sounding like stud earrings. Just a little further might be just the ticket.

This is exactly how I am going to try it tomorrow morning.

Thanks Steve.

 

 

Ya know I been reading a lot of Steve's stuff for a long time before I found this forum and the conclusion I have come to is this..... Steve is a purdy dang smart you feller....

I am glad to have found this forum I sincerely believe it to be one of the best....

Thank you Steve for all your hard work and the sharing of it with all of us.... kudos to ya.

 

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