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Two Questions


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Hello everybody, I have 2 questions today.

 First, I would like to inform me if there is any trick to understand the mineralization of the ground that you are about to search with your metal detector in the fields and in the woods.

 Second, I am a minelab safari owner, (I am interesting about coins and jewelry mostly) and except the stock coil (11’’), I also have the Mars MD sniper coil (10’’X 6’’). What would you recommend for bigger coil? Consider that except fields and woods, I do a lot a lot a lot of beach metal detecting. I want something deeper but not losing in target separation and if it is possible the less effect of ground mineralization and iron masking.

 I was thinking about mars md tiger (13’’x 10’’), mars md discovery (13’x13’’), nel tornado (13’’x12’’) and nel thunder (14.5’’x10.5’’).

I am waiting for your recommendations. Thanks.

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The only way to know the true Mineralization of a site is to measure it directly via use of a an Fe3O4 mineralization meter.  These can be obtained standalone but several mid to higher end FT detectors such as the T2 and F75 have these bargraph meters built in (hence statements like "3 bar soil"), as well as the XP Deus and Orx and most recently, Nokta added a mineralization meter to their Simplex via a recent update. 

Trying to infer mineralization from GB readings is really not the way to go because other time variable factors such as soil moisure content and other soil constuents besides the mineralization  that directly impacts detector performance play into the ground phase readings that register on a detector at any given time.  IOW high GB/ground phase readings do not necessarily equate to high mineraliztion.

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Also maybe consider the Detech Ultimate 13" coil, extremely light for the size of the coil and good sensitivity to small targets. Still lighter again than the smaller Mars Tiger which is 500 grams vs 480 for the Ultimate.

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Ground balance numbers do not equate to how bad the mineralization is. It is a guide to the type of mineralization, not the amount. It is the amount that matters most, and that is what a Fe3O4 meter measures. It is common on quite a few First Texas and Nokta/Makro models.

For other models with a manual ground balance, you can get an idea from the way the ground balance acts. Low mineral ground is easy, and will ground balance well over a range of the setting. As mineralization increases, it will be harder and harder to get a good ground balance. In the worst ground, just one number off either way, and the machine reacts. Plus, you get the balance perfect, but move two feet, and now it has changed. It is also common to have to reduce sensitivity in very bad ground just to get the machine to balance at all. Too high settings will cause overload situations to occur - an obvious indication of bad ground.

In mild ground one setting works great everywhere. You may not even need to ground balance a lot of mild ground. In bad ground constant ground balancing is required, and eventually ground tracking is beneficial due to this fact.

Finally, drop a small, powerful magnet in the loose soil. If it comes up looking like a spiky golf ball, you’ve got serious magnetite iron mineralization. Not all bad ground is magnetic, so lack of magnetic mineral does not really prove it is low mineral ground. However, Fe3O4 is the formula for magnetite, which is common enough to be the problem in many locations. In Australia the offending material is more likely to be maghemite.

As far as coils go, all I will note is that if the ground really is bad, going to a larger coil may not provide much benefit, other than ground coverage. In the worst ground, a large coil may actually get no more or even less depth than a smaller size coil, especially when dealing with a VLF. PI detectors are less affected by ground mineralization, to such a degree that coils can be far larger on a PI and still be effective.

Super magnet covered with gob of magnetite....

7E171711-48E2-4F72-8571-8C6548DFBFEA.jpeg

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  • The title was changed to Two Questions

To answer your other questions, a bigger coil will usually give you a bit better depth, but, they are also worse when it comes to target separation and masking. There will also be a difference between mono and DD coils on those subjects too.

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10 hours ago, George1971 said:

Thanks Chase Goldman for your reply. What is your suggestion about the coils I mentioned?

 

 

 

 

 

George, I have little experience with third party coils and ML non-PI detectors so can't give specific advice for the Safari, but I second a previous recommendation to look into the Detech ultimate coil as an option.  Great coil used on my MXT and F75 though I seldom use those detectors now.

However, I will echo Steve's statement that especially in mineralized ground, large coills really provide diminishing returns on depth performance due to the fact that they see more ground and are subject to greater ground feedback.

Also, as far as non-PI detectors are concerned, the potential depth gain is seldom worth the trip if you are starting from a stock coil of greater than 10 inches based on the other drawbacks (higher ground feedback, less separation, less small target sensitivity).  I mainly pursue the larger coils solely for the swing coverage advantage.

HTH

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For beach hunting, I really like the NEL 15" Attack coil. More depth and coverage than the stock coil, and I seem to get just as much sensitivity in finding small targets. It's been very stable too.....even more than the Coiltek coils I have.

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