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Wet Spots Or Mud Spots And VLF Vs. Pi

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Good evening,

I’m venturing into the spotlight here with my first post to ask what likely amounts to a novice’s question.  

It stems from an experience I had about a year ago with finding my largest nugget. The location was in a small creek bed, which had been conveniently cleared of cobbles and overburden down to a small patch of bedrock surrounded by smooth, silty clay by a dredger.

Using a GM 1000, I had detected out several small nuggets from within the bedrock cracks that had been exposed, but not properly crevassed by the prior prospector.  However, the thick clay surrounding the exposed bedrock had pockets of varying degrees of moisture.

This was providing me a bit of challenge since the wetter spots seemed to be behaving just like hot spots. After an extended wrestling match with the wetter signals and the available settings, I gave up.  

However, by the time the next weekend came around, I just couldn’t get those wet spots out of my mind.  With the heat of the summer and record drought conditions, I guessed those spots may have dried just enough to deserve one final pass.

Within minutes of returning, I had found a solid, repeatable, 2 bar non-ferrous signal in the deepest clay pocket on the upstream side of the rock. (This exact spot had seemed masked the week before.)  Digging 4-5 inches down into the smooth clay I found a “rock” that made my detector sing.  Cleaning it off revealed a beautiful 1/3 ozt. nugget. Call it beginner’s luck—because I do. 

Now for my question. Were those wet spots of clay giving me fits because of greater relative mineralization, heterogeneity of moisture, or VLF technology?  Perhaps it was some of each?  

Part of my curiosity stems from never having used a PI detector.  For those of you with plenty of PI experience, do you also struggle with wet spots or mud spots for lack of a better term?  And, if so, are certain PI detectors more resistant to the struggle?

Thanks for any input you might spare.

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If the one spot is different from the surrounding matrix you will have an area that is not balanced ...

the simple answer is YES...

fred

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 What! Someone besides me reports gold weight in troy ounces and not grams! May God bless you my friend.

  There are some clays around here that are so hot they will make your detector squeal like a pig, vibrate and shake, especially when they are damp (well, maybe not that hot) . Any time yo have clays in a wash or a stream course it is a good indication that the area has not been mined thoroughly. About all you can do with a VLF is start digging through the clay and see if the target signal improves and becomes more defined in a smaller area. Plus you may also find something that was beyond the initial range of the detector.  

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Did the clay keep getting quieter as it dried out more?

Ground that gets hotter when wet usually means salt. Water mobilizes ions, ions conduct electricity much like a metal conductor. It doesn't have to be sodium chloride (table salt), it can be anything ionic including things that might not seem like salts. Metals like to form salts so they are found in mining regions. Especially since mining regions also tend to have acidic or basic soils. These can leech into things like clays and concentrate longer since clays tend to erode less quick, or the clays themselves can be derived from alkaline soils which are already salty. 

Clays also capture heavy, hot particles like magnetites (and 1/3 oz nuggets), but those should be just as hot wet as dry.

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Those are really helpful comments.

Yes, the clays did get quieter as they dried out more. But, now that I think of it, even the completely dry clay still had a hot response.  And, now that you mention it, further upstream where the spring originates there are surface salt crystals in abundance. 

So, with what you’ve shared, it was likely a little bit of everything—salt, water, mineralization, and using a VLF. 

Do you find that PIs still struggle with those ingredients? I know enough to say that hot rocks should be less of a nuisance, but what about a salty mud pie?

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Yeah salty soils will still have salt response when dry too or even with an unmeasurably small amount of moisture - there is a place in Arizona, completely dry, that makes my 4500 go absolutely crazy even with the coil raised above my head 10 feet in the air. It's the top of a salt dome or something. Freaked me out at first, like I seriously thought I had stumbled on a hidden government buried transmitter station or something hahaha, I put a pinch of the soil in my mouth and it tasted like drinking the ocean, almost pure salt.

I've never really used a VLF in salty areas so I can't answer that question. But yeah PI's struggle with salt especially with larger coils (the 4500 and newer have a setting to deal with this a bit though), and the GPZ struggles far (far, far) more, so I'm guessing VLF's do too. Ionic electron conduction is not much different from regular electron conduction in a metal when it comes to induced mag fields from that current, so seperating the two responses is probably very difficult.

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Salt

This post and the one following it may clarify the salt issue for people. It’s an issue for any very sensitive metal detector:

https://www.detectorprospector.com/forums/topic/8257-my-tarsacci-mdt-8000-commentary-pics-and-videos-unit-received-12-15-2018/?do=findComment&comment=96925

Clay

from the Minelab Eureka Gold manual, page 34:

”11.2 Clay Domes
A common occurrence in nugget-bearing country is soil mineralisation commonly known as ‘clay domes’. These are regions of rather broad sound which could be confused with the sound which would come from a large deep nugget.
The following procedure will quickly establish whether or not the sound comes from clay or a metal target:
a) Pinpoint the target as best you can.
b) Remove about 4 cm (1.5”) depth of soil from over the target response.
Dish the hole so that there are no sharp edges around the hole.
c) Sweep the coil across the target from a few directions, keeping the
coil as low as possible. Listen to the signal and note if it is:
— Any louder or more defined than before. By bringing the coil closer
to a metal target the signal should become louder.
— Note if the signal seems to come from one direction only (a mineral signal will often come from one direction only, or at
least be less defined from the return sweep).
d) If you are still not sure, continue to dig deeper and again, note the
points above.
e) Be sure to dish the hole when digging to ensure there are no sharp
edges. Sweeping the coil across the sharp edge of a hole can cause false spurious signals due to the change in distance between the ground and the coil.”

Thread on mineralization issues:

https://www.detectorprospector.com/forums/topic/1599-gb-numbers-mineralization/

 

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There is lots of gold on the salt lakes in WA.  The only combination I have found to work well without driving you insane is a GPX with a coiltek AI coil, I use the 14” round AI.  It can run beautifully smooth even in normal timings, doesn’t like hot rocks but I don’t usually get them on lakes anyhow.

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Thanks for the helpful information, all.  Your comments have opened my mind to what should have been more obvious to me.  I’m baffled why I didn’t think of digging out those mud spots.  It may have been that I thought that digging deeper would have just gotten wetter and louder. But, it sounds like that is actually what would have happened if there was a target—not mineralized clay.  How ironic. Thank goodness curiosity got me thinking about rechecking those holes.

A54BAC3F-2C3D-4ABF-97EF-670E58B5F181.jpeg

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Awesome nugget! You've got to be happy with that ?

 

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