PI detectors in Iron rich red clay soils

[Anonymous]

I have been planning to purchase a PI detector for deep gold in reddish clay soil which usually indicates that it is also rich in Iron--their is also probably some basalt since this is what the bedrock here often consist of. However, I have come across a few post in this and other forums warning that Iron rich soils often give PI systems a lot of trouble.
Any further information would be appreciated.

 

[Anonymous]

Hi Jon,
Since nobody has jumped in to try to answer your question, I will try.
First, I have tried a PI with no ground balance in several areas having reddish clay soil. Yes, you will get get a ground response from the red clay. You will get a ground response from other colored clays also.
If you bob the coil up and down over such red clay type ground, most likely you will get a strong response. However, I have found a couple of areas where the red clay really didn't produce the strong response I expected either. Now, the intensity of the ground response depends upon the sensitivity of the detector, the delay, and other factors, so there will be differences between PI's.
I have done a lot of controlled testing with a PI at my home, and similar test while I was hunting in areas having the "bad ground". While in the areas having the adverse ground, I did spend a lot of time testing and trying different things. In fact, initially, since I was trying to determine what seemed to work best, I really spent more time testing than I did actually hunting while in the gold producing areas. Unfortunately, my in the field time has been limited simply due to the time I can allot and the distance I have to travel. Since I have limited time, I prefer to test a lot both at home and in the field so I know what to expect in the field.
Now, does this fact that because the red clay ground will produce signals mean a PI can't be used effectively in such areas? Nope, it just means you have to be more careful in your search techniques and use the autotune feature if the detector has one.
This autotune thing has generated a lot of discussion recently so I might as well throw my two cents in about it now. Yesterday, I buried a 5 grain nugget somewhere between 2" and 3" deep in "bad ground" and tried several things. What surprised me was increasing the autotune speed made it easier to obtain a more consistent response from the nugget. Air testing showed the increase in the autotune speed would decrease the depth capabilities, but in ground tests displayed the opposite. In mentioned this because I think it is important that people try similar testing to better know their detector.
If you search slowly and are careful to try to maintain a constant coil height, you can easily minimize the "bad ground" signals. Yes, you will some false signals when the coil snags on a bush or bumps a rock and the coil is suddenly raised or lowered, but overall, the detector will work quite well.
I have found it is best in the areas having the worst ground conditions to just raise the coil a little. This reduces the ground signal dramatically. This raising of the coil has the greatest negative effect on the detection of real small nuggets. Larger nuggets, even deep will still give a nice strong signal.
Remember, that most PI's that do not have a ground balance are about 1/3 the price and probably 1/3 the weight of those that do have ground balance. So, there are tradeoffs when considering just which one to buy.
About the only way a person will really know if such a PI will work for them is to simply try one. Unfortunately, that is difficult since there are so few in the field used for gold hunting at this time. Hopefully, others who are using PI's for nugget hunting will jump in and post their opinions.
Reg

 

[Anonymous]

Reg
I am starting to realize like you say, that I am just going to have to take a gamble and see what works best because after nine years in tropical areas, I have never seen anyone using a metal detector and I am always outdoors. However Its not just spending cash on the wrong machine but also the thousands of miles and the chucking and jiving to get them to seemingly difficult soils containing clay, Iron volcanic basalt, ash, black sand and who knows what else. However, if the detecting doesn't work out,I at least love being their.
Thanks for being upfront and informitive.
Jon

 

[Anonymous]

Thank Reg. for responding.
I didn

 

[Anonymous]

I agree with Reg but manufacturers have to be carefull when giving the operator too much to fiddel with. An adjustable SAT if impoperly used
could give the thing a bad name. Such as the case if the operator could speed it up to much. It is
great having all these knobs if homemade and your
the operator though. One method is to find the
most troublesome, rappidly occuring material, GB
most but not all of the signal out and then
increase SAT speed to quieten the average ground,
then test for sensitivity on a known target and
hope that GB setting doesn't enhance some other
unwanted material.
I built the PW Sandbanks PI in around 1979, raised the frequency, fitted an adjustment for the delay, got rid of the audio circuit and fitted an audio amp and tested it on the rich
red, orange and black pit clays at the local coal
open cut mines and it performed great, I thought!
drove 4 hours to a goldfield and couldn't get it
to within a foot of the ground and also couldn't
detect an Australian 20cent piece on the surface.
Some ground material such as natural ironstone
will have little or no effect but if it has been
superheated by nature then it can be very noisy.
What I am trying to say is be carefull with your
choice and get something with ground balance.
An American gold detector club should help you
there.
I haven't ever been to the <IMG SRC="/forums/images/flag.jpg" BORDER=0 ALT="USA"> but it appears that
you may have some fairly quiet ground there in
comparison to ours as when my father bought a Whites 6000D we found that it was impossible to
ground balance on most of our goldfields. I had to
fit a 10 turn pot and an adjustable SAT to overcome this problem but the one turn worked
great over the above mentioned coal mine clays
and ironstone, not a murmer.
The bad ground has made the Minelab PI's popular
here but may be a bit overkill in your soils,
pricewise? Some of the detectors frequently
named here may suit your needs?