Is it just mineralisation...or my lottery win?

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Is it just mineralisation...or my lottery win?

Post  johnny_boy on Mon Oct 26, 2009 2:56 pm

Hi everyone,

I am trying to find out how vulnerable the GPX4500 is to giving false strong readings due to high mineralisation.

I was recently running an 11" mono in one of those typical areas that has a gradual shedding slope where I have found a few small nuggets in the past. At a minor crest of the slope I was getting faint signals within a small line about 2m long - any softer and I'd put it down to a vein of mineralisation, but there were a couple of spots with just that 'little bit extra' to make me think it could be something more than mineralisation and worth digging.

With a bit of digging the signal strengthened to be what I would call definite, but now I'm down about 2 feet and whilst I'm still getting a very strong signal, it hasn't switched to a 'squeal' and I don't think the signal is getting any stronger. I'm starting to think its just concentrated ironstone.

i've taken samples, but I can't pan anything out...the samples don't seem to give signals form the 4500 though.

What are the chances of their being something this deep? Is it likely to be just mineralisation?

The general conditions are mainly hard ochre, but with a couple of thin crumbly quartz veins (about 1cm) running down but which have farily obvious ironstone traces with it.

I thought the GPX4500 all but removes the false mineralisation signals especially in the enhance mode (which I'm running)?

I would really welcome any thoughts!

Thanks,

johnny_boy
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Re: Is it just mineralisation...or my lottery win?

Post  Jonathan Porter on Mon Oct 26, 2009 7:43 pm

Enhance though extraordinary is not infallible so yes it can become flummoxed sometimes, best bet in a situation like yours is to check the signal response in another timing such as Normal, paying particular attention to the response. Generally if the response is a low/high in Enhance and remains the same in Normal (on a suspect target) then chances are its ground.

The fact that you have dug so deep and the response has not lifted suggests you have discovered a special set of mineralisation circumstances where the Enhance timings can and will generate a much more obvious response over any other timing, like I said above use the detectors other timings to cross check the response and you will soon realise what the odds are of it being your retirement signal.

Hope this helps,

JP
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Re: Is it just mineralisation...or my lottery win?

Post  mulgadansa on Mon Oct 26, 2009 10:33 pm

Gday JB
I've had very similar experience with mine on more than one occasion.
If the signal you're getting is quite loud and large, flip to Special on the front end cap and then Sensitive Smooth on the digital menu and if it's ground noise it will disappear completely.
As usual JP's spot on but I find this type of signal gets worse in Normal timings.
Hope it doesn't disappear .
cheers
Brett
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Re: Is it just mineralisation...or my lottery win?

Post  johnny_boy on Tue Oct 27, 2009 2:58 pm

Thanks guys - that's given me a few great tips to try! I'll be crossing everything that the signal stays with the other settings even if it means another few hours of 'diggin and chippin'!

I guess like someone else said, better to keep digging until you're sure than to bemoan the one that got away!

JB

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Re: Is it just mineralisation...or my lottery win?

Post  johnny_boy on Wed Nov 25, 2009 2:57 pm

Thought I'd post an update on this...

....alas it wasn't to be!!! I tried the different settings suggested, but the signal was still strong and definite - I have never heard such a strong signal from mineralisation before! Anyway, after much digging I got down to around 2 feet down with enough space to get the 11" down. That was hard work!

Anyway, whilst there was lots of squeeling, I have finally concluded it was all just mineralisation. My reason was that when I moved the coil extremely slowly I could remove any varience in tone - particularly at the bottom of the hole where raising and lowering the coil an inch or so had no tone. This is something I don't believe happens with a true nugget. It was a real shame as this could so easily have been a great spot! I put it down to very fine linear veins of quartz and ironstone.

Still a lesson to be learned...

JB

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