smaller bits in the arvo

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smaller bits in the arvo

Post by grasshoppernt on Fri 10 Apr 2015, 11:45 pm

On our weekend trip to Kal, I pulled out my .2 gram test piece to make sure the detector was working properly. It wouldn't pick it up and I had to change for a .3 before I could clearly pick it up with the 5000. This was at 8am.
We found nuggets through the day and around 4 pm I picked up a .1 grammer that was clear as day.
I didn't think that there would be that much of a difference in the detector's ability and wonder what this was due to.
Any ideas?

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Re: smaller bits in the arvo

Post by dryblower on Sat 11 Apr 2015, 6:42 am

Hi Hopper!
I have noticed the soil mineralisation , ground balance setting being slightly out , and EMI interference can all reduce the 5s sensitivity . Also ground temp makes a difference at times .
Doubt it will be a fault in your 5. I have two and have seen the above happen with both.
Mono coils dont ground balance perfectly on the heavy laterite soil around Kal , and you may find a DD coil set in "Mono" will GB better and can be run right on the deck, with good sensitivity. Works for me !
Cheers
Jim

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Re: smaller bits in the arvo

Post by grasshoppernt on Sat 11 Apr 2015, 8:18 am

Thanks Jim,
Didn't think there was a problem with the 5000, given that we picked up 13 pieces for the day. Wink
We probably only covered an area of 500 square metre or so through the course of the day, checking around all of the shrubs and spinifex.
I could only put it down to the heat of the ground, although mineralisation can change pretty quickly I know.
Interesting also was that I was using a 15 by 12 Nugettech coil I bought a couple of years ago from Prospectors Patch. Reeds didn't have the equivalent Nuggetfinder coil at the time when I was over from Darwin and I couldn't wait the 2 weeks. This has found close to 10 ounces over the time I have used it. I went in to PP the other day and couldn't see any. The comment by the lady in the shop was that when they worked they were great. Thankfully the first coil I bought was one that worked!

cheers,
Em

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Re: smaller bits in the arvo

Post by boobook on Sat 11 Apr 2015, 9:18 am

Em.
I have a 12x18 nugget tech which I won.
Initially it simply did not work, a dud.
Sent it back to PP who had a couple of stories about it, but I believe the problem was poor or incorrect connections at the lead/plug.
Since then it has performed well and compares favourably with NF and ML coils.
Mike
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Re: smaller bits in the arvo

Post by grasshoppernt on Sat 11 Apr 2015, 9:47 am

thanks Mike.
I bought the 18 by 12 at the same time, can't say I've warmed to it the same. It was a very noisy coil and tends to sit at the bottom of the detector box. I haven't been anywhere for long enough to persevere with it and have since picked up a NF 17 11.
Will have to get it out and give it a run again in Laverton next month when I head up for a couple of weeks. Looking forward to that for sure, but with what has happened in Sandstone, am reviewing the safety side of things.
Looks like a bit more money to spend, although I have 2 epirbs from the boat that I will take, a handheld gps, compass. It's a start.
Thanks for sharing

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Re: smaller bits in the arvo

Post by Flying kiwi on Sat 11 Apr 2015, 7:14 pm

Sounds like the halo effect grasshopper
A nugget that is undisturbed in the ground for millions of years is Easyer to pick up than a loose nuggie
Why- buggered if I know scratch

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Re: smaller bits in the arvo

Post by Bignuggs on Sat 11 Apr 2015, 7:32 pm

Yep, it's also had me buggered why a target that is in untouched hard compacted ground (like concrete) is supposed to give off a better signal. Why??
I've never understood the principle when you take into consideration you can stir up the ground or even rip it and you find what you are looking for. Why the difference ??
The same goes for damp ground. you would think with damp soils the target is easier to be found, apparently not.
But when you see some of the videos of finds, they are found in wet ground.
I can also say, buggered if I know. But I have found stuff in moist ground back in the days of the old VLF's.

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Re: smaller bits in the arvo

Post by boobook on Sun 12 Apr 2015, 6:19 am

The phenomenon of halo effect is very interesting.

In our time of boulder opal mining (W.Qld) an excavator is used in the pit to open the wall, top to bottom.
Ironstone boulder concretions are located in the sandstone matrix at varying levels. A boulder is distinctly heard when the bucket teeth rattle against it.

Probably 1% of boulders contain opal, mostly potch, the one containing seams of gem is the money.
Always when a gem boulder is located there is a circular, rainbow coloured halo in the surrounding sandstone face, you cant tell if the halo is spherical because you are only looking at a flat face.

This brilliant play of colour is quite spectacular if the sun is shining on the face, but then as the sun dries the slightly damp freshly exposed face, the halo disappears.

We reckon it is weak remnants of the chemical solution which caused opal to form in weathered cracks in the ironstone.
In some very old underground drives the halo effect is still visible after the boulder has been removed, dark and dampness?
Maybe there is a gold solution (halo effect) which precipitates into solid gold nuggets?
Mike
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Re: smaller bits in the arvo

Post by Nightjar on Sun 12 Apr 2015, 7:19 am

Morning Mike, GrassH & all,
Very interesting your experiences with opal mining. No doubt you have heard about peacock ironstone?
Worked on Koolan Island for a number of years, a very rich iron concentrate, so rich some of the ore had no resemblance to haematite vastly mined in the Pilbara.
When the shovels exposed a pocket of rich fines in the face of the quarry all the colours of the rainbow could be clearly seen, they disappeared when the pocket was broken up.
Could this much talked about "halo" effect extend through the gold fields because of the high content of iron mineralisation within this ground?
So many questions unanswered in the oldest known geology worldwide.


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Re: smaller bits in the arvo

Post by grasshoppernt on Sun 12 Apr 2015, 11:57 am

Interesting phenomena, particularly as it applies to other minerals. I also recall detecting at Tennant creek a couple of years ago in the evening. Would find targets that appeared to be close to the surface. After a scratch with the flat of the pick the signal disappeared! No doubt very fine gold, but once the ground around it was disturbed, too fine to pick up

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