Re: GPZ 19 inch depth increase ?? - I don't think so.......

slimpickens Mon Nov 21, 2016 2:03 pm

Axtyr wrote:Hi everyone.

Thank you to Martin R for providing that video about the Minelab Testing Ground. A lot of breath is expended on air tests and their value, and exactly how Minelab test their coils and detectors.

I have only seen one Minelab video of how they went about testing the GPZ and it looks like it was out at Echunga. I was a little put off by it, and you can see a very small part of it in the video supplied, because they basically dug a deep hole then excavated other holes parallel to the ground at different depths and placed pieces of gold into these holes. Although there was "undisturbed" ground sitting above these pieces, there was no halo effect provided by the ground and nuggets. I am of the opinion, and it is only my opinion not scientific fact, that some of Minelab's testing is very similar to air testing.

The Testing Ground will only be a valid test if the ground has been left undisturbed for several years after the items were placed at their appropriate depths so that the pieces begin to display a halo effect. This may be the case but it not mentioned in the video.

I do own a GPZ but for 2 reasons I decided not to purchase the 19" coil. As I am unemployed I could not afford the new coil and I felt that I could find just as little gold with the 14" as I could with the 19", and at my age digging really deep holes is taking it out of me.

I see GoldGypsyAu's point in regard to Minelab's claim of an AVERAGE 30% depth increase, AVERAGE means just that, AVERAGE. In Australia's goldfields the depth increase might be as little as 5%, but in extremely benign ground there may be an increase of 80%. These are just my made up figures and in no way reflect what results Minelab may have ended up with.

The word "Average" in their advertising also made me wait until I could see what results others were getting with their new coils before heading to the bank manager (wife) with a proposition for purchasing a new coil. Having been stung paying the full price for the detector didn't help either.

I certainly hope that all those who purchased the coil get some satisfaction in the future, especially Kon61, who waited so patiently for the Kraken to be released.

Regards Axtyr.

Hi Axter, A halo takes many thousands of years to maybe form around a nugget. No test bed gold nuggets will have a halo around them. This is why I believe that an air test is just as good when comparing coil against coil. Others will say to drill a hole into a gully wall so you do not disturb the dirt, but totally forget that the gully wall is made up of throw out dirt..... there is nothing natural about it.

Guest Mon Nov 21, 2016 2:39 pm

With you Harry on this and also about the halo affect, as once the ground has been disturbed you have also disturbed the halo. There for no more halo. T10

Hope this makes sense.

Cheers.

Mike.

adrian ss Mon Nov 21, 2016 4:11 pm

I am not so sure that PI metal detectors respond to a halo effect.
The very nature of the machine dictates that it does not respond to iron and other diffuse mineralisation very well if at all. Eddy currents have great difficulty flowing through oxides and even crystalline gold. Carbon fire ash can be quite conductive and a PI can respond to that at times.

VLFs on the other hand do respond to certain halo effects because they do not rely totally on eddy current generation in order to detect a target.
The actual presence of the conductive halo can disturb/ deform the coil field causing a magnetic imbalance between the TX and RX coil resulting in a generated signal.

My test patch is over 10 years old and those targets that have been there all of that time still produce the same signal strength in my PIs as they did in the beginning. The PIs being a CS4PI, Sand Shark, Infinium and one home built job.

My Sov XS still struggles to find one of the dollar coins buried at 8 inches but will nail these coins at better than 12 inches in wet beach sand.

Some of my other VLFs EG. A 6000DIPro, 6000DI Series 3, Lobo ST, an ancient Fisher 553D, Gold Seeker 15000, Pro Scan 2, and a couple of others all seem to be detecting these test patch targets better than in the beginning.

One other thing I noticed is that My SDC2300 detects these targets way way better in Salt mode than in the Normal Mode.......So maybe use the salt mode whenever and wherever possible. scratch

Guest Mon Nov 21, 2016 4:34 pm

GOLDGASM wrote:
Ismael wrote:Someone else on another forum tended to agree with my wish that ML would actually make a smaller coil for the GPZ so we can get into those places that the 14" is had to use.

Hi Ismael, I am very keen on the smaller coil aswell, realistically how small could minelab go with one? I've been told 6" is a no go with the new tech, maybe an unusual 9" size at the other end of the spectrum, compared to the 19" coil?

Cheers GG

I'd get more use out of a smaller coil than the GPZ19 Q41

. Personally I think 14" is a good all round size with larger & smaller coils good for specific jobs or areas. Don't see too many people on the eastern side of the island using big coils?
I've heard that the Super D configuration is a limiting factor too? A 10"x9" or thereabouts would be nice.

kon61 Mon Nov 21, 2016 5:05 pm

For all that may be interested,go back to page 1. I'v added those promised pictures, of the gold nuggets first tested a couple of days back,with a short story of my experience, in the 3 days of testing/detecting with Bill & Slim.

Cheers Kon. Q11

Guest Mon Nov 21, 2016 5:17 pm

adrian ss wrote:I am not so sure that PI metal detectors respond to a halo effect.

Halo or no Halo, there is something other than imagination that makes the detector (GPZ or GPX or GP) respond better on an undug millions of years undisturbed piece of gold still in the ground, than after it has been dug out and then replaced in the hole or on the ground and re tested at the same depth or height.

Is it real or is it just wishful thinking.

cheers dave

Guest Mon Nov 21, 2016 5:22 pm

G'day Kon

It might be stretching your memory a bit, but if those larger nuggets in the picture were found with a GPX or GP model detector and not the GPZ, do you by any chance remember how deep they were, and how deep/air test by comparison now with the testing you blokes are doing?

cheers dave

Guest Mon Nov 21, 2016 5:40 pm

Thanks Kon,

For yours and the teams honest test results, I can see how disappointed you all are with your results, after the long wait we had for the new 19" coil to be finally released.
Thanks again for sharing your results with us all.

Cheers.

Mike.

adrian ss Mon Nov 21, 2016 6:02 pm

davsgold wrote:
adrian ss wrote:I am not so sure that PI metal detectors respond to a halo effect.

Halo or no Halo, there is something other than imagination that makes the detector (GPZ or GPX or GP) respond better on an undug millions of years undisturbed piece of gold still in the ground, than after it has been dug out and then replaced in the hole or on the ground and re tested at the same depth or height.

Is it real or is it just wishful thinking.

cheers dave

No it's real dave . PIs do detect deeper on in the ground targets......I have yet to hear a good explanation why. There are lots of theories but nothing solid and proven that I know of.

kon61 Mon Nov 21, 2016 6:55 pm

G'day Dave

If memory serves me right,the larger 6oz slug, was found 4/5 years back with my old 2200D. Being trapped up on the side wall of a gully bank, 4 foot high from the gully floor,with the smallest of coils available at the time (the Commander 10x5 DD). The 89gm speci with approximately 2.5 oz of gold in it, was found by Bill (Vasilis) sitting just under, a flat,solid, 6 inch thick chunk of broken slate boulder,in the middle of a small narrow feeder.
No worries Mike cheers. I can only hope that your new large 19 inch coil,together with any other members here, exhibits far better test/depth results than what we've seen from our 19s so far.

Cheers Kon. Q11

vasilis Mon Nov 21, 2016 8:12 pm

Good day Dave

I concur with Kon on the depth of the 2 nuggets mentioned. No 'mumbo -Jumbo' there.
I found the 41 grammer not far from the 6 ouncer but it was after 4 people including myself had walked over it/passed it on many occasions.
I was using the 4500 and after getting sick of the lack of depth. I put on a coiltek 14'dd and it was a faint target at aprox 10".
There has to be more gold in these areas but we just cannot reach them underground unless we do what some culprits are doing and that is digging the **** out of these beautiful areas replicating the old workings. I would rather dig one hole and back fill the hole instead of shifting tons of soil and gutting the areas.
As you noticed in the test results, the speci achieved 20' whilst the 6 ouncer got max 18 to 19 inches. Obviously the rough surface on the speci catches the signal response better than the smooth surface of the 6 ouncer.
Cheers Bill

Guest Mon Nov 21, 2016 8:27 pm

Thanks Kon & Bill, for your replies to my wonderings about things like that, at this stage I'm just trying to understand what goes with what.

cheers dave

vasilis Mon Nov 21, 2016 8:50 pm

I should also mention that I found the 16 gram nugget in the Kimberley region aprox 5 years ago on a trip with Kon and Tiboo Dave.
This was with the GPX 4500 and the 16' nugget finder spoked coil in Enhance settings.
There was a boot tack and the nugget tucked in the spinifex. So from memory I was pushing along and over the spinifex and had a faint target at aprox 10 to 12 " but hard to determine due to the spinifex being in the way.