Idea For Creating Test Nuggets Of Various Sizes?

[ironrock]

I had a light bulb moment the other day, thinking about testing my sd2200d on it`s maximum depth on medium to large nuggets (2 up to 100 ounces) for example`s sake; let`s say 2,5,10,20,50,75,100 ounces. Since i don`t have these lying around i thought about GOLD LEAF. How about wrapping rocks or let`s say melted lead in the shape of a possible nugget in gold leaf. Gold leaf is 24 carat gold ,is it not?, and most gold found in Australia is around 20 to 23.5 carats, so the signal should be as accurate as possible in regards to a deep nugget(sound wise) don`t you think?

Also; regarding non mineralised ground which i live on (sandy soil - citrus farming area) , would testing in this ground give me dramatically differing results, than if i was testing in highly mineralised ground like vic goldfields .If so; why?
I do recall ready about vlf`s and pulse induction machines being similar in depth on quite ground, but pulse induction drills vlf`s on high min soil. Can anyone explain to me why this is the case, it would be interesting to know the answer to that?

 

[GypsyGoldAu]

I don't see the 'leaf' making much of a material/significant difference myself...

Seems a lot of trouble/expense to go to for the sake of a test target, when you'd be better served to just get out in the field and find genuine targets...and pocket the $$ difference imo.

Buried targets compared to 'test' buried targets will still respond differently, and to be honest, your testing will still not be 100% definitive of the machines capability as the test target will not have the modified mineralisation halo of a genuine target...

This, and vlf v's pi has been covered elsewhere on a multitude of occasions...

Cheers
Gypsy

 

[rego7]

I use aluminium ingots of various sizes/weights, usually with a piece of wooden dowel as a handle. No need for gold-leaf, just use the aluminium as it gives a very close response at the same weight and sizes as gold. Close enough, in my opinion, for testing.

The test pit I use is on a bank with various depths drilled vertically using an auger, that way the soil above the level is not disturbed and this gives a better depth reading through 'virgin' ground and as Gypsy said above - no halo. The vertical is lined with a PVC pipe to avoid any collapses. Most test pits are similar that I have seen. This is all on mineralised ground (Central Vic goldfields). If you do your testing on quiet soil, it will give a far higher response and better depth than mineralised soils.

To test coils and settings, its best to do it in the soil you intend to detect in. Test pits or areas are still only a rough guide anyway and can give an indication of performance but are a good neutral venue to test coils and various machines against each other. For example, a 4500/5000/GPZ were all tested against each other using this sort of test area.

As for VLF versus PI - a technical issue very well discussed on this forum and elsewhere but the bottom line is PI will out perform VLF on mineralised soils. PIs can be run much harder than a VLF.

 

[Ridge Runner]

The problem with you Idea is going by the weight even using lead will not be equal to Gold because gold weighs 19.32 grams per cubic cm and lead weighs 11.37 or 11.39 per cubic cm, Because if you made them of equal weights the lead piece would be 1.6992 X bigger because it is lighter and to match the weight won't work so you would have to go by the size instead to be more accurate, Which is why people say lead is louder when they use bits of lead of equal weight to Gold hence the Detector sees a bigger Target. So using Lead or Aluminium of equal weights to Gold will not work because depending on which metal you use will be way too big, A Detector see's Shape / Mass, NOT Weight so you need to go by the items Physical size, Ok.

A VLF will match a PI in Normal ground and in some cases could even go deeper, But throughout 85 - 95% of Australia that will be a very rare Event indeed, In the UK and throughout the EU there is a good chance that could happen, I have dug some seriously deep items with VLF's using a 10" DD, I have a 15" Concentric Coil that can see things at Extreme Depths and that will match a PI using a 15" Mono, I know of a person who found a 1 ounce nugget at 18 inches using a 12" Concentric Coil and it was a loud signal, But how the nugget is laying in the ground and the skill of the user along with the machine being used has a lot to do with the results, And if the Ground minerals are not too high you would be better off using a VLF because you will dig less junk, But If you are hunting for Gold in OZ then a PI/ SD, GP, GPX, SDC, TDI etc is King. When you go out searching the mullock heaps a good VLF might be more use from people like Whites Nokta/Makro and Garrett, Fisher, Minelab, Using them will save you a lot of back breaking work all for nothing,

Hope this helps,, John

 

[B5MECH]

For a small target cut a piece of gold jewellery to the weight of the targets you want, cut the top off a potato and melt it with a map gas torch inside the potato, less than 1 gram should melt with a good propane torch, and you can sort of shape it as it melts into a nugget. Bit of a waste of jewellery but if you have some old scrap gold around could be handy.

 

[ironrock]

Thanks for your replies people. I was thinking to test (when i come down to vic, soon i hope) in the side of a creek bank, i have detected in a few, so i know where there are some good spots. There are some area`s on these creek banks that are at a 90 degree angle and are 6 feet deep ,some even more. All that would be needed is a measuring tape and a good hole digger. What i think you could do is dig about 2 feet into the bank, actually a small hand auger would work great, tie some rope on the test piece( for easy removal) place piece in hole then perhaps wet some soil and fill in the hole. I believe the halo effect should mostly still be there, and gold leaf is quite cheap (look on ebay) so i will think about what exactly i`m going to do!!

And i do understand that detectors read the surface of the object , not necessarily the density, the objects i would make would have to be an estimation of size/weight of a possible nugget of equivalent size.

 

[Ridge Runner]

A detector will give you a good signal from one of those little round bits of foil from a paracetamol pack even though it is wafer thin, so no matter what metal substitute you use ( Lead or Alloy ) it must go by the physical size, Not the weight because a metal detector does not Care about the weight,

 

[GypsyGoldAu]

I believe the halo effect should mostly still be there, and gold leaf is quite cheap (look on ebay) so i will think about what exactly i`m going to do!!

If this is the case, then you do not understand 'halo effect'.....

GGA

 

[Ridge Runner]

I believe the halo effect should mostly still be there, and gold leaf is quite cheap (look on ebay) so i will think about what exactly i`m going to do!!

If this is the case, then you do not understand 'halo effect'.....

GGA

It might be a good Idea if he studies the basic's of how a Detector works, And about the leaching effect of such metals like copper, brass and Iron, At this stage I would be forgetting about compatible metals for testing,

I once found a large Bronze coin that was about 14/15 inches deep, when I got the coin out I noticed that the soil had a big dark green stain on it so I waved the lump in front of the coil and it let out a signal, So I put in in a plastic bag and and I kept it for about 6 months, well after that long it dried out so I fired up the detector and Not a sound, So I sprayed it with water and right away it start to signal again, So I put it away for about another year and it did the same again, eventually it fell apart due to drying out after about 5 years and I threw it out, But It did work and Iron does the same but it breaks down releasing small particles in the soil, But Brass, Copper and Bronze will all stain the soil and that dark green stain will be picked up by a Detector,

John.

 

[GypsyGoldAu]

It might be a good Idea if he studies the basic's of how a Detector works,

Well, ...he's gonna do what he's gonna do. Guess asking for advice was to get his post count up perhaps?

The tone of the last post appeared to disregard all info. from guys who know, so i revert to my earlier post to just go and practice on real targets on the ground he's walking...:dunno:...

Gypsy

 

[Ridge Runner]

I think the first year or so of detecting we absorb so much and there is so much fun to be had, even coin hunting is a blast even now, maybe he would do well to join a local club whether it be treasure or prospecting either way it will fast track him to success being around like minded people,

john.

 

[GypsyGoldAu]

Orrr...he could book a training course when he hits the GT with Miners Den or Coiltek....

 

[SteelPat]

Just on a side note here - the detector will behave differently depending on the density of the gold. A reefy flat bit will sound different to a solid slug of the same surface area.

Unfortunately with gold, there is no ideal test alternative. The easiest method if you are just interested in depth comparisons is just to cut some old lead sinkers up, flatten some and keep others solid and of different shapes. While not exactly the same, lead will give a similar response to gold and is good enough for depth comparisons.

On the halo effect - it occurs generally with iron objects (or other materials that corrode). As they oxidise the rust leachs into the soil causing the object to appear bigger (to the detector) than it is. Gold does not oxidise like this and therefore does not cause a halo effect. Sometimes gold is found in ground with a heavy iron component. This can give the appearance of a halo but its not from the gold.

 

[GaryO]

Gold and lead of the same pysical size will test identically .

 

[GaryO]

https://www.prospectingaustralia.com/forum/viewtopic.php?id=15903&p=2

 

[SteelPat]

Gold and lead of the same pysical size will test identically .

Similar maybe but not exact. A small bit of lead shot sounds slightly different to the same size and shape bit of gold (on a GPZ7000 anyway). The lead sounds sharper on the signal where as the gold tends to soften on the edges.

Electrically if you look at the output on the receive preamp on an oscilloscope, you will see the decay rates between lead and gold are different. On a lot of detectors, the circuitry wont allow this difference to be heard.

But as I said previously, for depth testing/comparisons, lead is good to use. When I have been testing some of my experimental circuits, small bits of aluminium (3mm or 4mm sq cut from drink can) is a very good simulation for small SDC type of gold.

 

[Ridge Runner]

Gold and lead of the same pysical size will test identically .

Similar maybe but not exact. A small bit of lead shot sounds slightly different to the same size and shape bit of gold (on a GPZ7000 anyway). The lead sounds sharper on the signal where as the gold tends to soften on the edges.

Electrically if you look at the output on the receive preamp on an oscilloscope, you will see the decay rates between lead and gold are different. On a lot of detectors, the circuitry wont allow this difference to be heard.

But as I said previously, for depth testing/comparisons, lead is good to use. When I have been testing some of my experimental circuits, small bits of aluminium (3mm or 4mm sq cut from drink can) is a very good simulation for small SDC type of gold.

I have noticed that on the GMT, with Lead The rise and fall is sorter and so is the ZIP sound, But even 9ct gold has more of a ramp up and down and the signal is longer too,

john.

 

[SteelPat]

It is quite interesting to see it on an oscilloscope. Depending on how good the input circuitry (including coil response) there can be quite a marked difference in decay rate. Bearing in mind this is all only relevant to PI machines.

VLF/IB machines detect differences in materials by looking at the phase shift. Not having done much experimenting with VLF/IB machines I am not sure how much difference there is between lead and gold. In theory there will be a difference, as phase shift is dependent on the inductance and resistance of the target. While I am not sure of the inductance difference, there is a definite difference in the resistance of lead and gold.

 

[Ridge Runner]

It is quite interesting to see it on an oscilloscope. Depending on how good the input circuitry (including coil response) there can be quite a marked difference in decay rate. Bearing in mind this is all only relevant to PI machines.

VLF/IB machines detect differences in materials by looking at the phase shift. Not having done much experimenting with VLF/IB machines I am not sure how much difference there is between lead and gold. In theory there will be a difference, as phase shift is dependent on the inductance and resistance of the target. While I am not sure of the inductance difference, there is a definite difference in the resistance of lead and gold.

I should imagine the ZED would respond similar to a VLF because it is closer to a VLF than a PI although it is neither,

john.

 

[Dignit]

I would also think, and am no expert, but the conductivity of a thin bit of gold leaf wrapped around a rock would be vastly different to a solid piece of gold so the signal response could be vastly different.
I'm with Steelpat. Pieces of lead are more than adequate for depth testing. You'll get approximate relative signal response across different sizes.