northwest Imitating Gold Nuggets
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Interfacion Pty Ltd is pleased to announce that the QED PI Detector has been modified to allow the use of DD (double D) coils. This change involves a simple change to the electronics within the control box.
The firmware has also been upgraded to include a further improved Ground Balance.
All detectors being delivered to new customers from Monday 5th August 2019 will already have the above upgrades included.
As a show of commitment to all QED owners, the hardware modification to allow use of the DD and CC coils will be provided at no cost.
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Any QED owner who plans to attend the Laanecoorie Bash is encouraged to bring their detector along and have it upgraded at no cost.
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australian electronic gold prospecting forum.com  |  Common interest forum.  |  General chat and discussion forum (Moderator: bugwhiskers)  |  Topic: Imitating Gold Nuggets 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: Imitating Gold Nuggets  (Read 637 times)
GARY
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« on: Thursday January 17 2019 16:22:53 AEDT PM »

Trying to imitate a gold nugget for in the ground test is very difficult due to the variable of alloys within a gold nugget. For example two nuggets that I tested against one another, a 23 gram and a 101 gram the depth difference was only an extra 1 inch to the much larger 101 gram nugget which had not only extra mass but a much larger surface area. Both nuggets were detected from two different areas.

I was sent from a friend a screen shot written by the great man himself Eric Foster in regards to gold alloys when he performed tests with a PI on a set of gold standards. The set of standards were all square pieces of metal of identical size & thickness with the only difference being the alloy makeup. The standards varied in steps of 10% from pure 24k gold with the normal metals that gold is alloyed with being either silver or copper.

Using an 8 inch coil on the PI with a sample delay of 20 microseconds the 24k gold standard was detected at 7.5 inches. The next standard was 90% gold & 10% silver (or copper) equivalent to 22k and the detection range dropped to 3 inches. For 80% gold & 20% silver 19K the detection range dropped down to 2.25 inches. It was not until the standard was down at 20% gold & either 80% silver (or copper) that the detection range started to rise again.  For 0% gold & 100% silver or copper the range was back up at 7.5 inches.
  
The conclusion from his experiment was if you alloy two good conductors you end up with a much poorer one and even 5% of an additional metal has a dramatic range on detection range.

I have also been trying to follow and understand a long discussion on Geotech in regards to gold nugget simulation where Eric has been posting as well. Aluminium and Lead has been mentioned on several occasions in regards to gold nugget simulation. From some charts it looks like if you can detect lead, gold of the same size and shape should be easier to detect. Further charting showed the time constant for small pieces of aluminium and lead are similar to gold.

I have a selection of different types of targets for test purposes in shapes, sizes and conductivity as the photo below displays. I also use a 100mm x 50mm x 10mm aluminium piece hoping to imitate a large gold nugget.  


In another thread on Geotech another member said he had been told that when Eric was in Australia he had measured TCs of some gold nuggets. Eric relied saying when looking at the total decay time down into the noise level a 15oz nugget was 2mS and a 5oz was 700us. He was unable to measure a 31oz nugget but guessed it to be 4mS. He went on to say nuggets from Victoria were very pure and WA nuggets of a similar size may have decays that are ½ as long due to more silver in alloy which makes a big difference in conductivity.  


Gary.


* Test Targets.jpg (85.66 KB, 569x395 - viewed 178 times.)
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bugwhiskers
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« Reply #1 on: Thursday January 17 2019 17:07:45 AEDT PM »

One of the problems with Aluminium is that it is most often alloyed with other metals. Pure Aluminium is very close to Gold in conductivity but where do you source pure Aluminium? The profile area of the targets also plays a significant part in detection distance. Take a 0.033g nugget that is spherical and compare the detection distance with a 0.033g nugget that is a thin wafer and the detection distance difference can be huge.
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« Reply #2 on: Thursday January 17 2019 18:22:17 AEDT PM »

A piece of single sided copper circuit board 215mm * 215mm can be seen at 3ft with an 18" coil.
The actual copper on this circuit board amounts to a tad over 1 cubic mm !
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GARY
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« Reply #3 on: Thursday January 17 2019 18:43:47 AEDT PM »

Imagine what that 1 cubic mm of copper and its profile area could be seen at with the 18" coil.

Gary.
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« Reply #4 on: Thursday January 17 2019 19:19:24 AEDT PM »

The same applies to an Aluminium drink can.
What would be its cubic size if melted down?
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GARY
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« Reply #5 on: Thursday January 17 2019 19:33:17 AEDT PM »

Here is an interesting chart.

Gary.
 


* Material Sizes For Equivalent Conductivity.jpg (69.26 KB, 618x496 - viewed 140 times.)
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GARY
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« Reply #6 on: Friday January 18 2019 09:01:33 AEDT AM »

When testing different coils, detectors and their settings I use the test pieces in 1st pic below to imitate larger gold nuggets of several ozs.
  
Aluminium Block info:  The grade is 6060-T5. Worst case it is 99.6% pure Aluminium.
The conductivity of this grade is 32MS/m at 20 deg C.
For comparative purposes, the electrical conductivity of the value of 100% of the International Annealed Copper Standard is 58 MS/m.
The conductivity of pure gold is 42.57MS/m.

Lead info: Moulded by a friend who spray painted its gold colour.

Copper info: Created from pure copper during a copper smelter pour.
Both ends had been cut flat to act as a paper weight.

I also out of curiosity have used a standard Aluminium Drink Can.

Some results from air testing back in 2012 with an 18” mono on a GPX in General FP settings.

When Set in Fine Gold Timing:
Aluminium Block- 21”
15oz Lead - 30”
30oz Copper - 27”
Aluminium Drink Can – 41”

When Set in Normal Timing:
Aluminium Block - 29”
15oz Lead - 36”
30oz Copper- 32”
Aluminium Drink Can – 46”

In regards to the 2nd pic it is results from air testing different sized pieces of aluminium to imitate smaller gold.
Also included in the results are actual gold nuggets for a comparison.
The results were with a QED set for small targets using an 8" coil.

Gary.



* Large Test Targets .jpg (200.83 KB, 1450x743 - viewed 101 times.)

* QED results with 8 mono coil.jpg (37.12 KB, 458x217 - viewed 97 times.)
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Muntari
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« Reply #7 on: Friday January 18 2019 10:53:52 AEDT AM »

Interesting discussion...

I can say from experience working at Boyne Smelters some years ago, that the the billets of aluminium used to make drink cans is 99.9% aluminium.
I doubt that has changed, it has to be pure as possible.

cheers

muntari
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« Reply #8 on: Friday January 18 2019 10:54:17 AEDT AM »

 Thanks Gary for the info. However i doubt that most  nuggets would have the conductivity of pure gold or pure aluminium. Most in Vic are at best 90-95% gold and the impurities  will effect the conductivity as will the internal structure.Some nuggets have very fast Tc which would imply poor conductivity. Its also worth noting that the gold responses have  range of distributed TC and do not  display pure first-order-like time constants.
doug smile
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« Reply #9 on: Friday January 18 2019 11:12:46 AEDT AM »

  

In another thread on Geotech another member said he had been told that when Eric was in Australia he had measured TCs of some gold nuggets. Eric relied saying when looking at the total decay time down into the noise level a 15oz nugget was 2mS and a 5oz was 700us. He was unable to measure a 31oz nugget but guessed it to be 4mS. He went on to say nuggets from Victoria were very pure and WA nuggets of a similar size may have decays that are ½ as long due to more silver in alloy which makes a big difference in conductivity.  
Gary.
Based on Eric's results its easy to see why most  nuggets never give a pure first order (exponential) response because to achieve a pure first order response in a highly conductive  nugget the TX pulse length must  be close to or longer than the Tc!!! ie for the 5oz nugget a pulse length of 700u secs!
doug smile
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« Reply #10 on: Friday January 18 2019 11:17:58 AEDT AM »

 Here is a paper on Tc
Dynamic analysis and time response
  
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« Reply #11 on: Friday January 18 2019 11:38:38 AEDT AM »

Review of First- and Second-Order System Response
  
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Huego
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« Reply #12 on: Friday January 18 2019 13:35:11 AEDT PM »

  
One of the problems with Aluminium is that it is most often alloyed with other metals. Pure Aluminium is very close to Gold in conductivity but where do you source pure Aluminium? The profile area of the targets also plays a significant part in detection distance. Take a 0.033g nugget that is spherical and compare the detection distance with a 0.033g nugget that is a thin wafer and the detection distance difference can be huge.

BW, notwithstanding all that has been said ...

I have just inquired (for a quote) to order some pure aluminium (99.999%) for your testing purposes. This will be gratis for product development and testing purposes by you, or anyone you wish to nominate, for performance measuring purposes.

My request was for rod in 1, 5 & 10 mm diam. which you can cut with pliers or chisel to length and mass and maybe hammer some flat if you wish. Couple of small blocks  too. I will confirm status when I know.  smile

Huego  happy face


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« Reply #13 on: Friday January 18 2019 13:47:43 AEDT PM »

  
  
One of the problems with Aluminium is that it is most often alloyed with other metals. Pure Aluminium is very close to Gold in conductivity but where do you source pure Aluminium? The profile area of the targets also plays a significant part in detection distance. Take a 0.033g nugget that is spherical and compare the detection distance with a 0.033g nugget that is a thin wafer and the detection distance difference can be huge.

BW, notwithstanding all that has been said ...

I have just inquired (for a quote) to order some pure aluminium (99.999%) for your testing purposes. This will be gratis for product development and testing purposes by you, or anyone you wish to use it for performance measuring purposes.

My request was for rod in 1, 5 & 10 mm diam. which you can cut with pliers or chisel to length and mass and maybe hammer some flat if you wish. Couple of small blocks  too. I will confirm status when I know.  smile

Huego  happy face




That's fantastic Huego, many thanks.

All those diameters will fit in the standard plastic/clear top nugget case.
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egixe4
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« Reply #14 on: Friday January 18 2019 13:48:31 AEDT PM »

I'm really enjoying the discussion on this subject at the moment
and a number of others that have sprung to life recently.

Thanks Contributors

Mal

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« Reply #15 on: Friday January 18 2019 14:04:30 AEDT PM »

  
Thanks Gary for the info. However i doubt that most  nuggets would have the conductivity of pure gold or pure aluminium. Most in Vic are at best 90-95% gold and the impurities  will effect the conductivity as will the internal structure.Some nuggets have very fast Tc which would imply poor conductivity. Its also worth noting that the gold responses have  range of distributed TC and do not  display pure first-order-like time constants.
doug smile

My near spherical (1.1mm) 0.033 gram (1/30th of a gram) test nugget was analysed with an XRF machine at the recent Laanecoorie Bash. 97% Gold - 3% Iron
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GARY
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« Reply #16 on: Friday January 18 2019 14:56:45 AEDT PM »

My friend sent a nugget from our area away to be analysed and came back showing:
 
Gold   Silver   Calcium   Copper      Iron       Mercury   Magnesium   Zinc
91%   6.63%   0.4%    0.0002%   0.02%    0.0003%   0.03%       0.00002%

The above were main elements that made its composition up 98.08%.
The rest were other elements in tiny PPM readings for the final 1.92%.

Actually the 23 gram nugget I mentioned in my opening post is from the same area.

Gary.
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Huego
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« Reply #17 on: Friday January 18 2019 15:01:23 AEDT PM »

  
  
Thanks Gary for the info. However i doubt that most  nuggets would have the conductivity of pure gold or pure aluminium. Most in Vic are at best 90-95% gold and the impurities  will effect the conductivity as will the internal structure.Some nuggets have very fast Tc which would imply poor conductivity. Its also worth noting that the gold responses have  range of distributed TC and do not  display pure first-order-like time constants.
doug smile

My near spherical (1.1mm) 0.033 gram (1/30th of a gram) test nugget was analysed with an XRF machine at the recent Laanecoorie Bash. 97% Gold - 3% Iron


Bugs, re your "near spherical piece" It may appear near spherical because it may have once been a crystalline polyhedral piece, which I found a few of around Talbot. The points may have worn off. I posted pics somewhere, some time ago, of some I found ~2-3 mm diam. The iron may be from the outside (ie a surface impurity) and below that the purity could be higher. Not sure about the penetration of XRF .. I think its surface analysis but could be wrong.

edit: My point is that chemical purity is often linked to crystallinity  smile
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« Reply #18 on: Friday January 18 2019 16:37:38 AEDT PM »

The tiny 0.033g "nugget".
The ruler divisions are 1mm.


* 0.033gram.jpg (252.01 KB, 868x688 - viewed 78 times.)
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Dontbstme
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« Reply #19 on: Sunday January 20 2019 01:48:22 AEDT AM »

Hi guys. Do you think this imitation of mine would do the job? 600 grams of Tin and Lead.


* 9304fbd2-590c-44a7-b459-6fabde587b92.jpg (162.79 KB, 1600x1200 - viewed 44 times.)
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