# Gold Test Kit



## Traveller11 (Oct 15, 2010)

Hello

Does anyone have any experience with gold test kits? There are two in particular I found on the Internet that piqued my interest.

The first is from a company called The Gold Hunter. It is a type of leach and uses stannous chloride to test for the presence of gold. A test sample of ore or placer material is placed in a test tube and covered with the leach. After a suitable time, a drop of leach is placed on a paper towel and a drop of the second liquid is placed on that. A colour change of the first drop to purple indicates the presence of gold.

The second is from a company called Goldmine World. Their test solution is, according to the site, based on their exclusive sodium thiosulphate leach. A test sample of ore or placer material is placed in a test tube and covered with the thio leach. After a suitable time, the precipitant from the kit is added to the leach; dropping out dissolved gold. They do not mention it but I was thinking stannous chloride might be useful at this point as an indicator of the presence of gold in the thio solution. 

From what I have read on this site and others, sodium thiosulphate is a very tricky leach to use although it is non-toxic and environmentally friendly. Most say that it is almost impossible to regulate but Goldmine World seems to have overcome this problem.

Anybody?

Bob


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## Anonymous (Oct 15, 2010)

Caution is warranted.

jim


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## dev (Oct 16, 2010)

I bought the gold hunter kit and was disappointed by it. I tested it using only gold 'pickers' from my collection and was unable to get a positive result. The kit instructions note that the leach portion of the test can 'flatten' after 90 days or so and can be regenerated with the addition of nitric acid. I suspect the kit I received contained old chem, suggesting poor quality control. I don't doubt that with fresh chemicals the test probably works fine, but even then I don't think it would be worth the price. The bottom line for me is that for the price of the gold hunter kit you could buy enough HCl and tin shot to make a lifetime supply of Stannous Chloride.


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## Traveller11 (Oct 16, 2010)

Yes I suspected that the kit was actually a saturated salt-nitric acid leach; able to be recharged with fresh additions of nitric acid.
It is the other one that fascinates me although many claim it to be doubtful in ability too. It is supposed to be a leach based on sodium thiosulphate. They also market just the thio solution and recommend using an aquarium bubbler to oxidize the leach container.
Bob


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## dev (Oct 16, 2010)

I'd be inclined to trust a positive result from a thiosulfate based gold test. But a negative result would have no meaning because it's so easy to have a thiosulfate leach shift itself outside of effective parameters - pH, oxygen, copper catalysis, ammonia levels. It would be very possible to test gold-bearing material with thiosulfate and get a negative result.

Stannous chloride to check for gold in a thiosulfate leach... my chemistry isn't good enough to say yea or nay to that, but I'll go ahead and have an opinion anyway. My understanding is that the stannous test is only effective with acid solutions, and thiosulfate is an alkaline leach.

Last but not least - Robert Service rules. 8)


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## Traveller11 (Oct 17, 2010)

Dev
Yes, from the research I've done on the Internet, thiosulphate leach will be a wonderful thing if and when some bright person works all the bugs out of the system.
Just today, I happened to visit a metal detecting site. The good people there introduced me to the Falcon MD20 Gold Probe. It is similar to a metal detector but, rather than detecting large pieces of gold far away, it detects the tiniest flakes up close; touching the ore or placer, if need be.
As I am only looking for a "go/no go" indicator to tell me if the hardpan clay has microscopic gold on it or not, this seems like a much better proposition. It has a feature that distinguishes between black sand and gold, as well.
Robert Service does, indeed, rule. Like most Canadian school children from the 60's, I was required to commit a goodly portion of "The Cremation of Sam McGee" to memory and, to this day, can recite almost all of it without help.
Regards
Bob

"Now Sam McGee was from Tennessee, where the cotton blooms and blows,

Why he left his home in the South to roam, 'round the Pole, God only knows,

He was always cold but the land of gold, seemed to hold him like a spell,

Though he'd often say, in his homely way, that he'd "sooner live in Hell" "


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## dev (Oct 17, 2010)

Checked out that Falcon detector - very tempting. I'm also in an area where a microscope is a lot more useful than a gold pan. Thing is, I am only seeing references to the Falcon detecting 'barely visible' gold, and the stuff I'm usually after can't be seen at all with the naked eye. Still, it does seem to be an excellent option for finding the little bits, I think I need one.


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## Traveller11 (Oct 17, 2010)

Dev
They claim to be able to locate gold down to 2/100ths of a grain. Interesting. I wonder what that would convert to in mesh size?
Bob


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## dev (Oct 17, 2010)

Ok, decided to get my geek on and try to get a mesh size on 2/100 grain gold. Feel free to skip to the conclusion unless you want to check my work. Here goes:

density = mass/volume

Gold density (specific gravity) is 19.32 grams/cm^3
2/100 of a grain, aka 1/50th of a grain, is about 0.0013 grams. I got this number from the actual weight of a 1 grain balance scale-weight that I weighed in grams on a very accurate digital scale.

Subbing the numbers into the equation:

19.32 grams per cm^3 = 0.0013 grams/volume in cubic centimeters

Isolating volume:

Volume = 0.0013 grams/19.32 grams/cm^3
Volume = 6.73 e-5 cubic centimeters, or 0.0000673 cubic centimeters.

The cube root of 0.0000673 is 0.04, so a piece of pure gold weighing 2/100 of a grain would make a cube 0.04 cm (0.4 mm) on a side. Small enough to pass through 40 mesh, based on this mesh conversion table:
http://www.azom.com/details.asp?ArticleID=1417

Of course in reality the gold isn't pure, so the particle would be larger. And it is likely to be in a flake form. Squashing my cube to a flake of 0.1 mm thickness would make a gold square 0.8 mm on a side. That's 20 mesh.

It's hard to get a clear number for minimum visible particle size (rather, it's easy to get a bunch of very different numbers). The most consistent number I can find is that the eye can resolve down to 1/60 of a degree of arc. Converting that to a particle size at a specific distance goes beyond the scope of this post. :shock: I'm going with good ole wiki: http://en.wikipedia.org/wiki/Naked_eye which states that an object measuring 0.05 mm is clearly visible at a range of 20-25 cm.

Conclusion, a gold piece weighing 2/100 of a grain would be an absolute minimum of 40 mesh, and much more likely 20 mesh or bigger. Definitely visible, and downright chunky compared to the stuff I see at 30x magnification.

Cheers,
Devon


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## Traveller11 (Oct 17, 2010)

Dev
It wasn't unitl after I posted my reply that I remembered that a grain is a measurement of weight and not dimension.
However, this certainly doesn't seem to have hindered you at all. I'm quite impressed with how you have approached this question.
So, 20 to 40 mesh doesn't seem all that small. If there was gold of this dimension present in the placer I am dealing with, I should think a gold pan and a screen would be the only testing equipment one would need. Unfortunately, there is nothing larger than 100-150 mesh.
There is a fellow on the detector site I visited that markets these units somewhere in Arizona. I shall query him as to the claim of detecting a piece of gold weighing 2/100th's of a grain. Could it be, perhaps, that this was the smallest weight they could practically measure? I noticed that the detector crowd typically will describe their finds by weight; likely because each piece of gold is located individually.
I will share the information I glean with you as soon as I receive a reply from him.
Regards
Bob


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## Traveller11 (Oct 26, 2010)

Dev
Interesting development. The fellow I was talking about, who actually lives in Nevada, not Arizona (my mistake), and markets detectors there, has generously offered to lend me his Falcon MD20 Gold Probe to try out on my super fine micron beach gold. He is going to box it up and send it by mail to me. 
Imagine, in this modern age, a man actually prepared to trust another at his word. I must say, I was deeply touched by this gesture and intend to take the utmost care of his detector while it is in my possession.
I think I have sparked his imagination with our "golden" beaches and he is just as eager as I am to see if the MD20 proves to be a useful tool in locating beach placers. It would certainly be a coup for the Falcon company if their detector were able to detect gold in the 150-200 mesh range.
As before, I will share whatever knowledge I gain with you.
Regards
Bob


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## dev (Oct 26, 2010)

That's some impressive customer relations. I'm also very eager to find out how the Falcon performs, I'm thinking about it every time I pick up an interesting rock. Only the exertion of maximum impulse control, and the pending outcome of this thread, are preventing me from buying one. It will probably happen sooner or later. And your guy in Nevada will certainly be getting my business when it does.

Do you have some known gold bits to test with? Spouse's broken chains and lone earrings can be had for chopping up with minimal protest, I've found. If you have to get past a snarl and a shotgun to get to the jewelry box, it's probably not worth it. In that case, pm me with shipping details and I'll be happy to send some samples for the Falcon test drive. I'd size'em under the scope as best I could so we'd know exactly what can and can't be detected.

Aside from the minimum detectable mass, my main concern is how well the Falcon picks out wee bits in an iron-rich environment. I wonder if the ground balancing will do the trick. Looking forward to your evaluation, I hope you get that thing soon!

Cheers,
Devon


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## dev (Nov 15, 2010)

Psst, Traveler! Didja get it, didja get it? Is it cool? Is it fun?


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## DarbyGloss (Aug 26, 2013)

gold test kits? You mean gold metal detector or anything else?


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## butcher (Aug 26, 2013)

DarbyGloss,

I did not read the whole thread, but from skimming it it looks like they are talking about field test kits sold on the market to test for gold in ore, these are basically kits put together of commonly known leaching and testing procedures, one problem I see beside the price and waste of money on them,is that many times these kits chemicals have a shelf life, the companies are also limited to the chemicals they can use in their test kits,their chemicals can also have a shelf life, and when you buy a kit the chemical may have been sitting past the expiration date, also because of mailing and other factors the chemicals used in these kits may not contain chemicals or tests that would work better for testing the ore in your situation, the company will pick a leach and would pick a test with a chemical they can sell and mail, but that could still do the job.

With a little education you can put together a better field test kit for testing gold in ore, than you could buy on the market.

Example :
A simple field test for gold in sulfide ore, a pinch of the finely ground ore, fused in a surplus mix of one part ammonium chloride and 2 1/2 parts of ammonium nitrate, cool the melted salt fusion, and dissolve in a few drops of HCl acid, taking a few drops of this solution in a spot plate and adding a crystal of ferrous sulfate, where a brown ring of gold precipitate will form if gold is in solution, or taking a few drops of the solution to be tested on a Q-tip or filter paper, and a few drops of stannous chloride where if positive for gold you get violet reaction for gold in solution.

A couple of places to begin your study, C.M. Hokes book refining precious metal wastes (and also Hoke's book of testing metals), C.W. Ammen's book refining and recovery of precious metals is also a good read on this subject.

Here are a just a few of the things you will find on the forum:


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## GoldHappy (Aug 31, 2013)

Traveller11--I'm very interested to hear how the detector worked, as well. I hope you'll post again soon and let us know.


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## rabbit (Sep 12, 2013)

Ok, this thread seems to have split in two. 
I can comment on the Gold Hunter Test Kit first: I bought one a few years ago before I learned about this forum. I have used it for at least two years, kept it tightly closed and have had satifactory results. Even tried it on gold ore that was visible. Since then I've been sendiing samples to a service in Talent, Oregon for XRF verification (Noll Assay) and am happy with that. So the Gold Hunter Kit lasted me longer than I thought it would. Now, after reading Hoke, I make up my own solution.

:lol:


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## rabbit (Sep 12, 2013)

My personal experience with the MD 20: I use it at my work desk to check on samples that I have questions about. It works as described. I tried it in the field and did not have good results. After a few minutes it started making too much noise. Even with the earphones on my wife could hear it 10 feet away. Adjusting as directed in the instructions could not clear it up. Best use for me has been at the work bench.

8)


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