Best methods of gold concentrate analysis

[sar]

Unfortunately, I disagree.

Melting process should (!) implies the possibility of the forming of eutectic, the absence of liquation and phase crystallization, take into account the limits of the solubility of metals in each other, and take into account slag and matte formation.

This is all quite difficult to take into account even when melting systems of 3-4 known metals.

Therefore, melting an alloy from unknown metals leads you to direct losses of unknown base metals (usually rare earth) in matte, slag, and hidden internal crystallization (hello XRF).

Therefore, the direct melting method is not very suitable for qualitative analysis of complex ores.

You speak on microstructure of the metal but sampling takes macrostructure of the metal. As Deano said dip sampling and drilling will give you a good representative sample. Besides that the volume of the cons is much greater than the volume of the metal with same weight so the errors will increase in sampling of powder.
When you deal with powder you have to dry the powder to zeroing the errors of calculating the moisture of the powder and it costs to dry the cons.
One of the main reason that I didn't want to melt the concentrate was that the specific surface of the powdery concentrate is so greater than specific surface of the metal even after graining the metal as flakes. Of course you better than me know powder cons will dissolve imidiately after pouring in aqua regia even when the silver content is high ( no need inquarting) but metals take a long time (some cases take hours) especially when the silver content is high. Inquarting will add another process to the refining process. But the buyer and I have to reach an agreement on analysis and metal analysis is more accurate than powder.

Thank you all.

 

[Yggdrasil]

I wrote about the problems of analyzing complex ores but not about precious metal powders of more or less known composition after electrolysis. These are just completely different things.

P. S. Also, I didn’t write anything about the problems of accounting for losses and methods of extracting precious beads entangled in slag during the smelting of precious metal concentrates. This is a slightly different topic?

Yes, but it is what the OP asked about.
This thread is like many others, the discussion strays off the track a bit

 

[Man Kesh]

I agree with you that you named some of weakness of XRF instrument, I should add ED-XRF is a standard method for assay gold jewelry and precious metals. It can be calibrated ≤ 1 ‰ for gold measurements, one of the main problems of the instrument is Certified Reference Materials to calibrate the instrument. For each about 50 range of fineness of gold you have to prepare the CRM of that range near the composition of main included elements and they are very expensive especially for gold. I've used XRF to analyze the metal bead of fire assay for precious metals.
Anyhow I've learnt a lot in this thread, and found that analyzing powder of concentrate has a lot errors and it is better to melt the concentrate for more accurate analysis.

ED-XRF can accurately confirm gold content only for a smelter in the refinery because the refiner knows his bars.
Big problem comes in if you try to buy gold bars in untrusted sources! The top coating/ plating will indicate gold but inside the bar could be no gold at all. This is because ED-XRF can only probe to a few millimeters (often only micros).
In Africa there is this saying that "the sword is not evil, rather its the user who can get evil". Similarly, it depends how well you use your equipment..
NB: WD-XRF is more accurate compared to ED-XRF. It has higher resolution and less spectral overlaps.

 

[Ultrax]

Apparently, the main disagreements arose due to the lack of a clear formulation of the concept of concentrate in the context of the discussion:

I wrote about the analysis of raw ore concentrate (with the separation of primary gangue), the smelting of which degrades the analysis results.

But the author of the topic writes about the analysis not of the concentrate, but of the processing of almost the final product of the gold refining plant. In this case, the analysis scheme is completely different.

 

[Yggdrasil]

Apparently, the main disagreements arose due to the lack of a clear formulation of the concept of concentrate in the context of the discussion:

I wrote about the analysis of raw ore concentrate (with the separation of primary gangue), the smelting of which degrades the analysis results.

But the author of the topic writes about the analysis not of the concentrate, but of the processing of almost the final product of the gold refining plant. In this case, the analysis scheme is completely different.

C'est la vie, in this forum.
We often need to almost decode what the users ask

 

[sar]

ED-XRF can accurately confirm gold content only for a smelter in the refinery because the refiner knows his bars.
Big problem comes in if you try to buy gold bars in untrusted sources! The top coating/ plating will indicate gold but inside the bar could be no gold at all. This is because ED-XRF can only probe to a few millimeters (often only micros).
In Africa there is this saying that "the sword is not evil, rather its the user who can get evil". Similarly, it depends how well you use your equipment..
NB: WD-XRF is more accurate compared to ED-XRF. It has higher resolution and less spectral overlaps.

Yes you are right, and I nearly know what the content of my bar is.

 

[sar]

But the author of the topic writes about the analysis not of the concentrate, but of the processing of almost the final product of the gold refining plant. In this case, the analysis scheme is completely different.

Nowhere in this thread said about analysis the ore, It is your assumption that concentrate is equal the ore.

 

[Ultrax]

We have a concentrate of gold and silver, it has about 35 % Au and 50 % Ag rough estimate . The rest is Zn Cu Fe and other base metals and very low content of other precious metals.

It is cathode of electrowinning of gold cyanide solution .

The result of electrolysis is not a “concentrate” in the formal definition.

Therefore, when you first used the term “concentrate,” I meant ore concentrate, also in its formal definition.

Therefore, the correct formulation of the question is 99% of the correct answer.

That's why we have some misunderstanding here.

 

[sar]

The result of electrolysis is not a “concentrate” in the formal definition.

Therefore, when you first used the term “concentrate,” I meant ore concentrate, also in its formal definition.

Therefore, the correct formulation of the question is 99% of the correct answer.

That's why we have some misunderstanding here.

I'm here to clear misunderstanding.
Thank you

 

[kurtak]

The result of electrolysis is not a “concentrate” in the formal definition.

Therefore, when you first used the term “concentrate,” I meant ore concentrate, also in its formal definition.

I have to agree with Ultrax here & in fact that is exactly what I thought when I read the OP (Original Post) & in fact was going to ask the question --- "what is meant by concentrate" ?

Concentrates to me is what you have after tabling or froth floatation of milled ore - black sands from placer or something you get after tabling incinerated & milled IC chips - etc.

Metals recovered from leach solution on activated carbon or resins could also be considered concentrates

Mixed metals recovered from a leach solution as metal powders by cementation/precipitation or electrolysis I have always understood to be "sponge"

If the metals (mixed) are recovered by smelting then it is dore

That all said - this has been a very interesting thread

Kurt

 

[Yggdrasil]

This is a good reminder that to get good answers, the question itself must be "good" in the sense in proper terms.

 

[4metals]

This is a good reminder that to get good answers, the question itself must be "good" in the sense in proper terms.

I guess in the future it will benefit all involved to press for details to clear these things up right from the start. My assumption from the start was the material came into a refinery as a bar as that is how most of the feedstock I have seen comes in.

Still this was a good thread which evolved and was very informative.

 

[Yggdrasil]

I guess in the future it will benefit all involved to press for details to clear these things up right from the start. My assumption from the start was the material came into a refinery as a bar as that is how most of the feedstock I have seen comes in.

Still this was a good thread which evolved and was very informative.

I do not disagree, and as the OP also got some decent replies it should all be good.

 

[Shark]

Yep, it is amazing what can be accomplished when egos don’t get in the way. Thanks to all it has been a very informative post.

 

[sar]

We often need to almost decode what the users ask

and maybe because of those you are interested to solve the puzzle.

 

[Alondro]

Hi everyone
We have a concentrate of gold and silver, it has about 35 % Au and 50 % Ag rough estimate . The rest is Zn Cu Fe and other base metals and very low content of other precious metals.
What method or methods do you recommend for complete analyzing of elements?

If you want a REALLY thorough analysis, then spectroscopy would be the way to go. But with a gold and silver content that high, I doubt it's even worth the effort, unless you have at least 1 or 2% platinum-group metals (PGMs). The base metals won't be worth anything in comparison.

A simple smelt with a collector metal (such as lead or bismuth), assuming this is an ore, will isolate all the precious metals (PM) from the base minerals. Then you can analyze the alloy for the percentages of each PM in the lead block, or cupel the lead away and end up with a PM button to analyze.

 

[sar]

If you want a REALLY thorough analysis, then spectroscopy would be the way to go. But with a gold and silver content that high, I doubt it's even worth the effort, unless you have at least 1 or 2% platinum-group metals (PGMs). The base metals won't be worth anything in comparison.

A simple smelt with a collector metal (such as lead or bismuth), assuming this is an ore, will isolate all the precious metals (PM) from the base minerals. Then you can analyze the alloy for the percentages of each PM in the lead block, or cupel the lead away and end up with a PM button to analyze.

For the first time It is better to test for PGMs by spectroscopy method. If PGMs are not included so there is no reason to continue spectroscopy method. So Fire Assay is .......... (You complete the sentence.) we express one and all.

 

[4metals]

Story of "IBC container hood" was something similar. Bunch of knowledged poor guys discussing options and opinions. This came out, we thought about it, tested it, worked it out, and now it is spread out through refining comunity here.

That thread came out of nowhere from a new member and after a bunch of sound useful information the OP just vanished. Threads that go to completion are so much better, they have closure.

 

[orvi]

That thread came out of nowhere from a new member and after a bunch of sound useful information the OP just vanished. Threads that go to completion are so much better, they have closure.

Yeah, that is kinda sad. My answer was focused on my local "enviroment", where the idea spread among some small scale refiners and had some impact. Construction of such a hood is modular, and materials are available all aroud the globe (as IBC containers are accessible and common in many many places). I don´t know if these folks are members here, but that do not matter very much.

I saw positive improvement locally, and I am happy with it. If I manage to get some pics of the setup (+owner permission to post) working somewhere in the refining shop, I will let you updated.

That was my sole point - idea that was tested, word spread, few people adopted the idea, built their own setups and in the end, some positive things were accomplished.