This is all very interesting and would make for an interesting thread. But for this thread we are debating methods without enough facts.
Best methods of gold concentrate analysis
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For now, the answer will remain 42!
We are debating not about methods without enough facts.
We are debating about the applicability of available methods in possible different conditions
As long as that is the ultimate answer to the ultimate question, I’m good.
The number 42 is, in The Hitchhiker's Guide to the Galaxy by Douglas Adams, the "Answer to the Ultimate Question of Life, the Universe, and Everything", calculated by an enormous supercomputer named Deep Thought over a period of 7.5 million years. Unfortunately, no one knows what the question is.
Well they ended up asking the question of the meaning of life or everything, can't remember just now.
Interestingly 42 was one of the answers of one of the mathematical conundrums recently solved
Douglas Adams was a programmer as well as a writer, and many scholars of his work believe that the number 42 means the asterisk (*) in computer ASCII, which is a pointer or reference to a variable; also the stars (*) are the source of all life and everything
I want to sell the cons. as a powder not metal and I have to know complete and exact analysis of it. Fire assay, XRF and ICP-OES are available instruments for me, I have done many tests and have an estimation of main elements content .I just want to check if any other methods and advice than mine is better and here got a good advices.
Of course I will send the cons. to a professional lab as a third party.
yes I melt it for the test but no for selling the con.
I test the gold and silver bead by fire assay and ICP, and another two samples were shipped one for XRF and the other one for XRD.
I hope get a good result.
Everything that is old is not always unusable. Fire assay is very older method than wet chemistry method but it in some occasion is the best and precise method for assay of the gold.
It is cathode of electrowinning of gold cyanide solution .
Interesting. There was a thread a while back about beads hanging up in slags from this process. Deano, a member from Australia has a lot of experience with this and he has experienced better recovery if the cons are leached in Hydrochloric Acid before melting. Hopefully he see’s this and joins in.
Hello guys!
Geologists normally use XRF as a first-option analytical method in preliminary exploration projects. XRF, especially handheld, main pros include making field logistics simpler & more convenient in rapid delineation of mineral or ore deposits. Main cons include inaccuracies in quantification due to 'bad' sample preparations and also the method cannot detect elements lighter than Mg (benchtops cannot detect C and lighter elements). Additionally, XRF cannot detect some elements including Te, for those interested in analysis of telluride gold and must use XRD to check the structure.
Generally, XRF is good only for giving initial leads as to what the 'whole rock' comprises but at unspoken confidence levels.
To increase accuracy, the sample has to be properly prepared through drying in an oven, seiving, grinding, mixing, quartering & pelletizing all while avoiding contamination.
NB: XRF cannot be used to authenticate a bar of gold at all since2 the X-Ray beam can only probe to very shallow depth into the bar; often a good way to be scammed. Always insist to refining, in hurry!
In whole rock anaysis, it's best to use (each time with an objective) other instrumental analytical methods (XRD, ICP, AAS etc but fire assay is the most accurate for gold) to compliment XRF results especially with one sample all across to monitor correlations.
Cheers and good luck!
Geologists normally use XRF as a first-option analytical method in preliminary exploration projects. XRF, especially handheld, main pros include making field logistics simpler & more convenient in rapid delineation of mineral or ore deposits. Main cons include inaccuracies in quantification due to 'bad' sample preparations and also the method cannot detect elements lighter than Mg (benchtops cannot detect C and lighter elements). Additionally, XRF cannot detect some elements including Te, for those interested in analysis of telluride gold and must use XRD to check the structure.
Generally, XRF is good only for giving initial leads as to what the 'whole rock' comprises but at unspoken confidence levels.
To increase accuracy, the sample has to be properly prepared through drying in an oven, seiving, grinding, mixing, quartering & pelletizing all while avoiding contamination.
NB: XRF cannot be used to authenticate a bar of gold at all since2 the X-Ray beam can only probe to very shallow depth into the bar; often a good way to be scammed. Always insist to refining, in hurry!
In whole rock anaysis, it's best to use (each time with an objective) other instrumental analytical methods (XRD, ICP, AAS etc but fire assay is the most accurate for gold) to compliment XRF results especially with one sample all across to monitor correlations.
Cheers and good luck!
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.
That's the beauty of this forum, a free exchange of refining knowledge which has been missing from the industry for most of its existence. And by listening to others and processing what is said we all benefit. I personally have learned a lot from this forum simply from hearing other perspectives and changing how I process information.
Yeah, I see this as an opposite of any "industrial" approach. People exchanging information for free, without expecting anything in return.
In industry, we are looking for best performance and profit. Here we focus on best performance given the few hundred bucks in the pocket. Similar situation, opposite sides of the coin.
And I can truly say that all around the world, there are bright minds that can combine multiple fields of research to one, connect the dots on the screen and see the consequences.
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.
I love this kind of cooperation.
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.
When looking at processing alternatives the first thing to look at is what the major processing industries associated with that product are using as their methods.
When trying to get a reliable assay of electrowin material for gold values there are two major factors in play.
The first is that it is more difficult to control theft if the material is in powder form, much easier if it is in the form of large bars.
This leads to gold mines producing only bars which are sent to refineries for processing and sale, it at least minimises the theft problem.
The assaying of bars is a much simpler process than assaying powders.
Bars can be drilled to get representative samples or can be melted and a representative dip sample taken.
With powder a large number of subsamples need to be taken in order to get a representative head sample, the problem is always in the sampling.
When smelting electrowin concentrates some of the metals will always report to the slag as prills sized from centimetres to fractions of a millimetre.
These prills have a coating on them which prevents the metals coalescing in the smelt.
These coatings are not only resistant to the high temperature of the smelt but are self healing when mechanically attritted.
If the price are collected by passing the slag through a series of jaw crushers with narrowing gaps and then hand picking the prills from related screens, a high level of prills can be accumulated, much higher than that revealed by milling and leaching the slag.
Smaller prills are separated from the milled slag by tabling the screen tails.
The separated prills can be placed in 20% HCl and left there until the coatings have been removed, heat speeds up the process.
They are then dried and smelted without any flux, if you have cleaned the prills properly there will be total coalescence of the metals.
Deano
When trying to get a reliable assay of electrowin material for gold values there are two major factors in play.
The first is that it is more difficult to control theft if the material is in powder form, much easier if it is in the form of large bars.
This leads to gold mines producing only bars which are sent to refineries for processing and sale, it at least minimises the theft problem.
The assaying of bars is a much simpler process than assaying powders.
Bars can be drilled to get representative samples or can be melted and a representative dip sample taken.
With powder a large number of subsamples need to be taken in order to get a representative head sample, the problem is always in the sampling.
When smelting electrowin concentrates some of the metals will always report to the slag as prills sized from centimetres to fractions of a millimetre.
These prills have a coating on them which prevents the metals coalescing in the smelt.
These coatings are not only resistant to the high temperature of the smelt but are self healing when mechanically attritted.
If the price are collected by passing the slag through a series of jaw crushers with narrowing gaps and then hand picking the prills from related screens, a high level of prills can be accumulated, much higher than that revealed by milling and leaching the slag.
Smaller prills are separated from the milled slag by tabling the screen tails.
The separated prills can be placed in 20% HCl and left there until the coatings have been removed, heat speeds up the process.
They are then dried and smelted without any flux, if you have cleaned the prills properly there will be total coalescence of the metals.
Deano
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?
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?
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