# How can I safely remove leftover gold from old crucibles?



## nzobdr (Jan 19, 2015)

Hi all
I have more than 20 crucible's used for melt gold and silver.
Some crucibles are crashed.
I need to recover and extract the gold and silver!


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## philddreamer (Jan 19, 2015)

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=12291&p=121229&hilit=clean+crucible#p121225


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## 4metals (Jan 19, 2015)

If the gold and silver is in the form of visible beads you can crush the crucibles into powder in a ball mill and screen the powder, the beads will remain in the oversize fraction where they can be collected and melted into a bar.


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## nzobdr (Jan 20, 2015)

4metals said:


> If the gold and silver is in the form of visible beads you can crush the crucibles into powder in a ball mill and screen the powder, the beads will remain in the oversize fraction where they can be collected and melted into a bar.


Thanks bro, but the gold is invisible and its inside the crucible Component.


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## rewalston (Jan 20, 2015)

hmm invisible gold...if it's invisible what tests have you done to conclude that there is any gold or silver left in the crucibles?


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## nzobdr (Jan 20, 2015)

rewalston said:


> hmm invisible gold...if it's invisible what tests have you done to conclude that there is any gold or silver left in the crucibles?


I have XRF, and I take samplees and read it by XRF.
The measurement give me that there're gold and silver with different concentrations.


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## 4metals (Jan 20, 2015)

An XRF reading invisible gold concentrations on graphite. I assume you have calibrated your instrument for that result. 

Truth is the XRF is a valuable tool for buying metallic scrap but I see it used all the time to read powders and material it was not intended to be used on and the instrument spits out absolute crap for results. And the uninformed jump through all sorts of hoops to get out the gold they have left behind, all to no avail. This is particularly true with gold jewelers sweeps that have been processed in aqua regia, the refined sweep residue is read on an XRF and they reprocess the material looking for what isn't there. Simply put, an XRF is not the answer for all materials. 

After you have crushed the material and produced a fine powder (and removed any oversized pieces of gold and silver) send the powder out for a fire assay. That will tell you its gold content. 

If you cannot see any gold and are basing your entire premise on pretty shaky ground.


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## g_axelsson (Jan 21, 2015)

I totally agree with what 4metals said. XRF is only measuring the surface composition as the X-rays are absorbed by the material quite fast.
XRF is actually quite good to measure powders though. Crush the crucible into fine powder, mix it thoroughly and take a reading of the powder and it should give a quite good hint about the amount in that crucible. Do it a couple of times and take the mean of the measurements and you should come quite close.
If there are any over sized pieces it must be taken into account separately as it could end up in the bottom of the powder and be missed by the sampling.

In the end, a fire assay is the safest bet but an XRF can be a powerful tool if used correctly.

Göran


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## goldsilverpro (Jan 21, 2015)

Fire assay is always the safest bet if you want accurate numbers. 

About 4 years ago, I consulted for a guy that went around shooting everything in sight with an XRF gun that had any possibility of containing PMs. That included powders and solutions. With these, it proved to be much more of a qualitative tool than a quantitative one. The presence of the PMs as indicated by the XRF was usually (not always) confirmed by other means. The actual numbers, however, could not be relied upon, at all.


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## 4metals (Jan 21, 2015)

Goran,

I have seen powder read in both uncompacted (loose powder) and pelletized powder in attempts to make an XRF result an acceptable means to buy prepared sweeps. I have yet to see it perform well enough to regularly use it to quantify a result and put your money on the line. 

As GSP said it may be a qualitative tool but not a quantitative tool. 

If anyone can contribute some information as to how an XRF has been used to successfully (and accurately would be nice) read powdered samples it would prompt a discussion that may benefit all of us.


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## g_axelsson (Jan 24, 2015)

Apparently I have to back off on my statement of powdered samples but there lies some truth in it anyhow. According to this article : http://www.icdd.com/resources/axa/vol44/v44_056.pdf



> *Abstract*
> 
> It is well known that the preparation of metals and liquids for XRF analysis is fast, easy, and
> usually requires little strategy. The preparation of powder samples such as silicates, carbonates,
> ...



They used boric acid as a binder (doesn't show up in XRF) or cellulose and pressed pellets out of powdered samples. The pellets were polished to reveal a correct sample surface for XRF analysis.
XRF is a tool and a lot of the usefulness of a tool is in the ability of the user of the tool. If the material isn't properly prepared for the analysis the results may differ a lot.

This article Exploring Potential Errors in XRF Analysis goes into details on errors in XRF analyzes.


> Most commercial laboratories offering XRF analyses use either the pressed powder
> pellet (also referred to as a powder briquette) or fused glass bead (fusion bead) sample
> preparation techniques.



I have no personal experience in using an XRF but I was close to buying one once and I was given a demonstration by one of the scientists on my last job and he told me they used it for analyzing metal contents in oil and dust filters and that it could measure bulk properties of powdered specimens. My main interest at that time was to measure iron contents in meteorites, both metallic and in silicates. The XRF would have been perfect for that application as it doesn't care if an element is in a chemical compound or elemental. The surface of the meteorite is easily polished too to create a good surface for sampling.

Göran


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## Palladium (Jan 24, 2015)

:arrow:


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## g_axelsson (Jan 24, 2015)

Palladium, that is a very good document explaining XRF.

It reminded me that I actually have an XRF system but it sits on one of my electron microscopes and I haven't tested it yet to see if it's still working. I've got two SiLi detectors but only one analyzer with a broken computer. That is another story and I'm going to renovate the computer just for fun, it's a naked alpha LSI core memory computer from 1974 and actually worked when I first turned the power on but crashed when I pressed the reset button.

The microscope, a Jeol Jem 100 CX TEM was broken when I got it and it took me a year to get it up and running to full spec.

Göran


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## Palladium (Jan 24, 2015)

When i do my melting dishes all i'm worried about is the gold. There's not enough silver that i'm even going to worry about it. I take the whole dishes and put them in a stainless pot and add a diluted solution of nitric to it. I then boil them like crab in a pot and turn it off to cool. Once it's cool all the flux has released from the dish and all the oxides and gold is easily filtered from the bottom of the pot once the clean dishes are removed.


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## 4metals (Jan 24, 2015)

Looks like there's still a use for us old fire assayers.

It's nice to be needed!!!!


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## necromancer (Jan 25, 2015)

4metals said:


> Looks like there's still a use for us old fire assayers.
> 
> It's nice to be needed!!!!



your knowledge has always been most helpful, (thank you 4metals) you are a GRF mod for very good reason !

i have always wondered where & how Noxx compiled such a wonderful group. taken into account he was a teenager when he put the site up.


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