Assaying, Microscopy, Mineralogy & XRF/XRD

Assaying, Microscopy, Mineralogy & XRF/XRD 2017-03-23T09:37:54+00:00
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Processing Gold from Sulfide Ores (3 replies)

1 month ago
JRC 1 month ago

We are trying to process gold from arsenopyrite and chalcopyrite ore. Our XRF indicated that there was a high concentration of gold along with a variety of minerals. We have tried various methods of refining without much luck, due to all of the other minerals with different melting points.

We had a fire assay done (providing a piece of ore rather than processed concentrates). They said it had a lot of silver and copper, but no gold. A geologist said that the fire assay may not have extracted the gold from the ore, because of the various gold-silver-copper sulfur refractory compounds within due to a limited process that was used. This type of ore requires more extensive process steps to reduce the gold.

We have tried various different methods of recovery, without success. Do you know what is the best method/process steps for recovering gold from this type of ore with sulfides and multiple minerals (lead, sulfer, arsenic, cinebar, titanium, etc.)?

1 month ago
Makc 1 month ago

There are a few approved methods that are tried and tested successfully. of course the depth of these methods cannot be discussed in the confines of this form. If you would like to get in touch and discuss your material, the facts and results can be posted here for the education of everyone.

Bob Mathias
1 month ago
Bob Mathias 1 month ago


A geologist said that the fire assay may not have extracted the gold from the ore, because of the various gold-silver-copper sulfur refractory compounds within due to a limited process that was used.

It sounds like you are surrounded by voodoo doctors and alchemists.

"trying to process gold from arsenopyrite and chalcopyrite ore":

What have you tried? What have been your results? What are the elements % in your sample?

Please do describe what you have tried so far. You can upload/attach PDF and images in your reply.


4 weeks ago
Colette 4 weeks ago
2 likes by Sachin Prakash and David


Fire assay is commonly accepted as a definitive method for determining gold content in the sample provided - I know that some folk believe that "nano gold" is not picked up by fire assay, but that is another whole topic on its own. 

It is entirely possible that the sample of ore that was tested by fire assay either did not contain any gold, or that the gold content was so low that it was not detectable. Your comment that you provided a "piece of ore" makes me suspect that either are highly likely. In order to get a reasonable idea of gold content you should really start with a fairly big sample, which then gets separated according to a set of sampling rules in order to give you a good chance of actually having some gold int he final samples that are assayed.

Processing complex sulphide ores - which are commonly refractory - is an enormous topic, which as the other respondents have indicated, is pretty difficult to address in this forum - although there are several articles on it here, for example

If you are a potentially commercial operator or exploration company then you should do the mineralogy of various samples, from that determine where the gold is deporting to, and then you can start looking at ways of getting it out in a cost effective way.

If the gold is free then you are lucky - you might get reasonable recovery by using gravity separation, and if you are incredibly lucky then all you would need to do is calcine the concentrate and smelt it. Artisanal miners frequently take this route - they are content to get lower gold recoveries because they do not have capital to invest to get a greater return by maximising recovery.

More commonly in a sulphide ore you would need to float the sulphide minerals, assuming the gold is associated with them, which it often is, and then oxidise it to free the gold for cyanidation.

In your case and with the mix of sulphides you are mentioning you are possibly looking at a refractory ore, and you are going to have issues with arsenic and mercury, not to mention copper - all of which means that you really want to have a good grade to justify all the capital you are going to need to process it.

Your first step then should really be to speak with a lab, and get an idea from them how much ore they would need to give you a decent idea of your grade - your geologist friend may be able to help with this too.

If you are running an artisanal type mine, then I would STRONGLY recommend that you not simply roast or smelt this material without taking great care with the off-gases from these two processes - you will in all likelihood be releasing arsenic and mercury into the environment, and could potentially poison anyone working in the area, leaving aside the environmental issues associated with this.

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