Smelting and Gold Refining Part 3: Smelting the anode slimes and recovering the gold

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• published: 23 Nov 2015
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This is the third and final installment of our smelting and gold refining series. In this last video we smelt the dried anode slimes and recover a button of precious metals. *** Gold recovery clarification. I wanted to mention the copper button with the ~8 grams of gold from the first video in this series was not used in part 2 and 3. I sent the first copper button to a refiner as a test piece to see if it was something they could refine and to find out what percent they would pay on the gold recovered. This is why there is not at least 8 grams of gold recovered in this final video. The material I smelted to recover the ~2 grams of gold in part 2 and 3 was from some other sulfides from a different source. Thanks to CoinSilver800 for pointing this out.**** ***I wanted to post this response here in the description too as it brings up some good points about this process and why I am using this method to recover the gold. This is in response to a comment by Greg Burnside, thanks for the comment Greg!: Thanks for the comment and question. I guess I should clarify a few things about this process and this is the perfect post to do it. My goal is to find an scale-able process for direct smelting hardrock gold ore concentrates from gravity separation (off our shaker table specifically, but could work with any concentrate) without any roasting or pre-treatment and end up with a salable product. By this process the roasting step can be eliminated which is very environmentally hazardous, is expensive to do in larger batches, and takes a lot of expensive equipment. Secondly, by direct smelting the handling is greatly reduced, ie take your shaker table cons, mix them with some flux and collector metal and smelt, pour your product. Now I should also mention here that the copper button I ended up with in the very first video is a perfectly salable product. AAA precious metals in Portland, OR paid me 80% of the gold value in that copper button (for nuggets, placer, etc. gold they pay 95% of the assayed value on batches under 100 oz for comparison). The second two videos (electroplating and slimes smelting) were mostly just an experiment to see if they would work and to try and end up with a gold product. Didn't quite work out like I planned, but I think with some more experimenting it could be done. Even if it does work its not easily scale-able, takes a long time, produces some by-product (sulfuric acid with heavy metal ions that needs to be disposed of) and only increases the value by 15%. Each operator will have to decide if the cost of further refining from a copper button is worth it, for me personally I think sell copper with 1-10% gold content for 80% value and be happy. I think in your original post you were hinting at the a wet chemical separation of the gold/values from the concentrates, correct me if I am wrong. So to answer the root of your question: gold concentrates are very tricky for wet chemistry methods. Unlike with electronics, gold plated jewelry, etc. in hardrock cons the gold values are not always available to the leach because they are encapsulated by the sulfide crystals. The free/liberated gold in the concentrates can easily be leached, but I have seen concentrates with only a 10% recovery rate by leaching due to this encapsulation problem. Some ores will be easily leached due to their high percentage of free gold, others will need to be treated in other ways. The fire assay is the universal way ores are tested for gold values. By melting everything to a liquid and collecting the precious metals in a button a very very high percentage of the precious metals can be recovered in the assay process and that is why it is still used today on all types of ores and by all companies. I am trying to essentially re-create the assay process on a large scale so no matter what type of ore concentrate you have (free gold, sulfide matrix, or a combo of both) you can recover a high percentage of the gold with minimal cost and have a easily salable, non toxic, product with minimal work and equipment. I plan to do another smelting video in the near future with a measured amount of gold and then assay the slag, matte, and copper button so we can see exactly where the precious metals ended up and what percent recovery can be accomplished by this method. Thanks again for the questions, we all learn from each other and by asking questions/clarifying and it is a great peer review process. Thanks again!*****