# Questions on refining gold from rich ore with HNO3 + HCl



## Anonymous (Nov 4, 2010)

I recently found some interesting meta-sedimentary rocks in a nearby stream that runs through my property, which contain a healthy mixture of metal chunks and veins. Some of the stones have chunks of metal large enough that a few small dull yellow/black metallic "domes" are present on rounded surfaces (seemingly from malleable metal rolling down the stream bed).

I got excited and picked up a small bottle (about 10mL). of HNO3 + HCl solution from a friend who had an 18K gold testing kit. I know the solution is supposed to go bad over time, but this mixture seems to be pretty stable...no apparent pressure in the bottle, and it's never been opened it since he bought it (a few months back). Furthermore, the acid is very effective at dissolving pretty much everything but the quartzite and other silicates from the multicored rock (about 70% Silicate 30% Metal).

For what it's worth, I did some scratch testing and such before crushing/dissolving, and there seemed to be just as much
brittle iron ore and pyrite as there was malleable metal in the diverse rock...including small amounts of copper and lead

Last night, I carefully contained and partially crushed the rock, and dissolved about 0.2kg in all 10ml of acid in a 6" wide pyrex dish. I left it overnight on a warm ceramic tile near my wood stove air intake, and added some water this morning. I came home from work this evening, and I now have a relatively thick faintly brown/yellow solution, which contains:

- Countless small golden flakes/plates
- A pile of rusty orange "mud" covering the bottom of the dish
- A few crusty black chunks that I can crush by carefully prodding (which then dissolve almost instantly)
- 5 ~2-3mm diameter heavy black metallic chunks, which seem to be pretty solid and not malleable.

I then removed all the leftover fragments of quartzite, sand, and mica with tweezers. What was interesting to me is that there were many more golden flakes in the dish this mornig than when I set it down last night...and when I added a drop of water this eve (with a few crystals of Baking Soda dissolved in it), a couple more tiny flakes seemed to precipitate out of the solution.

Fear not, no need for the safety lecture here  ... I am a degreed and enthusiastic scientist, not in chemistry, but I've aced (and enjoyed!) enough chemistry classes/labs in college to understand the basic reaction processes and safety precautions when dealing with caustic liquids and dangerous fumes.

I just want some advice on what steps to take next....

1) How should I refine/purify any metals (particularly gold) that may be present both in both flakes/plates and within the solution?

2) What material should I use to filter the flakes? I fear the solution will disintegrate a coffee filter, and I don't want to make a mess. The acid doesn't seem to bother plastic much, but not sure where to get a plastic filter...and I don't want to neutralize the acid until after filtering out the flakes, which have an impressive luster!

3) Once filtered, Is there anything "household" that I can use to carefully adjust PH and precipitate any aqueous gold that may be present? I do not want to spend any money on chemicals/supplies until I know _for sure_ that the material is of at least some value.

Just trying to get some purified specimens so that I can identify the content of any valuable metals present in the rock. Any advice would be much appreciated! Thank you.

Thanks

BC


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## goldsilverpro (Nov 4, 2010)

Keep mining questions in the mining category. This is a scrap forum, not a mining forum.


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## Lino1406 (Nov 5, 2010)

Not clear how 0.2kg got into 10ml?


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## butcher (Nov 5, 2010)

Ore treating with acids, without pretreatment would not yield much if any results.

If I had some ore and I wanted to know if they contained values:
Crush and classify, concentrated by gravity, crush to fine powder, roast slowly at first then bring to red, in air > 900 deg C if sulfides Iron added, now smelting with litharge and flux (depending on ore type oxidizing or reducing), to get lead button containing values, then this is cupel this to rid lead, smash and part button, now the metals can be determined, with acids.

Easier method, concentrate by gravity, send concentrates to have them assayed.


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## manorman (Nov 24, 2021)

If you have much of this material it would be a great idea to have an assay done to know if it's worth while. They do not cost much and save you a ton of wasted time.


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## orvi (Nov 24, 2021)

assay, assay, assay... treating gold ore with acid is one of the worst methods to determine the presence of gold, not to mention that determining the content of gold. if it was that simple, every assay lab in the world would do that way. 
best results are obtained with fire assay (mentioned above), very good results are given with just panning (if gold is visible) and smelting the roasted concentrates with some kind of oxidating flux. metal button is produced, which can be directly assayed with XRF (professionals) or IN THIS STEP dissolved with aqua regia (if there isnt big silver content) and tested for presence of gold (eg stannous chloride solution). 
i recommend crush the ore and send it directly for fire assay, or get it zapped with X-ray.


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## Reno Chris (Nov 25, 2021)

If you look historically at old posts, there are probably more than 100 previous posts about how to treat gold ore with Aqua Regia - and the answer is always the same. *DON'T DO IT!* It does not work. Lots of things (like sulfide minerals) can contaminate your acids and consume them before they can get to dissolving the gold (if there is any). I have many folks ask about their gold ore finds from my Youtube channel and its almost always the same - unless they are well experienced, the percentage of people who think they have made a big discovery but are wrong is very nearly 100%.
So get an assay test done by a competent professional lab to see what you really have. Until the lab assures you that you have good quality gold ore, dont even bother to think about the chemistry of how to treat your ore.
What is quality ore? I would say at a bare minimum of 10 ppm, much better in the range of 20 or 30 ppm. 10 ppm is roughly 1/3rd of a troy ounce per ton of rock. If you want to see a video about how I extracted the gold from moderately rich gold ore and made a button from the gold, I did this YouTube video on the topic: https://youtu.be/rJqFxu0Wko0


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## butcher (Nov 25, 2021)

Reno Chris,

Great to see you still hanging out here on the forum, your advice and help as a professional gold miner are always welcome, and lucky for us, you also know the refining side as well.


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## Rreyes097 (Dec 9, 2022)

What if you only have a few rocks not much bigger than gold balls? They look to contain gold. Or pyrite at the very least. How would one go about testing for gold content? Wouldn't want to pay for an assay for a few rocks would you? I was watching a YouTube video. I know that's my first mistake. Well there's a video of them extracting the gold and or testing it for gold in ore using acid. Well aqua regia, sulphuric acid, and some other unnamed liquid. (The video wasn't very clear on the ingredients.) When I didn't understand the video I looked for others like it but found only more videos from the same people from the first video) so before I started to try this video I came here. And just started to read up on and low and behold! The video is another YouTube no-no video as I like to call them, then ones that contain bad information and dangerous practices. So I'll continue to research but is this acid method completely out of the question even when dealing with a few rocks?


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## Lino1406 (Dec 9, 2022)

Post deleted


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## Yggdrasil (Dec 9, 2022)

Rreyes097 said:


> What if you only have a few rocks not much bigger than gold balls? They look to contain gold. Or pyrite at the very least. How would one go about testing for gold content? Wouldn't want to pay for an assay for a few rocks would you? I was watching a YouTube video. I know that's my first mistake. Well there's a video of them extracting the gold and or testing it for gold in ore using acid. Well aqua regia, sulphuric acid, and some other unnamed liquid. (The video wasn't very clear on the ingredients.) When I didn't understand the video I looked for others like it but found only more videos from the same people from the first video) so before I started to try this video I came here. And just started to read up on and low and behold! The video is another YouTube no-no video as I like to call them, then ones that contain bad information and dangerous practices. So I'll continue to research but is this acid method completely out of the question even when dealing with a few rocks?


I'm guessing the No-No acid is something that have a nasty habit of killing people if it gets on your skin in too much amounts.
It will dissolve Quartz, Glass, ceramics and more.
It is used to dissolve the structure around Gold samples in Ore to liberate them from surrounding rocks.
This work is slow, dirty and very dangerous, NOT RECOMMENDED at all


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## Rreyes097 (Dec 9, 2022)

Yggdrasil said:


> I'm guessing the No-No acid is something that have a nasty habit of killing people if it gets on your skin in too much amounts.
> It will dissolve Quartz, Glass, ceramics and more.
> It is used to dissolve the structure around Gold samples in Ore to liberate them from surrounding rocks.
> This work is slow, dirty and very dangerous, NOT RECOMMENDED at all


The use of aqua regia on the ore or just acids in general?


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## Yggdrasil (Dec 9, 2022)

Rreyes097 said:


> The use of aqua regia on the ore or just acids in general?


Using acids on ore you do not know the composition of are always no no.
But this refers to a specific acid most professionals will not use, due to its toxicity.


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## Rreyes097 (Dec 9, 2022)

Ok well I won't be doing anything until I find the right information but not finding anything on here yet.


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## Yggdrasil (Dec 9, 2022)

Rreyes097 said:


> Ok well I won't be doing anything until I find the right information but not finding anything on here yet.


I reread the post, and it seems I misunderstood you.
The explanation I was talking about was liberating whole "nuggets" from the rocks.
For your purpose it still needs to be crushed, panned and roasted in the order suited for that ore.
Then one can smelt or dissolve in AR(for test purposes)
Basically an Assay.


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## Rreyes097 (Dec 9, 2022)

So I have to learn how to do an assay? Which I have no idea how to do and if I can even do it in the first place.


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## Yggdrasil (Dec 9, 2022)

Rreyes097 said:


> So I have to learn how to do an assay? Which I have no idea how to do and if I can even do it in the first place.


Depending on what you are going to do with what, maybe.

There is no problem testing ore for Gold with AR, if you know there are no Arsenic, Mercury, Cadmium and such in there.
Same you can smelt safely if you know these are not in there.

For small lots (a few grams) one can roast with very good ventilation and then smelt with the same good ventilation and then have an XRF done on the bead.
But if you are going to process an Ore you NEED to know whats in there.
Both to avoid toxic substances but also to be able to device an effective process.


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## goldshark (Dec 10, 2022)

If you only have a couple of pounds of suspected ore, and do not have access to hundreds of pounds or tons of this suspected ore, here are the steps I would take;
1- Find a geologist, or someone very knowledgable about rocks, and have them identify the minerals.They can be found at gem and mineral shows. This would be the very least, cheapest way to at least identify what you have. They also would have to assay it, if you want grade of ore results. No one can look at a rock, and tell you what is in it, and how much. That is what an expensive lab is for.
2- If you want to find out what elements are in the rock, an ICP and fire assay are recommended. Cost, about $250 for shipping, prep, and tests.
3- Crush it yourself, pan, roast, regrind, and pan again.First, weigh a thoroughly dry amount of your material. Crush so all passes a 100 mesh screen. Pick out any flattened particles of metal, and set aside. Do the previous steps mentioned. When all metal is collected, weigh it on a scale accurate to .001 of a gram. Then convert to either parts per million, or ounces Troy per ton or tonne. The only problem with doing it yourself in this manner, is that it will only give results for the 100 mesh + gravity recoverable gold. No accuracy for Au/Ag, PGM quantity. You could be throwing out the bulk of the metals, which could be caught in either a floatation circuit, or leach system, depending on liberation and chemistry of ore analysis.
In closing, if you have several tons of high grade, it would be best to at least invest the $250, as described in suggestion # 2. If you only have a couple pounds, #3. Using acids to try to get a determination of minerals, is not a good method. The best mineral determination tests are the streak test on unglazed porcelain tile, and the blow pipe, which will give a certain color flame. Other identifiers can be found in" Dana's textbook of Mineralogy". 
During the "Pandemic/shortage", my lab couldn't get the Litharge for doing a fire assay. When I inquired about digesting in acid (s), this world class lab said that it is not as effective, too dangerous, generated to much hazmat. "Just wait a couple more weeks for the fire assay", they said.
If your golf ball size pieces show definitive visible Gold, they are probably worth more as specimens, then crushing for a small amount of Gold.
If you are not willing to spend the $250 for ICP/fire assay, then spend the $10,000 for your own assay lab. After a couple of years, you will find what a bargain the pro labs are.
Nobody on this site can definitively identify your ore from pictures, or give you a quantitative assay by just looking at your pics. I hope this answers your questions adequately. Search the library for books on assaying and mineral identification testing available in the GRF Library. Got to learn to help yourself.


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## Southfork (Dec 12, 2022)

Rreyes097 said:


> Ok well I won't be doing anything until I find the right information but not finding anything on here yet.


We crush and run the slurry across a fluid bed concentrator / recirculating ribbed mat sluice then pan the cons and use a snuffer bottle to pick up the free gold. And melt the free gold into buttons some of this gold is in a matrix of rock / minerals that I separate when panning it flattens out when I use the mortar and pestle and the same ore balls up in the chain mill. Now what I have are balls of gold with rock inside some I direct smelt as much as we can with borax and washed sand when I get a good melt, I drop in water pick the gold out and remelt into buttons if the slag looks dirty with mat It gets reground and added to the next smelt. I also have powdered the ore up and placed in jars and covered with muriatic acid let it soak for a week. Then swirl and slowly pour off the acid into another plastic / glass container and rinse the slurry carefully shaking down and dump the slurry into a gold pan and pan down it cleans the rest of dirty solids out and any residual acid. There is so much gold in the bottom of the jars we must be doing something right I wear goggles and rubber gloves and a respirator. I'm new here and my methods my not be a good way to process our ore but we have recovered a lot of gold. Also, I clean specimen pieces in muriatic acid let soak and keep checking sometimes days. Then rinse and neutralized with bicarbonate of soda then the process starts over with a product called Whink it slowly dissolves the remaining quartzite / rock and brightens the gold. Since we purchased a chain mill and are able to get a fine grind, we haven't been using muriatic on the ore only specimen cleaning same with Whink . We are only smelting small amounts I'm waiting on a steel mold to try larger amounts.


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## Southfork (Dec 12, 2022)

Just a little more info we have not had an assay to find the best way to process our ore samples. The reason being is they come from multiple mine waste dumps mostly metal detector finds. There are over 130 gold mines in our township or was along with countless prospects we just got started taking samples from a half dozen or so


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## goldshark (Dec 13, 2022)

FYI, an assay will only determine whatever metals you specify for in the assay, in grams per kilogram, or ounces per ton, depending on lab reporting. It will not determine a milling process, or determine what other elements are present. Different properties may contain ores with varying elements, which would change milling techniques, especially if you get into floatation, or leaching, rather then using a simple gravity technique. An assay would be valuable on your tails, to see what you are leaving on the table ( throwing away).


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## Southfork (Dec 13, 2022)

goldshark said:


> FYI, an assay will only determine whatever metals you specify for in the assay, in grams per kilogram, or ounces per ton, depending on lab reporting. It will not determine a milling process, or determine what other elements are present. Different properties may contain ores with varying elements, which would change milling techniques, especially if you get into floatation, or leaching, rather then using a simple gravity technique. An assay would be valuable on your tails, to see what you are leaving on the table ( throwing away).


I guess that was for me lol I'm missing something. I've been reading a lot of old post it's suggested over and over again to get an assay first.


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## goldshark (Dec 14, 2022)

I don't know your level of knowledge, so I am just letting you know the pros and cons of what info an assay can be used for.


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