Aqua Regia Digest 500 g material.

[Yggdrasil]

Greetings Yggdrasil
Thank you for getting back to me.
Here are the answer to the questions you have as outlined part and partial in the previous posts.
30 g material.
Total volume of the AR leach solution.
200 ml.
Total HNO3 is 50 ml.
Total sulfamic 20g temperature 80C.
Total SMB 10 g and the 0.8 ph.
Regards Avled

This do not make much sense.
Just to get the facts straight.
The assay showed 15OzT per ton?
That is more than 150g per ton which will be the richest I have heard of!
What did it say regarding Cadmium Mercury and Arsenic?
The only reason this would react like this, will be that the Gold cements out on base metals.
Have you tried to leach out the base metals first?

Ther is supposed to be somewhere around 0.1g of Gold in this heap if your Assay is correct
.
That means you can cut the Nitric down to approximately 5ml or so.
Then Cement the PMs out in stead of using SMB, that means no Sulfamic is needed.
Make another try this way, leach the sample with Hot HCl or Hot Nitric 50/50 with water.
When the reaction dies down stir and add a bit more acid.
When there is no more reaction, you can go to AR.
Cover the material with HCl and add 5ml Nitric to Hot HCl and stir well.
When there is no more reaction add another ml of Nitric to see if the reactions comes back.
Test with Stannous,
If no more reaction, pour the whole lot into a filter and wash well with HCl
Then water until the filtrate has no more color.
Then Filter again until it is crystal clear, test with Stannous again.
Put in a slab of Copper and cement while stirring well.
After a few hour /a day pull out the slab while brushing/spraying what ever is sticking to the slab into the solution.
Let settle until all is settled.
Siphon off the solution and collect the powder.

For a production setting AR is not a solution, Cyanide/FerroCyanide/FerriCyanide will most likely be a much better solution.

 

[Aled]

Greetings Yddrasil
Thank you for your response and the tips that have been provided.
And yes the numbers are what they as I am dealing with a concentrate as stated in the previous posts.
When i do the fire assay that is what i get in the form of a bead from this super concentrate.
I am of the believe as you also pointed out that the base metals are interfering.
I have also mentioned the steps that i have taken in previous posts regarding leaching out removing the base metals.
I was just curious what the white salts could be?
Knowing that many variables come into play.
I will follow the above steps that you have provided and see what changes I observes.
It is all part of the discovery process.
As each type of ore materials reacts in different ways.
I am aware that AR is not the solution for a production setting.
Again your input is much appreciated.
Regards Avled

 

[Yggdrasil]

Greetings Yddrasil
Thank you for your response and the tips that have been provided.
And yes the numbers are what they as I am dealing with a concentrate as stated in the previous posts.
When i do the fire assay that is what i get in the form of a bead from this super concentrate.
I am of the believe as you also pointed out that the base metals are interfering.
I have also mentioned the steps that i have taken in previous posts regarding leaching out removing the base metals.
I was just curious what the white salts could be?
Knowing that many variables come into play.
I will follow the above steps that you have provided and see what changes I observes.
It is all part of the discovery process.
As each type of ore materials reacts in different ways.
I am aware that AR is not the solution for a production setting.
Again your input is much appreciated.
Regards Avled

AR are rarely used in production settings.
I'm pretty confident that your powders are due to salts crashing out when the solution cools.
You are over saturating your solution.

How are the assay done, you do it yourself?

 

[Aled]

AR are rarely used in production settings.
I'm pretty confident that your powders are due to salts crashing out when the solution cools.
You are over saturating your solution.

How are the assay done, you do it yourself?

Greetings Yggdrasil
I agree with you regarding the AR not being used in a production environment.
For me personally I am just exploring the possibilities as to what is left in any given material after the free gold has been removed. Targeting the Micron Au.
And yes i suspected the powders dropping out of solution being oversaturated as i had no idea in the past on how much Sulfamic acid or SMB to add to the solution. Mind you after these previous experiments I am now able to dial it in. And if all else fails Cu cementation.
Regarding the assays I do all of the Fire assays myself. If i need to get the beads tested to get an accurate value i would send those to a lab to get a more accurate analytical done.
I will follow your previous steps for the leaching protocol.
Your input is greatly appreciated.
Regards Avled.

 

[Yggdrasil]

Greetings Yggdrasil
I agree with you regarding the AR not being used in a production environment.
For me personally I am just exploring the possibilities as to what is left in any given material after the free gold has been removed. Targeting the Micron Au.
And yes i suspected the powders dropping out of solution being oversaturated as i had no idea in the past on how much Sulfamic acid or SMB to add to the solution. Mind you after these previous experiments I am now able to dial it in. And if all else fails Cu cementation.
Regarding the assays I do all of the Fire assays myself. If i need to get the beads tested to get an accurate value i would send those to a lab to get a more accurate analytical done.
I will follow your previous steps for the leaching protocol.
Your input is greatly appreciated.
Regards Avled.

With other words, you really do not know if it contains toxic elements as Cd, Hg and As?

 

[Aled]

Only if one where to do a complete analysis with a scanning electron microscope. And every ore body has some form of the above mentioned metals.
Working in a safe environment is very important.

 

[Yggdrasil]

Only if one where to do a complete analysis with a scanning electron microscope. And every ore body has some form of the above mentioned metals.
Working in a safe environment is very important.

Not all ore bodies has any measurable amount of said elements and you do not need an electron microscope for that.
Any ICP or AAS will suffice.
And you will have the peace of mind that you are not messing with something that will kill you.

 

[Aled]

This do not make much sense.
Just to get the facts straight.
The assay showed 15OzT per ton?
That is more than 150g per ton which will be the richest I have heard of!
What did it say regarding Cadmium Mercury and Arsenic?
The only reason this would react like this, will be that the Gold cements out on base metals.
Have you tried to leach out the base metals first?

Ther is supposed to be somewhere around 0.1g of Gold in this heap if your Assay is correct
.
That means you can cut the Nitric down to approximately 5ml or so.
Then Cement the PMs out in stead of using SMB, that means no Sulfamic is needed.
Make another try this way, leach the sample with Hot HCl or Hot Nitric 50/50 with water.
When the reaction dies down stir and add a bit more acid.
When there is no more reaction, you can go to AR.
Cover the material with HCl and add 5ml Nitric to Hot HCl and stir well.
When there is no more reaction add another ml of Nitric to see if the reactions comes back.
Test with Stannous,
If no more reaction, pour the whole lot into a filter and wash well with HCl
Then water until the filtrate has no more color.
Then Filter again until it is crystal clear, test with Stannous again.
Put in a slab of Copper and cement while stirring well.
After a few hour /a day pull out the slab while brushing/spraying what ever is sticking to the slab into the solution.
Let settle until all is settled.
Siphon off the solution and collect the powder.

For a production setting AR is not a solution, Cyanide/FerroCyanide/FerriCyanide will most likely be a much better solution.

Greetings Yggdrasil
Just wanted to get some clarity regarding the above mentioned protocol.
I will start another leach with fresh materials.
I understand to cement out the PMs instead of using SMB and no use of the Sulfamic acid.
You said leach the sample with HCl or hot Nitiric with 50/50 water. Until there are no more reactions.

Which acid would you work with for removal of the base metals. HCL or HNO3.?
If i understand it correctly. This is where I then filter the solution to remove the base metals.

Then start the AR leach following the above steps.
Until there are no more reactions.

When cementing with copper i have started using an fish tank aerator so that the copper bar does not get a film stuck on it. And it does a great job.

Looking forward to any feed back.
Regards Avled.

 

[Yggdrasil]

Greetings Yggdrasil
Just wanted to get some clarity regarding the above mentioned protocol.
I will start another leach with fresh materials.
I understand to cement out the PMs instead of using SMB and no use of the Sulfamic acid.
You said leach the sample with HCl or hot Nitiric with 50/50 water. Until there are no more reactions.

Which acid would you work with for removal of the base metals. HCL or HNO3.?
If i understand it correctly. This is where I then filter the solution to remove the base metals.

Then start the AR leach following the above steps.
Until there are no more reactions.

When cementing with copper i have started using an fish tank aerator so that the copper bar does not get a film stuck on it. And it does a great job.

Looking forward to any feed back.
Regards Avled.

Maybe both, it all depends on what your Base metals are.
And the availability of Nitric.
Always remember to roast the material when switching from HCl to Nitric or the other way around.
Unless you are at the last leach after decanting/siphoning and washing,
then just add HCl to cover the material and start adding Nitric in increments.

 

[Aled]

Maybe both, it all depends on what your Base metals are.
And the availability of Nitric.
Always remember to roast the material when switching from HCl to Nitric or the other way around.
Unless you are at the last leach after decanting/siphoning and washing,
then just add HCl to cover the material and start adding Nitric in increments.

Greetings Yggdrasil.

I will do both and have it leach overnight. Maybe a bit excessive but time will tell. And yes roasting in between leaches. Which I have done in the previous leach removal of the base metals. Thank you for the update.
Regards Avled.

 

[Alondro]

I think HCl will at least remove iron and other base metals. Since you have leached with AR and are still breathing there are no nasty things in there ore you were just lucky.
A nitric leach should remove any other base metal HCl did not get.
But did you roast and grind and reroast the black sands? And separated anythingcwith a magnet?

It takes a LOT of HCl to dissolve a significant amount of black sand. It's far better, and safer, to smelt with a collector metal.

I did a test with just 10 grams of highly washed black sands from one of the many local sand pits. Even 50mls of conc HCl barely dissolved half of it over DAYS. With 500g of black sands... looking at 4L of HCl just to dissolve the majority of it (if it's mostly iron oxides), probably a week of time WITH heating, and then you're left with a gallon of mystery solution which could have all sorts of metals in it. It's not very practical!

A smelt with the same amount of material and then cupeling would take only a few hours.

 

[Aled]

It takes a LOT of HCl to dissolve a significant amount of black sand. It's far better, and safer, to smelt with a collector metal.

I did a test with just 10 grams of highly washed black sands from one of the many local sand pits. Even 50mls of conc HCl barely dissolved half of it over DAYS. With 500g of black sands... looking at 4L of HCl just to dissolve the majority of it (if it's mostly iron oxides), probably a week of time WITH heating, and then you're left with a gallon of mystery solution which could have all sorts of metals in it. It's not very practical!

A smelt with the same amount of material and then cupeling would take only a few hours.

Greetings Alondro
Thank you for your input.
I am aware the it would take lots of HCL to dissolve a large amount of black sands. Right now I am just doing these for testing purposes no intention to go large scale production with this system.
I am right now just checking and targeting the micron gold.
Yes smelting the materials and cupelling would only take a brief time.
As i have done this as well.
Even treating the black sands roasting and then fracturing it in water.
Or pulverizing to a very very powder.
Thank you.
Regards Avled.

 

[Martijn]

It takes a LOT of HCl to dissolve a significant amount of black sand. It's far better, and safer, to smelt with a collector metal.

I did a test with just 10 grams of highly washed black sands from one of the many local sand pits. Even 50mls of conc HCl barely dissolved half of it over DAYS. With 500g of black sands... looking at 4L of HCl just to dissolve the majority of it (if it's mostly iron oxides), probably a week of time WITH heating, and then you're left with a gallon of mystery solution which could have all sorts of metals in it. It's not very practical!

A smelt with the same amount of material and then cupeling would take only a few hours.

It was meant as a test on a small amount.
But i agree. Smelting is lots better.

Did you roast and grind the black sands before leaching?

I have about 5ml of black sand I collected over the years crushing rocks

 

[Aled]

Greetings Martijn
Thank you for your input. (Vriendelijk Bedankt)
I always roast and grind the black sands before leaching.
And yes it would require more than 5 ml of black sands. We are dealing with lots here.
Have a great day.
Thank you ( Dank u well)

 

[nickton]

I think you are using an incorrect term there: "AR leach". I would always use an hcl leach with bubbler for quite some time before wasting nitric acid on dissolving base metals, though I am admittedly coming from working with E waste. Its really pretty simple at this point. You want your material as free of base metals as possible before using AR.

 

[Aled]

I think you are using an incorrect term there: "AR leach". I would always use an hcl leach with bubbler for quite some time before wasting nitric acid on dissolving base metals, though I am admittedly coming from working with E waste. Its really pretty simple at this point. You want your material as free of base metals as possible before using AR.

Thank you for your input.

 

[goldshark]

Greetings Alondro
Thank you for your input.
I am aware the it would take lots of HCL to dissolve a large amount of black sands. Right now I am just doing these for testing purposes no intention to go large scale production with this system.
I am right now just checking and targeting the micron gold.
Yes smelting the materials and cupelling would only take a brief time.
As i have done this as well.
Even treating the black sands roasting and then fracturing it in water.
Or pulverizing to a very very powder.
Thank you.
Regards Avled.

A bit of charcoal in your roast, will help convert (reduce ) the sulphides present in your black sand concentrates, to metallic metal. This is helpful in dissolving the base metals out with HCL, before Nitric.

 

[Aled]

A bit of charcoal in your roast, will help convert (reduce ) the sulphides present in your black sand concentrates, to metallic metal. This is helpful in dissolving the base metals out with HCL, before Nitric.

Thank you for the tip goldshark. I have been doing the roasting this way in the past even using wood chips has shown to work well.
Have a great day regards Avled.

 

[Alondro]

It was meant as a test on a small amount.
But i agree. Smelting is lots better.

Did you roast and grind the black sands before leaching?

I have about 5ml of black sand I collected over the years crushing rocks

I tossed the sands right into the HCl. They're from that old glacial moraine in NJ, which has been washed and oxidized for over 10,000 years. Anything easily soluble is long-gone. All pyrites have weathered to iron oxide (the mud and clay there is very rusty, orange and sandy, or red and sticky depending upon the composition of the different parts of the moraine I sample).

It was for the sake of curiosity, to see if HCl could conveniently dissolve heavily weathered ores. Answer: nope.

 

[Bongo-ognob]

Greetings to the Forum.
Just wanted to give you a brief update and see what other input advice can be given.
I have continued doing the AR leaches on the black sand nugget trap materials upon which most of the free gold has been removed and targeting any micron gold.
Following the advice and steps given by the group.
Plus reading the C-M Hoke book and finding many hidden treasures and applications. And reading a multitude of other treads from the group to gain a much deeper understanding.


I worked on 50 g samples yes they are small but I wanted to see and experience the different reactions and precipitates that evolved from this.

Pictures will be included.

And any further advice or direction comments is always appreciated.


This sample was pulverized with the Disk pulverizer just to give more surface area and liberate more values within the material.
As mentioned in this tread before remove the base metals prior to the Aqua Regia Leach.
The material does contain a very small amount of Au.
This was tested by Fire Assay and having done the Stannous chloride test on previous leaches.


I pretreated the material in a HNO3 leach overnight 30 C.
The next day filtered and washed the material.
Proceeded to do the AR leach.
HCL first and slowly adding HNO3 just enough to have the reactions going.
Again I left this overnight on low heat 30 C.
This was filtered and the solids recovered.
Added an equal volume of water and heated this to 85 C.
Added Sulfamic acid fizzing and slight foaming reaction.
Since I am new to using Sulfamic acid as I used to evaporate three times in the past to a syrup and adding HCL to remove nitrates.
Did not know what to expect with the Sulfamic acid and how far to go.
But I stopped till there where no more reactions.
I then started adding the SMB to the warm solution. But nothing precipitated out of the solution.
I decided to evaporate the solution to a syrup just to make sure all of the nitrates were removed.
And I did not see any Nitrates. Working under the fume hood.
But a crust was forming on top of the syrupy solution which disappeared once I slowly started increasing the volume of the solution with HCL.
Added more water and doubled the volume.
I added a copper plate to cement out any of the values. After a few hours a very very tiny amount of black precipitate.
I did the stannous chloride test prior and a very small trace of gold showed. Nothing to significant.
As the chloride solution cooled white crystals formed on the bottom of the beaker. And I was wondering what this could be. And how to proceed any further.

Any suggestions are welcome.

I have done the same test to remove the base metals but this time first using HCL overnight low temperature. Filtered washed and roasted as to remove any possible chloride that might be left in the solution. And then proceed with HNO3 overnight. Again filtered and washed before I proceeded with the Aqua regia digest.
Thist is still AR leaching for the moment.

Knowing this is a long tread just wanted make sure I did not leave out any details and to describe a clear picture.

Again much appreciate any input. And also happy if anyone else gains anything from this.

Regards Avled.

Hi Avled,

I’m doing very similar work and wanted to give me experience as being novice, reading hokes book and listening to the advice given here.

I start by going to a concentrate micron of under 40. It’s very very fine and what I’m looking for is the black sands/precious metals beginning to “clump” or move en masse as one in a sifting pan. I did much trial and error with sulfides and creek bed concentrates at over 40 micron and it just wasn’t concentrated enough for me personally to break the ratio possible in aqua regia.

After the concentrating I then roast the cons to help liberation (it appears sulfide rich ores tend to clump together or slime up) and from there I’ve noticed it’s actually better to not magnet these as it appeared to me that gold was being lost in the end.

Then I place about a pound of this material in a beaker and add HCL and boil it for 30 mins to an hour or more and pour off/rinse with water and toss the liquid into your stock

Then I add hcl to cover the material and add 5-10 mls of nitric and boil it to get a nice bubbling/reaction. I will then do this until the reaction calms down and add splashes of HCL to bring the temp down in the solution (it seems if you add straight nitric it will boil over) followed by a splash of nitric to start the reaction again.. continue till done..

Before doing this I was pre mixing or trying to at best run through 1-5 boiling reactions and then precipitating. Depending on the levels of precious metals or gold I was getting color changes and at best all the gold would go into colloidal/small amounts would begin to precipitate but never a full drop.

I can only venture to understand the high science of this but if you look at the different sol’s of gold concentrations in solution you can see different colors that go from red to orange to red to purple… these correlate to concentrations and SIZE of gold particles in solution. I’m sure a chemist or experienced worker can explain this much better than my limited understanding.

From here I tried various methods of expelling nitric and always found the sulfmaic acid method to be a bust for me. I’m not sure why but it didn’t work for me and so I went to the evaporation method. My methods follows hokes to the best I can..

I will evaporate down to approximately the amount of nitric milliliters I used (I’m not sure if you run into the same problem but when evaporating concentrate aqua regia you eventually come to a spot where all the lead salts and silver chloride prevent full evaporation to a syrup as a refiner of scrap or jewelry would encounter, so you either pour off the liquid and leave these solids behind and continue the evaporation or get as close as you can and add hcl) then add hcl. I’ll do this a minimum of 3 times.

An assay on the material you are working with is invaluable however I do believe it’s possible with keen observation and knowledge to perform this refining without the need of an assay; an assay would be invaluable not to warn you of the toxins potentially in the cons but as a benchmark for how to perform your refinement and expelling of nitric and precipitation of the precious metals


Have you had luck in your venture? What kind of material are you working with? How long have you been at this?

Did you notice these black sand concentrates having gold near invisible as I have as well? Under a microscope they are there but otherwise it’s extremely difficult to tell, I end up going by feel and weight and the sluggish look of the lighter material in a gold pan to give me an idea. when you roast so you notice brown specs appear that look like precipitated gold from solution as well? I have started using color as an indicator of particle size as well… the more dark brown and light brown/black the better… sulfides like I said tend to be much lighter and clump together but potentially could be of better yield …

Also.. when evaporating I started by taking the sulphuric acid out of a car battery and using it as the sulphuric acid to help drop the lead when evaporating.. while this worked if I used enough (it’s around 30%) you can buy a 32oz bottle of 95%+ sulphuric acid from your local ace hardware sold under the trade name “roto”… lol. follow hokes suggestion and add slowly to a hot evaporating aqua regia and you will be pleasantly surprised (around a ounce per liter).

If you can’t drop the gold out of your aqua regia save your liquids and eventually in theory you could have enough gold to do a drop.. but this could take time and you would still need to add a properly concentrated aqua regia to these other solutions to drop