# Leach process for large quantity of black sands



## goldshark (Aug 17, 2022)

Does any body know of a good leaching process for a 5 ton a day operation? Cyanide is very difficult to permit. The sands are predominantly magnetite, but still contain about an ounce per ton in unrecoverable ( by tabling) Au. I haven't done an ICP to see what all contains. This would be processing from multiple areas, on a 5 ton per day basis. Any thoughts would be appreciated, TIA.


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## orvi (Aug 18, 2022)

It would be helpful if you will know if the gold is in the matrix of the black sands (locked in minerals or so), or it is just so small to be tabled/panned efficiently. If it is just a too small mili-gold, I would suggest that flotation unit might be of great help, if tuned right. 5 ton a day require vast quantity of chemicals, and if it wouldn´t be cyanide, then it start to be expensive. With nicely tuned sieve (for smallest fraction) and one/two flotation vat, I think you will be able to do this at good recovery rate.
If it is locked, you will either need to destroy the matrix or dissolve it, which will require additional milling and chemicals. Oz per ton is very nice number tho. Allow to process also by more expensive processes.


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## kurtak (Aug 18, 2022)

goldshark - I am no expert in this field - however I have a friend that ran a fair size placer operation & one night (over a few glasses of whiskey) talked about black sands

From our whiskey clouded talk a couple things I remember



orvi said:


> It would be helpful if you will know if the gold is in the matrix of the black sands (locked in minerals or so)



milling the black sands to much finer mesh freed up more gold - by a lot



orvi said:


> I would suggest that flotation unit might be of great help



& if I remember right flotation used for ultra fine recovery

I will try to get with him & pick his brain more - may take a few days

Kurt


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## goldshark (Aug 27, 2022)

Thanks all. I grabbed a core out of the tote to have an independent lab give an umpire assay . I viewed the sample under a microscope. It is hard to quantify the distribution, but what I saw was a quantity of fine Au particles, and pyrite. From a previous sample of panned pyrites from this area, I have received assays of 16 ozs. per ton. I will have assays performed on various particle sizes to see where the greater values may be found. All for now, until the assays come back.


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## Ultrax (Sep 6, 2022)

goldshark said:


> Does any body know of a good leaching process for a 5 ton a day operation? Cyanide is very difficult to permit. The sands are predominantly magnetite, but still contain about an ounce per ton in unrecoverable ( by tabling) Au. I haven't done an ICP to see what all contains. This would be processing from multiple areas, on a 5 ton per day basis. Any thoughts would be appreciated, TIA.


We are taking gold from limonite and magnetite crusts using thiosulfate-ammonium leaching. This is expensive but the most effective method after cyanidation. Unfortunately, acidic ways are not applicable for magnetite. Of course, if you have a technologist who can develop the technology of gold precipitation on anion resins. It's a VERY complex problem. For more than a year we strive to get at least 65%. As the German miners say: Gold wears an iron hat


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## Alondro (Sep 6, 2022)

It's possible if you roast magnetite it will convert into a form that is soluble in HCl. I have a small sample of black sands with gold in them, and I'll be testing that method once I've constructed a simple tube kiln.


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## orvi (Sep 7, 2022)

Alondro said:


> It's possible if you roast magnetite it will convert into a form that is soluble in HCl. I have a small sample of black sands with gold in them, and I'll be testing that method once I've constructed a simple tube kiln.


5 tons a day dissolving magnetite... From process point of view... I think this way is not very efficient one. 
Smelting would also be tough due to iron. 

From what I know from my experience, gold isn't locked up in magnetite (at least I never experienced this). So maybe magnetic separation (cheap) could remove some unnecessary mass, high-grading the cons.
Then, also less leachant would be necessary.

Maybe some "hidden" cyanide based leach like EcoGoldex would be applicable - not cheap, not very elegant in some ways but maybe under your legislation, it isn't classified as cyanide


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## Alondro (Sep 7, 2022)

orvi said:


> 5 tons a day dissolving magnetite... From process point of view... I think this way is not very efficient one.
> Smelting would also be tough due to iron.
> 
> From what I know from my experience, gold isn't locked up in magnetite (at least I never experienced this). So maybe magnetic separation (cheap) could remove some unnecessary mass, high-grading the cons.
> ...


Maybe very fine milling, down to a powder, would release the tiny gold particles. Smelting with lead as a collector, then cupelling, is also possible. Since it's magnetite, there's not going to be much in the way of sulfides to produce the dreaded matte.


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## stoneware (Sep 7, 2022)

Alondro said:


> Maybe very fine milling, down to a powder, would release the tiny gold particles. Smelting with lead as a collector, then cupelling, is also possible. Since it's magnetite, there's not going to be much in the way of sulfides to produce the dreaded matte.


Clarkson Rod Mill.


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## Ultrax (Sep 7, 2022)

orvi said:


> 5 tons a day dissolving magnetite... From process point of view... I think this way is not very efficient one.
> Smelting would also be tough due to iron.
> 
> From what I know from my experience, gold isn't locked up in magnetite (at least I never experienced this). So maybe magnetic separation (cheap) could remove some unnecessary mass, high-grading the cons.
> ...


EcoGoldex is exactly sodium cyanide (based on XRF analysis) in a shell of organic compounds for transportation. There are no miracles in our business 

It is possible to melt magnetite into iron-sodium slag and use lead as a collector in arc ore-thermal furnaces. It is profitable if you have your own electric power plant


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## stoneware (Sep 7, 2022)




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## goldshark (Sep 7, 2022)

Alondro said:


> It's possible if you roast magnetite it will convert into a form that is soluble in HCl. I have a small sample of black sands with gold in them, and I'll be testing that method once I've constructed a simple tube kiln.


Since Magnetite is FeO, what does a calcining roast do to the Magnetite, if it is already an oxide? Does roasting oxidize the Magnetite further ( FeO2), or are you oxidizing some form of PM's adhered to the surface?


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## Ultrax (Sep 8, 2022)

Roasting with oxidizing of iron: Fe->FeO -> Fe2O3 ->Fe3O4. 
Each step of oxidation impairs solubility in acids.

Roasting with reducing of iron: Fe3O4-> Fe2O3 -> FeO ->Fe.
The reducing agent usually is a (C) carbon (as in Primitive Technology video) or hydrogen (H).

Hydrochloric acid is a very expensive way to oxidize iron oxides. Yes, it is considered the most active, but it is almost impossible to achieve complete quantitative dissolution - the excess of concentrated (!) Acid should be from 20 to 30 times. And, of course, closed cover and heating up to 100C! Boiling hydrochloric acid is a very unpleasant substance. And as I already wrote, all iron oxides will NOT dissolve anyway.


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## stoneware (Sep 8, 2022)

Method for the assay and recovery of precious metals

Patent, US5238485A.

Abstract​ 
Complex ores of the precious metals which also contain iron spinels and similar compounds are assayed and their precious metals content is extracted by subjecting the ores or concentrates thereof together with an iron-embrittling agent to a pyrometallurgical process which reduces at least a major portion of the iron compounds to liquid metallic iron.

The liquid iron serves as a collector metal for the precious metals and, after cooling, the iron is brittle and easily comminuted and can be separated from the precious metals through use of either an electrolytic process or a selective chemical dissolution of the iron and other base metals leaving the precious metals available for analysis and recovery.





​​


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## goldshark (Sep 9, 2022)

Sounds expensive. Would it be feasible on a 1 OZ/Troy per ton, with 100 tons or more available?


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## orvi (Sep 9, 2022)

Ultrax said:


> EcoGoldex is exactly sodium cyanide (based on XRF analysis) in a shell of organic compounds for transportation. There are no miracles in our business
> 
> It is possible to melt magnetite into iron-sodium slag and use lead as a collector in arc ore-thermal furnaces. It is profitable if you have your own electric power plant


I totally understand that EcoGoldex is only nicely suited cyanide. But if cyanide is hard to permit for him, then EcoGoldex is branded good which you can purchase and use. It says no cyanide, so you will play dumb and if it will work, use that for leaching. It has MSDS, everything, you gear yourself up with some nice PPE, build one vat for treatment of the used liquid and you are done. In the eyes of law, everything nice and green 

By the way, how the cyanide is measured by XRF ? I would try Raman or IR spectroscopy first, but by what machine it can be measured ?


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## Yggdrasil (Sep 9, 2022)

I think they usually use AAS or similar to measure the leach.


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## orvi (Sep 9, 2022)

stoneware said:


> Method for the assay and recovery of precious metals
> 
> Patent, US5238485A.
> 
> ...


Say we make optimistic 1,5 ton of iron metal from that 5 tons cons... Electrolyse this ammount in a single day would require extreme ammount of electricity. Dissolving 1500 kg of Fe in a day... How ? With what ? What would we do with all that waste ? :/ Assuming 4L of HCL for one kg of iron, that is insane ammount of acid. 6000L for just the dissolution of Fe... Then energy for melting it down, waste treatment wouldnt be cheap also... And then you get 1800USD for the gold. I think this dissolving route is dead end.


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## orvi (Sep 9, 2022)

Yggdrasil said:


> I think they usually use AAS or similar to measure the leach.


My point is how we determine CN- anion in the powder or solution via XRF. We all know very well that anything below Mg is hard to measure by XRF due to small atomic radius. C and N are way off from the magnesium, much lighter. I am just intrigued how they measured it. Powder diffraction ? Does CN- have specific pattern on powder XRF reading ?

Also, if it is encapsuled CN- with organic additives, how you distinguish carbon from that encapsulation from CN- carbon.

Guys from one mining company tested the EcoGoldex in certified lab by certified methods for CN- detection, but they found no free CN- in the solution. That is why I am intrigued about Ultrax method to prove/disprove free cyanide in EG.


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## Yggdrasil (Sep 9, 2022)

orvi said:


> My point is how we determine CN- anion in the powder or solution via XRF. We all know very well that anything below Mg is hard to measure by XRF due to small atomic radius. C and N are way off from the magnesium, much lighter. I am just intrigued how they measured it. Powder diffraction ? Does CN- have specific pattern on powder XRF reading ?
> 
> Also, if it is encapsuled CN- with organic additives, how you distinguish carbon from that encapsulation from CN- carbon.
> 
> Guys from one mining company tested the EcoGoldex in certified lab by certified methods for CN- detection, but they found no free CN- in the solution. That is why I am intrigued about Ultrax method to prove/disprove free cyanide in EG.


Aah, I see.


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## stoneware (Sep 9, 2022)

Titration of Cyanide Solutions.


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## orvi (Sep 9, 2022)

stoneware said:


> Titration of Cyanide Solutions.


Yeah, that is roughly what they did. But also very sensitive qualitative CN tests were negative. That is why I am interested in the method Ultrax described. And how they know that there is any organic substance in it.


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## FrugalRefiner (Sep 9, 2022)

Did they expose it to sufficient UV in the lab tests. According to what I found when researching eco-goldex, it is the ferricyanide and/or ferrocyanide that does the work, but it requires UV light to break the iron bond and free the CN-.

Dave


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## orvi (Sep 9, 2022)

FrugalRefiner said:


> Did they expose it to sufficient UV in the lab tests. According to what I found when researching eco-goldex, it is the ferricyanide and/or ferrocyanide that does the work, but it requires UV light to break the iron bond and free the CN-.
> 
> Dave


I do not know the details exactly, but as far as i know, it also work in glass vessels on regular daylight, where passage of UV isnt very good. They used it according to the manual and measured the CN content along the way. But they didn't found any.


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## Ultrax (Sep 10, 2022)

orvi said:


> My point is how we determine CN- anion in the powder or solution via XRF. We all know very well that anything below Mg is hard to measure by XRF due to small atomic radius. C and N are way off from the magnesium, much lighter. I am just intrigued how they measured it. Powder diffraction ? Does CN- have specific pattern on powder XRF reading ?
> 
> Also, if it is encapsuled CN- with organic additives, how you distinguish carbon from that encapsulation from CN- carbon.
> 
> Guys from one mining company tested the EcoGoldex in certified lab by certified methods for CN- detection, but they found no free CN- in the solution. That is why I am intrigued about Ultrax method to prove/disprove free cyanide in EG.


Sorry for the confusion, I'm simplifying a bit for the forum 
It is quite obvious that we use a laboratory and complex physicochemical multi-stage method for determining the composition. XRF is used to determine the type of complexing agent, not CN ligands (and by the way with XRF we can start with Na, not Mg  Further we use other methods - sorry, they are under NDA.
I can only say that in the EcoGoldex solution works free CN groups, just like in ordinary cyanide 
In general, we have had more problems with recycling and decomposition of waste after EcoGoldex than after ordinary cyanide


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## orvi (Sep 10, 2022)

Ultrax said:


> Sorry for the confusion, I'm simplifying a bit for the forum
> It is quite obvious that we use a laboratory and complex physicochemical multi-stage method for determining the composition. XRF is used to determine the type of complexing agent, not CN ligands (and by the way with XRF we can start with Na, not Mg  Further we use other methods - sorry, they are under NDA.
> I can only say that in the EcoGoldex solution works free CN groups, just like in ordinary cyanide
> In general, we have had more problems with recycling and decomposition of waste after EcoGoldex than after ordinary cyanide


Thanks for explanation


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## campbellj46 (Sep 10, 2022)

Keep it simple and do what nature does, is usually the best way to go. 2 words...ball mill. I usually mill about 3 tons a week of black sands and sulfides to 400 mesh. That will release 95% of gold that is locked up and run it back over the table. 5 tons a day, is going to require a larger ball mill than I have but it will be the same process, no chemicals needed. 

run the ore, crush, and extract. what's not collectible, put in ball mill, grind to 400 mesh, extract again on table. regrind and crush as needed to ensure all (or most) of gold is extracted...wash, rinse, repeat... It's the same process mother nature uses and by far the most cost effective. 

Simple effective DIY ball mill idea to process 5 tons or more a day..... cement mixer, steel balls and water. (but it can be done dry, wet is faster and more effective and easier on the equipment) You want to use roughly 1/2 the weight in steel balls as what you're grinding. 1000 lbs black sands, 500 lbs steel balls...2000 lbs black sands, 1000 lbs steel balls, etc. I use a DIY ball mill from a small cement mixer and 200 lbs steel balls, processes about 1000 lbs a day and about 3 tons per week. 

keep it simple.


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## stoneware (Sep 10, 2022)

campbellj46 said:


> Keep it simple and do what nature does, is usually the best way to go. 2 words...ball mill. I usually mill about 3 tons a week of black sands and sulfides to 400 mesh. That will release 95% of gold that is locked up and run it back over the table. 5 tons a day, is going to require a larger ball mill than I have but it will be the same process, no chemicals needed.
> 
> run the ore, crush, and extract. what's not collectible, put in ball mill, grind to 400 mesh, extract again on table. regrind and crush as needed to ensure all (or most) of gold is extracted...wash, rinse, repeat... It's the same process mother nature uses and by far the most cost effective.
> 
> ...


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## Ultrax (Sep 10, 2022)

orvi said:


> Thanks for explanation


Do you use portable XRF with start detecting from Mg? Just curious


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## campbellj46 (Sep 10, 2022)

stoneware said:


> View attachment 52131


Not sure what that's supposed to say. -50 mesh is easily collected on the table. Most of the gold I was referring to is going to be -150 or still locked in black sands and/or sulfides. Grinding in the ball mill extracts down to 400 mesh, easily retrieving the 1 oz+/ton in the original post. It's specifically for not using chemicals because processing 5 tons/day will run into millions $$$ IF anyone can get a permit for cyanide leaching.


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## orvi (Sep 10, 2022)

Ultrax said:


> Do you use portable XRF with start detecting from Mg? Just curious


I am not sure if it can do Na, but it shows Mg, and Geochem shoot quite OK the bulk of constituents of matrix... OLYMPUS Vanta  better advertised than really functioning  sharp step from older Elvax or NITON devices tho


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## Ultrax (Sep 10, 2022)

campbellj46 said:


> Keep it simple and do what nature does, is usually the best way to go. 2 words...ball mill. I usually mill about 3 tons a week of black sands and sulfides to 400 mesh. That will release 95% of gold that is locked up and run it back over the table. 5 tons a day, is going to require a larger ball mill than I have but it will be the same process, no chemicals needed.
> 
> run the ore, crush, and extract. what's not collectible, put in ball mill, grind to 400 mesh, extract again on table. regrind and crush as needed to ensure all (or most) of gold is extracted...wash, rinse, repeat... It's the same process mother nature uses and by far the most cost effective.
> 
> ...


Gold is never in the crystal lattice of magnetite - usually, it is hydrothermal co-precipitation (in the geological sense) in which gold particles are physically overgrown with hydroxides and iron oxides, binding very firmly precisely mechanically (!).
No amount of crushing by pressure (let aside mill with steel balls) will help free these gold particles from hydroxide shells. Moreover, oxides are often covered with a dense layer of organic bitumens - which make magnetite generally insensitive to any(!) acids or mechanical actions. Even roasting at 700-800C does not help 100%. So practically, such magnetite totally does not dissolve in anything without an autoclave and very aggressive oxygen oxidation. We have such type of ore (ferroaurates), and we were able to wash off bitumens coating from ferroaurates only with xylene - and then only partially.
Therefore, if you have ferroaurate (gold in magnetite), your only way is chemical leaching after opening the magnetite.
Opening the magnetite is a more complex problem than opening the sulfides. You can find the best solution on your specific ore in practice.


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## orvi (Sep 10, 2022)

Ultrax said:


> Gold is never in the crystal lattice of magnetite - usually, it is hydrothermal co-precipitation (in the geological sense) in which gold particles are physically overgrown with hydroxides and iron oxides, binding very firmly precisely mechanically (!).
> No amount of crushing by pressure (let aside mill with steel balls) will help free these gold particles from hydroxide shells. Moreover, oxides are often covered with a dense layer of organic bitumens - which make magnetite generally insensitive to any(!) acids or mechanical actions. Even roasting at 700-800C does not help 100%. So practically, such magnetite totally does not dissolve in anything without an autoclave and very aggressive oxygen oxidation. We have such type of ore (ferroaurates), and we were able to wash off bitumens coating from ferroaurates only with xylene - and then only partially.
> Therefore, if you have ferroaurate (gold in magnetite), your only way is chemical leaching after opening the magnetite.
> Opening the magnetite is a more complex problem than opening the sulfides. You can find the best solution on your specific ore in practice.


interesting...


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## Punterr (Sep 11, 2022)

FrugalRefiner said:


> Did they expose it to sufficient UV in the lab tests. According to what I found when researching eco-goldex, it is the ferricyanide and/or ferrocyanide that does the work, but it requires UV light to break the iron bond and free the CN-.
> 
> Dave




As far as I am aware, there is no Ferri/Ferro cyanide in the LV/Eco-Goldex/JinChan leaches. They are essentially all the same with slight changes in the embodiments.

They use Sodium Cyanate, some Thio, oxidisers and bases.. here is the patent number CN107287439A


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## Punterr (Sep 11, 2022)

9


Ultrax said:


> Gold is never in the crystal lattice of magnetite - usually, it is hydrothermal co-precipitation (in the geological sense) in which gold particles are physically overgrown with hydroxides and iron oxides, binding very firmly precisely mechanically (!).
> No amount of crushing by pressure (let aside mill with steel balls) will help free these gold particles from hydroxide shells. Moreover, oxides are often covered with a dense layer of organic bitumens - which make magnetite generally insensitive to any(!) acids or mechanical actions. Even roasting at 700-800C does not help 100%. So practically, such magnetite totally does not dissolve in anything without an autoclave and very aggressive oxygen oxidation. We have such type of ore (ferroaurates), and we were able to wash off bitumens coating from ferroaurates only with xylene - and then only partially.
> Therefore, if you have ferroaurate (gold in magnetite), your only way is chemical leaching after opening the magnetite.
> Opening the magnetite is a more complex problem than opening the sulfides. You can find the best solution on your specific ore in practice.





stoneware said:


> Method for the assay and recovery of precious metals
> 
> Patent, US5238485A.
> 
> ...


So what is the 'embrittling agent' ??? Any ideas


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## Punterr (Sep 11, 2022)

orvi said:


> My point is how we determine CN- anion in the powder or solution via XRF. We all know very well that anything below Mg is hard to measure by XRF due to small atomic radius. C and N are way off from the magnesium, much lighter. I am just intrigued how they measured it. Powder diffraction ? Does CN- have specific pattern on powder XRF reading ?
> 
> Also, if it is encapsuled CN- with organic additives, how you distinguish carbon from that encapsulation from CN- carbon.
> 
> Guys from one mining company tested the EcoGoldex in certified lab by certified methods for CN- detection, but they found no free CN- in the solution. That is why I am intrigued about Ultrax method to prove/disprove free cyanide in EG.



Regarding the residual CN in Eco-Goldex, in a test in Africa, with CN against JGD (Jin Chan Gold Dressing agent - same as Eco-Goldex), they did find residual Free CN. Please see attached table. The optimal concentration they found for CN was around 250ppm and for JGD was 400ppm.


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## Ultrax (Sep 11, 2022)

Punterr said:


> 9
> So what is the 'embrittling agent' ??? Any ideas


Dissolve PGM in molten iron as a collector? Did the author of US5238485A even see the state diagram of the Au-Fe system? This is obvious economic madness  Author filed a patent for the sake of the patent itself 

P. S. Yes it is possible to collect gold in matte from sulfide ore (it's old multi-stage Hungarian medieval technology) but molten iron is NOT a matte.


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## stoneware (Sep 11, 2022)

Punterr said:


> 9
> So what is the 'embrittling agent' ??? Any ideas


Both steel and cast iron are made from the same mineral, cast iron comes in many grades some of which are easier the break than others.

It's only a guess but I'm thinking you want to turn the iron into something very brittle.

To make steel they inject oxygen into the molten metal.

In the video Primitive Technology he used carbon in his furnace which in turn consumed the oxygen from the oxides, leaving him with globules of metal.

Would have been interesting to see an assay of his metal then we would know which other elements is had picked up from the source material.

Iron will alloy with a lot of other metals.

If you focus on black sand and not the precious metals your after your research will stall.

Metals smelting-collection method for recycling of platinum group metals from waste catalysts: A mini review.

How to Smelt Iron: The 6 Steps to Iron Smelting | The Crucible.

During medevil times the metal used to make a sword was of such poor quality the word would often break during battle.


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## orvi (Sep 11, 2022)

Ultrax said:


> Dissolve PGM in molten iron as a collector? Did the author of US5238485A even see the state diagram of the Au-Fe system? *This is obvious economic madness  Author filed a patent for the sake of the patent itself*
> 
> P. S. Yes it is possible to collect gold in matte from sulfide ore (it's old multi-stage Hungarian medieval technology) but molten iron is NOT a matte.


Agree


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## Deano (Sep 11, 2022)

If you dissolve some of the powder in water you measure the cyanide level in the water using a cyanide probe, usually on a handheld meter.
This is technology which has been around for well over a decade and is widely used in the gold mining industry.
Deano


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## Platdigger (Sep 11, 2022)

The embrittling agents are mentioned in the patent. 
The elements are in the sand they were treating
I found this patent even way before I found this forum.
Sort of started me down this path.


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## kurtak (Sep 17, 2022)

kurtak said:


> goldshark - I am no expert in this field - however I have a friend that ran a fair size placer operation & one night (over a few glasses of whiskey) talked about black sands
> 
> From our whiskey clouded talk a couple things I remember
> 
> ...


As an update to my above post I talked to my friend again

He has a couple tons of black sands

He took "random" samples (about 32 samples of about 1 oz each) mixed well together (so about 2 pounds)

Divided that into two 1 pound samples

Milled 1 pound to 150 minus mesh

Milled the other 1 pound to 300 minus mesh

Sent the two samples in for assay

The assay on the 150 mesh came back at 7 ozt/ton

The assay on the 300 mesh came back at 17 ozt/ton

The point being that milling frees up more gold - by a lot

He has not actually processed his black sands as he sees them as money in the bank - so don't know actual best method for actual recovery from sands milled that fine would be

Knowing that "fine" gold can be encrusted in the matrix of the iron oxide he simply wanted to see how much more gold could be freed up by milling

Black sands - like ore - are going to vary - by a lot - depending on location etc. etc. 

For what it is worth

Kurt


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## Lydia Huang (Sep 21, 2022)

*Black sand is usually magnetite*, and the iron content is generally 30% to 60%. It is an iron oxide mineral with the chemical formula Fe3O4. The Mohs hardness is 5.5~6.5. Black sand may also contain other minerals, such as limonite.

If you want to extract iron metal from these 5 tons of waste, it can be converted into strong magnetic magnetite after pretreatment by calcination.

After calcination, *the magnetic properties of iron minerals are enhanced, and the magnetic properties of gangue minerals have little change.* Then use a magnetic separator to effectively separate minerals in a weak magnetic field. I also got other extraction methods from this magnetite post.


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## finargle (Nov 17, 2022)

A lurker from Australia. Just to show you how rich black sands can be, I saw an assay from one of our Mines Departments where a sample ran 103 ounces to the cubic metre of black sands. Unfortunately our mining regulations have blocked access to the bonanza. The report didn`t state what assay methods were used. I haven`t found any other assays of BS across Oz, so it might be a one-off. One of our geo gurus, Allan Wilson (now deceased), wrote an interesting article which I posted on Doc`s old forum about the creation of auriferous solutions in iron-infested country which led to deposition in swamps of nuggets that grew to impressive sizes. Might this be how gold was deposited within black sands? I can post it here if you`d like a copy.


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## Alondro (Nov 17, 2022)

finargle said:


> A lurker from Australia. Just to show you how rich black sands can be, I saw an assay from one of our Mines Departments where a sample ran 103 ounces to the cubic metre of black sands. Unfortunately our mining regulations have blocked access to the bonanza. The report didn`t state what assay methods were used. I haven`t found any other assays of BS across Oz, so it might be a one-off. One of our geo gurus, Allan Wilson (now deceased), wrote an interesting article which I posted on Doc`s old forum about the creation of auriferous solutions in iron-infested country which led to deposition in swamps of nuggets that grew to impressive sizes. Might this be how gold was deposited within black sands? I can post it here if you`d like a copy.


I want to get an assay done of the black sands I'm recovering from an ancient glacial moraine here in New Jersey. They are heavily weathered, with the sulfides already oxidized. I notice a sizeable portion of them (about 20%) is a very fine, very dense 'silver sand', far heavier than iron, close to the density of the gold specks I see. I suspect it's a multi-metal oxide, probably of lead and silver and one other heavy metal.


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## cosmetal (Nov 17, 2022)

Alondro said:


> I want to get an assay done of the black sands I'm recovering from an ancient glacial moraine here in New Jersey. They are heavily weathered, with the sulfides already oxidized. I notice a sizeable portion of them (about 20%) is a very fine, very dense 'silver sand', far heavier than iron, close to the density of the gold specks I see. I suspect it's a multi-metal oxide, probably of lead and silver and one other heavy metal.


Have you tested the "silver sand" for Pt?

Here in No. Calif., the bucket line dredges that were used to dig deep and go after old tertiary deposits within our rivers were digging up Pt deposits along with the Au. So much so, that the State geologist suggested that the miners accumulate the Pt also.

*"*_*If the miners could be persuaded to collect the platinum minerals, an industry might be established of *_*considerable importance. There is no reason why platinum should not be manufactured in San Francisco and an industry might be established of American demand in part or wholly supplied by this State. The process of manufacture is simple, the plant required inexpensive, and there are skillful chemists in the State fully competent to manage it. The control of the platinum trade is in the hands of a single English manufacturing firm, which has been the case for *_*many years."*_
*CA State Mineralogist_4th Annual Report - Minerals of California_1884*

Unfortunately, since Pt won't amalgamate with the mercury used within the dredge's accumulators (as Au does), the operators simply viewed Pt as waste and it was discarded by the dredge's side chutes back into the rivers.

PM me if you are interested in reading this historic 1884 report. It is ~35MB so it's too big to post here.

Peace and health,
James


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## cosmetal (Nov 17, 2022)

Alondro said:


> I want to get an assay done of the black sands I'm recovering from an ancient glacial moraine here in New Jersey. They are heavily weathered, with the sulfides already oxidized. I notice a sizeable portion of them (about 20%) is a very fine, very dense 'silver sand', far heavier than iron, close to the density of the gold specks I see. I suspect it's a multi-metal oxide, probably of lead and silver and one other heavy metal.





https://www.amazon.com/Royal-Gold-Concentrating-Miller-Table/dp/B00ZH21ZNW/ref=sr_1_1?crid=14QV4COMQTKBC&keywords=miller+table&qid=1668707716&s=sporting-goods&sprefix=miller+table%2Csporting%2C355&sr=1-1



I would suggest that you get (or build) a small Miller Table - ball mill your sands to <100 mesh - and slowly (that's the only way a Miller Table seems to work) run your sands over the Miller Table and send that sand sample in for assay.

Peace and health,
James


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## Alondro (Nov 17, 2022)

cosmetal said:


> https://www.amazon.com/Royal-Gold-Concentrating-Miller-Table/dp/B00ZH21ZNW/ref=sr_1_1?crid=14QV4COMQTKBC&keywords=miller+table&qid=1668707716&s=sporting-goods&sprefix=miller+table%2Csporting%2C355&sr=1-1
> 
> 
> 
> ...


The sands are already so fine, I think a simple smelt-and-cupel assay using lead as a collector will work just as they are. They've been crushed and ground by ice, water, and rocks grinding for 10,000 years. Much of it is fine dust, especially the interesting silver sands fraction.

Since it all comes from panning, I won't have more than 10 pounds of it every year. This is just to see if there enough PMs to make it worth saving the sands up year after year until I have a good pile.

If a pound of it sent for the assay produces a noticeable bead of metal after cupeling, then it's certainly rich enough to save.

Sent an email to Mount Baker to see what their price for a fire assay is. I've watched dozens of the smelts on Youtube, and Jason is exceedingly skilled at the process.


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## Deano (Nov 17, 2022)

Gold assays on black sands are always subject to nugget effects.
This is minimised by running the assay in triplicate, it often stops you getting excited over one large piece of gold in a single assay.
Deano


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## Alondro (Nov 18, 2022)

Deano said:


> Gold assays on black sands are always subject to nugget effects.
> This is minimised by running the assay in triplicate, it often stops you getting excited over one large piece of gold in a single assay.
> Deano


There won't be any 'nuggets' in my sands. They've been panned down to only the finest particles and mixed thoroughly. Also, they're the combined sands of half a dozen spots in the area I'm working. It's a very good general homogenized sample,


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## Wolfpacker1 (Dec 2, 2022)

goldshark said:


> Does any body know of a good leaching process for a 5 ton a day operation? Cyanide is very difficult to permit. The sands are predominantly magnetite, but still contain about an ounce per ton in unrecoverable ( by tabling) Au. I haven't done an ICP to see what all contains. This would be processing from multiple areas, on a 5 ton per day basis. Any thoughts would be appreciated, TIA.


We use a thiourea based leach to recover gold from magnetite, black sands and sulfides where cyanide has failed. You can visit our website at tcbinter.com
We have a page devoted to black sand processing

Edited due to forum rules and strange double quoting


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## Wolfpacker1 (Dec 3, 2022)

goldshark said:


> Does any body know of a good leaching process for a 5 ton a day operation? Cyanide is very difficult to permit. The sands are predominantly magnetite, but still contain about an ounce per ton in unrecoverable ( by tabling) Au. I haven't done an ICP to see what all contains. This would be processing from multiple areas, on a 5 ton per day basis. Any thoughts would be appreciated, TIA.


Depending where this material is located and how far from a port , I have clients that would be interested in this material.


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