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Author Topic: Roasting black sand to extract fine gold?  (Read 30507 times)

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Offline sluicemonkey

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Roasting black sand to extract fine gold?
« on: May 25, 2009, 07:53:46 PM »
Anybody try this? I found some info on the web that says that you can screen you b/s down to under 20 mesh and then tumble it with vinager. Wash it and mix it with equal parts table salt and roast it in a pan over fire. Once the b/s is hot a dry, you dump it into cool water so the sand and sulfides break up and release the gold. I tried this with some b/s that I had run through a blue bowl 2 times and got a decent amount of gold out of it, again!  {cool^sign} Screened it down to 30 mesh and 60 mesh. Thought that this seemed far fetched but it seemed to work unless I lost that much free gold the 1st couple of times. Think I will save the sand again and run it though a 100 mesh screen and blue bowl it again. Anyone ever heard of doing this? Was wondering what the salt does?
Will dig for gold!

Offline Mooseman

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Re: Roasting black sand to extract fine gold?
« Reply #1 on: May 26, 2009, 02:13:47 AM »
Salt and vinegar form sodium acetate and hydrogen chloride which is a strong acid. The acid will help break down impurities and remove them from the gold which is unaffected by the acid.

Offline GollyMrScience

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Re: Roasting black sand to extract fine gold?
« Reply #2 on: May 26, 2009, 08:52:47 AM »
This process has been used for a long time and you see variations on it but the main theme remains.
Some do a vinegar bath before and some after. Many just use the salt roast.

The salt is added to washed ore (no vinegar left in it) and in most cases the technique says heat to red hot then drop into cold water.

At the heat levels and available oxygen the sulphides convert using the salt to chlorides. The sulfur will combine with the Sodium from the sodium chloride to make Sodium Sulphate so a lot of the sulphur will get trapped and not sent into the atmosphere.

Once the various metal sulphides have converted to chlorides they are water soluble.
So what you have done by heating with salt is break the sulphides down to varying degrees depending on how fancy you get with the process and taken the other sands to high heat.
When the mix hits the cold water you get thermal shock which fractures the mineral grains and the now soluble chlorides (former sulphides) are broken down.
If there is gold in either the sulphides or the other black sands it may be released.

For a panner only a small portion of the gold might be recoverable as a significant amount of the gold that is locked into sulphides and black sand is microscopic. You will be recovering the "nuggets".

I would stay away from salt and vinegar mixed though the vinegar can be used to clean free gold prior to amalgamation and some people think that it can be used to clean the gold liberated from the salt roast though I see little benefit to it at that point.
Also do not drive the heat too high as the chlorides will volitize at around 1500 degrees F. Lower in the presence of some exotics like tellurides. I would stay under 1000F.

For many panners just fracturing the sands will reduce the mineral grains and even if there is no new gold the fine gold that got away from your first pass at recovery will be easier to get out of the now much finer sands.

Kind of like fine grinding but with preservation of the gold sizes and lots of steam and fire - always fun.  ;D
The usual safety precautions apply.

What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!


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Re: Roasting black sand to extract fine gold?
« Reply #3 on: May 26, 2009, 12:02:28 PM »
Tom, Mooseman

Tom: at the bottom of your post, you use the CIA phrase:
The usual safety precautions apply.

Since panning is the first experience of many in this endeavor, and vinegar/salt/heat are the first "steps beyone panning" thing they feel they can "safely" experiment with, there customarily isn't any real helpful response except perhaps confusion and intimidation by such a safety phrase reminder.

Would you take a few and flesh "it" out a wee bit?

please chime in, as well.  We all have valuable experiences to share.  <-good_>

you chime in, too, after the guys take the first two mighty swings at the SAFETY piñata.  <-laugh->

Offline Chuxgold

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Re: Roasting black sand to extract fine gold? vs Rockers
« Reply #4 on: May 27, 2009, 12:37:02 PM »
The gold you get from smaller than 80 to 100 is lost to just panning. And your blue bowl is a forced water system. There is no perfected small scale way to deal with cons that gets it all in one pass This is why I have went to making a better rocker.  And also is simple to use and even learn how to perfect its use. Without knowing how it exactly works. With a rocker box you can condense more into a smaller place. Without loosing the ultra fine gold while collecting the coarser gold. So when screening down to 20 mesh and then fracturing with heat you can get most of all sizes of gold less than the size of the screen. And it will not get dislodged by the passing larger material. So will build and build. Without building much other heavy fines, for the gold gathered. But will eventually fill with it and raze the cohesion to a point of loosing gold. I like to think of cohesion as like a barrel of monkeys with all there arms locked together. With water and action the arms are pulled apart so they can't hold the gold up from the bottom. Or grab it and pull it up off the bottom. So it just builds.  This means that more can be pushed into a smaller space. This puts a hole days work into one pan or bucket. When many days off work have been gathered they can be run all at once and not loose much gold. this puts more gold in your concentrates so its cohesion is the greatest. Gold that makes it to the bottom with other gold, has a cohesion like the monkeys were hugging. With loosening cohesion up from there. As the cohesion lessons near the top. So dues displacement increase.
If wanting to see the most from fracturing it should be dun twice once for pre running all cons at 20mesh, then once when they have been worked down and screened to 100 or finer. I can not see any reason that it could be dun more if some one wanted to.
I have not seen the reason or understand correctly why to use vinegar if your going to heat it. Heating kills all the organics. but salts will clean the gold and give it more cohesion to its self. And lesson all others.
Another point is to grind lightly. With a hammer mill or pistil and mortar. The keen bucket top hammer mill sounds like a good use for it. They were out fast on larger material. So hammers  would last a long time. Even if running all the gravel collected, 1/2 inch stones and the sand in the pre concentrating end of working your cons. A small keen crusher would eliminate needing of a second grinding. But with grinding all material to dust, you need to load apron with some clean pea gravel or a hand full of small steal balls. When ground, cohesion go’s thru the roof. But massive amounts of material is easily displaced out of the cons. By being made so small it is locked in the water and just flows across and out of the apron. This material has no cohesion no more. So is completely displaced. I originally made the first one, to work ore. Trying to concentrate something out of it. There was not much gold but there was lots of zinc.. Which I could concentrate to the point of using a propane torch to melt it.  
Many of the procedures of a rocker go's against what other processes require. So can cheat the curves. like not needing to work material down more than a few times, to get it all. Kind of like the back wash and tap method. Your not trying to remove the gold from the sand your trying to displace the black sand from the gold. So the more gold left that is large enough to not get kicked out will gather more of the finer. With a rocker you do not remove the larger flower gold, You use it for a better trap.
Every prospector should have a rocker box for cons. Even if what you make is dysfunctional to the extreme. You will find more from your cons with one than a blue bowl and gold pan. And then you will see that it is a thing with limitless potential. And know I do not over step the boundaries of truth on anything I have to say about them.
Chuxgold. <-thinking->
Give self, to gain wisdom,