What to do with black sand

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[willthedancer]

Lots of talk here on this subject. here is my take on it. I have the copyright. Similar to thermite welding, but less energetic

Step 1 Remove the silica and other light materials by whatever method suits your fancy.

Step 2 Get the gold that you can out by your method of choice. No Mercury though.

Step 3 Requires that you have some idea of the constituents of your sand. Make sure your black sand is bone dry. Weigh it. Add the gram equivalent of finely divided aluminum to replace all of the iron and chromium in your black sand.

Step 4 Place the mixture in a crucible with a false steel bottom over a sheet mold so that the liquid iron will burn through and run onto the sheet mold. All crucibles and the sheet mold must be preheated.

Step 5 Initiate burning with a magnesium ribbon, or do the process in a furnace. You now have a pregnant iron sheet.

Step 6 using a plating bath containing ferrous sulfate and a little sulfuric acid, plate the iron onto a thin pure iron sheet. Use magnetic grade pure iron for the cathode, as you will want to sell the iron as electro refined pure when you are done. Its worth fair money BTW. Use an anode bag to catch the anode mud, as there will be your precious metals. No loss.


Please put this to use. Make zillions of dollars.

[sluicedog]

Lots of talk here on this subject. here is my take on it. I have the copyright. Similar to thermite welding, but less energetic

Step 1 Remove the silica and other light materials by whatever method suits your fancy.

Step 2 Get the gold that you can out by your method of choice. No Mercury though.

Step 3 Requires that you have some idea of the constituents of your sand. Make sure your black sand is bone dry. Weigh it. Add the gram equivalent of finely divided aluminum to replace all of the iron and chromium in your black sand.

Step 4 Place the mixture in a crucible with a false steel bottom over a sheet mold so that the liquid iron will burn through and run onto the sheet mold. All crucibles and the sheet mold must be preheated.

Step 5 Initiate burning with a magnesium ribbon, or do the process in a furnace. You now have a pregnant iron sheet.

Step 6 using a plating bath containing ferrous sulfate and a little sulfuric acid, plate the iron onto a thin pure iron sheet. Use magnetic grade pure iron for the cathode, as you will want to sell the iron as electro refined pure when you are done. Its worth fair money BTW. Use an anode bag to catch the anode mud, as there will be your precious metals. No loss.

willthedancer

Do you have any photos of this process...I tried to form a mental picture of the process..but you left me in the dust     
pregnant iron sheet....  
an anode bag....

[willthedancer]

Basically this process is to reduce the iron in the black sand, taking the precious metal content with it. That is why the iron sheet is called pregnant. Its full of PGMs and gold. Then the iron is plated away in a porous bag to catch the precious metal powder, while the iron accumulates on the cathode. That pure iron is worth considerable money, since most iron made in the world is made in blast furnaces and is full of impurities like carbon.

Sorry, no pics.

[GollyMrScience]

Hmmmmm...
Would be hard to do at large scale.
Electrowinning of iron is certainly doable but I would likely head straight for leaching if doing recoveries of gold from large volumes of black sand.
Temp and atmosphere would be an issue. Temp is high enough to volatize gold and without a reducing atmosphere or a flux cap there could be significant losses at the fusion point of iron. Not to mention that unless protected even the iron you are reducing would be trying to grab O2 and not cleanly reduce to metallic iron.
I am not sure if I would try it but I know I would sure like to see somebody ELSE try it.
As a branch off from this idea you could consider reduction of the oxides using a reducing roast to make sponge iron and then head straight for dissolution of the sponge iron in low strength acid  then dropping the iron out as high purity iron salts either as iron chloride or iron sulphate. In this case you would be aiming for a high quality insol left behind in the process that you would recover the gold from. It would still be a bit of a dogs breakfast of insol products (as would the mud from the fusion you suggest) and would still need further treatment that might add up in cost, time and energy to more than just going for selective leaching.
It would lack the drama and showmanship of the molten iron burning through the false bottomed crucible though.
The mud left behind would still be darned impure as a gold product as any metals reduced in the initial melt would be left behind if they did not go into the solution or get dragged across the electrowin circuit. They could be a pain to deal with in their own right.

[willthedancer]

I am going to run this in one kilo heats in my smithy, but there needs to be a scrubber on the stack. Thanks for the heads up about a flux cap. I disagree about the issue of boiling off the gold, as gold melts at 1064, and boils at 3080, whereas iron melts at 1535, and boils at 2750. the boiling point of iron will cap the reaction temperature at 2750. Spectacular it would be, but since we are reducing ferrousferric oxide, I 'am pretty sure' (for what thats worth) that it will be less spectacular than industrial thermite. The impurities will also hold down the reaction rate as dampers.

As to the plating process for the iron refinement, as in copper matte refinement, it should be pretty clean. certainly several orders of magnitude cleaner than pig. I think wet chemistry will do for the mud.

[GollyMrScience]

Things do not have to boil to vaporize and the action is more complex than a simple boiling action anyway.
You have some pretty complex reactions (some totally unknowable without some complex chemistry on a specific sample).
In its simplest form as soon as gold melts it has the potential to evaporate which is a surface phenomenon rather than a bulk materials vaporization though the amounts would be very low if other factors were not introduced. Adding a few things like complex oxides dumping their O2 into the fusion, exotic chemistry as various mineral complexes are reduced or burned off, chemical bonds broken and recombined, wide ranges of temperature throughout the melt as the fusion under the conditions described would not be uniform and a bunch of other variables and things are not so easy to predict.
Consider the temperatures actually generated in the mix you describe. A burning mixture of aluminum, magnesium and iron is way hotter than the actual melting point of iron.
The other factor is the fight for the fusion which is supported by the burning of metals to grab enough O2 to burn while at the same time reduce metals from oxides.
Making my head hurt.
I say mix it up and set it on fire - sell tickets - its gonna be neat no matter what happens.

[Johnny]

Howdy... Seems to be great soil acidifier... good for roses or how about the christmas tree farm, it's great stuff for evergreens.
Happy Trails
Johnny

[willthedancer]

Things do not have to boil to vaporize and the action is more complex than a simple boiling action anyway.
You have some pretty complex reactions (some totally unknowable without some complex chemistry on a specific sample).
In its simplest form as soon as gold melts it has the potential to evaporate which is a surface phenomenon rather than a bulk materials vaporization though the amounts would be very low if other factors were not introduced. Adding a few things like complex oxides dumping their O2 into the fusion, exotic chemistry as various mineral complexes are reduced or burned off, chemical bonds broken and recombined, wide ranges of temperature throughout the melt as the fusion under the conditions described would not be uniform and a bunch of other variables and things are not so easy to predict.
Consider the temperatures actually generated in the mix you describe. A burning mixture of aluminum, magnesium and iron is way hotter than the actual melting point of iron.
The other factor is the fight for the fusion which is supported by the burning of metals to grab enough O2 to burn while at the same time reduce metals from oxides.
Making my head hurt.
I say mix it up and set it on fire - sell tickets - its gonna be neat no matter what happens.

Tom, you make it sound positively exciting. Its still on the drawing board, and no telling what will happen with great certainty, but I will try. Where is my face shield and asbestos suit?

I think it merits the attempt. If it works as it should on paper, then one might make a dollar or several by doing it.

[hardtofreegold]

This thermite method sounds messy and inefficient. this formerly was known as "reduco fusion" and is a good methiod for doing assays on small samples containing a lot of sulfides with a overwhelming amount of Mg not Al thermite in the mix

I know quite a bit about treating black sands i prefer to smelt with silver at 2,900F But for the back yard guy this is probably the best method save one  critical fatal flaw

Ferric sulfate/Sulfuric acid is the method that throws the baby our with the bath water, your "pure cathode iron" will also contain all of the Rhodium, Palladium, ruthenium, iridium and some of the silver, that's some expensive alloy steel there partner!!!!!!!  i guess you could market it as Forrest grump super alloy or dip steel alloy - replacing the word steel Bottom line is keep that sulfate ion SO4-O5-O6-O7-O8-O9-10 away from PGMS At the ANODE!!!!!!!!!!!!!!!! They will exchange in a hot minute expecial when it takes on extra Oxygen to become super sulfate!!!!!!!!

Use sulfamic acid instead, it wont lixivate the pgms from the anode might loose a little silver but don't worry about that its not worth enough. you can buy it as pure powder in home-depot as dry-loc concrete echent, (don't buy the liquid formulation its not pure) mix with distilled / RO filtered water no added minerals Na / k / Mg chlorides will really screw everything up bad insuring huge losses and a horrible mess so use distilled H2O if in doubt!!!!!, about one lb bottle to 5 gallons also don't think tap water is fine any source of alkaline metals will make dubble salts that will just amount to an unrecoverable mess, at that point you would have to smelt with boric acid to breakup the salts and reduce the metals again.

well now that you have all this nice mud from the sulfamic acid treatement, don't do something stupid and alloy it into a sliver dorea bar, send the mud to a refinery, pay the inital $450 bill for the analysis and they then buy it as is, if you alloy it with silver it will throw off the analysis.

one final tip, only use no more than 3 volts per cell 1.9 - 2.4 would be ideal at you target amperage, a Varic on a 50 amp battery charger works well

Ocean

[willthedancer]

I know this is an old thread, and I just read the last post. Great info!

Since I have just started playing in the microwave, I thought I would try step one of my thermit process. I did my math, weighed the sample, and the right amount of aluminum powder, put it in an old yucky crucible, and away we went. I got a good easy burn, but it required a little literal prodding. I could not get it to mix, but I did get several Iron nodules out of the mass afterward. They seemed to weigh out ok. Slightly higher than expected probably due to oxide contamination. There were pyrotechnics for sure, but nothing like the videos of a real thermite reaction going on. More later...