# Halide Leaching Black Sands



## seanengman (Sep 29, 2011)

I had just a simple question and it is probably based on personal preference, but how fine do you classify your sands before you start using some sort of leaching process. I believe I have mine at 20 mesh, I can go finer. I think I only have three or four pounds of material to process. If you are wondering why I chose halide leaching, it is because iodine runs like water in my business, so it is cheap.

Thanks

Sean


----------



## solarsmith (Sep 29, 2011)

if you only have a few lbs get a rock tumbler at the hobby store.
and a pound or two of ball berrings or nuts from the hardware store..
then grind down to smoth as silk. (no feal of grit between the fingers)
remove iron with a magnet... now you leach will go fast if you keep it warm.
good luck . Bryan in Denver Colorado....


----------



## Reno Chris (Sep 30, 2011)

Do an assay first. Most black sands do NOT contain significant values beyond what can be recovered using much simpler gravity methods. Test first to see if yours is one of those very rare few before investing lots of time and effort chasing something that isn't there to begin with.


----------



## seanengman (Oct 1, 2011)

Reno Chris- The black sands contain gold and platinum. It is what I have left over from cleaning up my dredge and all of my supplies are free or cost me next to nothing, plus the learning experience makes it all worth it.

Bryan- Thanks for the tip on the mini ball mill. I will leave out the magnet part though. In my experience I have found that I can't use a magnet without losing gold. I have a vibratory tumbler... will that do?

Cheers

Sean


----------



## Harold_V (Oct 1, 2011)

seanengman said:


> I have a vibratory tumbler... will that do?


Logically, no. A tumbler has the wrong action. Sure, over time it may reduce everything to powder, but it's safe to say it isn't suited to the task at hand. 

For that matter, few of the "ball mills" that have been built by readers, here, are well suited to crushing. Most have simply put together a drum that rotates, paying little attention to the theory involved in successful crushing. 

Do they achieve results?

Yes, of course they do. 

Would their particular tool serve then in a situation where efficiency was a factor? 

No. In fact, make that hell, no!

Ball mills, in order to work efficiently, should carry the balls to the apex of the top curve, then drop them on the material below. That way they work by *crushing*. That's the intended purpose. No lifting devices are desired internally---lifting is accomplished by operating the crusher at the *proper speed*. Anything less than that is a compromise, which wears the material down instead of crushing. That creates far more wear on the charge and mill than does proper crushing, and takes a much greater amount of time, although the less than acceptable method may yield much finer material. That's to be expected when the ore is worn away instead of crushed. 

Harold


----------



## seanengman (Oct 2, 2011)

Harold-V

Funny I just read your post as prior my friend and I were discussing building a small ball mill or something of that nature.

I have another question (my first time... sorry)... or two:

What is the best acid to use to precipitate the gold out of solution? I have read both muriatic (HCl) and lye (NaOH).

And when I go to smelt my AuI2 what should I use as a flux?

Cheers

Sean


----------



## Geo (Oct 2, 2011)

i saw a mill once that was made from one and a half foot diameter steel tubing with plate welded on the ends square. it had a hatch in the side of the tube about a foot and a half long with the tube itself being three feet in length. but the part that interested me the most was the weight used to crush the material. instead of balls it used a piece of rod stock six inches in diameter and two and a half foot long. very heavy piece of steel. you put sand in and add a couple of gallons of water seal it up and turn it on and in about an hour you would have mud with particles the size of talcum powder.


----------



## Geo (Oct 2, 2011)

seanengman said:


> Harold-V
> 
> Funny I just read your post as prior my friend and I were discussing building a small ball mill or something of that nature.
> 
> ...


why not use sodium metabisulfite to precipitate gold. ferrous sulfate will precipitate gold but i dont use it, though i may try it later to see how it works. as for flux Borax works good. i use twenty mule team borax. ive never heard of hcl precipitating gold, it will precipitate silver from solution but i recommend that you not use it for that purpose as it produces silver chloride (then you will need the lye to convert to elemental silver).Borax is used when melting gold to form buttons or making bars, as for fluxing to seperate metal from slag not sure that will work so well. i have heard old miners talk about using flour as a flux, not sure how it would work as ive never tried it.


----------



## Harold_V (Oct 2, 2011)

seanengman said:


> What is the best acid to use to precipitate the gold out of solution? I have read both muriatic (HCl) and lye (NaOH).


Many substances will precipitate gold--even acetylene gas. However, the idea in precipitating is generally to use something that is selective, so ONLY gold is precipitated. HCl isn't a precipitant of gold-----so that's not an option. I liked to use SO2 gas, from a cylinder, and did so until I retired. I also used ferrous sulfate and was satisfied with the achieved results. Stopped using it only because it wasn't as convenient as SO2, and because it required larger vessels for use due to the added water in pre-dissolving the crystals. Not a problem for small lots, by the way. 

As for the use of lye, I'd rule that out. When you shift a solution from acidic to basic, anything in solution will precipitate, so the selective precipitation so highly desired (for refining) is lost. There has been some talk of tightly controlling pH, so you retain selectivity----but I see no real benefit in fighting with something that can be so easily accomplished by other means. 

Read Hoke. She will teach you all you need to know. 



> when I go to smelt my AuI2 what should I use as a flux?


The proper term is melt, not smelt. Smelting refers to the extraction of values from ores. 

As has already been suggested, borax is the flux of choice for melting gold. However, you will come to understand that using it carelessly can be a disadvantage. When melting gold powder, you are far better served to do so in a seasoned melting dish (you are highly unlikely to need a crucible unless you handle large volumes). 

Pour your gold powder to the dish without adding any borax. The dish should have already been preheated and coated with a thin film of borax. Heat the powder carefully, to avoid loss by turbulence, then, as it skins over, you can pour on more heat. Do NOT mix the powder with borax, as that creates miniscule prills that may not agglomerate, so you lose some of the values to the resulting slag. Once the entire lot is molten, it does no harm to sprinkle a little borax on, to help absorb oxides. 

Key to good melting is to produce pure gold. it needs no flux at all. If, after melting, you find the slag in the dish discolored anything beyond purple or pink, your gold was not pure. 

Harold


----------



## Reno Chris (Oct 2, 2011)

> The black sands contain gold and platinum. It is what I have left over from cleaning up my dredge and all of my supplies are free or cost me next to nothing, plus the learning experience makes it all worth it.



There is a reason I recommend gravity first (its the same reason its done that way commercially) - visible sized particles of gold and platinum react very slowly and may take days or even weeks to react and dissolve unless you are using very strong leach solutions. Get what you can by using a blue bowl or careful panning (depending on how much you have). Then have an assay done to see if anything worthwhile is left. Its a waste of time to leach 50 pounds of black sand if the best you might do is recover 1/1000 th of a gram of gold. 

Many guys figure they will get lots more by leaching - but leaching is not 100% efficient and you may well recover more gold by gravity methods. I've been doing this for more than 30 years - I am not trying to lead you the wrong way.

Chris


----------

