How do I refine "Hi Sulphide Ore"?

[Paige]

I bought some ore, stated to be high sulphide. It warns that you must first smelt it.

Can one of our experts give me some help on how to refine this ore?

Thank you.

Paige

 

[lazersteve]

Paige,

I'm no expert on refining ore, but the idea behind heating is to drive off the sulfur before processing. I have a prospecting book at the house that has some testing procedures for sulfide gold ores. I'll post some realitive information when I get home here in a few hours.

Steve

 

[Paige]

Thank you, Lazersteve.

Paige

 

[lazersteve]

Paige here's what the book says:

Sulfide ores must first be roasted. Pulverize the ore and place it in an oven, campfire, or hot coals for about an hour, or roast out the sulfides with a blowtorch or blowpipe. Then place the ore in a glass container and cover it with nitric acid until all reaction ceases. Gold will not react with the nitric as will pyrite, silver, and most other impurities. When cool, flush or rinse the solution with clear water then pour off all of the liquid. Any gold present will appear as fine black powder, which can then be placed on a charcoal block and flushed into a yellow globule of gold with the reducing flame or the blowpipe. This button will flatten if hammered.

A few comments on the above quote:

1. Read this (click link) MSDS for Gold Sulfide before starting! Gold Sulfide MSDS
   
2. The sulfides are gone when the sample no longer gives off sulfur smelling gas. Gold(I) Sulfide (Au2S) decomposes at 240 C. Gold(III) Sulfide (Au2S3) decomposes at a mere 200 C.
   
3. When performing the nitric step, I would add an equal amount of distilled water to the mix before adding the nitric acid.
   
4. Save what you pour off as it will likely contain silver.
   
5. Redissolve the black powder and then drop with SMB BEFORE melting into a button.

Steve

 

[Harold_V]

Having worked with a gold complex ore (sulfide/telluride mix), I recommend you don't get involved unless you have but a small sample. If you have pounds of the stuff, you'll work yourself to death, and create problems best left uncreated. Roasting to remove sulfides (I've done that, too!) will bring the SO2 cops in a heartbeat. I don't think you can begin to understand the amount of smoke and stink you'll generate if you run any volume.

I can think of no way you can perform these duties without extensive air scrubbing. Smelters that handle such ores used to have smoke stacks that reached over 400' in the air to discharge the pollutants (I grew up in a smelter town like that), which did nothing more than to spread the SO2 all the further. Such smelters were pretty much gone from the scene by the early 70's, with those that remained forced to take steps to reduce the SO2 they discharged. One of them, Kennecott Copper, in Utah, installed an H2SO4 plant, converting the SO2 to acid for market. Prior to their acid plant, the Oquirrh Mountain range, on which they are located, was barren of plant life for a huge distance---a few miles, all dead from the SO2. Since the acid plant was installed, there has been an effort to re-vegetate the mountain. I've been gone from Utah for 11 years now, and have no idea of the outcome.

Harold

 

[Paige]

I got about 2 ounces off of eBay.

Paige

 

[Harold_V]

Any idea of the content? The stuff I worked with (sulfide/telluride) assayed over 300 ounces/ton gold. I still have the assays from those fun days!

Yeah-----it really did! Over 300 ounces!

They are actively mining ores that yield as low as .10 ounce/ton------to put this in perspective. I recovered what I recall to be over 20 ounces of gold from 4 partially filled 5 gallon buckets. Ran this stuff a long time ago, prior to '83.

The material in question was not roasted, that is a whole different mess I got involved in, one that was a loser. The high grade I speak of was crushed, run in a ball mill, then an agitation tank in cyanide and bromine.

The two ounce sample you speak of will be a fun learning experience without creating a huge nightmare. I say go for it-----unless the sample means more to you than the values contained within. If the gold isn't visible, you might be very disappointed in that there will be so little that it won't be worth running. Please do remember, iron pyrite is often passed off as gold to unsuspecting people. While gold can be found in the crystal structure of pyrite (see Sir T.K. Rose, The Metallurgy of Gold), it's not exactly common.

I still have several really nice samples of the high grade ore I ran, some of them slabs cut from the rock before it was crushed. The gold is quite evident. The guy for whom I ran the material was a rock hound and appreciated nice samples. If I can find the time, I'll try to post some pictures of natural nuggets and really pretty gold ores.

Harold

 

[lazersteve]

iron pyrite is often passed off as gold to unsuspecting people.

Also known as Fools Gold.