Stamp Mills Merc vs Cyanide use

[ratled]

Looking for a little mining history but when did cyanide take over for Merc in the stamp mill process?

TIA
ratled

 

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[arizau]

Mercury was used to recover tiny raw gold particles that were not otherwise gravity concentrated from ground ore and cyanide in a leaching process to liberate microscopic gold that cannot be gravity separated is what I recall.

 

[Clay Diggins]

Depends on the ore as to which is best used ratled. I don't know of any effective direct stamp mill cyanide treatments ever being used commercially. Mercury amalgamation is commonly used just past the stamp mill in the grind amalgamation cup or on slick plates

Free milling ore with mercury amalgamation is cheaper and easier than cyanide. If the ore has sulfides mercury won't work. If the ores have silver or several other minerals cyanide won't be effective.

For processing those deposits with sulfides the cyanidation process was discovered around 1887. It didn't take long for mines with ores that needed cyanide treatment to begin using it. The Forrest Process was in popular use by 1890.

Cyanidation became the dominant process because all those worked out free milling orogenic deposits could be worked again in their sulfide ores at depth. Not because it was any more effective at treating free milling gold ores but because the deeper sulfide bound gold ores couldn't be processed effectively with mercury. Some old tailings became valuable too.

Free milling gold ores as well as silver and copper tend to slow the cyanide process down to where it's not very effective. Often the situation is much more complex than a simple cyanide treatment. Pretreatments are often necessary to prepare the milled ore for the cyanide beds.

Heavy Pans

 

[arizau]

Depends on the ore as to which is best used ratled. I don't know of any effective direct stamp mill cyanide treatments ever being used commercially. Mercury amalgamation is commonly used just past the stamp mill in the grind amalgamation cup or on slick plates

Free milling ore with mercury amalgamation is cheaper and easier than cyanide. If the ore has sulfides mercury won't work. If the ores have silver or several other minerals cyanide won't be effective.

For processing those deposits with sulfides the cyanidation process was discovered around 1887. It didn't take long for mines with ores that needed cyanide treatment to begin using it. The Forrest Process was in popular use by 1890.

Cyanidation became the dominant process because all those worked out free milling orogenic deposits could be worked again in their sulfide ores at depth. Not because it was any more effective at treating free milling gold ores but because the deeper sulfide bound gold ores couldn't be processed effectively with mercury. Some old tailings became valuable too.

Free milling gold ores as well as silver and copper tend to slow the cyanide process down to where it's not very effective. Often the situation is much more complex than a simple cyanide treatment. Pretreatments are often necessary to prepare the milled ore for the cyanide beds.

Heavy Pans

I haven't really studied the circuit beyond the stamp mill but I suspect there must have been scalping screens or whatever to divert the larger gold, etc. to a gravity circuit while the fines were directed to the mercury circuit. Is that correct? I have a piece of gold, about 1/4 oz, from a stamp mill and it is clean of mercury so I don't think it went over the tables or whatever.

 

[Clay Diggins]

On a slick plate setup there is normal gravity separation from the stamp output to the slick plate at the end of the sluice. Sometimes a plate diverter or screened undertow box were added depending on how the ore mills.

On a grind amalgamator (the most common modern setup) the stamp product is reground and introduced back into the slurry in the amalgamating "cup" or barrel so there is no need to use gravity separation.

Each stamp mill is set up for the ore being run. They are truly custom installations by the time they are tuned for the ore. No two stamp mills can be the same if they are going to be effective recovery machines.

Heavy Pans

 

[KevinInColorado]

You can still tour through the Argo gold mill in Idaho Springs CO and see all of this. They processed material from a number of different mines on a contract basis so they have a variety of gear to handle the various types of ore. Very worth taking time to see!

 

[russau]

Kevin ,been there , done that back in 2006 at the "Rocky Mountain Miners Rally" I was in the Dredge Earth First tent giving out FREE chances for a gold nugget. It was a good time! some people wouldn't take the free ticket! But a FREE gold nugget was given away on Friday , Saturday , Sunday at three oclock! there was even a Washington Fish and wildlife officer there for the 3 days! EVERYONE liked her for comeing!!

 

[Hoser John]

Sulfides,sulfites and such complexing agents mandated different procedures. Even floatation was utilized on a massive scale at the American Flats op near Virginia City Nevada for a particular ore body recovery-John

 

[goldenIrishman]

Yet another case of having to let the conditions at your location dictate what equipment is needed to get the job done. Stamp milling (or crushing of any type) isn't all that different from any other crushing operation. You're making the big stuff smaller. It's the makeup of the ore that will determine what is needed next in the processing to recover the gold.