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Colorado Prospector - Gem and mineral prospecting and mining forums _ Prospectors and Rockhounding Field Work _ Recovery of fine gold

Posted by: gold_tutor Nov 30 2003, 11:34 PM

ME CO: Sorry the enlarged combo image is a little grainy below, but enlarging small .jpgs often does that. I added the labels to help explain the photos. You spoke of not seeing where the smaller view showed "vented." I think enlarging will help.

Venting aka off-gassing IS the problem in a nutshell that I have with all retorts.

As we were all taught in school, all matter exists as solids, liquids, or gasses.

To go back and pick up my earlier "cake-mix combo" allegory regarding how to physically separate Hg (mercury) from Au (gold), retorting takes advantage of the different physical properties addition or removal of heat from the two metals employs.

In the case of our "cake mix" analogy, the physical VISUAL characteristics of flour and sugar particles were all that were required in order to physically separate those to "unalloyed organic particles." IN the case of amalgam, separating the dissimilar particles using visual differences isn't so easy. Go back and review the string of amalgam in my earlier post...the gold isn't even visible as yellow particles anymore. EVERY particle is completely covered with slimy, liquid state Hg.

So,
because Hg turns to a gaseous state in the 72-ish Degree Farenheit temp range-- yes basically room temperature--it takes VERY LITTLE heat to turn the whole of the Hg liquid into a total gas and "off-gas" it, leaving behind the now separated and "cleaned up" gold particles in their coveted glory.

Checking the boiling point of the two metals, Hg and Au, one sees why this temp differential is a handy physically property variance, and so usable to miners.

In the old days, a shovel would be left in the coals of the campfire, with amalgamated gold in it. In the morning, the mercury would be vaporized and the
gold removed and tucked safely into the pouch. Of course, one had to sleep up wind and with one eye open all night long to make sure the other campfire mateys were asleep instead of messing with your shovel

Also, gassified mercury isn't visible to the visiting F/S or BLM ranger when one uses the shovel method. However, as our Kalamath River friend, Dave McCracken of the Old 49ers club in No. California learned, a miner's life can be made a living hell from just one tiny shiny globuble visible if F/S or BLM wishes to get nasty with you. And there is no way to prove, or at least Dave wasn't permitted to prove the high probability the mercury he was charged with illegally possessing was native leached cinnebar sourced mercury. It is NOT above the planted lynx hair F/S types to taint the evidence, aka plant mercury either, so be careful out there.

AND THEN there is the whole state by state legality issue. I've been told at GPAA gold shows where I've been an exhibitor that the great state of Wisconsin has totally outlawed even the possession of Hg by miners within their state. Can't buy it, can't sell it, can't possess it.

Back to shovel off-gassing...
Nowadays, shovel off-gassing is frowned on for obvious reasons; which discourages the discharge of the gasified Hg into the atmosphere. Also, because Hg off-gasses at such a low "room temp," many believe storing Hg--covered by water--prevents all gasification. That is simply NOT borne out by science, but it is still a commonly held belief. Don't get me wrong--Water helps to a limited extent.

I personally have handled formerly cleaned mercury that is over 15 years old. It was securely lidded. It even had a small layer of water on top of the Hg.

BUT, on top of the water atop the mercury, were DRIED mercury particles, which are extremely dangerous to disturb and breathe. So, be careful!!

As I promised earlier, tho'...
MY primary difficulty with supporting use of a retort is this: gasified Hg is breathable Hg, and that is deadly, as in used to be deadly in the gold rush days and is still deadly to this new millenium day.

The feature on all retorts, aka the "part" that supposedly prevents gasified Hg from escaping is the close tolerance of screwed metal base to screwed metal cap of the heated reservoir that contains the amalgam. Most retorts I've seen are VERY poorly machined and "close tolerance" is simply an advertising gimmick.

The close tolerance of a tightly screwed shut retort resevoir is supposedly enhanced by a employing a gasket of some type between threaded screw cap female part, and the threaded male resevoir part. It is my observation that subjecting that gasket to heated metal expansion and the dissimilar expansion properties of the gasket material leads to escaping deadly fumes, which can still pose a real off-gassing problem with deadly consequences to"man and beast!"

I also submit further, that those who make and sell retorts seldom- IF EVER- instruct the purchaser in what type of replacement gasket material is suitable, where to find it and how an "ordinary Joe/Suzy Miner" is supposed to cut said gasket material even IF it was offered in the prospector outfitters' stores. Most hobbyists are loathe to physically handle Hg, let alone remove and handle a busted gasket between reservoir and cap!

I've seen many a miner wrap his metal resevoir "seam between cap and reservoir" in bandanas, wetted rags, or just about anything else they can grab in an effort to slow this off gassing under heat. I remain unconvinced of the efficiency or safety of ANY retort method.

I've seen a lot of guys NOT make an effort to condense aka drop out the gasified Hg into an awaiting container below the cooling tube, but just let the gasified Hg escape into the air and think nothing of it or make jokes about it.

I personally practice what is called "substitute reaction" Hg/Au amalgam separation and reclaimation of my gold values claudminer@aol.com taught me years ago by Claud, so I am a loyal user of that method. He didn't invent anything new, he just taught me how to do it differently and safely, and I like it well enough to continue, that's all.

That completes my efforts to describe why I don't like retorts, but why retorts are used.

 

Posted by: gold_tutor Dec 3 2003, 11:22 PM

In the "vein" of recovery of fine gold, a nifty build it yourself if ya'wanna lightweight sluice for catching those fines showed up on another forum in the last few days.

I'll post the pictures of it as it was presented, and then I'll post my idea of a modification.

This separation method takes into account the physical property of differential specific gravity of particles being sorted in this manner.

 

Posted by: gold_tutor Dec 3 2003, 11:35 PM

Graphic enlargement of the rain gutter sluice with endcap modification and water manifold.

I'd remove the (green) quick connect, and place a sturdy PVC ball valve inline just after the 90 elbow and prior to placing the garden hose quick connect on "plumbing circuit."

PVC ball valve keeps the clean line of the original designer of this sluice. Also, the PVC ball valve gives more tweak increments and longer service than the cheaper garden department "Y" double ball valve will provide...in my opinion.

I've also seen water manifolds with the backside (toward the endcap, removed, which would give a more uniform waterflow.

I don't ever like my full out pump output dictating water flow when I'm working with fines in a setup like is pictured here.

 

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