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Author Topic: Water Column Separators  (Read 18757 times)

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Offline GollyMrScience

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Re: Water Column Separators
« Reply #20 on: September 07, 2010, 07:37:08 AM »
Yes Walter (Lashley) and I spent may an hour on the phone discussing things like the e-towers.
There was some discussion about the tower within a tower idea. Using the drag of the water against the sides of the tower to advantage. In the end though it was becoming more work than it was worth.
The incline plate clarifier that I mentioned uses that drag to advantage but to get specific gravity seperation on gold and black sand it would be a pain to get it balanced.
As Nugget suggests a vibrating table on the high side and a Miller to the low side.
All a balancing act of economy over convienience all underpinned with the understanding that one should not spend an ounce of gold to get half an ounce.
For a primary concentrator on the high side would be centrifuges - low side sandard sluice. In the upper high side Jigs and on the upper low side a rocker like the type that Chuck is developing.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline Traveller

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Re: Water Column Separators
« Reply #21 on: September 07, 2010, 11:02:39 AM »
Hello MrScience
Thank you again for your reply.
Your post led me to a site showing an Australian machine called the Reflux Classifier. It appears to be an e-tower with the addition of the lamella plates you mentioned. Although a very intriguing concept, it seems any production plans they have are for machines capable of many tonnes/ hour; hardly the portable small scale unit I had in mind. I did, however, e-mail the company regarding the possibility of them making a portable unit. I will share any reply I receive with this forum.
I should share a bit more info regarding the placer I am pursuing. As I stated earlier, it is a beach placer deposited by the violent Pacific storms we receive here in the winter months.  Often, lenses 25 cm. thick and 6 metres wide will be deposited for many miles of beach. The beach in question, though, is very remote and accessible only by quad, foot or horseback.
Back when Au assays only cost $10, I had two assays done on samples taken 150 metres apart on the beach. One came back with no Au values at all in it and the other came back at .32 oz. Au/ton. Given that this sample was taken from the upper side of the lens and was mostly magnetite (next down being hematite (purple) and the lower part of the lens was garnet (red)), it can be assumed that the specific gravity of that sample was well over 5. This would mean that, if there were .32 oz. Au/ton, a cubic metre of this material would have easily over 1.5 oz. Au. It would also, sadly, weigh in the neighbourhood of 5-6,000 kg. and would break the back of any animal or machine attempting to haul any sizeable amount of blacksand out over the rough beach.
For this reason, plus the facts that placer claims are not allowed on this material (any work is restricted to recreational mining involving only hand tools) and the difficulty of separating the very fine gold, there has been little success in recovering gold from this placer over the years. Mercury is frowned upon and is actually quite useless in a salt environment due to rapid oxidation of both the mercury and impurities in the gold.
Quite recently, I had a revelation which may change everything here. Remember how I said the one assay came back with no values for Au at all? I was puzzled by this as there was no physical difference between the two sample sites. I asked a few people here, who were supposedly in the know, what became of the gold and was told it had been washed out of the placer by the waves of the following tide. It seemed to make sense at the time but, the more research I did, the less sense it made. It was only after reading an article by a beach miner in Oregon that the real reason for no gold in the black sand became apparent. In his words, one had to "sneak up on a beach placer" as the wet environment, the high s.p. of gold and the flaky nature of beach gold all made it very easy for merely the vibration from one's footsteps to cause the gold to slip downwards below the lens of black sand.
This may seem like a bad thing but there is more to it. There is a layer of hardpan (marine clay) only a few feet below the surface of the beach. As these deposits seem to always occur on an eroding section of beach, the toe of the sand and gravel beach always has a flat section of clay protruding from the toe of the beach.
So, I think one could assume that each incoming wave during a storm may make any gold from previous waves sink down through black sand and gravel to the clay. Assuming there to be several thousand waves during a storm, this could equate to a sizeable deposit on the hardpan of fine gold from just one storm. Each winter, there are a few dozen of these storms. Also, by my calculations, in one area it has taken roughly twenty years for enough erosion to take place to transform what was the high tide mark into the toe of the beach. Therefore, multiply the few dozen storms by twenty and the possible value of the upper hardpan layer (under the toe of the beach) could be, quite literally, staggering. Who knows, a metre by metre by 3 mm thick section of hardpan may be loaded with gold.
Armed with this knowledge, I am now forced to await the arrival of a couple of good winter storms, likely in October, to re-deposit the black sand lenses which are mostly lost during the summer months. This will, of course, identify areas where it will be most likely that there are deposits on the hardpan. I will ride in on horseback and procure a sample for assaying.
One other thing I didn't mention about this placer. Everything in the black sand will pass through a 100 mesh screen and a goodly portion of it will pass through a 150 mesh screen. I don't know how this would affect the particle size of flakey gold but I would assume it would have to be even smaller.
Regards
Bob
"He was always cold, but the land of gold seemed to hold him like a spell.......Though he'd often say, in his homely way, that he'd "sooner live in Hell"......"
~~Robert W. Service~~

"When you live next to the graveyard, you can't cry for every funeral."   -  Russian Proverb

 


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