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Wis49er
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Gravity concentrator versus Wave table ( 15:12:53 TueJul 11 2017 )

I have a hardrock claim and the majority of the gold is smaller than the holes in a 100 mesh screen. I've read a few opinions on line whether gravity or wave tables are better. I'm hoping the knowledgeable people here can give me their experiences on the two types of recovery.

  
micropedes1
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Re: Gravity concentrator versus Wave table ( 18:00:25 TueJul 11 2017 )

If you know that all if your gold is 200 mesh, then you should go with the gravity separation advantages of a good bowl. The only difficulty is reducing the volume of material to an amount that the bowl can handle.

  
911Metallurgy
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Re: Gravity concentrator versus Wave table ( 17:03:17 SunAug 6 2017 )

What tonnage/volume are you trying to process?

The topic of Fine Gold Recovery is very illusive but 100 mesh is not what I call fine gold.

Give me a call if you want to discuss what's best for your specific gold recovery system.




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geowizard
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Re: Gravity concentrator versus Wave table ( 16:00:21 TueAug 8 2017 )

I'm looking at a potential hard rock operation.

The ICON I-150 meets a need that I may have in the near future. I sent a request for pricing.

- Geowizard


  
911Metallurgy
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Re: Gravity concentrator versus Wave table ( 13:50:47 SunAug 20 2017 )

Hi, for Falcon iCon 150 price please see one of the gold concentrator for sale I have.
[2 edits; Last edit by 911Metallurgy at 00:04:56 Mon Aug 21 2017]



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Jim_Alaska
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Re: Gravity concentrator versus Wave table ( 23:10:06 SunAug 20 2017 )

Quote: geowizard at 16:00:21 Tue Aug 8 2017

I'm looking at a potential hard rock operation.

The ICON I-150 meets a need that I may have in the near future. I sent a request for pricing.

- Geowizard



I used one at hard rock mine a few years ago. never got to see how well it could work because the mine owner wouldn't stop over feeding it.

I tried everything I could to get him to understand that the object of mining is gold recovery, not just to see how much material he could put through the system in the shortest amount of time.

Frustrating when you know there is good gold there but the guy in charge both doesn't know much about gold recovery and won't listen to anyone that does. :eeekyellow:



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geowizard
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Re: Gravity concentrator versus Wave table ( 02:06:08 MonAug 21 2017 )

Jim,

I'm trying to determine if this is a "finishing system" or primary recovery system that takes milled feed.

The feed is specified at 2 mm = less than a tenth of an inch or about 10 mesh feed.

I note the $20K system with vibrating screen and oversize to sluice with minus 2 mm going to the icon bowl.

This might be a good cleanup system. (it's a batch mode system).

- Geowizard

  
911Metallurgy
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Re: Gravity concentrator versus Wave table ( 02:47:34 MonAug 21 2017 )

Hi GeoW,

this is a primary recovery. The iCon itself is fit for -2mm. The sluice will take the oversize; in an alluvial setting.

For hardrock, you'd have a rod mill (or grate discharge ball mill) after a crusher but before the iCon.
You'd use a screw/spiral classifier between the rod mill and the iCon. Target 200 mesh grind into the iCon to get all the possible GRG gravity recoverable gold.

You clean the iConc gold concentrate with and RP4 Gold Shaker Table as you would a sluice concentrate.
[1 edits; Last edit by 911Metallurgy at 02:49:33 Mon Aug 21 2017]



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geowizard
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Re: Gravity concentrator versus Wave table ( 14:34:20 MonAug 21 2017 )

David,

That's kind of what I expected.

In an alluvial setting, there is reasonably $12 GOLD. That's $12 USD per cubic yard. GOLD could be nuggets on down to micron or smaller.

Sluice cons in a preferred setting are screened to a desired size - usually one inch (25mm) or less.

The feed to the icon screen in this case is 25 mm and smaller

Considering $12 per cubic yard and given the weight of one cubic yard being nearly two tons, after screening off the 1" plus, the feed to the icon screen will be about 50 percent of the input feed.

Given the above information, a system could be fed four cubic yards of placer material per hour. The four cubic yards are screened and the icon screen receives 50 percent = about four tons per hour. About half of that = two tons per hour goes through the bowl and the other half = greater than 2 mm goes over the sluice.

At the rate of four cubic yards per hour (Input), it will take 25 hours to process 100 cubic yards = $1200 USD. in GOLD at 100 percent recovery.

There remains the probability that the Icon will recover additional small GOLD that the prior production missed.

Placer GOLD mining is not a PURE science. Unfortunately, the value in GOLD changes with every cubic yard and the amount (volume) as a percent of over-size changes with every cubic yard. A system would need to be put on line and ran for a sufficient amount of time to measure the recovery and compare with prior production.

- Geowizard

  
geowizard
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Re: Gravity concentrator versus Wave table ( 14:44:54 MonAug 21 2017 )

Volume is a factor;

In a system as described above, the recovery of $1200 USD per 25 hours results in a gross revenue of $48. per hour.

The objective in placer mining on a for-profit scenario is to process a sufficient VOLUME of material.

The system cannot be over-loaded. As Jim pointed out, there has to be control over the rate of feed at the input.

The process has to be designed to meet the VOLUME of feed required to meet the demands of economic profitability.

- Geowizard
[1 edits; Last edit by geowizard at 15:44:32 Mon Aug 21 2017]

  
geowizard
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Re: Gravity concentrator versus Wave table ( 17:00:33 MonAug 21 2017 )

Cleanup;

The conventional sluice box generates a concentrate that goes to a cleanup process. Cleanup frequently is done with a shaker table like the RP-4.

The Icon requires cleanup using the same process.

Centrifugal recovery is understood to have an advantage in the recovery of very fine GOLD. From an investment standpoint, there has to be confidence that the Icon provides a pay-off in recovering GOLD that would be lost.

- Geowizard


  
geowizard
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Re: Gravity concentrator versus Wave table ( 17:16:03 MonAug 21 2017 )

What will work;

It doesn't look like an Icon bowl will handle the front end of a commercial placer mining operation based on the above discussion.

Because of that, a placer miner has to review the other options. The original option is a conventional screen and sluice or grizzly with trommel and sluice.

The RISK involved is the LOSS of very fine GOLD.

Fine GOLD can escape recovery in a sluice. Most operators check their tailings as they exit the end of the sluice - looking for GOLD that is NOT being recovered. Is there a potential falicy in this method?

An operator holds his pan or a bucket under the spillway at the end of the sluice and recovers a representative sample of the material that has gone through the sluice.

Usually, there is NO additional screening to get particle sizes down to 20 mesh or smaller. The "check pan" is given a quick check for values and tossed aside.

- Geowizard
[1 edits; Last edit by geowizard at 17:17:22 Mon Aug 21 2017]

  
911Metallurgy
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Re: Gravity concentrator versus Wave table ( 22:20:13 MonAug 21 2017 )

the iCon will only take -2mm. otherwise, you will plug up the cone.
the solution you pick is often capital cost dependent.

This Highbanker Sluice is an interesting alternative for it is effectively 15 feet long and does allow you for a coarse feed. Have a look and watch the video.

As far as sampling the sluice tails; yes. You take a sample of 25 lbs of solids and send it out for a Falcon/Knelson test (i do those) and see how much gold is left (and recoverable) in the sluice tailings. Based on that you can run your economics and decide on the iCon purchase.
[1 edits; Last edit by 911Metallurgy at 22:22:17 Mon Aug 21 2017]



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geowizard
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Re: Gravity concentrator versus Wave table ( 13:21:43 TueAug 22 2017 )

David,

Yes, the GMS-200 is interesting.

The video on the GMS website shows one of these in operation. It has a feed hopper and conveyor feeding a large trommel. The screened ouput of the trommel reports to another feed conveyor. The second feed conveyor feeds the GMS-200.

When I acquired the assets at Ophir, one of the artifacts was a GMS-200. It was in good condition but missing the upper deck. The upper deck had been removed - probably to make a sluice box.

Two seasons ago, I sold the GMS-200 to a friend. He talked with the Manufacturer and negotiated on a top box. Then he had the box freighted to Alaska. The box was flown out to Ophir with a load of materials including pumps and a power plant. By the end of the season it was operational and one ounce of GOLD was recovered.

I run two - eight foot sluice boxes in series with a drop of two inches per foot. The total drop is 2 x 16 = 32 inches.

The GMS-200 requires a reach of about six feet. The new design has a two inch per foot drop on the top box - maybe more. The reach approaches seven feet with the highbanker on support blocks . Without a feed hopper and conveyor, lifting a half of a cubic yard - over 1000 pounds of feed to a height of seven feet on uneven ground is a challenge.

The important thing to keep in mind is that the feed includes moss and broken willows not to mention tree limbs and roots.

Fun stuff!

- Geowizard
[1 edits; Last edit by geowizard at 13:49:49 Tue Aug 22 2017]

  
geowizard
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Re: Gravity concentrator versus Wave table ( 14:45:18 TueAug 22 2017 )

A 25 pound sample;

Having ran many thousands of cubic yards of placer gravels through a wash plant, I have been able to make a few observations that I would like to share.

On a good day, the placer gravels will contain $12.00 (USD) in GOLD per cubic yard. That works out to .01 Troy ounces = 311 milligrams of GOLD going into the box. Twenty five pounds of front end feed represents 25 / 2000 of a cubic yard assuming a cubic yard weighs about 2000 pounds. The GOLD contained in a 25 pound sample of front end feed in this case weighs about 3.9 milligrams. The output of the Icon still needs to be cleaned by running over a wave table.

The Icon cannot be used on the front end of a placer GOLD mining operation as per the discussion above. The capacity is not sufficient to handle the VOLUME of material entering the process.

So it is understood that the Icon is a fine gold recovery machine that would fit into the process at the end of a sluice. The objective being to recover fine gold that has escaped the sluice. A sluice in very rough terms will recover 90 percent of the gold that enters the box.

A 25 pound sample of tailings from the sluice would represent 10 percent of 4 milligrams or about 400 micrograms of GOLD in the sample.

That's not very much gold to run over a wave table.

- Geowizard

  
911Metallurgy
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Re: Gravity concentrator versus Wave table ( 18:17:51 TueAug 22 2017 )

there is no wave table involve in the lab test.

just the Falcon

the conc is weight is measure and the whole thing goes to assay.



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geowizard
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Re: Gravity concentrator versus Wave table ( 19:17:35 TueAug 22 2017 )

That's where it gets dicey.

Placer miners may not have a smelter handy.

A smelter or fire assay return would show metallurgically bound gold in sulfides that a placer miner would NOT recover on a wave table.

There's probably a very short list of placer GOLD miners that digest concentrates chemically to recover fine gold.

It makes the Icon recovery "optimistic".

- Geowizard
[1 edits; Last edit by geowizard at 19:18:39 Tue Aug 22 2017]

  
911Metallurgy
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Re: Gravity concentrator versus Wave table ( 23:40:46 TueAug 22 2017 )

you dont need 'a smelter'.
sulphides or not, if it recovers in an iCon = it is gravity recoverable gold.

you can sell all gold concentrates directly to a trader without any further processing if it contains around 3 oz/ton.

96% payable
$300/ton treatment charge
the smelter will pay you gold spot - minus as much as $20 per once.

otherwise, table the concentrate for any upgrade and melt or sell what is clean.

there is no "optimistic" recovery. in any case, a gravity concentrator test is just to tell you if your sluice is leaving good gold behind. gold that is too fine for the sluice but OK for an iCon for example.

you dont know until you test. counting it out before the start is a great way to leave money behind.
[1 edits; Last edit by 911Metallurgy at 23:41:13 Tue Aug 22 2017]



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geowizard
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Re: Gravity concentrator versus Wave table ( 13:37:51 WedAug 23 2017 )

David,

Thanks for the outstanding information.

Conventional sluices have been proven to do a good job of concentration. The question that remains is whether an added level of concentration is warranted.

The benefit of adding an additional step to the process comes at a cost. Obviously, there is a cost of around $7K to $20K for the Icon. The additional cost is the cost of additional pumps and power supply to support the Icon. Material handling comes at an additional cost if conveyors are added to the circuit.

The benefit is upgrading the concentrate and potentially capturing the very fine GOLD that might be lost.

HERE's the problem as I see it;

The Icon is Not the finishing step in the process. Gold recovered from the Icon requires additional cleanup with a wave table. The wave table requires TUNING for very fine GOLD. The output from the Icon will be a concentrate of 2 mm gold on down to whatever micron GOLD there is to be recovered. The process of cleaning GOLD with a range of sizes from 2 mm on down to micron is where the losses occur. Very fine GOLD can be lost AFTER it goes through the Icon and runs off of the wave table. I have video of the RP4 wave table running with very fine gold going down the tube with the reject. The reject requires re-screening and running over a second wave table (RP4) that is tuned for very fine gold.

- Geowizard
[1 edits; Last edit by geowizard at 13:39:06 Wed Aug 23 2017]

  
911Metallurgy
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Re: Gravity concentrator versus Wave table ( 15:31:18 WedAug 23 2017 )

This is why you do a $1000 gravity concentrator test before you go buying heavy equipment.
you get test results and numbers to do math with.

YOU DON'T KNOW UNTIL YOU TEST.

If you picked up the gold in the iCon and run your RP4 properly, you will have a gold concentrate/middling/tailing from which you do further math.

Example:
The gravity concentrator test gives you 50% recovery on your sluice tails. The RP4 gives you 90% recovery.

50 x 90 = 45% overall net.

It all depends.
Those who do not test may go broke for buying gear to process unrecoverable gold.
Those with assumptions and suspicions with not test and not buy either but may leave unmeasured gold behind.

a iCon uses 1500 watts with its 2 HP motor. if you pay say 20 cents/kWhr for electricity you will burn 30 cents/hr of energy.

Anyways, I am done with this one. All I was trying to say is test before you buy. Don't assume, don't hope, just test and do grade 12 mathematics.

David

  
growler
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Re: Gravity concentrator versus Wave table ( 15:36:49 WedAug 23 2017 )

A Neffco centrifuge is a good "front end" concentrator. Think they cost around $5k. Jim

  
911Metallurgy
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Re: Gravity concentrator versus Wave table ( 17:29:59 WedAug 23 2017 )

Not all "centrifuges" are created equal.
Verify how many Gs it pulls: how many times stronger than the natural force of gravity does the machine generate.

A Neffco http://www.americangoldminer.com/index.php/neffco-centrifuge-bowl at $6000 does .... very few Gs

and iCon i150 generates 150X or 150G and sells for $7500

G calculator http://www.artificial-gravity.com/sw/SpinCalc/
[1 edits; Last edit by 911Metallurgy at 17:38:40 Wed Aug 23 2017]



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geowizard
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Re: Gravity concentrator versus Wave table ( 18:07:29 WedAug 23 2017 )

David,

Your expert advice is appreciated as always.

Having spent most of my career as a Test Engineer, I agree with the importance of testing. It's good advice to recommend testing before making an investment in recovery equipment.

Placer GOLD mining when done on a commercial level introduces all of the expected checks and balances. Someone is in the position of having investment in the form of cash and other resources. The investor has responsibility for getting a return. That is all a matter of writing checks and receiving checks. A smart investor looks at the process, the people and the plan.

The math is easy to understand.

The process has an input and an output. GOLD enters input of the process at a given value. If the GOLD is typical Yukon or Alaska placer GOLD, the value might run on the order of $12 per cubic yard. In my specific application, that is the case.

Feeding a wash plant at a rate of 20 cubic yards per hour is a moderate rate of INPUT. After five hours, it is reasonable to expect that an ounce of GOLD is in the sluice box. After 50 hours, maybe 10 ounces of GOLD in the sluice box.

I clean out the sluice and put the contents into four - 5 gallon plastic buckets. They're not full - let's say half full.

Do the math;

The INPUT was 20 cubic yards per hour x 50 hours = 1000 cubic yards.

The OUTPUT is 10 gallons of concentrate = .05 cubic yard. The value went from $12 per cubic yard to $12000 per .05 cubic yard. The concentration is x 20000 on the GOLD.

Cleanup;

The GOLD concentrate needs further processing. At this point a decision is made to use an Icon concentrator.

1. The concentrate requires screening to 12 mesh (approximately 2 mm). This leaves the oversize for manual processing on another circuit.

About 50 percent (the screened material) reports to the Icon.

The Icon concentrator can be expected to reduce the 5 gallon bucket of concentrate to less than a couple of kilograms of concentrate.

The OUTPUT of the Icon must be further refined using a wave table.

The RP-4 Wave table receives the 2mm minus concentrate.

The issue at this point is that the RP-4 has feed composed of 2 mm grains of black sand and fine (micron) gold.

The recovery process is just beginning. The challenge is to classify the fine gold and run it across the RP-4.

An assay doesn't help with this part of the process - this is unquestionably the object of the discussion.

- Geowizard


  
911Metallurgy
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Re: Gravity concentrator versus Wave table ( 22:05:39 WedAug 23 2017 )

boy oh boy, i wish people were as chatty on my Metallurgy forum as here.
[1 edits; Last edit by 911Metallurgy at 22:06:25 Wed Aug 23 2017]



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geowizard
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Re: Gravity concentrator versus Wave table ( 01:17:08 ThuAug 24 2017 )

Does the Icon improve recovery?

From the discussion above, it adds an expensive extra step in the process.

In the example I provided, a high grade concentrate is recovered from the sluice including micron gold. The concentrate is contained in two 5 gallon buckets.

The concentrate could be fed to the Icon concentrator ($20K system) that includes the vibrating screen that splits 2 mm plus to a #2 sluice and the feeder / slurry pump that pumps the 2mm minus to the Icon.

We have TWO paths now;

One path is through the #2 sluice to recovery circuit "B". Circuit "B" has oversize concentrate mixed with GOLD.

A second path went through the Icon to recovery circuit "C". Circuit "C" has 2 mm minus GOLD and concentrate

So, the added process served only to split the concentrate into TWO fractions - each needing further processing.

Oversize circuit "B" will need screening to classify into 4 mesh and 8 mesh. Each of those sizes require separate recovery paths.

Undersize circuit "C" will require further screening to classify 20, 40 and 80 mesh. Each of those require separate recovery paths.

Micron GOLD that passes an 80 mesh screen requires special handling to recover.

Send in a sample;

Either the Icon recovered fine GOLD or it didn't. The fine gold is still mixed with 2mm (12 mesh) minus concentrate.

The nature of free GOLD is that it includes FINE GOLD.

SAMPLE RESULT: THE ICON RECOVERED FINE GOLD.

The process of recovering GOLD from a placer and concentration of the GOLD requires attention to the details of sampling all of the inputs and all of the outputs.

From this discussion, it can be seen that the sluice carries the majority load of concentration. Concentrates can be screened and classified as needed to recover GOLD down to micron levels or less (Nano) using conventional methods.

- Geowizard

  
geowizard
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Re: Gravity concentrator versus Wave table ( 13:02:29 ThuAug 24 2017 )

What is the definition of "FINE" GOLD?

Dave McCracken serves as a good reference.

He says 20 to 40 mesh is "FINE" GOLD.

Smaller than 40 mesh is "FLOUR" GOLD.

http://www.goldgold.com/gold-prospectingcharacteristics-of-gold.html

Discussion on the topic is less confusing when terms are consistent.

- Geowizard
[1 edits; Last edit by geowizard at 13:03:10 Thu Aug 24 2017]

  
geowizard
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Re: Gravity concentrator versus Wave table ( 15:06:17 ThuAug 24 2017 )

Mesh sizes and microns;

Here's a reference on Mesh sizes and microns;

https://www.industrialspec.com/resources/mesh-and-micron-sizes/

Will the Icon recover 100 mesh GOLD?

- Geowizard

  
geowizard
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Re: Gravity concentrator versus Wave table ( 16:30:28 ThuAug 24 2017 )

The Answer follows;

Using the "Ratio of the Masses" Thread for reference, we can evaluate the masses of the particles and their response to gravity concentration in an Icon Bowl.

The ratio of the masses must be less than 11.1 to 1.

Given a sphere of sand with a diameter of 2 MM (2000 Microns) as published, the GOLD must have a diameter of 2000/11/1 = 180.18 microns.

From the reference given above, the diameter of a 100 mesh sphere of gold is 149 microns. Gold passing 100 mesh will be too small and will be rejected from the Icon Bowl along with 2000 micron sand.

- Geowizard

  
geowizard
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Re: Gravity concentrator versus Wave table ( 20:07:52 ThuAug 24 2017 )

What does the 150 G centrifuge add?

Answer;

The "Ratio" of the Masses remains the same! The sand is subjected to the same force as the GOLD.

Does a VFD make a difference?

Answer;

Changing the frequency of the VFD changes the motor speed. It can be programmed to provide a "soft" start. Changing the speed and changing the resulting "G" Force doesn't change the "Ratio" of the masses.

- Geowizard

[2 edits; Last edit by geowizard at 21:08:11 Thu Aug 24 2017]

  
geowizard
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Re: Gravity concentrator versus Wave table ( 21:18:11 ThuAug 24 2017 )

THE MISCONCEPTION:

The misconception is that a centrifuge will concentrate GOLD.

Centrifuges separate solids from liquids. At best because of the liquid suspension of solids in water, the iCON will recover GOLD that meets the 11.1 to 1 Ratio of Masses.

That's where ultra-fine gold gets into the flour GOLD range and screening to reduce the size of the competing heavies is needed.

The FALCON BOWL is designed to SEPARATE suspended micron GOLD from flotation chemicals. Anyone interested can read all about the Falcon. The iCON is/was developed from the Falcon Bowl - it gets a little murky. I don't find a patent to support the magic - if there is any.

The iCON is shown in flow sheets as a "Rougher". The output requires additional cleaning.

- Geowizard
[2 edits; Last edit by geowizard at 01:59:47 Fri Aug 25 2017]

  

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