Simple solution to fine gold recovery

[johnedoe]

This was developed by Randy Clarkson, an expert in gold recovery designs.

A simple gizmo to help miners snag lost gold..... New gizmo could help placer miners snag lost gold | Yukon News

Also this by Randy Clarkson on fine gold recovery which is somewhat misleading in that this is mostly about commercial ops and 1" minus classification is considered fine....... The Clarkson Study Fine Gold Recovery

Here is a PDF presentation of the process....... http://www.geology.gov.yk.ca/pdf/141114_Nov1014_Grinding_for_Gold_Presentation.pdf ....... Thank you arizau for finding that PDF

Enjoy the learning.

 

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[KevinInColorado]

Yes, I did. The link to the discussion about them is below. I am happy with them for what I wanted them to do (sieve cons). They are 60, 90, and 120 micron or about 215, 170 and 115 mesh. Aluminum frames and steel mesh wire for about $20.

http://www.treasurenet.com/forums/gold-prospecting/457285-120-90-60-micron-6-sieve-report.html

I got this set too based on gpDave's comments. I've used em enough to say they're solid for cons processing at home. I even ran a bunch of my old dried super cons thru the two finer meshes and found a few specks of gold. Boy howdy that -215 gold shore iz tiny!

 

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[GoldpannerDave]

Actually Bob I'm liking the disks they offer. A short section of 4in ABS pipe to be used as locking rings, a couple of joiners with the ring in the middle of them and I'd be set. Slip the disk into the joiner then a section of pipe cut to the length of the joiner from the edge to the middle and a little ABS glue and it's ready to use as soon as the glue cures.

goldenIrishman; I like your thinking but to get 6" disks of screen is starting to get somewhat expensive. Just the screens for say 80 mesh, 100 and 200 mesh in the 3" diameter is over $30 and then the costs of the ABS or PVC added to that. I can buy 12 inch + sized screens for $12-$15 each

 

[mytimetoshine]

So I haven't been out since Thanksgiving morning. Busy season at work, holiday stuff and the cold short days..

Been working on several projects though like my rod mill. I'm currently running a 2x4 diameter ABS barrell with a 110v drill as the motor. I have my Sands classified to -100 but have only been running the -20 +50 stuff. A 15 min run will crush about 35% of the material going through the 50 classifier. Gold every time... 80% of the gold stays in the classifier with just a few small specks of gold being recovered from the stuff that went through. Unfortunately after running a batch for an hour and then return running for 30 more minutes I still didn't get it all through the classifier so being left with just gold on top is unrealistic probably. Maybe with a larger set up..

So I've noticed that a 15 min run seems to be the most efficient. Even though it doesn't all go through the classifier and you have to pan out the gold it seems to be enough to get most if not all of the hidden gold. My theory is that the gold hiding in an iron she'll fractures off pretty easily but some of the larger, harder pieces won't crush. , even when ran for long periods.

This is from 5 tablespoons of material. Over 30 pieces!!!!

 

[KevinInColorado]

Great info and congrats on your success! I

totally agree that the pieces with gold in them are fairly fragile and likely to crush quickly. I too have found some of the material (I've been crushing the same size range in fact!) doesn't want to crush but I figure that means there's no gold in there

 

[goldenIrishman]

I've noticed that gems like Garnets and even some of the tiny Quartz crystals don't want to crush in my little rod mill. I've found complete crystals that are so small that you can only tell they're complete when looking at them through the microscope. They look like little pieces of sand to the naked eye.

 

[arizau]

So I haven't been out since Thanksgiving morning. Busy season at work, holiday stuff and the cold short days..

Been working on several projects though like my rod mill. I'm currently running a 2x4 diameter ABS barrell with a 110v drill as the motor. I have my Sands classified to -100 but have only been running the -20 +50 stuff. A 15 min run will crush about 35% of the material going through the 50 classifier. Gold every time... 80% of the gold stays in the classifier with just a few small specks of gold being recovered from the stuff that went through. Unfortunately after running a batch for an hour and then return running for 30 more minutes I still didn't get it all through the classifier so being left with just gold on top is unrealistic probably. Maybe with a larger set up..

So I've noticed that a 15 min run seems to be the most efficient. Even though it doesn't all go through the classifier and you have to pan out the gold it seems to be enough to get most if not all of the hidden gold. My theory is that the gold hiding in an iron she'll fractures off pretty easily but some of the larger, harder pieces won't crush. , even when ran for long periods.

This is from 5 tablespoons of material. Over 30 pieces!!!!

Just a thought on your grinding results....Not running at or near CRITICAL SPEED, an essential component to making this process work as originally formulated by the inventor, may account for the incomplete grinding you are encountering.

If my assumptions and calculations are correct then your cylinder should be spinning somewhere between 218 and 234 RPM. The formula for critical speed is: 75 to 80% of 265.45/square root of cylinder inside diameter minus the average diameter of the rods (if my interpretation of the formula is correct). Here is what I used: 265.45/1.41*-.5=291.7. 75 to 80% of 291.7 is about 218 to 234 RPM. I assumed that the ID of the tube was 2" and the average rod size was 1/2".

Thanks for your contribution to this thread by your reports.

Good luck.

PS: Check here for the formal presentation of this process which includes the formula for critical speed. http://www.geology.gov.yk.ca/pdf/141114_Nov1014_Grinding_for_Gold_Presentation.pdf

*Square root of 2.

 

[mytimetoshine]

Idk.. at like 150 RPM you don't hear the rods "tumbling" anymore. So far my best results are around 125 RPM but maybe I'll give it a go.

I am using 1/8 -5/8 variety of rods

 

[arizau]

Idk.. at like 150 RPM you don't hear the rods "tumbling" anymore. So far my best results are around 125 RPM but maybe I'll give it a go.

I am using 1/8 -5/8 variety of rods

Just a little more...The effect to the rods is that they actually counter rotate in the drum. While in operation RPM creates centrifugal force and tries to pin everything to the wall but the rods still roll backwards.* This is where critical speed comes in to play. That assures that gravity takes over and allows the contents to drop back down before top dead center and not just stay pinned to the wall all the way around. While this is going on the rods are rolling over/crushing/squeezing the material in counter rotation to the drum and that is the desired effect. A little wordy but maybe it will help clarify things.

Speeds less than critical speed, which may not be obtainable depending on what equipment is being used, still result in some desired effects (and you and others have seen some) but not near as efficiently as it would be at critical speed. eg. resulting incomplete grinding or reduction and little to no flattening of gold.

Keep up the good work and good luck.

*The larger size rods will roll easiest at startup while smaller ones may not roll until the material is somewhat reduced in size and has transformed into a slurry.

 

[mytimetoshine]

Well I guess it would depend on your formula/math being correct.

I'm not a mathematician but I can hear the rods and got a pretty good idea of when they are pinned to the outer wall. 200 plus RPM is ridiculous when you actually try it. Based on what your saying why not 500 rpm?

 

[arizau]

Well I guess it would depend on your formula/math being correct.

I'm not a mathematician but I can hear the rods and got a pretty good idea of when they are pinned to the outer wall. 200 plus RPM is ridiculous when you actually try it. Based on what your saying why not 500 rpm?

Don't get me wrong as I am not being critical of what you are doing but instead trying to be helpful by offering some explanations.

Any reduction of waste material that you achieve is beneficial to you and other users trying this method even if it is not done up to it's most efficient point which is what the original methodology is designed for. That point is where all of the brittle waste material is reduced or substantially reduced in size, gold is separated or mostly separated from quartz or other material it was attached to and most of the other gold is flattened so that it will no longer pass through the screen that it passed before the shape was changed. By following the parameters set out by the inventor that efficiency can be mostly achieved.


As to the 500 rpm question...My rpm calculation is just the math of the inventors formula with what I guessed to be the ID of your cylinder and the average diameter of the rods that you use inserted. The graphic that you show in your last post shows what happens at higher and lower rpms as well as what happens when the rpms are in the critical speed range. As explanation...At lower rpms there is relatively inefficient grinding taking place, at critical speed rpms there is maximum efficiency grinding and flattening of gold taking place and at excess rpms the grinding becomes less efficient again and approaches zero efficiency the higher they go due to centrifugal force negating gravity. By the way, the math for increasingly larger ID cylinders computes to increasingly lower critical speeds. You mentioned that you are going to switch to 3" and that will require a lower critical speed to operate at maximun efficiency and if you go larger, even lower speeds.

Good luck.

 

[mytimetoshine]

Don't get me wrong as I am not being critical of what you are doing but instead trying to be helpful by offering some explanations.

Any reduction of waste material that you achieve is beneficial to you and other users trying this method even if it is not done up to it's most efficient point which is what the original methodology is designed for. That point is where all of the brittle waste material is reduced or substantially reduced in size, gold is separated or mostly separated from quartz or other material it was attached to and most of the other gold is flattened so that it will no longer pass through the screen that it passed before the shape was changed. By following the parameters set out by the inventor that efficiency can be mostly achieved.


As to the 500 rpm question...My rpm calculation is just the math of the inventors formula with what I guessed to be the ID of your cylinder and the average diameter of the rods that you use inserted. The graphic that you show in your last post shows what happens at higher and lower rpms as well as what happens when the rpms are in the critical speed range. As explanation...At lower rpms there is relatively inefficient grinding taking place, at critical speed rpms there is maximum efficiency grinding and flattening of gold taking place and at excess rpms the grinding becomes less efficient again and approaches zero efficiency the higher they go due to centrifugal force negating gravity. By the way, the math for increasingly larger ID cylinders computes to increasingly lower critical speeds. You mentioned that you are going to switch to 3" and that will require a lower critical speed to operate at maximun efficiency and if you go larger, even lower speeds.

Good luck.

I get your only tying to be helpful. But your wrong...I'm sorry but you are. Until you are actually running your own rod mill you should probably reduce your "advice".. 200+ rpm on a 2x4 barrel is TOO MUCH...

Is it possible your math is off? You said my avg rod diameter was 1/2 inch which it is not and the rods size I'm using has been posted as well as pictures several times. The "avg" rod diameter is probably closer to 3/8.

I have a variety of 1/8 to 5/8 with mostly 1/4 and 3/8 rods being used. I wish more people would actually set up a mill and give field data rather then reposting the original presentation/formula. The rod mill they are using probably weighs a 50 lbs or more. we are using drastically scaled down version and only real field tests are gonna get it dialed in...

 

[arizau]

I get your only tying to be helpful. But your wrong...I'm sorry but you are. Until you are actually running your own rod mill you should probably reduce your "advice".. 200+ rpm on a 2x4 barrel is TOO MUCH...

Is it possible your math is off? You said my avg rod diameter was 1/2 inch which it is not and the rods size I'm using has been posted as well as pictures several times. The "avg" rod diameter is probably closer to 3/8.

I have a variety of 1/8 to 5/8 with mostly 1/4 and 3/8 rods being used. I wish more people would actually set up a mill and give field data rather then reposting the original presentation/formula. The rod mill they are using probably weighs a 50 lbs or more. we are using drastically scaled down version and only real field tests are gonna get it dialed in...

OK. Here you go. I redid the formula with your numbers* (2" ID cylinder and average 3/8" rods) plugged in. The calculation shows that the RPM range for critical speed is 156.8 to 167. By your previous comments, I'm thinking that you will not like these numbers either. They are about double an 8" device's critical speed determined by using the same formula and, again, guessing the average rod size. The inventor did imply somewhere, in the literature I read, that users do testing (various speeds, time, rods, etc.) to the point that the concept works for them. That is kind of the stage you are in now and of course, you can accept or reject what the formula recommends for speed in your testing.

As of this time, you are the guinea pig since you are the only one currently actively posting your testing parameters and results. I can remember at least three other testers who have posted in the past and maybe when they begin retesting or at least post about what they are doing then some consensus can be come to as to what exactly is the best method to approximate the original concept's goal with the use of scaled down equipment that most people may be able to afford or justify.

*Using 1/2" in an earlier post was my guess as to what the average size of your rods was prior to knowing what it is.

 

[GoldpannerDave]

[snip]
As of this time, you are the guinea pig since you are the only one currently actively posting your testing parameters and results. I can remember at least three other testers who have posted in the past and maybe when they begin retesting or at least post about what they are doing then some consensus can be come to as to what exactly is the best method to approximate the original concept's goal with the use of scaled down equipment that most people may be able to afford or justify.

Yes, KevinInColorado and I were posting results and I think Ducky was also; perhaps even another person in addition to MTTS. I plan to try to get back to it after I finish my wife's Honey Do list for the Christmas Break. I need to do some testing with the new motor I got from Ducky along with the used printer for rollers so that I am not restrained by my rock tumbler motor. Of course, I do like the electric drill idea, but want to try the motor and printer set-up first.

 

[mytimetoshine]

Big difference between 150 RPM and 200 + See the math was off...

Last night I noticed the drill taking some time to "warm up". Started out at about 90 rpm and took about 5 min to build up to about 170. Other then that its still running fine but only time will tell if the motor will end up burning out.

It actually crushed more material then runs earlier in the week so somewhere between 100 and 175 rpm is best for my device.

I think the reason that there is not a complete crush of the Sands has more to do with size and overall weight of the drum and rods that result in overall impact force on the materials. That and the barrel material being ABS and not steel.

 

[GoldpannerDave]

Big difference between 150 RPM and 200 + See the math was off...

Last night I noticed the drill taking some time to "warm up". Started out at about 90 rpm and took about 5 min to build up to about 170. Other then that its still running fine but only time will tell if the motor will end up burning out.

It actually crushed more material then runs earlier in the week so somewhere between 100 and 175 rpm is best for my device.

I think the reason that there is not a complete crush of the Sands has more to do with size and overall weight of the drum and rods that result in overall impact force on the materials. That and the barrel material being ABS and not steel.

Yes, there is a big difference. I only need to get up to 90-100 rpm to get the correct speed due to a larger diameter tumbler. I want to keep my work in the 30-60 mesh range for now since I have no screens between 60 and 100 mesh; I need a 70 or 80 mesh one for this sized material. But I do have 100 and a 115 to check results in that range mesh size.

I want to first get the rpm's to the correct range. Then dial in the time; if that doesn't improve results, I plan to get more (and larger diameter rods) than perhaps a larger diameter tumbler--maybe a steel paint can like others have used. Maybe the can before the rods since I will need probably new rods for the new can anyway.

I probably will not get anything done until after Christmas, but who knows. Off to start on Honey do items.

 

[GoldpannerDave]

The idea with having a screen in the 70-80 mesh range would be to have screens from about 20 to 115 mesh at increments of about 10 to 20 so I can continuously take the undersized, run it in the tumbler, and separate the flatten gold from the rest using the next smaller mesh size. Then repeat. After than, I have the 170 and the screen that is about 215 to 240, depending on your source. (These last two are part of the set of 3 mentioned above that came in 60, 90, and 120 microns).

The last two are pretty small, but might still give me two more shots and "rolling" gold (though a different type of gold than the sellers of the micron sieves had in mind) and separating it.

Any tails at that point I guess I will save. I would not think there is much gold left in them at that point.

 

[KevinInColorado]

Dave have you tried using the 60 micron sieve yet? I did with a bunch of my old non-mag cons and panned out the material that fell thru. I did recover a little pinch of gold, wow is that ever fine stuff!!! (I put my 20x magnifier to use to be sure of what I had)

 

[arizau]

Dave have you tried using the 60 micron sieve yet? I did with a bunch of my old non-mag cons and panned out the material that fell thru. I did recover a little pinch of gold, wow is that ever fine stuff!!! (I put my 20x magnifier to use to be sure of what I had)

A demonstration of the power of classification in gold recovery. That should serve as an eyeopener for those who do not. Good job!

 

[GoldpannerDave]

Dave have you tried using the 60 micron sieve yet? I did with a bunch of my old non-mag cons and panned out the material that fell thru. I did recover a little pinch of gold, wow is that ever fine stuff!!! (I put my 20x magnifier to use to be sure of what I had)

No, I haven't. I will eventually, but like you said, it is tiny, tiny. And you still got some gold--that settles it; I _will_ hand on to the stuff that goes through. Above I said "I guess I will save...."

I have an 8x magnifier, but am hoping to get a USB type scope to look at stuff like that (and larger) and to take pictures of it.

 

[arizau]

Dave have you tried using the 60 micron sieve yet? I did with a bunch of my old non-mag cons and panned out the material that fell thru. I did recover a little pinch of gold, wow is that ever fine stuff!!! (I put my 20x magnifier to use to be sure of what I had)

Hey Kevin,

If memory serves me, you recently received some of the black beach sand that OregonViking offered. I often mine the same stuff and I find that that sand is virtually all minus 100 mesh but since I do not have the smaller mesh screen set that you and Dave have I don't have a clue what the break down of sizes are below 100 mesh. Any chance you can screen a tablespoon or so of it and let us know the break down? A bonus would be if you were to pan the fractions too. I'm pretty sure what he sent you is raw beach sands that were concentrated by wave action. I have panned as little as a mere pinch of randomly selected, naturally concentrated beach black sand and have separated gold from it. The gold was almost invisible and there were several specks to be seen.

Thanks