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geowizard
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Ratio of the Masses... ( 16:14:55 ThuAug 24 2017 )

Hi All,

Most readers of this forum have probably had an opportunity to pan GOLD.

Panning is an interesting process of concentrating GOLD to ultimately obtain a nearly pure end product.

Because GOLD is more dense, it is easy to separate from lighter (less dense) rocks. It's called gravity separation.

The process of "Gravity Separation" requires that particles have different MASS that is weight per unit volume.

Sand (Silica) has a mass of 2.65 grams per cubic centimeter and GOLD has a mass of 19.32 grams per cubic centimeter.

Screening is important because it sizes particles to the same or similar volume. Particles having greater weight per unit volume are subjected to greater force of gravity and remain in the GOLD pan.

The ratio of the masses of GOLD and sand are 19.32 to 2.65 in air.

The ratio of the masses of GOLD and sand in water is different because the particles of GOLD and sand become buoyant. So, a cubic centimeter of water weighs 1 gram per cubic centimeter and when placed in water, one cubic centimeter of GOLD weighs 18.32 grams and one cubic centimeter of sand weighs 1.65 grams.

The Ratio of the masses of GOLD to Sand in WATER is 11.1 to 1.0.

Screening must keep particle sizes (volume) equal to or LESS than 11.1 to 1.

- Geowizard

[2 edits; Last edit by geowizard at 21:32:20 Fri Aug 25 2017]

  
geowizard
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Re: Ratio of the Masses... ( 14:01:29 FriAug 25 2017 )

Geo,

This makes my head hurt. What are you talking about?

  
geowizard
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Re: Ratio of the Masses... ( 14:26:07 FriAug 25 2017 )

The reason for screening is to keep particle sizes compatible.

An experienced GOLD panner has screens - yep, it costs money to buy the screens, and the screens are certain sizes.

The first screen is a #4 or four mesh screen. It classifies particles to 0.185 inches. Use a 5 gallon bucket, wash your sample through the #4 screen. Place the over size in a second bucket.

The oversize can be visually examined for GOLD and discarded.

Things begin to get interesting...

We have four minus that we screened into the first bucket. Additional screen is need to further classify the particles.

Using the empty second bucket, place a #8, 8 mesh screen on the bucket and wash the sample through the screen. The bucket now contains 8 mesh minus and the screen contains "four to eight".

GOLD in the range of "Four to Eight" is usually referred to as "pickers". Depending on the amount of material, it may be visually inspected for pickers or panned. The "ratio" of the masses dictate that with 0.185 inch maximum size particles, GOLD can be panned having a size 11.1 times smaller. That size = .0167 inches. The screen was .093 inch, so the smallest particles of GOLD will be larger than .093 inches. This assures that the particle sizes are compatible and within the 11.1 ratio of masses.

http://espimetals.com/index.php/faq/334-understanding-mesh-sizes

- Geowizard
[2 edits; Last edit by geowizard at 14:37:20 Fri Aug 25 2017]

  
geowizard
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Re: Ratio of the Masses... ( 14:52:00 FriAug 25 2017 )

What next?

After the 8 mesh screen comes the #12, 12 mesh screen. Given the information above, what is the minimum size GOLD that can be separated in the eight to twelve?

Then comes the #20, 20 mesh screen. Same question... What is the smallest size GOLD that can be separated?

Fine GOLD;

The purist keeps on going with the #40, #60 and #80 screens.

That takes us to #100. Particle size is 0.0058 inch (149 micron).

- Geowizard

  
Jim_Alaska
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Re: Ratio of the Masses... ( 15:34:05 FriAug 25 2017 )

This is a great thread. Threads like this are what have made this message board stand out from among others.

Nothing wrong with any of the other mining message boards, people discuss the things that they like and choose.

But this board has always been a place that has attracted the more technical and complicated aspects of mining, as well as the everyday aspects of mining.

A big thank you to everyone that has contributed and freely given of their knowledge and expertise.



---
Jim_Alaska
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geowizard
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Re: Ratio of the Masses... ( 19:55:57 FriAug 25 2017 )

Jim,

In spite of my alzheimers (sp) can't even spell anymore, the LAWS of PHYSICS prevail!

I can't spell sh#t, can't smell sh#t, can't hear sh#t, can's see sh#t.There's some other sense too I forgot.

Thanks!

- Geowizard

  
geowizard
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Re: Ratio of the Masses... ( 21:10:17 FriAug 25 2017 )

Lost Gold?

When placer material is NOT properly screened, you will lose GOLD.

Why, Geowizard?

When the 11.1 to 1 rule is NOT complied with, I.E. YOU DID NOT SCREEN...you have large "ROCKS" and related over-size that stays in the pan.

IF YOU ATTEMPT TO PAN THEM OUT...

You WILL also ROLL fine GOLD out of the pan!

YOU WILL LOSE GOLD!

BUY SCREENS AND YOU WILL BE THE MASTER OF YOUR GOLD. :smile:

- Geowizard

  
geowizard
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Re: Ratio of the Masses... ( 21:25:23 FriAug 25 2017 )

We're making progress!

IF the ratio is GREATER than 11.1 to 1, you have ROCKS in your PAN and in your HEAD!

YOU WILL LOSE GOLD.

If the ratio is LESS than 11.1 to 1, you have sized your material so you have particle masses that are closer to the same mass.

The Worst day panning is when you FORGOT your SCREENS.

When the ratio is 10 to 1 or BETTER... 5 to 1 or BETTER... 1 to 1 then and ONLY then will you be in control of what is happening in the PAN. :smile:

- Geowizard

  
geowizard
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Re: Ratio of the Masses... ( 21:43:02 FriAug 25 2017 )

Can GOLD float on water?

YEP!

Flour GOLD can float. The GOLD is so small and the "surface tension" so GREAT that the GOLD floats!

(Secret Gold Panner Trick:smile:

Keep a small bottle of (Dawn) Dish Washing Detergent handy!

While panning, I add one small drop into the water in the pan. It actually helps the panning process keeps GOLD from deciding to FLOAT out of the pan.

- Geowizard

  
Jim_Alaska
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Re: Ratio of the Masses... ( 01:03:46 SatAug 26 2017 )

Both of your tips are some that I have used for many years. The first was screening, the second was floating gold.

They not only work, but are a necessity or you will lose gold.



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geowizard
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Re: Ratio of the Masses... ( 13:33:16 SatAug 26 2017 )

Jim,

I agree.

Screening may seem to make panning into a science project.

In the ideal situation;

MORE screens - especially the #20, #40, #60 will improve fine GOLD recovery.

The REASON is that you can selectively pan Twenty to Forty, and Forty to Sixty. At 60 minus, you have removed a BUNCH of larger ROCKS and HEAVIES.

Black Sand;

Fine GOLD mixed with BLACK SAND is challenge.

A MAGNET will remove magnetic black sand. There are still "HEAVIES" that stay in the pan!

Screening will keep MASSIVE particles of black sand from competing with fine GOLD.

- Geowizard

  
Jim_Alaska
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Re: Ratio of the Masses... ( 15:12:48 SatAug 26 2017 )

Although I do use a magnet for black sand, I don't recommend it for the beginning stages with wet material. It is really conducive to dragging gold with the black sand and trapping it in the resulting black sand "brush" on the magnet.

Here on the Klamath there is a lot of black sand. I usually do not try to pan down to the gold all in one batch; just depends on how much black sand is in the pan. I pan smaller batches because it is easier to see the gold and wash off the black sand. I am not talking sampling by pan, but panning concentrates, which is a lot harder than just simple panning along the river banks.

Where the magnet really shines is on my finishing clean-up. Once you have got the concentrate down to just gold and a bit of very fine black sand, you then dry the remaining concentrate. Now you can fan out what is left either in the pan or like I do on a piece of paper. Now the magnet will only pick up the black sand and leave you will very clean gold.

It's a lot of work and slower than most people like, but the cost savings over other methods are significant. Plus I enjoy the process.



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geowizard
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Re: Ratio of the Masses... ( 15:37:06 SatAug 26 2017 )

Jim,

I Agree, that's a very good point.

A magnet should be used with discretion in a wet pan. The black sand that is removed needs to be set aside - preferably in another pan for later inspection for values.

The "Check Pan;

While we're on the subject, I always have a second pan UNDER the pan I am using to pan my tailings into. I always find a small amount of GOLD that mysteriously jumps out into the check pan! :smile:

After drying, there's still a little black sand that can often be picked up with a magnet.

- Geowizard
[1 edits; Last edit by geowizard at 16:35:57 Sun Aug 27 2017]

  
geowizard
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Re: Ratio of the Masses... ( 13:35:26 SunAug 27 2017 )

Cassiterite;

One of the "Heavy" particles that competes with GOLD in a GOLD pan is Cassiterite.

Cassiterite is a Tin mineral and has a mass of 7.0 in air and 6.0 in water.

The ratio of the mass of cassiterite compared to GOLD is 1 to 3.

This is IMPORTANT to know.

A particle of Cassiterite 3 times larger than GOLD will have the SAME mass as GOLD having 1/3 the size.

GOLD CANNOT be separated because they have the SAME MASS.

Example:

SCREEN to 10 MESH = 2mm = 2000 microns including Cassiterite.

GOLD that is SMALLER than 667 microns CANNOT compete.

GOLD smaller than 667 microns will roll OUT of the pan BEFORE the 2000 micron Cassiterite.

The particles having the HIGHEST MASS DEFINE the LOWEST MASS that can be separated!

This is THE important TAKE-AWAY from this discussion.

- Geowizard

  
geowizard
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Re: Ratio of the Masses... ( 15:15:10 SunAug 27 2017 )

Experiment;

Experimentation is a good way to learn about physics!

Experiment #1;

Place a GOLD pan with some Pay Dirt and water in it on a table.

Watch the GOLD pan very carefully.

Get a piece of paper and write down your observation.

What happened? :smile:

Question;

What must be done to get the GOLD separated from the DIRT?

Stay with me a minute...

Answer; We must use FORCE (F).

We don't (normally) think about the SHAKE we apply to the GOLD pan when we begin panning. Moving the pan is IMPORTANT.

How fast? What direction? Up and down? Left and right? Swirl?

Too much acceleration, it gets messy! :smile:

Too little acceleration and NOTHING happens.

The GOLD has MASS. We apply the "Acceleration" the resulting FORCE causes the process to work. Too much or too little and it does not work!

Multiply MASS times ACCELERATION and you get FORCE.

GRAVITY is a FORCE. ACCELERATION of a MASS represents a FORCE. All of these FORCES work to separate and RECOVER GOLD.

- Geowizard
[1 edits; Last edit by geowizard at 16:40:31 Sun Aug 27 2017]

  
geowizard
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Re: Ratio of the Masses... ( 01:11:31 MonAug 28 2017 )

Lead shotgun shot;

One of the common metals to find in a GOLD pan is lead shotgun shot.

Typical shot is called #7 shotgun shot. It is 2.5 mm or 2500 microns.

Lead has a MASS of 11.34 in air and 10.34 in water.

GOLD has a MASS of 19.3 in air and 18.3 in water.

The ratio of the masses is 18.3 / 10.34 = 1.8. GOLD has 1.8 times MORE MASS than LEAD.

The shotgun shot will pass through a #8 Mesh screen.

The ratio of 1.8 is used to determine the equivalent GOLD MASS by dividing 2500 by 1.8 = 1389 microns.

Small GOLD less than 1389 microns will roll out of the pan before the Lead shot. In a mining district with lead, small particles of native lead can be prevalent.

- Geowizard
[1 edits; Last edit by geowizard at 01:12:56 Mon Aug 28 2017]

  
geowizard
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Re: Ratio of the Masses... ( 02:54:33 MonAug 28 2017 )

The SCALE of Gravity Separation;

Everything is scaleable. From a Gold pan to a wave table or sluice on up to full blown Falcon Bowls, the process of Gravity separation and the RATIO of the MASSES CONTROLS the RECOVERY of GOLD.

Gravity is all around us. It is reliable, low cost and predictable!

- Geowizard
[1 edits; Last edit by geowizard at 02:59:00 Mon Aug 28 2017]

  
geowizard
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Re: Ratio of the Masses... ( 13:40:09 TueAug 29 2017 )

Centrifugal Concentration;

Does more FORCE change anything?

The RATIO of MASS remains the same.

Separation occurs in a FALCON Bowl because the shape of the bowl creates an INCLINE.

An interesting experiment you can perform at home;

If you place a small amount of fine GOLD in a glass beaker with a small amount of clean sand and water... and SWIRL the contents

The GOLD stays in the center of the beaker. The sand is forced into suspension. This demonstration shows the principle of centrifugal separation.

- Geowizard
[1 edits; Last edit by geowizard at 13:53:13 Tue Aug 29 2017]

  
geowizard
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Re: Ratio of the Masses... ( 14:04:29 TueAug 29 2017 )

Elutriation;

https://en.wikipedia.org/wiki/Elutriation

When you look at a GOLD PAN... it becomes obvious that the pan has INCLINED edges.

The process of PANNING GOLD is really a demonstration of the concept of ELUTRIATION.

Water in the pan is applying force against the particles having different MASS. The water is able to MOVE the particles having LOW MASS UP the INCLINE and out of the PAN.

The amount of ACCELERATION applied is controlled by the PANNER.

Discretion is used in every stroke of the pan. The RATE of motion and the exact DIRECTION of motion asserts a given amount of ACCELERATION.

HEAVY particles require MORE force to move up the incline. The HEAVY particles become segregated from the LOWER MASS particles.

- Geowizard
[2 edits; Last edit by geowizard at 13:12:45 Wed Aug 30 2017]

  
geowizard
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Re: Ratio of the Masses... ( 21:29:20 FriSep 1 2017 )

Particle MASS;

Caveat...

When comparing particle MASS, the VOLUME of the particle is assumed based on the SIZE of the particle. Actual particle VOLUME will vary according the the geometry of the particle.

Assuming particle VOLUME based on particle SIZE saves the debate on particle behavior as might be related to "shape" or "geometry".

MASS is calculated by multiplying DENSITY x VOLUME.

- Geowizard

  

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