Separating gold from quartz

[Agmix]

Hi to all !
This is my first post to this forum and i hope i will describe my "problem" correctly

I start to play with gold flakes that i filtered from river sand.
It's actually a mix of 60% quartz and 40% gold.
I can filter it to 50/50 or 40/60 but quartz will always be in this mix

Question:
if i melt this mixture with borax, what will happen ?
Will quartz melt with the gold into one compound ?

Anyhow, what would be the best way to separate quartz form gold.
I dont want to use HF acid...

A.M.

 

[g_axelsson]

Quartz and gold should be easy to pan to get rid of the quartz.

50% gold mixture isn't a problem to melt directly, that's enough to separate and get the gold to melt together.

But from your description I'm not totally convinced that you actually have gold. Pyrite and mica is often mistaken for gold and is a lot harder to separate, but if it melts together into a metallic blob then it was probably gold.

Göran

 

[Agmix]

Thank you for reply.

According to the structure of flakes, it looks like its gold and i can melt it with burner.
As far as i know "fools gold" does not look as flakes , it's more sand like...

Quartz and gold should be easy to pan to get rid of the quartz.
** The problem is that quart flake is a bit bigger than gold and it looks like it have the "same" weight.
Am not pan/gold expert so until i learn this i will try alternative methods

Btw. tell me, how to check if the gold flake is real gold ?
Is this flake "conductive" ?
I have tested with strong magnet and there was no iron or magnetic in this mix...

So , you are suggesting that i burn altogether...
Ok. i will try.

A.M.

 

[anachronism]

Fools gold is brittle, gold is malleable. If you crush one it will shatter, the other will deform.

 

[g_axelsson]

Mica comes in flakes and is hard to separate from quartz in a pan, it is sometimes mistaken for gold.

If you want a good tip on learning to pan, put a tiny piece of lead in the pan. If the lead is still there when you finish off panning then the gold should also be there. If the gold comes in flakes, flatten the lead so it has the same form and it should behave similar to any gold.

Göran

 

[Agmix]

I try to melt this but i fail.
I have used gas torch and gold mix was in iron mold.
I can see that the mix changed the colour to red but i could not melt it .
After 10 minutes i give up...

BTW. i forgat to write that i didn't use any borax, just plain gas torch...

How long should i try to melt this mix ?

A.M.

 

[FrugalRefiner]

I try to melt this but i fail.
I have used gas torch and gold mix was in iron mold.
BTW. i forgat to write that i didn't use any borax, just plain gas torch...
How long should i try to melt this mix ?

You shouldn't try to melt it all in an iron mold. Gold, and many other metals, will alloy with iron. If you do/did have gold, and you had succeeded in melting it, the molten gold would have dissolved some of the iron it was in contact and made a real mess.

The best way to melt gold is in a melting dish, a shallow bowl shaped dish made from clay, silica, or some similar material that the gold will not blend with. In a pinch, you can use a piece of charcoal with a hollow area carved into it. If you're desperate to melt it, you can use a piece of drywall or a block of wood. Only use these while you're waiting for a melting dish to arrive.

I can see that the mix changed the colour to red but i could not melt it .
After 10 minutes i give up...

That's not a good sign.

 

[Agmix]

OK. i will try your suggestions regarding melting technique.
-------------------------------
That's not a good sign.
*** i was thinking about that too, but i guess we can not be fully sure until i try it.
What can be worst case scenario ? That all this is mica ?

I forgot to write that i try one other option for separating quartz from gold (or what that is ) and this was quite good one, but i didnt have more H202. Shortly i have put 30% H202 into this flakes mix and after one day, mostly all quartz was dissolved and the the rest was on the bottom of plastic box, while the "gold" was floating.

After i separate the gold with pipette and wash it, flakes have drooped down in the box full with water...
This is the flakes that am using for test.

Btw. would not mica also dissolve, like quartz ?

One more thing, after all that heated up i spill it in cold water.
As far as i understand, mica is mineral and i this temperature change would force it to break ?

Few photos of purified and not purified mix:
https://ibb.co/h5Jed5
https://ibb.co/bLcuBQ
https://ibb.co/iE3ed5

A.M.

 

[g_axelsson]

H2O2 doesn't dissolve quartz so then the quartz wasn't quartz either.

The rest looks like mica to me.

Göran

 

[Agmix]

Hi.
It didnt disollve it completely, the mix just separate. Quartz stayed on the bottom.
Am pretty sure that this is quartz because they are digging for sand there and this river is full of it.
They are also selling this as "quarz sand"...

Mica or not:
- am also not sure. I think that the only option is to burn this and try to break it after ?
Is there some simple chemical test that can be used to "color" the gold flakes ?

A.M.

 

[g_axelsson]

If you crush mica you will get a white powder. It might be colored by iron so it would look like a yellow powder, but washing it in an acid (HCl, oxalic acid, citric acid...) will remove the iron and only leave the white powder.
Crushing gold is really hard since as anachronism pointed out, gold is malleable and will only deform and smear.

Crush a grain with a flat nosed pliers, if it is crushed it wasn't gold, if it just flattens out it's probably gold.

Dissolving gold in aqua regia would also work, but if there are a lot of silver mixed in then the dissolving might not go to 100% as the grains get encrusted in silver chloride. The liquid could then be tested for dissolved gold with stannous chloride.

You can also test if the flakes is conductive, in other words, if they conduct electricity. It's easily done with a multimeter with the "beep test". I've used this method for small grains in rocks a long time ago when I started collecting minerals.

Göran

 

[Agmix]

Thank you for your suggestions and support.

Conductivity test was my first test, but i was thinking that there is to big resistance so it can not be measured.
Now that i think a bit more, if there is a gold this test should pass anyhow....
------------------------------------------------------------
Before burning, i tested for magnetism with big neodimium magnet.
Nothing happened. After burning in clay pot ( nothing melted ) the "gold" flakes turn into silver / dark brown.
The funny part is that those flakes are now very, very low magnetic.
So now am confused. Those flakes ware gold alike and few of them gold brown.
------------------------------------------------
There is still no conductivity in those flakes but like i wrote, they are semi magnetic.
What kind of material is this ? Some ferrite ?

A.M.

 

[g_axelsson]

My guess, mica flakes colored by iron hydroxides so it looks yellow to brown depending on how much there is. The heat drives off water and creates iron oxides, Fe₂O₃ is magnetic. That would both affect the color and the magnetism of the flakes.

Gold is a very good conductor so a test should show it like a short circuit. Gold is used as wires connecting IC:s to the pins and those wires are thinner than a hair.

Göran

 

[everydayisalesson]

Im with Goran on this one. It does not look like gold, it does look like mica.

I would hammer it. If it turns to powder, its mica. If it just spreads out, it might be gold.

Mike

 

[Connie Saxe]

This is quite an argument, that took place years ago - but this question is an age-old basis question beginners in the gold industry always have ....... First and foremost - No known metal usually ever presents itself in nature as a pure form. Assume any metal is some percentage of an alloy, containing 2 or 3 metals - at least. Always use a microscope when examining quartz specimens. Precious metals can be spotted inside and out of quartz after about 5 years worth of field experience. For the past 5,000 years or so (albeit advent of modern tools), the simple solution to separating quartz from mica, pyrite, gold, silver, platinum, copper, iron etc (after a microscopic exam has confirmed PM's) is to grind the quartz rock into a fine power (using a stainless steel mortar and pestle) adding water if you want to keep things of value from flying around. Then throw the pasted fine powder into a tungsten crucible ($100 - $300 each) and heat to above 3,000 degrees F (necessary because of the possibility of Platinum group metals) while adding as much borax is needed to saturate your paste - 3,000 F is basically yellow - white heat, once you have a truly liquid charge, sprinkle in lead oxide powder. The lead will trickle-down through the liquid charge and collect all the metals (continue heating) and form one-big-happy-family of alloyed metals as a "button". Once you see the button and are pretty sure you have captured all the metals (about 1 hour of heating). Turn off the burners and break the slag out of the crucible and procure the button. Then do the same process on the button in a bone-ash crucible where the lead button undergoes oxidation and separates from the PM's ......... the rest is history.

 

[Yggdrasil]

This is quite an argument, that took place years ago - but this question is an age-old basis question beginners in the gold industry always have ....... First and foremost - No known metal usually ever presents itself in nature as a pure form. Assume any metal is some percentage of an alloy, containing 2 or 3 metals - at least. Always use a microscope when examining quartz specimens. Precious metals can be spotted inside and out of quartz after about 5 years worth of field experience. For the past 5,000 years or so (albeit advent of modern tools), the simple solution to separating quartz from mica, pyrite, gold, silver, platinum, copper, iron etc (after a microscopic exam has confirmed PM's) is to grind the quartz rock into a fine power (using a stainless steel mortar and pestle) adding water if you want to keep things of value from flying around. Then throw the pasted fine powder into a tungsten crucible ($100 - $300 each) and heat to above 3,000 degrees F (necessary because of the possibility of Platinum group metals) while adding as much borax is needed to saturate your paste - 3,000 F is basically yellow - white heat, once you have a truly liquid charge, sprinkle in lead oxide powder. The lead will trickle-down through the liquid charge and collect all the metals (continue heating) and form one-big-happy-family of alloyed metals as a "button". Once you see the button and are pretty sure you have captured all the metals (about 1 hour of heating). Turn off the burners and break the slag out of the crucible and procure the button. Then do the same process on the button in a bone-ash crucible where the lead button undergoes oxidation and separates from the PM's ......... the rest is history.

First and foremost - No known metal usually ever presents itself in nature as a pure form.

This is inaccurate, most PMs can be found as pure metals, not common, but it happens.
Even Copper from time to time.

In the old days they harvested pure Gold as metal in placers and veins in the rock.
And as scarcity and knowledge increased, they developed methods to wring even more Gold and other metals from the rocks.
They had no microscopes nor Tungsten crucibles. Mineral knowledge and clay vessels was what they had.
And that is for the most part sufficient today too, with some tweaks
And today many of these techniques are obsolete, not because they do not work, but we have better more efficient ways.

 

[kurtak]

This is quite an argument, that took place years ago - but this question is an age-old basis question beginners in the gold industry always have

First of all let me say hello & welcome to the forum - next I would like to say that what you have posted is A method of testing (not true assay) & thank you for posting

However - although your method is one that will certainly work there are somethings in what you posted I feel I need to correct

First of all ----------

Always use a microscope when examining quartz specimens

You don't Aways need to use a microscope --- in fact in all my years of prospecting/testing of ores I have never used a microscope - any magnifier will work - I carry & use a 10 or 15 X jeweler's loop for looking at ores

But even that will not always tell you what you have --- I one time worked with some ore that paid (plus/minus) 4 ozt gold per ton --- you could spend all day busting rocks (including grinding to fine powder) & look at it with a magnifier & never see so much as a speck of gold - you simply would not see any gold until after crushing the ore to fine powder & panning it after which you would see the gold in the concentrates in the bottom of your pan

In fact - I am currently playing with some ore samples I have brought home & magnification tells me nothing definitive - crushing & concentrating tells me the real story

In other words - although magnification is certainly a useful tool it is not always the definitive answer to determining there are PMs (Precious Metals) in the ore - crushing & concentrating (panning) is much more definitive - AND - that (both magnification & panning) is only somewhat definitive if the metals you are looking for are in actual metal forum --- if they happen to be in a state of oxidation (such as gold sulfides) then nether magnification or concentrating will really tell you the full story --- you will need to implement other methods of testing - to insure what you have

This is all I have time for today - I will post more when I have time

Kurt

 

[kurtak]

Then throw the pasted fine powder into a tungsten crucible ($100 - $300 each) and heat to above 3,000 degrees F (necessary because of the possibility of Platinum group metals) while adding as much borax is needed to saturate your paste - 3,000 F is basically yellow - white heat

Picking up where I left off yesterday this thing about needing to heat to 3,000 F being necessary because of the possibility of Platinum group metals is flat out not true

Yes when melting pure PGM metals then those high kind of temps are necessary - however - that is not what we are talking about here

Rather - we are talking about smelting ore concentrates that are primarily gold/silver ore with "maybe" some traces of PGMs

When melting a combination of metals (in a smelt) the lower the melt point of the primary metal (in this case the gold with maybe some silver) the gold - once it becomes molten - becomes a solvent for the higher melt point metals thereby bring down the melt point of the higher melt point metals

In other words - with gold at a melt point of 1950 F (& being the primary metal) once it becomes molten it becomes a solvent for any trace PGMs in the ore/smelt allowing those PGMs to become molten & alloy with the gold at MUCH lower temps

So a temp of between 2,150 - 2,250 F is plenty high enough to get the PGMs to melt & alloy with the gold - & that is if you are using no even lower melt temp metal as a collector metal

So ----------

once you have a truly liquid charge, sprinkle in lead oxide powder. The lead will trickle-down through the liquid charge and collect all the metals

If you use lead (or lead oxide - which requires a reducing agent in the flux) it will reduce smelt temp by even more allowing all metals - including PGMs to alloy with the lead --- a smelt temp of 1,850 F is plenty high when using lead (or lead oxide) as a collector

once you have a truly liquid charge, sprinkle in lead oxide powder.

Although sprinkling the lead oxide into the charge after the charge has become molten may well work - I would be concerned about not getting complete collection of all the PMs (precious Metals)

You are MUCH better served to mix (well) all of you charge ingredients together - including the lead oxide - to start with - put the charge in your crucible - put the crucible with the charge in the furnace & let the smelt do its thing once it all becomes molten

Then throw the pasted fine powder into a tungsten crucible

Although you can certainly use a tungsten crucible - you certainly don't need one

If you are doing a one time assay a "one shot" fused silica crucible will work fine - if you are doing actual smelting & need to do multiple smelts then go with silicon carbide crucibles

Turn off the burners and break the slag out of the crucible and procure the button.

You should not be breaking anything out of the crucible - once the smelt is done & the charge is all molten - you should be pouring the charge to a cone mold

Then do the same process on the button in a bone-ash crucible where the lead button undergoes oxidation and separates from the PM's

This is not a crucible - this is called a cupel

Also - one final note; - after crushing your ore - if you concentrate your ore (panning or run it on a concentrator table) & you are able to get that concentrate to 30% or more metal - you do not even need a collector metal in your smelt - just flux --- there is no reason to add a collector metal - then have to separate the collector metal from the PMs - if you don't have to

Kurt

 

[goldshark]

This is quite an argument, that took place years ago - but this question is an age-old basis question beginners in the gold industry always have ....... First and foremost - No known metal usually ever presents itself in nature as a pure form. Assume any metal is some percentage of an alloy, containing 2 or 3 metals - at least. Always use a microscope when examining quartz specimens. Precious metals can be spotted inside and out of quartz after about 5 years worth of field experience. For the past 5,000 years or so (albeit advent of modern tools), the simple solution to separating quartz from mica, pyrite, gold, silver, platinum, copper, iron etc (after a microscopic exam has confirmed PM's) is to grind the quartz rock into a fine power (using a stainless steel mortar and pestle) adding water if you want to keep things of value from flying around. Then throw the pasted fine powder into a tungsten crucible ($100 - $300 each) and heat to above 3,000 degrees F (necessary because of the possibility of Platinum group metals) while adding as much borax is needed to saturate your paste - 3,000 F is basically yellow - white heat, once you have a truly liquid charge, sprinkle in lead oxide powder. The lead will trickle-down through the liquid charge and collect all the metals (continue heating) and form one-big-happy-family of alloyed metals as a "button". Once you see the button and are pretty sure you have captured all the metals (about 1 hour of heating). Turn off the burners and break the slag out of the crucible and procure the button. Then do the same process on the button in a bone-ash crucible where the lead button undergoes oxidation and separates from the PM's ......... the rest is history.

The only microscope that truly works, is a Scanning Electron Microscope. Not something everyone has just sitting around. Some very high grade ores, have no visible Gold, even under the most powerful of normal optical lens microscopes. The only way to assay, is with the conventional fire assay. There are some other assay protocols available, but the best bang for the buck, is the fire assay, when properly performed.

Edited by moderator: Removed double quote

 

[Nountaineer]

The only microscope that truly works, is a Scanning Electron Microscope. Not something everyone has just sitting around. Some very high grade ores, have no visible Gold, even under the most powerful of normal optical lens microscopes. The only way to assay, is with the conventional fire assay. There are some other assay protocols available, but the best bang for the buck, is the fire assay, when properly performed.

My platinum ore is running 9.37. oz/ton and No visible gold so this is true.