Old Prospector Makes Good

[kurtak]

Some pics of my smelting in operation with my #40 (crucible) furnace

The guy in the pics was my hired helper - not me

 

[kurtak]

using my smaller #4 (crucible) furnace to smelt silver sulfides recovered from photo fixer solutions

 

[kurtak]

some of my metals recovered by smelting - these pictures represent a VERY SMALL fraction of the metals I have recovered from smelting & EVERY ONE of those cones contain gold silver & PGMs

Edit to add; - just in those FEW pics you are looking at "about" 30 kilos of precious metals

 

[AlaskaLes]

Thanks for the pics and the detailed explanation.
I have a few questions.
1. Assuming that you built the smelters, what is your recipe for refractory lining/cement?
2. I am guessing that the copper was chosen as a collector metal because it is cheap and easy to find.
Does this cause any issues down the line when selling to a refiner?
3. Do you always use copper?

Thanks

 

[kurtak]

Actually I had those furnaces made for me - I was to busy running the hydro refining part of my operation to take time to build them myself (so hired it out) I just told the builder what I wanted

The reason I had the furnaces built was I wanted to get away from as much as possible the huge amount of chem waste created with hydro (leaching) - so adding pyro (smelting) to my operation cut WAY down on my chem waste

The small furnace is lined with just refractory cement (not sure what cement the builder used) but actual refractory cement holds up WAY BETTER then Koalwool (which I see a lot of furnace builders using) Koalwool alone wont hold up very long

The big furnace (chamber) is lined with 2 inch Koalwool - then 2 inch refractory brick - then topped off with 1/2 refractory cement - the lid is all refractory cement

Kurt

 

[kurtak]

2. I am guessing that the copper was chosen as a collector metal because it is cheap and easy to find.

Copper is a better collector if you have PGMs other then Pt/Pd in the smelt

If you have only Pt/Pd (&/or gold) I prefer silver as the collector

One reason for that is Pt/Pd alloys well with silver so those two PGMs collect well with silver - the other PGMs do not alloy well with silver & will "phase out" of the silver causing (at least) some of the other PGMs to go off with the slag --- so for example; - if I was sure there was only Pt/Pd &/or gold in the smelt I used silver (parting those metals - after smelt - is relatively easy) --- if Rh is in the mix then copper to prevent phase out & loosing Rh to slag

Does this cause any issues down the line when selling to a refiner?

Yes & no - there are copper refiners that will buy the copper dore & pay out on the PMs in the dore

Different copper refiners are going to have different minimums for the copper dore

So depending on how much copper dore you are able to produce is going to depend on your marketablity of the dore

Example; - I had two copper refiners within 2 &1/2 hours of me --- one of them would only take my copper dore if I had a ton or more (which was more then I was producing) the other one would take as little as 5 - 10 kilos so that is where my copper dore went

My silver dore I processed my self

3. Do you always use copper?

So no - I used silver as much as I could & copper when I had to

And for what it is worth - gold is also a good collector for PGMs - but - just like it takes A LOT of silver or copper for good collections - it takes A LOT of gold for good collection

Copper & even silver is WAY cheaper then gold when you need A LOT of metal for collecting

Kurt

 

[kurtak]

And for what it is worth - when it comes to the PGMs in dore metal - the only PGMs worth concerning yourself with is the Pt Pd & Rh --- MOST copper &/or silver dore processors are only going to pay on those three metals

They (dore processors) will only pay on the other three PGMs (Re Os Ir) if there is A LOT of those metal in the dore --- like MANY kilos of those metals

Kurt

 

[AlaskaLes]

Thanks for the detailed answers.
I appreciate you taking the time and I learned a lot of good information.

Les

 

[AlaskaLes]

Our ore is fairly straight forward.
Free mill gold as well as minor quantities of sulphides which hold a small percentage of PM's.
My cupelled buttons and the free mill gold nuggets that I had XRF'd last year were all very close to
87% gold and 13% silver.

I've been itching to get back to running the ball mill and the smelter again, but I'm too busy removing the 4ft of compacted snow and Ice that accumulated while I was away from home working.
Soon the Season of fun on the mountain will begin again.

 

[Nountaineer]

Kurt, I am very pleased with your willingness to help with this situation. I am also suffering with advanced Lyme disease which seriously complicates my ability to stay focused on all of this. My 85 year old Colorado prospecting buddy got here but 3 months late. He at 85 had to run a bull dozer in Texas to clean up tornado damage for a couple months so he will also assist me.

 

[Nountaineer]

I have a 100 mesh screen but cut corners previously and will be using a finer grind next time. I had it in my 10 kg furnace for nearly 4 hours and it started melting the platinum and formed metal on the sides but not a button. After grinding the slag I found that the small particles were combining to form larger pieces.

 

[Yggdrasil]

I have a 100 mesh screen but cut corners previously and will be using a finer grind next time. I had it in my 10 kg furnace for nearly 4 hours and it started melting the platinum and formed metal on the sides but not a button. After grinding the slag I found that the small particles were combining to form larger pieces.

What temperature did you have and which collector metal?

 

[Nountaineer]

This was my second firing and used flux and no collector metal. I was doing a flux combination. I used copper previously but without any flux but the kiln was not hot enough to stir it more than once.

 

[Nountaineer]

So - picking up were I left off Tuesday ------------

I have two furnaces - one that takes a #4 crucible which is used for melting pure metal &/or small assay smelts

The other one will take a #40 crucible & is used for actual larger smelting loads - the smallest crucible I have for this furnace is a #20 crucible which is what I used to determine how much - ore - flux - & collector metal I could put in that crucible - as if I was going to do the smelt on his ore

His furnace will only take a #10 crucible so his smelts will only be half of what my #20 crucible will do

I used sand from a bag of "play sand" I have --- play sand is sand that has the "dirt" washed out of it - so it is clean (fine) rock & therefore a very good representation of crushed ore

I sifted the sand through my 80 mesh screen - this is the largest mesh size you want for smelting other wise it will take a VERY extend smelt time for the flux to dissolve the gangue in the ore & slag the gangue off --- finer (100 - 150 mesh) is better but 80 mesh is just fine proved there is not a lot of it that big

The sand I have is mostly finer then 80 mesh - like only 15 -20% 80 mesh with the other 85 - 80% being 100 mesh & smaller so it will smelt just fine

So - as I posted the other day --------


Per the bold print - the question becomes - how much volume (how many cups) of ore does it take to get that 1,041 grams of ore - AND - can you put that much - or more - or less - that much ore in the crucible for the smelt --- keeping in mind that besides the ore you also need flux & collector metal in the crucible for the smelt

The ore + the flux + the collector metal = your "smelt load" --- that is the max combination of ore/flux/collector you can put in the crucible for the smelt --- keeping in mind that you need to leave head room in the crucible so that you don't have a "boil over" (the "foaming up that happens) when the smelt comes up to smelt temp

Due to the chemical reactions that take place in the smelting process there is A LOT of foaming for a period of time until those chemical reactions start to die down --- therefore you can only fill the crucible about half full - to two thirds full "at most" --- other wise you will most certainly lose part of you smelt to the boil over

Making the "smelt load" --- for every 1 part of ore you need "at least" 2 parts of flux - & when trying to collect 1 gram of gold from a kilo of ore the smelt load needs to have "at least" 30% of the load to be collector metal

If you do not have enough collector metal - when the smelt gets molten - the metals will not collect together properly & settle as a molten pool of metal in the bottom of the crucible --- instead (without enough collector metal) little beads of metal will form in the flux/slag - get hung up there - thereby loosing metal to the slag instead of pooling to the bottom of the crucible

So - back to the math - how much volume is the 1,041 grams ore (to recover 1 gram of PMs) & how much of a load can you put in a crucible

I started with filling a 1 cup measuring cup with my sifted sand & weighed it --- it weighed 352 gram

So 3 cups of ore = 1,059 grams (so very close to the 1,041 grams)

Next we need to know how much of an actual "smelt load" will fit in a crucible

So next I filled a coffee can with sand - one cup at a time - it took 9 cups to fill the coffee can

I then poured the sand into my #20 crucible to see if that was enough for a load - not enough for a load - or more then a load --- the result was that it actually filled the crucible to it's max load level --- there is no way I would put more then a coffee can of ore/flux/collector metal in a #20 crucible & in fact at that much of a load you are at the high point of risking a boil over --- so max 9 cups of ore/flux/collect all combined for the smelt load

Let's now do the math to make that load

The load needs to be "at least" 30% collector metal - lets call it 33% (or one third) to be on the safe side of good collecting

So - 1/3 of 9 cups is 3 cups fine chopped copper needed for the load --- that leaves 6 cups for the ore & flux

Side note here; - there is a reason why I put fine chopped copper in bold print - for proper collection you can not use large pieces of copper &/or wadded up copper wire --- if you need me to explain why I will be more then glad to --- fine chopped - shavings - or powder (copper) insures best collection

so - back to the 6 cups remaining for the ore/flux part of the of the load

You need at least 2 parts flux for every 1 part ore - so to make the ore/flux part of the load that comes to 2 cups ore + 4 cups flux = 6 cups ore/flux + 3 cups fine chopped copper = the 9 cups max smelt load that will fit in a #20 crucible

Your furnace only takes a #10 crucible so cut that in half which means you can only smelt 1 cup (350 grams) of ore at a time

As we have already determined - we need 1,041 grams to recover 1 gram of precious metals from your ore which means at best with your furnace you can recover only about (plus/minus) 1/3 gram of PMs per smelt load

Side note again; - in the event you have questions like --- ya but Kurt you are only talking about gold - what about PGMs &/or silver - simply ask & will be more them glad to better explain

Anyway - now that we have figured out how much ore you can process "per smelt load" with your 10K furnace we next need to figure how many smelt loads we can do in a day

That will be my next post - which I will try to do tomorrow

Kurt

Kurt, how do you finely chop your copper? I buy scrap wire or similar scrap .

 

[kurtak]

Our ore is fairly straight forward.
Free mill gold as well as minor quantities of sulphides which hold a small percentage of PM's.

Per the bold print - I am glad you brought this up AlaskaLes --- "free milling" gold (actual gold) in ore is quite different then gold that is sulfides in ore

Free milling gold is relatively easy to get a good concentrate (panning or run on concentrator table) sulfides on the other hand do not concentrate well this way - to get a good concentrate with sulfides you generally need to run the crushed ore though froth flotation

So - going back to what I posted the other day --- when smelting - in order to insure good collection of the metals at least 30% of the smelt load needs to be metal - other wise small beads of metal will hang up in the slag instead of pooling to the bottom of the crucible

So - if you are able to concentrate the ore to greater then 30% metal then you don't need a collector metal - just flux - and as I said - concentrating free milling ore - to a concentrate of better then 30% metal is relatively easy

As I understand (& please correct me if I am wrong) Nountaineer is dealing with a primarily sulfide ore

So - unless he is set up with froth flotation to concentrate the sulfides he will have to smelt the ore "as is" out of the mill --- in other words smelt the "whole" of the milled ore --- as I explained it in my post the other day

Also - what I posted the other day was speaking in general terms of smelting - call it a "starting point" of what it may - or not - take for any given smelt

In other words - depending on what is being smelted you need a starting point to see how the smelt is going to go & the odds are - more likely the not - you are going to need to make adjustments to the smelt until you find what is going to work best for the particular material you are smelting

There is NO one size fits all - there are MANY variations (adjustments) that are likely going to need to be made - from the starting point - to find what working best for the material you are smelting

You may need more or less collector metal &/or even a different collector metal - you may need more or less flux - &/or you may (or not) need to make changes to the flux ingredients them selves

Example; - I posted the other day ---------

Making the "smelt load" --- for every 1 part of ore you need "at least" 2 parts of flux

I put - at least - in bold print --- that is the starting point - the amount of flux you actually will need is going to depend a great deal on the amount of gangue you are trying to slag off --- the more gangue the more flux is needed - the less gangue the less flux is needed --- & as well - what kind of gangue you are trying to slag off is going to depend a lot on what flux ingredients work best for your material

The color of your slag as well as the texture of your slag (once solidified) will tell if &/or what adjustments may (or not) need to made from the starting point

Smelting - when first starting out - is almost always a bit of a learning curve until you find the right combination for the particular material you are smelting

For what it's worth

Kurt

 

[AlaskaLes]

That was good info!
Can you elaborate on using the texture and color of the slag as an indicator of needed adjustments?

 

[kurtak]

I have a 100 mesh screen but cut corners previously and will be using a finer grind next time. I had it in my 10 kg furnace for nearly 4 hours and it started melting the platinum and formed metal on the sides but not a button. After grinding the slag I found that the small particles were combining to form larger pieces.

This was my second firing and used flux and no collector metal. I was doing a flux combination. I used copper previously but without any flux but the kiln was not hot enough to stir it more than once.

Hmmm - not sure were to start here

So I will start by say as I read all the things you have been posting it becomes very clear to me that this is your first attempt (or very near your first attempt) at smelting - I say that with no bad reflection on you - everyone has to start somewhere

Also based on what you have been posting it is clear to me that other people that have been trying to help you ether are not giving you complete information - or flat out don't know what they are talking about themselves - or both

Again - no bad reflection on you - after all how do you know what is good advice & what is bad advice if you don't have a basic understanding about smelting in the first place

I will do my best to help give you at the very least with those basics so that you can better understand/figure out how to apply smelting to your situation

In doing this - I hope not only to help you but others as well

That said - smelting is not a one size fits all kind of thing - the MANY different kinds of materials that can be smelted need different combinations in order to get the best results from the smelting process

Before you can even start to work towards those better results you need to have at least a basic understanding of the purpose of smelting

What do I mean by basic understanding &/or purpose

The purpose of smelting is to separate (as much as possible) the good stuff from the bad stuff - in other words slag off the gangue form the target metal(s) so that the target metals collect

Smelting is in fact the practice of HIGH temperature chemistry - you need chemical reactions to take place at high temperatures in the crucible to slag off the garbage from the target metal(s)

Different flux ingredients provide different chemical reactions in the high temps of the crucible

Some fluxes act as reducing agents in the smelt - some fluxes act as oxidizing agents - some fluxes are what is call complexing

Some fluxes are acidic - some are basic (as in a base not an acid) - some are neutral

Some flux is very thick when molten so you may need to add a thinning agent (flux) so that the molten slag runs more fluid thereby providing good circulation in the crucible during the smelt --- if you don't have a good fluid circulation of the slag/flux when molten you won't get good collection

Just what kind of chemical reactions you want to take place in the crucible & therefore what flux ingredients you want to (at least) start with depends on the material you are smelting (in your case your ore)

So - your ore - as I understand it the PMs (target metals) in your ore are primarily sulfides & not actual metals

Is that correct

Also - I need to know what flux ingredients are in the flux you are currently using

Answer those two questions & we will then move on from there

Kurt

 

[kurtak]

Can you elaborate on using the texture and color of the slag as an indicator of needed adjustments?

Man - you don't ask for much do you

My book will be coming out next month

It's only going to cost $10,000 --- I will take gold in trade

not really - just kidding - if it had not been for all the free help given to me by the Real Masters - like 4metals, GSP, Lou, Harold_V etc. etc. etc. 13 plus years ago I would have never gained the experience to pass what I now know on - for free

So yes - slags will be covered before this thread is done

And thanks for asking the questions - it helps move the discussion along &/or helps in catching things that get missed

Kurt

 

[Nountaineer]

Man - you don't ask for much do you

My book will be coming out next month

It's only going to cost $10,000 --- I will take gold in trade

not really - just kidding - if it had not been for all the free help given to me by the Real Masters - like 4metals, GSP, Lou, Harold_V etc. etc. etc. 13 plus years ago I would have never gained the experience to pass what I now know on - for free

So yes - slags will be covered before this thread is done

And thanks for asking the questions - it helps move the discussion along &/or helps in catching things that get missed

Kurt

Slag is of interest to me also. The colors orange then light yellow to a darker yellow as the furnace heats up is of interest as well.

 

[kurtak]

Slag is of interest to me also. The colors orange then light yellow to a darker yellow as the furnace heats up is of interest as well.

I am out of time to post more today

I will answer your question about fine chopped copper tomorrow - the question about slags may or not be tomorrow but will get answered at some point in this thread

For right now the answers I really need from you are the answers to the 2 questions I asked here ------------

So - your ore - as I understand it the PMs (target metals) in your ore are primarily sulfides & not actual metals

Is that correct

Also - I need to know what flux ingredients are in the flux you are currently using

Answer those two questions & we will then move on from there

Kurt