Bismuth as a precious metal collector

fireguy

fireguy

Supermoderator
#1
#1
I was recently asked about using metallic bismuth as a collector in a precious metal refining operation. Silver was being used, but due to bismuths lower cost and lower melting temperature (530ºF) the change was being considered.

Bismuth should work well as a collector and has the advantages listed above over silver. There are also several advantages over lead- including the less toxic nature and lower regulartory requiremets and therefore may be more appropriate in some cases.

You can see more details on bismuth needles (shot) here:

http://www.lmine.com/go.mvc?ID=bismuth

Can anyone comment as to other advantages and/or disaadvantages?
 
N

Nevadamet

New Member
#2
#2
Source of granular lead

Hi:
We use granular lead for a collector in our process, but have been having trouble finding it. Can anyone recommend a source?

New to this forum :oops:
 
fireguy

fireguy

Supermoderator
#3
#3
Re: Source of granular lead

Nevadamet said:
Hi:
We use granular lead for a collector in our process, but have been having trouble finding it. Can anyone recommend a source?

New to this forum :oops:
Click to expand...
Asarco stopped making test lead (and litharge for that matter) when they closed the Globe Plant in Denver in 2006. Lead, like most other metals, has had a fairly steep price increase of late, but 30 mesh test lead can be found here:
http://www.Lmine.com/go.mvc?id=litharge_lead
 
J

JonSnow

New Member
#4
#4
Make sure to run a blank on your bismuth. As a rule, you should always run blanks on your chemicals, but for some reason the bismuth I have bought over the last 3 years has varied in both gold and silver content. This is not a problem as long as you know your base line for reporting your gains.
 
fireguy

fireguy

Supermoderator
#5
#5
JonSnow said:
Make sure to run a blank on your bismuth. As a rule, you should always run blanks on your chemicals, but for some reason the bismuth I have bought over the last 3 years has varied in both gold and silver content. This is not a problem as long as you know your base line for reporting your gains.
Click to expand...
Are you using assay grade bismuth oxide? This should have very low gold content and fairly low silver. If you are using metallic bismuth, you should be able to source material with very low gold content- but what you say is true if you are using material not specifically for assaying.
 
J

JonSnow

New Member
#6
#6
The last bismuth trioxide I bought in March was 25kg from Legend, so it is of good quality. Like I said, it is not a problem as I know the base line of how much gold it will report. When used in a 30g standard fire assay it is not of much concern, but when used in a smaller size test, like a 5 gram scorification, it reports 1 gram of gold per ton.
Let me rephrase this. Using 50g of bismuth trioxide with a 5g ore sample will report 1 gr/t gold.

I still use it and now that I think about it, need to re-order it soon.
 
F

Fred Stone

New Member
#7
#7
Bismuth Collector

Be very carefull using Bi as a collector if the material is going to a refiner for sale. Most refineries avoid Bi if possible or have large surcharges for it's presence. At our refinery we start to get excited if the material has over 100 ppm contained Bi.
 
fireguy

fireguy

Supermoderator
#8
#8
Re: Bismuth Collector

Fred Stone said:
Be very carefull using Bi as a collector if the material is going to a refiner for sale. Most refineries avoid Bi if possible or have large surcharges for it's presence. At our refinery we start to get excited if the material has over 100 ppm contained Bi.
Click to expand...
Is the surcharge for bismuth more than the surcharge for lead? Or is lead not an issue?
 
F

Fred Stone

New Member
#9
#9
Bismuth Collector

Surcharges for lead start in the percent range and surcharges for Bi start in the ppm range. If you had matereial that ran X percent bismuth I't would be tough to find a refiner to take it other then very samll quantities and high PM grades.
 
A

alikoba

New Member
#10
#10
Would anyone please tell me the detailed method of fire assay using Bismuth?
I am currently working on fire assay using lead but considering to use bismuth
as an alternative of lead. I, however, have no knowledge of bismuth fire assay
and could not find any useful information at the moment.

It would be also great if anyone know any tips about the scorification assay using
Bismuth instead of lead for metal collector.

Thank you so much for your help.
 
fireguy

fireguy

Supermoderator
#11
#11
alikoba said:
Would anyone please tell me the detailed method of fire assay using Bismuth?
I am currently working on fire assay using lead but considering to use bismuth
as an alternative of lead. I, however, have no knowledge of bismuth fire assay
and could not find any useful information at the moment.

It would be also great if anyone know any tips about the scorification assay using
Bismuth instead of lead for metal collector.

Thank you so much for your help.
Click to expand...
The "detailed method" would need to be developed for your ore type. You can find a copy of the original patent online here:
http://www.google.com/patents/US5279644.pdf

Several differences between the bismuth fire assay and litharge fire assay:
  • The bismuth button is brittle and cannot be pounded. Use pour bar rather than conical mold.
    Bismuth is more expensive, so the typical flux will not contain an excess of bismuth trioxide.
    Some brands of cupels work better than others. Use MgO cupels.

Other than that the two methods are quite similar.
 
A

alikoba

New Member
#12
#12
Many thanks, fireguy!

The "detailed method" would need to be developed for your ore type. You can find a copy of the original patent online here:
http://www.google.com/patents/US5279644.pdf
Click to expand...
I know this patent and have read it before. This one is very much helpful but
it is someone's intellectual property so that I could not use it freely. I wonder
if there is anything else, such as technical report or historical document refering
to Bismuth fire assay.

Some brands of cupels work better than others. Use MgO cupels.
Click to expand...
Does Mabor Magnesia Cupel work well?
 
fireguy

fireguy

Supermoderator
#13
#13
alikoba said:
Many thanks, fireguy!

The "detailed method" would need to be developed for your ore type. You can find a copy of the original patent online here:
http://www.google.com/patents/US5279644.pdf
Click to expand...
I know this patent and have read it before. This one is very much helpful but
it is someone's intellectual property so that I could not use it freely. I wonder
if there is anything else, such as technical report or historical document refering
to Bismuth fire assay.

[quote:2ohowrqs]Some brands of cupels work better than others. Use MgO cupels.
Click to expand...
Does Mabor Magnesia Cupel work well?[/quote:2ohowrqs]

There are several companies using the bisumth fire assay, so I don't think the intellectual property question is an issue. The Mabor cupels work well with the bismuth assay.
Regarding specifics, I would suggest you proceed on a trial and error basis using standard fireassay techniques, with attention to the differences noted above. For the flux composition, try something in the range of:
Bi2O3: 35%
Borax: 10%
Soda ash: 40-50%
Silica: 5-10%
If the slag is to thick, you might need to add some Flurspar- 5-10%
You will need to optimize for your particular samples and ore type.
 
A

alikoba

New Member
#14
#14
Thanks a lot, fire guy.

I would follow your suggestions when I try Bismuth fire assay.

Thank you again for your great help.
 
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