Hi, my name is Jason Gaber with Mt. Baker Mining and Metals, and today I wanted to do
a video on smelting.
We get a lot of guys who ask what to do with their black sand concentrates off of the table.
And they have high sulfide concentrates in their number one and number two high grade,
after they pan out all the free gold.
I wanted to do some experiments here, get them on video, and I’m really interested
in comments and tips from you guys, who have more experience with smelting than I do.
So I’ll show you what I’m going to do, how I’m going to do it, and all the tools
I’m going to use, and let’s see what you guys think.
Here’s some of the high-grade concentrates that come off the shaker table.
And this is the number one and number two port.
And I’ve panned out all the free gold.
I’m not going to roast this stuff, I’m going to smelt it as is.
And the strategy there is I’m going to actually have the mat form, then reprocess the mat
using a different flux.
But the reason I’m doing that is because it’s really hard to roast a bunch of material.
It’s easy to roast about a quarter cup or half a cup.
But when you want to do pounds and pounds of material, it takes a long time, and you
got to have it all exposed to the oxygen in the air and get it to 12 to 1300 degrees fahrenheit.
So I’m going to try to force it into a mat-phase with the first smelt, and then after the first
smelt, I’m going to take the mat and reprocess it using potassium nitrate, which is a very
extreme oxidizer, and some iron filings, so I can avoid the roast.
I took one cup of the high grade number one and number two, and mixed it with two and
a half cups of chapman flux, and added about a pound of fine copper wire to the mix as
a collector metal.
I’ve found if you don’t have enough metal in the charge, that when you pour the material
in your conical mold, you don’t get the button at the bottom, it all stays suspended
in the slag.
So you need a collector metal to filter down through the material and capture the gold
and other precious metals, and bring it down to the bottom in a button, or a little pyramid.
So I use copper.
Lead is another one, it’s the one they use in fire assay, but a lot of guys want to stay
away from lead since it’s toxic.
A lot of companies won’t take lead and refine it, whereas copper & gold refining is common
and easy to do.
I’m going to put another one pound of fine copper wire to the top, so as it melts it’ll
trickle down through and act as a collector metal.
So here’s the chapman flux recipe that I’m going to be using.
The sodium tetraborate is borax, and it’s covered up there a little bit but it’s 40%.
Sodium Carbonate is soda ash at 20%, Silica is just quartz, and Manganese Dioxide as an
oxidizer.
Here are the two other pieces that we made to go along with this.
This is a conical mold we made.
You can pour a number 10 crucible in there and it comes just to the top.
And these are some tongs we made to get the crucibles in and out of the kiln there.
And like we said earlier this is really an R&D experiment.
I got the kiln for a couple reasons, one it was fairly cheap.
But also you can put a pretty good size crucible, I have- sitting over there- I have another
segment that can go on top of there, so I can actually put about a number 80 or 100
crucible in there, so I can do a really big smelt once I get the hang of it, in an oven
that’s pretty cheap.
I probably have less than 500 dollars in this, including crucible and flux.
Let’s take a real quick peek in there.
I don’t know if you can see anything in there.
I’m going to give it a stir, then wait another half hour, then another stir, then we can
pour.
So there’s our conical mold, with pour in it.
So we’ll let that cool, and then we’ll dump it out, and see what the button looks
like.
So there you go, a couple taps on the table, and the slag and stuff fell out of the mold.
And you can see the copper and metal all came down to the bottom, and the slag was sitting
on top.
So I’ve broke our three different phases apart here, here is the metal pyramid at the
bottom of the cone.
This section here is the mat that formed, it’s the artificial sulfide because it didn’t
get all oxidized because we didn’t roast it.
And this black stuff is all the slag.
So here’s our copper pyramid from the smelt we did.
And it weighs 1 pound, 2.75 ounces.
And I went and polished a side here and had it analyzed with an XRF gun that my friend
has, and I think I can post a picture of the results.
So by doing the math with the results of the XRF gun, I can calculate the amount of gold
we recovered.
And we recovered right around 8 grams of gold, by doing our copper collector metal smelt
on the number one and number two table concentrates.
So here’s the composition of the potassium nitrate flux I’m going to be using to process
the mat.
And you can see there’s quite a bit of borax in there, and I’m going to add a little
bit more silica.
So here’s a look at our potassium nitrate flux, and here’s some of the iron filings
I’m going to be using.
And I’m going to add about one part flux, one part iron shavings, and one part mat,
and see how it goes.
And here’s a separate smelt I did on the mat that was recovered from the first smelt
we did.
So I took all the mat from the first smelt, broke it off, and re-smelted it with some
potassium nitrate and iron filings.
And as you can see, I didn’t use any copper, but we recovered copper from the mat.
By adding iron filings to the smelt, the iron removes the sulfur from all the different
types of sulfides in the mat, and forms FES, which is soluble in the slag.
And the only problem I had here is I added too much iron and not enough slag, so the
slag couldn’t absorb as much iron sulfide as I added.
So I essentially created an iron sulfide mat here, which is okay because most of the precious
metals and base metals ended down here in our copper button anyway.
So it was a successful processing of the mat from the first smelt, and we got away from
roasting any of our sulfides.
So I really appreciate you guys watching my video on smelting.
And I’d be really interested to hear from some of your tips and tricks on how to smelt,
and how I can improve my process, because as I said, a lot of our customers are interested
in the process about how to recover some of their gold from concentrates they have on
their table after recovering free gold.
I’ll also post some links in the description of the video that I found really useful when
I was figuring out how to get the process figured out.
So be sure to check those links for more information on smelting and fire assay.
So thanks for watching and feel free to email me with any comments or questions you have.