Pyrite or chalcopyrite?

[kjavanb123]

All,

Recieved this sample ore to smelt for gold. To me it looked like fools gold, I tested a little of nitric acid on the yellow pieces and got no reaction. Based on the ore color I would say it is pyrite or iron compound, what do you think? It is being smelted right now.



And this is another shot with rest of the ores



Regards

 

[Reno Chris]

It is so hard to tell from a photo, but it looks like gold. Sulfides like pyrite and chalcopyrite dont react quickly to acids. If it were chalcopyrite, you would have blue staining on the rock from the copper in the chalcopyrite. So its likely either gold or pyrite. Split off a piece of the gold colored stuff so that its separated from the rock, then put it on something very solid like some iron and hit it firmly with a hammer. If its a sulfide it will shatter into bits. If its gold it will mash down and flatten but hold together.

Even if you melt it and pour the golden stuff into a mold, just because it melts and pours, that does not prove anything. Sulfides also form a melt and can be poured. Hit the edge or corner of the bar firmly with a hammer and you'll get the same brittleness test - sulfides shatter, gold dents.

 

[Anonymous]

I agree with Chris when you blow the second image up it looks like bonanza gold. Is that quartz in the first picture Kevin?

 

[kjavanb123]

Reno,

Excellent tips on how to identify the gold from pyrite. As I mentioned, this sample bag was sent to me for smelting. We did not complete the smelting yet, due to a leakage of the bottom of furnace which my operator is fixing today so I will know the result if there was any gold in them.

Spaceship,
There was small amount of quartz in them, mostly what I believe is iron oxide compound, maybe hematite or geothit. There are IOG, iron-oxide-gold compound. Or is it ICG (iron-copper-gold) as my geologist friend once told me.

 

[Platdigger]

I see it too guys. When you blow it up really big it looks to be full of gold.
Wouldn't that be nice.

 

[g_axelsson]

All I see is a heavily weathered rock. It's impossible to say if it's chalcopyrite or pyrite since the surface is covered in iron oxides and hydroxides. My guess is a pyrite precursor as there are no signs of secondary copper minerals what so ever. Could even have been a siderite precursor.

We all know that iron hydroxides can easily form yellow rocks, so I don't think the yellow dots is gold. kjavanb should be so familiar with gold now so he should have at least commented on it if it was even close to metallic shine. They are probably only brighter yellow spots.
If the yellow spots are gold then I would recommend crushing and panning and not smelting.

I don't think there is a lot of sulfides in this material either, there are no fresh breaks and sulfides are brittle just as Chris says. There should have been broken surfaces all over this material if these rocks were made of mostly sulfides. I think that what we are seeing is actually the remaining minerals left after the sulfides have weathered away.

At least, break a rock open and show us the fresh surface. Identifying minerals from a picture of a weathered stone is virtually impossible, all you see is the dirt on the outside. It's as useful as holding up a bag asking what minerals are inside. The rust on the outside could just as easily have come from some rusty iron close by as from the rock itself.

Going back to smelting ore, you don't need much of gold before you have ore. Many ores doesn't even have visible gold but could be quite rich. Only way to tell is an assay, so what did the assay say?
To smelt ore you first need to know what the ore consists of. If it's a copper ore (chalcopyrite) you turn the ore into raw copper, then refine the copper to get the gold as a byproduct. If you don't have copper in the ore then you might need a collector to get any gold.
To just smelt the ore without any plan based on the content of the ore is just wildly experimenting and even a rich gold ore could result in no extracted gold. How are you going to tell if the smelting worked if you don't know what's going in as ore or out as slag? You need assays to tell you if the smelting worked.

I want to see the assay...

Göran

 

[Reno Chris]

goran - if you don't click on the photo and magnify it, the stuff which appears to be gold is hard to see. It may or may not actually be gold.

Either way, its not good to just dump the rock in and smelt it whole as that is likely to result in high losses of gold (if it is gold) or even a total loss of gold (as goran noted). The material should be crushed and the gold looking mineral concentrated by panning or some other method. Then the concentrate should be smelted. This will minimize any loss of gold. Smelting uncrushed rock chunks like these will result in a large loss of gold in the slag as the gold will not separate cleanly from the rock.

Before I bothered with crushing and processing, I would take a knife, pry off a chunk of that gold looking stuff and hit it hard with a hammer to see if its a sulfide or if its actually gold. If sulfide, I would just return the whole batch to the owner. If gold, I would proceed with crushing and processing and ultimately smelting.

 

[kjavanb123]

Gentelmen,

Smelting was completed today. I did pulverize them to fine powder prior to smelt. I have not weighed the gold recovered yet, but my operator said there is some 1 to 2g of gold powder left after nitric digestion. I will have to check it out tommorow, dissolve in AR, and drop it and finally melt it to see exactly how much gold was recovered from smelting 18.7kg of these rocks.

Thanks for your input.

Regards
Kj

 

[[email protected]]

Hi All

I am a new member, ,I am really asking for your help..I have a material that has lots of Iron and I believe also a lot of sulfides, ,I tried nitric leach followed by Aquaregia but stil failed to extract Gold from the material ,,I can see Gold from the material and yes even from the solution aftr filtration they can stil be Gold in it but I just don't know where to from now to be able to separate the Gold from the other metals, ,please please assist, ,thanks

 

[g_axelsson]

Hi All

I am a new member, ,I am really asking for your help..I have a material that has lots of Iron and I believe also a lot of sulfides, ,I tried nitric leach followed by Aquaregia but stil failed to extract Gold from the material ,,I can see Gold from the material and yes even from the solution aftr filtration they can stil be Gold in it but I just don't know where to from now to be able to separate the Gold from the other metals, ,please please assist, ,thanks

If you can see gold then crushing and panning is the way to go.

But be aware that many sulfides may look as gold to the untrained eye. Take one of the gold grains you see and crush it between two metal surfaces. Does it break up or just smear? Gold is malleable so it will just smear or flatten out while sulfides breaks down into fine powder, often a dark gray or black powder.

And welcome to the forum! A tip, add your location to your public profile so people can see where you are from without looking at your profile. It will help you getting better advice.

Göran