Why does my gold look like this?

[bpcp7208]

I did a small batch. Have been doing small samples to see how I do. I dissolved it doing nitric increments. Precipitated it with SMB, rinsed it and melted it. Why does it look like this?

After testing this, it is only passing as 18k. I'm curious as to why. What I started with was mainly gold and a small amount of nickel. I put 700mL HCL and increments of nitric. I didn't dissolve all of it because the day is fading quick so I filtered the solution, rinsed it and melted it. Why is it not more pure? Did I do something wrong?

 

[butcher]

The gold seems to be of high purity with something oxidizing on the surface.
The gold looks good, maybe just not the prettiest at the dance, but Hey, I would take-er out anytime and show her off.

Is this just a coating or crust of metal borates glazed over the gold from the borax flux, or is it an oxidized metal outer layer?

What are you using to melt the gold with could you be adding contaminants from your torch?

What does the melting dish look like, is there any color in the borax glazing or the ceramic glazing?

 

[bpcp7208]

The gold seems to be of high purity with something oxidizing on the surface.
The gold looks good, maybe just not the prettiest at the dance, but Hey, I would take-er out anytime and show her off.

Is this just a coating or crust of metal borates glazed over the gold from the borax flux, or is it an oxidized metal outer layer?

What are you using to melt the gold with could you be adding contaminants from your torch?

What does the melting dish look like, is there any color in the borax glazing or the ceramic glazing?

The gold seems to be of high purity with something oxidizing on the surface.
The gold looks good, maybe just not the prettiest at the dance, but Hey, I would take-er out anytime and show her off.

Is this just a coating or crust of metal borates glazed over the gold from the borax flux, or is it an oxidized metal outer layer?

What are you using to melt the gold with could you be adding contaminants from your torch?

What does the melting dish look like, is there any color in the borax glazing or the ceramic glazing?

Thank you for the swift response. I know those colors are not right and probably has something to do with it. It looks like a crust, I could see it form as the metal started to cool. I'm using a mapp+oxygen torch and regular borax. Now I didn't allow the Au to dry before melting it. My torch had a purple dust on the tip after I finished. What could that be? Also, would this cause the Au to be less pure? I'm curious if it was something along the way or the melting part. I've done a couple months of reading to make sure I do it right. It's kind of discouraging but I will get it right. I still have probably an ounce or two precipitating, going to let it settle overnight. I just wanted to see how it came out. I know I'm at fault because I have only focused on the refining process and didn't research the melting process as much as I should have.

Brandon

 

[butcher]

The pink or reddish color to the borate glaze is gold, the glaze on the dish looks clean, another indication you did a great job and have achieved gold with very high purity.

Some black, possibly soot from incomplete combustion of the torch gases (or the torch burning an over-rich fuel to air mixture)

From what I can tell from pictures your gold is good as gold, it just probably needs the borax crust cleaned from its surface.
You can try pickling it in some acid to remove the borax.

Something tells me the dish was not heated enough (or as well as I would like to see it heated when I melt gold), (glowing cherry red hot) during the melting process, allowing the bottom of the gold button to cool differently than the top sitting on the big heat sink of ceramic and excess borax flux conducting its heat.
The small beads of gold would have come together better in the dish as you melted and as you rolled the gold in the dish under the heat of the torch with the molten gold collecting the beads into its mass.

 

[bpcp7208]

The pink or reddish color to the borate glaze is gold, the glaze on the dish looks clean, another indication you did a great job and have achieved gold with very high purity.

Some black, possibly soot from incomplete combustion of the torch gases (or the torch burning an over-rich fuel to air mixture)

From what I can tell from pictures your gold is good as gold, it just probably needs the borax crust cleaned from its surface.
You can try pickling it in some acid to remove the borax.

Something tells me the dish was not heated enough (or as well as I would like to see it heated when I melt gold), (glowing cherry red hot) during the melting process, allowing the bottom of the gold button to cool differently than the top sitting on the big heat sink of ceramic and excess borax flux conducting its heat.
The small beads of gold would have come together better in the dish as you melted and as you rolled the gold in the dish under the heat of the torch with the molten gold collecting the beads into its mass.

So I melted it again and combined it with my last button. Still got this weird dull spot. I'm going to boil it in HCL tomorrow to see if I can remove it (assuming it's borax)

 

[butcher]

What was the original source of the gold?
Were there any possible platinum group metals involved?
Any lead?
Rainbow reflection of light.

Although the frosty appearance could possibly be a result of cooling rates, or some metal contamination or impurity boiling to the surface upon cooling.

I do not think I will be of much help solving this mystery, my experience here is lacking, too bad Harold is not here to help you with this, My preference would be to refine it again, others may suggest using a dash of niter in a melt with your borax.

Hopefully, someone will come up with an answer here.

At any rate, it is a very nice hunk of gold.

 

[butcher]

Maybe these will hold a clue.

Gold Plate Question - Why refine further after AP?

2nd Button - 8.5gr

How to clean gold.

Getting pure gold (shining)

https://goldrefiningforum.com/phpBB3/search.php?keywords=gold+frosty+after+melt

 

[Shark]

What are you using as a precipitant?
What kind of filter are you using to filter your gold solution with?

Heat the button in acid, it may require HCl, nitric or Sulfuric depending on the particular problem material. This will let you remove some offending materials before another refine. It can also remove the majority of the problem if it is trash floating on top as it cools. That gooey, brown is usually from a poor filtering/washing in my case. I have become obsessive compulsive about filtering, (and washing), using quality filter papers because of such stuff when I first started.

The button actually shows signs of good quality. Remelting in the same dish without cleaning it will cause the same problems, especially if it is surface contamination.

 

[Lino1406]

Precipitation was not mentioned, only dissolution and melting

 

[bpcp7208]

Precipitation was not mentioned, only dissolution and melting

I precipitated with SMB. Could it be some of the SMB if I had put too much? Also my precipitate is superfine, almost colloidal gold if it isn't and it makes filtering very time-consuming even with a bushner filter with a suction hose. Is there a way to get the precipitate any bigger?

 

[Shark]

Getting pure gold (shining)

SMB is soluble in water. If it is SMB a hot water wash of the precipitated powders will remove it, if done correctly. Having really fine powders is a good sign that the gold needs cleaning better. The purer the gold the more it will collect together and can become almost a lump if really pure. I don't filter my powders, I use the decanting method. Any powder that doesn't settle within a minute (on the second refine) gets poured off and reprocessed later. Anytime I have a fine drop, I wash thoroughly and and re run the AR process, using a different precipitant at times, and maybe even a different oxidizer. A different precipitant can allow some contamination's to not drop on the second refine, often improving the powders qualities. A filter is there to catch particle size, it won't remove impurities once you have dropped your gold. This filter allows the impurities to be trapped with the gold as it is melted.

In your first post you said:

Precipitated it with SMB, rinsed it and melted it.

Can you explain how you rinsed it?

 

[bpcp7208]

Getting pure gold (shining)

SMB is soluble in water. If it is SMB a hot water wash of the precipitated powders will remove it, if done correctly. Having really fine powders is a good sign that the gold needs cleaning better. The purer the gold the more it will collect together and can become almost a lump if really pure. I don't filter my powders, I use the decanting method. Any powder that doesn't settle within a minute (on the second refine) gets poured off and reprocessed later. Anytime I have a fine drop, I wash thoroughly and and re run the AR process, using a different precipitant at times, and maybe even a different oxidizer. A different precipitant can allow some contamination's to not drop on the second refine, often improving the powders qualities. A filter is there to catch particle size, it won't remove impurities once you have dropped your gold. This filter allows the impurities to be trapped with the gold as it is melted.

In your first post you said:

Precipitated it with SMB, rinsed it and melted it.

Can you explain how you rinsed it?

I poured hot distilled water over it a few times while it was still in the filter

 

[Lino1406]

If that's really matters, some use oxalic acid precipitation to get bigger crystals

 

[Shark]

When we drop gold, especially from a dirty solution, it can pick up other metals that may be in solution. When we wash it, it can mean water, especially hot or boiling water. This will remove certain contaminants that are water soluble, but leave some that aren't. So after a water wash we use an acid wash, usually hydrochloric, to remove any metals that came down with the gold that water can't deal with. Nitric acid as well as sulfuric acid can be used, and may work better at times depending on the other metals in solution. Here is how I wash most of my dropped powders.

Allow the powders to settle well in the beaker. (can take hours if not days)
Decant off the AR with out disturbing the powders to much.
Boil in water, 2 or 3 times. (Decant the water between heating and start with fresh water.)
Add acid and and allow to sit while cool for 10 minutes.
Decant this off and add new acid, this time add heat to just under boiling.
Decant and add new acid and heat to just below boiling.
Decant and add water and boil. Do this again two or three times.

So long as the water becomes even slightly cloudy or the acid changes colors repeat alternating between the water and acid wash until both remain clear. I do a water wash last to remove all traces of acid, then gently heat in the beaker until no moisture condenses on the sides of the beaker and steam is coming from the powders. I don't use a cover as we want to completely dry the gold at this point. I don't boil as this can cause gold to fly out of the beaker in small steam pockets bursting and send it flying. Just enough heat to see the steam and see moisture condense will get the job done. When it is dry, the color can give you a good idea of purity. The paler the color usually the better the gold. Use a clean dish and melt your gold.

 

[bpcp7208]

Getting pure gold (shining)

SMB is soluble in water. If it is SMB a hot water wash of the precipitated powders will remove it, if done correctly. Having really fine powders is a good sign that the gold needs cleaning better. The purer the gold the more it will collect together and can become almost a lump if really pure. I don't filter my powders, I use the decanting method. Any powder that doesn't settle within a minute (on the second refine) gets poured off and reprocessed later. Anytime I have a fine drop, I wash thoroughly and and re run the AR process, using a different precipitant at times, and maybe even a different oxidizer. A different precipitant can allow some contamination's to not drop on the second refine, often improving the powders qualities. A filter is there to catch particle size, it won't remove impurities once you have dropped your gold. This filter allows the impurities to be trapped with the gold as it is melted.

In your first post you said:

Precipitated it with SMB, rinsed it and melted it.

Can you explain how you rinsed it?

The only thing I'm processing is gold and nickel. There's nothing else in the solution. I'm only getting between 18-22k. Could smb drop any nickel? What else could I use to precipitate? The only impurities it could have is nickel so I'm confused as to why it's precipitating so finely.

When we drop gold, especially from a dirty solution, it can pick up other metals that may be in solution. When we wash it, it can mean water, especially hot or boiling water. This will remove certain contaminants that are water soluble, but leave some that aren't. So after a water wash we use an acid wash, usually hydrochloric, to remove any metals that came down with the gold that water can't deal with. Nitric acid as well as sulfuric acid can be used, and may work better at times depending on the other metals in solution. Here is how I wash most of my dropped powders.

Allow the powders to settle well in the beaker. (can take hours if not days)
Decant off the AR with out disturbing the powders to much.
Boil in water, 2 or 3 times. (Decant the water between heating and start with fresh water.)
Add acid and and allow to sit while cool for 10 minutes.
Decant this off and add new acid, this time add heat to just under boiling.
Decant and add new acid and heat to just below boiling.
Decant and add water and boil. Do this again two or three times.

So long as the water becomes even slightly cloudy or the acid changes colors repeat alternating between the water and acid wash until both remain clear. I do a water wash last to remove all traces of acid, then gently heat in the beaker until no moisture condenses on the sides of the beaker and steam is coming from the powders. I don't use a cover as we want to completely dry the gold at this point. I don't boil as this can cause gold to fly out of the beaker in small steam pockets bursting and send it flying. Just enough heat to see the steam and see moisture condense will get the job done. When it is dry, the color can give you a good idea of purity. The paler the color usually the better the gold. Use a clean dish and melt your gold.

Thank you for the detailed instructions, I will try that!

Brandon

 

[bpcp7208]

Getting pure gold (shining)

SMB is soluble in water. If it is SMB a hot water wash of the precipitated powders will remove it, if done correctly. Having really fine powders is a good sign that the gold needs cleaning better. The purer the gold the more it will collect together and can become almost a lump if really pure. I don't filter my powders, I use the decanting method. Any powder that doesn't settle within a minute (on the second refine) gets poured off and reprocessed later. Anytime I have a fine drop, I wash thoroughly and and re run the AR process, using a different precipitant at times, and maybe even a different oxidizer. A different precipitant can allow some contamination's to not drop on the second refine, often improving the powders qualities. A filter is there to catch particle size, it won't remove impurities once you have dropped your gold. This filter allows the impurities to be trapped with the gold as it is melted.

In your first post you said:

Precipitated it with SMB, rinsed it and melted it.

Can you explain how you rinsed it?

So this has been sitting for over an hour. I should refine this a second right? Will it dissolve faster where its colloidal?

 

[bpcp7208]

So this is the result after I leached then finish dissolving. Does anyone know why the first leech looked like that? Clearly the second round came out as it's supposed to. But I'm curious as to why the first leaching came out so fine and gray?

 

[Shark]

In the first picture those fine particles that are real slow to settle I usually decant off. It seems that very often they are overly dirty and affect the purity. I keep a separate container to catch them in and allow them time to settle completely. Siphoning off the solution as more room is needed, and reworking them later. Once that light stuff is decanted off, I start my washing procedure. You will notice that after each washing that the powders will settle faster and have less "floaty" stuff in them. That cloudy look is what you are trying to remove, but knowing just what it is will be hard to guess from looking at it. This is why I prefer to decant rather than filter the powders. I can see the cloudiness improve and know that it getting gone with the rinses.

I would decant it, and re refine the remaining, settled powders. Or allow to settle and siphon it off and start washing the powders, water/acid alternating until both come out clear. If happy, melt if not, refine again.

In the next picture, I am not sure what causes that dark color but it is sign that can mean some contamination. The other beaker looks good. I would still run it through a wash cycle, (acid/water, rinse repeat) just to make me feel better.

My math may be off, but if your starting with 18% nickle and 82% gold, you would have to add base metals to produce 18K gold from it. 18/22 would be around 19K to 20K starting off. I would take another look at my testing as well to be sure it isn't better than your thinking. File a small spot and test from the freshly exposed area.

 

[nickvc]

If you want larger particles precipitate from more concentrated solutions, if you re refine your powders you will see this, because the solutions are usually more concentrated you get larger particles and easier settling.

 

[g_axelsson]

One way to clean up a dirty looking powder is to decant off the top clear solution, add HCl and boil it for a while to see if it will improve. Add a lid to keep evaporation to a minimum. The acid cleans off the surface of the particles and lets them clump together easier. You will see that the gold powder goes from dark to pale over time as the acid cleans it up.

Another way that I've done a couple of times is decant off as much clear liquid as possible. Add a bit of HCl, not much, and a few drops of nitric acid. This will dissolve some of the gold, especially the smaller particles that doesn't settle well and then when the reaction dies down, precipitate the gold again. This will precipitate the last gold as larger particles.
Instead of nitric you could add a dab of bleach or strong hydrogen peroxide before precipitating the gold again. I've used all three alternatives.

This takes less time than just one cycle of washing gold which takes a long time to settle.

Göran