So How do You Purify Gold?

Originally posted Thursday, November 01, 2012

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So how exactly is gold extracted from gold ore?

The Primus Report recently gave an elegant account:

So how do you purify the gold?

More importantly do you have enough gold to make the process worth while?  Most folks think of just melting the whole thing down and viola there is the gold!  Not quite how it works.  There are actually 2 processes that are involved, assaying and smelting.

Gold furnace from lulusoso.com catalogue

Assaying is determining what you have or how much is in the sample.  If you have been out mining and have a lump or three of rock you need to know its composition detailing what is in that rock so that you know “IF” your in the right area to find what it is your looking for, in this case, gold.

When I say smelting, many people have visions of gigantic furnaces belching smoke and huge cauldrons bubbling with molten metal.  But the truth is that neither is really needed to take gold from its source.

In an assay you are reducing the sample to its component parts to determine its composition.
In a smelting you want to oxidize everything else and leave only, in this case, the gold.  To do this you need what is know as a flux.

Odds are that the gold you get will be in pretty good shape to begin with, containing only modest amounts of impurities like black sand, quartz or base metals.

These base metals become salts and are oxidized by the flux where they are trapped until the melt is poured. Other contaminants are also trapped by the flux that then floats to the top of the gold

WARNING:- Borax attacks the clay crucible so do not use much!

Small smelting furnaces can be purchased from  suppliers for a few hundred dollars, most are electrical and can be set up in a back yard shed or garage.  They usually have a crucible made of clay but you can also get one made of graphite that helps keep gold in its metallic form.

Heat until the mix until there are no bubbles, foam, or lumps in it. Then pour into a mold and cool.   Once cooled remove from the mold, the gangue on top can then be struck with a hammer and removed.

And be mindful!

Borax attacks the clay crucible so do not use much!