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Unequal Karat

G’day, Tom; I don’t know whether the following is worth 2c but
here goes anyway. Karat/carat gold is a true alloy; a solid
solution of one (or more) metals in another. The only way to
separate two (or more) substances from a solution is by fractional
crystallisation. Thus suppose a solution of sodium sulphate and
sodium chloride needs to be separated: some of the water can be
driven off by evaporation, and the two substances will slowly
crystallise out, and the different crystals can be picked out of
the vessel, but you can’t do that with gold /copper, etc solutions
The separation will occur if the metal is allowed to cool extremely
slowly - that’s how rubies separate from a pegmatite matrix
containing aluminium oxide in nature, and almost pure gold
crystallises out of an incredibly hot solution of water, quartz,
gold, etc in the ground. Now, having said all that, my point is
that a properly melted and stirred gold alloy (or any other metal)
poured into a mould and thus quickly cooled wouldn’t have time to
separate. So, my opinion is that any unevenness in a gold casting
would be due to the alloy not properly made in the first place.
Does that make any sense? Cheers anyway,

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At sunny Nelson NZ