What is going on with this 1931D Saint?

[GoldFinger1969]

Orange-gold is normal for $20s in this era. The banding seems to be on a planchet and probably comes from final whitening.

 

Since chemically gold is gold, irrespective of where mined or the era, what accounts for the different colors -- impurities added or the specific coinage methods employed ?

[CSdot]

Orange-gold is normal for $20s in this era. The banding seems to be on a planchet and probably comes from final whitening.

 

Since chemically gold is gold, irrespective of where mined or the era, what accounts for the different colors -- impurities added or the specific coinage methods employed ?

 

While it is technically true that Au is Au, in this case we are talking about Au + Ag + Cu + impurities, so I can see why some years might be more orange than others due to slightly different mixes of the above elements used to produce the primarily gold alloy for the double eagle planchettes.

[coinman_23885]

Orange-gold is normal for $20s in this era. The banding seems to be on a planchet and probably comes from final whitening.

 

Since chemically gold is gold, irrespective of where mined or the era, what accounts for the different colors -- impurities added or the specific coinage methods employed ?

 

The alloy is 90% gold and 10% copper, silver, and other trace metals. It is the 10% that can drastically affect the coloration of pieces. Coins with .100 copper tend to be orange in appearance. Coins that are high in silver content (such as Charlotte and Dahlonega gold lower denomination coinage) appear greenish in appearance. Different trace metals and compositions can affect the coloration of the planchets as struck.

 

An additional consideration that can affect the coloration is toning. The 10% trace metals can tone and acquire a patina over time. And when there is an uneven mixing of the alloy (which we know happens from time to time or else copper spots would not exist), the results are even more profound and more significant toning, even though rare, can also occur.

[GoldFinger1969]

Thanks, Coinman, great answer. (thumbs u

[RWB]

The mint learned that both temperature and the type of heating used had an effect on the color of gold coins. It wasn't until methane came into standard use for annealing planchets that the desired orange-gold became a consistent product. Other fuels produced different results.

 

Surface films also affect coin color, and plastic slabs further alter color and reduce apparent contrast.

[GoldFinger1969]

Thanks RWB....fascinating !! (thumbs u