Copper color pence

goossen

Got this coin from a lot some time ago. It's a 6 pence 1948, from Great Britain.
The thing is that according the Krause this coin should not be copper color! Comments, opinions?

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newsman

Is it possible the coin is just so badly corroded that it changed color?

goossen

I don't think it's corrosion, because the krause says the coin is made of Cu - Ni.

SYRACUSIAN

Is it possible the coin is just so badly corroded that it changed color?




Newsman, be nice to new members!



Welcome goosen.

newsman

Hi, goosen!

I have a Cu-Ni 6d that's toned black on the reverse, so I guessed it might be possible.

coinkat

This could get really interesting... the coin looks to have issues associated with copper... green virdegris...

goossen

<< <i>This could get really interesting... the coin looks to have issues associated with copper... green virdegris... >>



Yes I noticed that too, a Copper clad maybe ? Is there any method to know if it's copper clad or "solid" copper ?

spoon

I thought these were alloyed CuNi, rather than clad?? If alloyed, then either you have an extremely odd off metal strike or an extremely toned coin. If clad then it may indeed be a mint error (what's that called again?).

That said, I have seen coins with that earthy toning. But yours does look like copper at that scale. Any way you can give a bigger picture? A problem with this theory, though, is that Brit pennies and below were bronze, not copper. An off metal strike would have to have been deliberate and in that case would likely be recorded somewhere by now. (Perhaps it is, I don't have the right books to know!)

Ways that might narrow down the possibility... if you have another sixpence of this type, compare the thicknesses (though even if it is clad and lacking the nickel the difference may be negligible); try dipping it in acetone or xylene to remove the crud (if PVC), this won't remove the toning but may make apparent if it is indeed extreme toning on CuNi or full copper.

I dunno, but welcome anyway!

tbirde56

Similarly, I have a well worn 1928 Portuguese Escudo which, although it's also supposed to be copper-nickel, appears to be a uniform bronze color. Acetone didn't faze it but some wear on the edge reveals a slight bit of its true silvery color. I have no idea what caused it either.

Sylvestius

That coin has been buried at some point most likely.


The 'silver' coinage from 1947-prsent is a Copper-Nickel alloy and should be grey in colour. However under certain conditions they can turn brown, being buried is one of those conditions. I know because i have a brown coloured florin from 1951 that we found in the back garden.

I've come across CuNi decimal coins in circulation that have probably spent long times in puddles on the street and they turn a spotchy brown/black. I had a nasty 5p just like that the other week.

goossen

I'll try to post better pictures.
If the coin is toned, how you can explain the verdigris ?
Sadly I haven't another 6 pence to check. About the acetone test, where I can get it? I haven't experience with those methods.

spoon

The acetone likely won't do much to remove the toning and make the true color apparent, as Syl said. But it will likely get rid of some of the verdigris and so doing may make it a only slightly easier to tell. For how, try a search of the forum for acetone. (Just dip a few seconds in pure acetone from your local hardware store's paint section.)

Also, you might try putting an extremely small, careful knick on the edge with a razor to see the color.

goossen

Ok, here are high resolution pictures.

If it helps, the coin is not magnetic.

Sylvestius

<< <i>I'll try to post better pictures.
If the coin is toned, how you can explain the verdigris ?
Sadly I haven't another 6 pence to check. About the acetone test, where I can get it? I haven't experience with those methods. >>



If you bury a CuNi coin underground or leave it lying around on the street it will turn brown sooner or later due to corrosion. The copper in the mix will also develop verdigris because water (generally acidic, especially in certain soils and of course acidic rain water, often contains carbon dioxide). When carbon dioxide is dissolved in water it makes it slightly acidic, the H2O and the CO2 then react simultaneously with the coin and form a copper carbonate, a rather complex hydrated carbonate at that, which is verdigris.

goossen

Sylvestius, that was a "wow" explanation! Thank you!

Between parenthesis, it's awesome how collecting coins educate you in many other subjects. When you collect coins you learn about history, chemistry, geography, foreign languajes, etc....