Please Educate Me On Billon! They All Look Different!

@fd, here is the definition from the CCF glossary. This should get you started:





Added:

With respect to your statement:




The Ancients and Medievals Forum on CCF is my primary hangout, but I would hope that you are treated with respect and patience no matter where on CCF you are.

I also agree with Dave's definition.

In your defence, numismatists are pretty fickle in their terminology. Antoninianii from the time of Valerian until Allectus can range from maybe as high as 30-40% all the way down to the last issues of Tetricus and his son, which are under 2% fine. Technically they are all billon, as none of them are over .500. Likewise, (almost?) none are "AE" since they all have an intentional, controlled silver content. Yet you will often see coins from this period listed as any of the three (AR, BI, AE), especially the ones that are "silvered".

Realistically, all three are acceptable, as long as you don't use AR to describe a coin that doesn't have any visible silver content!

What does get me is that some people feel the need to describe anything that isn't classical Greek or Roman as billon... that is particularly prevalent with my poor Gadhaiya, which are generally well over 80% fine!

I agree, in fact, I rarely (if ever) use the Billon lablel on my ancients. Some reason I'm not comfortable with that term.

For a general book on coin terminology, I can recommend Richard Doty's "Encyclopedic Dictionary of Numismatics".

As to the specific term "billon", its use does seem to be bound more by the traditions of whatever series is being discussed, rather than any strict adherence to scientific delimitations. For example, I've never heard anyone call any Mexican coin "billon", even thought here are Mexican "silver" coins with a fineness of 0.100.

Part of the reason why "billon" can look so different is that, while silver is a small component of the composition, the other components are largely unknown, and can vary over time and from place to place. Romano-Egyptian tetradrachms, for example, are made of "billon", but the secondary components could be a mixture of copper, tin, lead and even iron. This of course will lead to differences in appearance, especially once the coins are buried, dug up again and cleaned.

A common treatment for certain series of billon coins, such as the post-Aurelian Roman antoninianii, was to make the coins appear more silvery than they actually were, by "pickling" the blanks in acid prior to being struck. The acid attacks the copper and other alloys on the surface, but leaves the silver alone, leaving a silver "sponge" that, when struck as a coin, compresses and flattens down into a thin layer of silver on the coin's surface. This method was still being used into th 20th century in some coinages (such as Australina silve coins post-1947), as it results in coins that "look good silver" when freshly struck, but such a layer is not stable long-term, either in circulation or after burial and during cleaning.