I have this ancient I cleaned harshly, thinking it would show something but I think not. It attracts to rare earth magnet, not strongly but enough so it doesnt fall off when spinning. I haven’t studied metallurgy but I’m guessing lead? Some alloy of nickel? All of the other small coins I cleaned didn’t stick at all to the magnet. Thanks, joe
Some ancient coins have a bit of iron in the mix. I have a page on metallurgy with the composition of some LRB's. http://www.constantinethegreatcoins.com/metallurgy/
All of these below are magnetic along with the Julian coin I mentioned in: https://www.cointalk.com/threads/lrb-what-is-it.367253/page-2#post-4889164
My guess is that the soil these coins were buried had high iron content, and over time the moisture made those iron containing salts to leach into the metal, and with some redox chemistry the metallic iron content became high enough to be magnetic?! I'm just basing this off my high-school chemistry!
It doesn't take much iron (or, less likely in ancients, nickel) for a coin to respond to a magnet, especially a powerful magnet. It is quite common among Chinese and other Asian cash and can be used to help attribute to mints. For example, Wang, Cowell, Cribb and Bowman's paper Metallurgical Analysis of Chinese Coins at the British Museum, notes (p.1) "Both the yuan coins and the 150 BC banliang coins contain traces of lead, tin and iron, consistent with them being made from the first refining of copper ores, suggesting that they were probably made close to the mines from which the ore was extracted. A distinctive characteristic of these coins is that the small amount of iron in them renders the coins susceptible to a magnet." It is likely that late Roman bronze coins, especially in periods of very high volume minting, would have used the cheapest materials available - and thus any "new" copper was likely the product of minimal processing - i.e. one refining cycle - and thus contained elevated Fe levels when compared to more refined products. SC
If the fact that some LRB's contain iron is surprising, get ready to be really surprised-- some LRB's are radioactive. The metal Indium is occasionally found in alloys of fourth century coins. It is similar to aluminum and its most common isotope is very slightly radioactive. Coupled with the dangers of lead, it seems LRB's might be dangerous. If you are concerned, send them to me for proper "disposal"
In fact, the rarer and more valuable the LRB, the more likely it is radioactive. So send you best coins to Victor first!! [joke! - unless I get my cut!] Seriously though, it would be interesting to see the figures for any measured coins. Do you know of any studies with something like Becquerel readings? Technically we are all radioactive as there are trace amounts of uranium in soil, seawater and us. It would be interesting to know how radioactive some LRBs are - simply measurable, or more serious. SC
thanks everyone, so it turns out it’s common to encounter this. Mine actually looks like a fouree of brass (or maybe gold?) over lead/iron etc. It’s really interesting to me, but too bad there’s no design left on either side. Ill have to start checking magnetism of all coins
LOL!!! WOAH! Now we just pushed LRB's back to 66,000,000 BCE ! Yeah, now we are i REAL ANCIENTS territory! WIKIPEDIA Cretaceous–Paleogene boundary presence[edit] The red arrow points to the Cretaceous–Paleogene boundary. Main article: Cretaceous–Paleogene extinction event The Cretaceous–Paleogene boundary of 66 million years ago, marking the temporal border between the Cretaceous and Paleogene periods of geological time, was identified by a thin stratum of iridium-rich clay.[61] A team led by Luis Alvarez proposed in 1980 an extraterrestrial origin for this iridium, attributing it to an asteroid or comet impact.[61] Their theory, known as the Alvarez hypothesis, is now widely accepted to explain the extinction of the non-avian dinosaurs. A large buried impact crater structure with an estimated age of about 66 million years was later identified under what is now the Yucatán Peninsula (the Chicxulub crater).[62][63] Dewey M. McLean and others argue that the iridium may have been of volcanic origin instead, because Earth's core is rich in iridium, and active volcanoes such as Piton de la Fournaise, in the island of Réunion, are still releasing iridium.
You are kidding, right? Or does Indium actually contain its radioactive isotope usually? I looked it up and find it is used in electronic screens such as cellphones.
I'm only kidding about LRB's potentially being dangerous, not the indium part. On the page I linked to-- http://www.constantinethegreatcoins.com/metallurgy/ I reference the article where the info came from-- King, C. E. “The Alloy Content of Folles and Imitations from the Woodeaton Hoard.” Journal of the European Study Group on Physical, Chemical, Biological and Mathematical Techniques Applied to Archaeology 1 (1977) : 86-100.
Sorry, it seems I mixed up my references when I made the page. If you look in Cope, L. H., C. E. King, J. P. Northover, and T. Clay. "Metal Analyses of Roman Coins Minted Under the Empire." British Museum Occasional Paper 120 (1997) you can see that Cope found indium in several coins.
Bump this one for a couple of things. I recently won a contest from @lordmarcovan which was Greek coins... Fully four of these were attracted to a strong magnet! On the matter of common radioactive things, lite salt and bananas are mildly radioactive due to the amount of potassium-40 present in the potassium compounds in them...and don't get me started about Coleman mantles...
All due credit for that giveaway belongs to the kind anonymous donor. I was merely the conduit on that particular batch. PS- I was allowed to keep one piece, and his young son also sent me a gift coin. I have not magnet-tested the one I got from that same coinucopia source lot.
