So, I recently won this denarius of Marcus Aurelius from an auction. The pictures don't have the best quality, but that's what was used in the listing. Anyhow, I recently found out about crystalization, but I find it hard to recognize. Could someone here help me out and tell me if the coin is crystalized? Thank you. (I don't have the coin yet. It's still in the mail)
Possibly crystallized or possibly acid-cleaned and with porous surfaces. It's also possible it's bad photography. You'll know when you get it in hand. Here's my example of that Marcus Aurelius. Marcus Aurelius, AR denarius, Rome, AD 169. BMCRE 49
Its difficult, if not impossible to tell based on a photo: you need to look in the flan cracks under magnification to find it out. To me, it looks like an overcleaned coin. It may have had a horn silver encrustation that was removed aggressively, resulting in a rough, pitted surface.
My experience, however limited it might be, with crystallized coins is that they are finer silver than was used by this time. More pure coins from the Archaic Greek period are more prone to the problem than are later coins with more alloy. I suspect this coin is just overcleaned. While that does not cause coins to break, it ruins many more coins than does crystallization which can add its own beauty to the coins. Welcome. Do post a follow up telling us what you discovered when you have the coin in hand. The drachm of Larissa below shows directional patterns from crystals most noticeable under the neck on the obverse. While I don't suggest dropping any ancient coin, I am especially careful with coins that show such signs. The drachm of Corinth below has classic columns above Pegasus. These are not scratches. The problem is that not all crystallized metal shows on the surface. Some are normal on the surface and a bomb waiting to go off on the inside. That is why I suggest not dropping coins to find out if it was a bad idea. I'm sure there are some who have studied metallurgy that have a grasp on the subject but, at my level, I prefer to avoid shock to very old silver.
Thanks for the replies. I think it may be improper cleaning rather than crystalization. From what I've read, crystalization makes the coin lighter? The weight is 2.82g, which is in the realm of possibility for a denarius. That makes me think it's either improper cleaning or really bad lighting.
Welcome @CoinZimm . I agree with those above about handling ancient silver coins. When I suspect a coin is crystalized, I put it in a Kointains holder. Others will do, but these are inexpensive and the sides are semi visible.
Welcome to Coin Talk, CoinZimm. Not an expert, but I'd agree with others have said, it probably just had an enthusiastic cleaning, rather than crystalization. In my experience, these coins tend to look better in hand than in the photos. Furthermore, I really like those liberalitas types - they can often be linked to specific donatives for specific events. I have two of them like yours (I think - RIC 206 - I've been re-checking my attributions from a couple years ago because I made even more mistakes than I do now). I've kept them both because the one on the left has a die-clash. Not very evident in my poor photos, but the reverse of the one on the left has an outline of the back of Marcus's head and some lettering around the cornucopiae. P.S. When you post on Coin Talk, if you hit the "full image" button next to your photo, it will appear full size in your post. It took me a while to figure that out.
