I've been cleaning some roman coins lately and I encountered this interesting problem. I've had the coins soaking in DW for a while and slowly been working on them and I came across this one. The reverse had a huge chunk of what I thought was dirt. So I pulled out a toothpick to try to scrap a bit of it off. Instead the toothpick sunk all the way and took a huge chunk out. And as you can see it left a part of the coin purple. Is that the bare metal or just a weird patina? Long story for a simple issue. Any ideas? I've stopped soaking and cleaning it until I find out more. Sorry about the bad photos. Didn't seem as fuzzy earlier.
I've never seen anything like it before but the coin looks like it also has BD because of the green on it and the coin is severely corroded.
if seen stuff like that before. usually an area of the coin that has lost its patina, and the metal is becoming corroded.
Shame. I figured it had something to do with BD. Any hope for the coin or just a write off? BD doesn't spread like a disease does it? I had this soaking with other coins.
BD will spread, but I do not necessarily see BD here. What happened IMHO is the patina was already unstable and the soaking simply accentuated the instability. It would have come off anyway. The purple is simply a weird color of toning, one that (rarely) happens. It appears the coin is bordering on corroded anyway. Clean it up the best you can and call it a day. It wasn't your fault if you clean a coin in distilled water and it turns out bad. It was just too far gone.
COVELLITE? CuS Trigonal Platy masses or thin six-sided platy crystals may be somewhat iridescent, turns metallic-purple when wet. Will sometimes mark paper. Hey, I usually chuck crap at Geologits, so I'm almost hoping that I'm wrong!! ... and "no" I didn't spell it wrong ...
haha I like the joke. It would be super cool if it was covellite. I could just see one of the mint employees now, "hey! lets make this into a coin!" And it does turn super purple in the water.
1. BD? 2. As a novice, are you joking or serious about the covellite? If it is that, is this a common occurence? If it is rare, is it possibly more interesting with the growth than without (the coin looks heavily corroded, if there even is anything recognizable under there).
BD = bronze disease. A light flaky green substance that will destroy a copper coin if not treated. I have no idea IF Steve is joking.....we never do.
Which of these images is a joke to you? After a weeks treatment: 3 years later after a second round of treatment. I failed to take a shot with the green before this one. The red is soft. These have been stable for decades now but they will not heal.
Man, now I am a sad puppy. You just had to pull out the 3rd century Chach with the cross that got bronze disease, didn't you Doug. I still haven't found one.
=> no, I was merely trying to take a friendly shot at any geology types ... hey, geologists rock (my bro-in-law is a geologist) ... but I spend most of my work-life sparring with them to boost the nickel grades in our mining areas (good times in the ol' engineering office)
