Green Powder on Coin

[Ian G]

I was looking at some coins today and noticed some tiny green pinpricks on the edge of a Cimmerian Bosporus Bronze. They were powder and easily came off when I rubbed my thumb against the edge. I immediately thought bronze disease but thought it would be sensible to check with wiser heads before treating it for BD because when I look at where the powder was with even 30x magnification I cannot see any difference or disturbance whatsoever in the metal. The coin has very sound metal generally and after rubbing the powder off it looks exactly as it was before. I have been collecting for some years and have been lucky enough never to have encountered BD so I don't have any experience to fall back on. Is my initial assumption that this is BD likely to be correct? Or might there be some other explanation? There is no point me sending you a photo as now I have rubbed the powder off there is nothing to see! I would be grateful to know if anyone has encountered this before and for any advice as to how to proceed.

[Pekka K]

Take a look here:

https://www.forumancientcoins.com/numiswiki/view.asp?key=Bronze%20Disease

Pekka K

[v-drome]

I would still like to see a picture of what the coin looks like now, if possible.  I have occasionally removed very small spots of BD with a microscope and tool, thoroughly dried it, and then treated only the spot, with mineral oil or something to protect it from air.  Sometimes it comes back, sometimes not.  

The Numiswiki article on BD is very interesting.

Regards, V-drome

[Ian G]

Thanks to Pekka and V-Drome for their replies.

V-drome, you said that you would like to see a picture. I have tried to attach one but have not been able to - from FAQs it appears that you need to have made 3 posts before you can do this and I am new to this forum.  All that I can say by way of description is that this is a very nice coin with very sound metal. The coin appears free from any corrosion or roughness. As I said in my first post, I have gone all over the coin with my 30x loupe and I cannot see the slightest evidence of any new pitting, scarring or other change. It is as though someone sprinkled a few tiny specks of green talcum powder on the edge of the coin and after they have been brushed off, everything is as it was before. That lack of visible change in the surface of the coin even under magnification is what made me question whether this was definitely BD, although clearly the presence of the powder suggests something is not as it should be and some chemical change is occurring.

Regards,

Ian.

[SC]

Bronze disease does need moisture to continue its process.

So often treatment can be as simple as wiping it clean like you did and ensuring it stays dry.  Store it differently, add some silica gell packets nearby, etc.

My point is that even if that was BD no need to jump right to any treatment yet.  Clean.  Monitor.  See what happens down the road.

SC

PS . Welcome to the forum!