It sounds like "bronze disease" - a particularly virulent form of corrosion. It is not mould nor anything else alive, though it can spread in a life-like fashion. Bronze disease can jump from coin to coin if the conditions are right, even "infecting" an entire roll as you have described if left alone for long enough.
Health-wise, it's no more hazardous than any other form of corroded copper although, if it's powdery dust, then like any other powdery dust, it can get into your lungs and cause or exacerbate health problems.
The coins are likely already ruined anyway from a collector viewpoint, so I'd suggest opening the roll under water to prevent the dust from flying anywhere. Give the coins a good wash in soapy water, then rinse them in distilled or deionized water and dry them in a cool oven (80 to 120 degrees Celsius). That should stop the "green death" from spreading further and contaminating any as-yet-undamaged coins they get re-rolled with.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
Posted 02/12/2013 01:28 am
