I'm Wiccan and I have never heard of such a thing. The only thing that comes to mind is that the silver must sluff off some of your skin and make that black slime. So therefore it appears you have some dark thing coming out of you. Obviously it is not a true healing spell, but it must be a trick to make people think they are getting rid of nasties. She got $20 bucks from you? eh.. better than paying $400.00 I say. Luckily you realized it after. Just a lesson learned. Hugs Laura