Hi everyone.  I came across a strange situation on a granite counter yesterday where a number of teh black stones in the granite have become rough.  I tested with my fingernail and i could chip away flakes of the stuff.  It feels like schist within the granite.  They said that this happened over time and they only treat the counter with granite cleaner.  I would be interested to know why this is happening and if there is something that could be done about it. I would think that diamonds would just break up the stones if I can scratch it with my fingernail.  I attached a picture.  Thanks.