I've noticed black specks around the inside of the toilet that don't go away after cleaning. What is causing this and how do I get of it?

I've noticed black specks around the inside of the toilet that don't go away after cleaning. What is causing this and how do I get of it?

Pop the lid on the tank and run your fingers around the flat part of the flapper. If they come back all black replace the flapper. If not then click on back and tell me about it. Good luck, Tom