Black Powder in Toilet Tank

[miket]

I have black powder in the tank of my toilet. Do I have a part deteriorating in there? Anyone know what it might be?

 

[havasu]

Many times the black particles are either the iron in your pipes or the rubber parts in your tank disintegrating from the chlorine in your water supply.

 

[SHEPLMBR]

Many times the black particles are either the iron in your pipes or the rubber parts in your tank disintegrating from the chlorine in your water supply.

With HAVASU on that. If well water, could be tannins.