Help needed to identify this substance

[chipmaker]

In my pico which is close to a months age now, I have a piece of nice FIJI rock.......It has numerous small caves and tunnels in it, and in one cave at the top it had this shiney black coating with what looks like a typical worm hole opening......There was also some of this black stuff on the very top of the rock outside the cave as well........Now this black stuff has grown all along the top of the original cave and is extending down and around the walls and upwards out of the cave, and the stuff on the top is growing larger as well. Its well adhered to the rock surface, not overly thick, but resembles a thick coraline coating but black in color, and its shiney black and smooth. If you touch it it feels smooth, just like cured black silicone rubber feels, yet it is also pliable just like a coat of silicone would be........Anyone have a clue as to what this stuff is and does it have to be removed or leave it alone. It has grown considerably since I have the tank setup, and sure do not want it to cover all my coraline but sure do not want to remove it if its beneficial......Any info greatly appreciated.....

[formerly icyuodd/icyoud2]

sounds like the black sponge i have growing on some of my indo live rock