Silicone like substance on Rock

[sixteengallon]

On the underside of one of my pieces of rock, there is a substance that looks AND feels like clear dried silicone however I am sure that it is not silicone becuase iI don't recall it being there when I bought the rock. It is about 2" in diameter. I have noticed my cleaner shrimps sometimes like to pick at it. Any ideas on what it might be?

[ganjero]

Rock implants? jk.

Is it hard or soft? clear or more like the dried silicone color? have you done anything around your tank with silicone?

[rustybucket145]

probably a sponge or tunicate of some type.

[sixteengallon]

it looks and feels exactly like dried GE Silicone I clear.

[Traechial]

did you save any of this substance?
if you did and have not determined what it is send it to me and i could ask someone to analyze it. has it changed?