What is this in my kenya tree?

[Saffier]

I am dipping a nee kenya tree and one branch had broken off in the bag and this black thing is on it. Is this part of the coral or a hitch hiker of some sort? It is stony hard and sand papery.

 

[Crabs McJones]

Possibly a bivalve that's attached itself to the stalk of your kenya tree

 

[Oscaror]

I agree with crabs, anyways doesn't look bad so no need to worry