Help we cracked an egg and it was black?!

[ChickChalk]

I gave my friend some eggs and she went to cook them and one was black inside. She threw it away so I don't know if it was yolk, white, or both, but I've never heard of it. The egg was one of my blue ones from my easter egger. That was the only egg like it and all the others have been fine. Why did that happen and is she sick?

 

[pom pom chook]

Maybe. If you have had the egg for a long time it may go bad.Is your hen active? If she is I think its a long time gone bad egg.