1st odd egg today

[carrieabn]

I have 6 Australorps that are 5 months old. I got my first egg on July 31. I now have 2 laying almost everyday and a 3rd laying about every other. As you can see one of my 3 was a little odd today, but its the sound of it that concerns me, it sounds like ceramic. When I tap on it and compare it to tapping on another "normal" egg it has a very different sound.

Any ideas on what might cause this or anyone else ever have this?

 

[hxgumdrop]

Iv had eggs that look like this although when cracked the inside is normal however I never thought to tap mine so no idea what it sounded like. I dont no what causes it but Iv had a few that are odd shapes makes me think the hen struggled to get the egg out