Dark lines on eggs

[dobimomof4]

I think 1 of my chickens are laying these odd eggs. They have a dark line on them that wraps over halfway aound. Egg shell is usually rougher textured also. Is this something to be concerned about? Thanks to any and all who might be able to help.
DC

 

[clankeyes]

following

 

[dobimomof4]

Would still love to know what this is? Any ideas are greatly appreciated.

 

[JeanR]

It is likely a glitch in her Shell Gland, the last part of the development of the eggs. Not to worry, can't fix it and it may distribute the shell pigment evenly, in time---or it may just be unique to that hen--you will always be able to identify her egg! Pigment variations are just that, individual,, and contents of the egg are in no way affected.------kind of attractive?