egg shell with "clear areas"

[chickgarden]

I'm not sure how to describe my question, and maybe that's why I haven't been able to find any posts on it. I have a 5 year old Brown Leghorn and she lays regularly, but I've noticed her last few eggs have looked a little different. Towards the pointy end of the egg there has been a small area that is clear. It feels rough/hard like there is a shell, but if you hold it to the light you can almost see in the egg.
Is that most likely related to her age? Are these eggs ok to eat? It's not soft at all, but I wasn't sure if the thin area was more porous?
Anyway, I hate to throw her eggs out, but want to be sure they are ok to use. And also wonder if the oyster shell would make a difference for this type of thing.

 

[Kiki]

Can you post a picture of the egg.

 

[chickgarden]

Yesterday it had two of the lighter spots. I did more research and found it's called a glassy or mottled egg shell. I'm guessing it has to do with the age of this chicken since she seems fine otherwise. Now I just wonder if they are safe to eat?

 

[Pork Pie]

This link may be helpful -
http://www.backyardchickens.com/a/common-egg-quality-problems

 

[chickgarden]

Thanks!