identification please

[dave r]

They would be Haliotis rubra. The inside does get like that sometimes. The 'mother-of-pearl'effect is due to different refraction indices in thin layers of shell, the layers are almost like the pages of a book but semi-transparent. These layers are bonded together by a protein which sometimes starts to break down and the layers 'de-laminate' resulting in the sort of staining you see on your shell. The only thing you can do is give it a thin coating of baby oil to stop it getting any worse, this will not cure it but it does slow it down. This is something that affects all Haliotis unfortunately, especially if they have been lying dead in the sea for a while.
Dave