Was Sesarto the Artist perhaps a Larnesti himself? Maybe he changed
the nature of the rocks when he built Whitewall. Perhaps it was just
Limestone originally but he changed it to something that would
(ironically) resist change and stay white and beautiful forever.
Which helps to explain how the walls resist the chaos attack.
Just a thought.
Oliver
PS I've added an HTML version of the history file since I saw five
very wide sentences when I opened it:-)