Ziede,
More on this conchilin thing. The bleaching eats the conchilon? My understanding is that conchilin is a glue like protein binder although some call it calcium carbonate, that is between the aragonite layers. Sort of thought of it as a lasagna, aragonite, conchilin, aragonite but sounds like the binder is everywhere between the crystals.

Why does the lack of it result in "murk"?

Have seen overbleached or Japanese process pearls that appeared to peal.