Remember when Nemo takes Aronnax diving for pearls? Well, we think that Nemo's been feeding, coveting, and scrutinizing the pearl for more than just a pretty piece o' jewelry. While most pearl divers would surely pluck as many pearls from the ocean's oysters as they could, Nemo refrains from harvesting this one. Why?
Well, maybe Nemo isn't in the pearl business for the money after all. We know he's got serious bank hidden away in some shipwrecks anyway. So maybe this pearl holds a different appeal for him (and Aronnax, we might add). It's really beautiful, and, so long as it stays a secret, it's uniquely his.
So, we think Nemo's giant pearl is kind of like the Nautilus. It's a piece of Nemo's private, self-constructed world that represents the allure of the untouched, of unsolved mysteries. Plus, it's shiny. And who doesn't love shiny things?