I definitely kept the mussel shells from restaurants until I learned you could find them at the beach. Then it was beach-sourced only!
I collected shells as a child and adult (my house is littered with shells), rocks, crystals, herbs, books about foraging for fungi and herbs, books about identifying the things I collect (shells, fungi, herbs, rocks), and things I want to identify but can’t collect psychically, like trees.
I guess I’m collecting knowledge? Is that how this works? As a child, they were pretty and interesting things. As an adult, they are pretty, interesting, sometimes edible, and knowledge collectible.