The persistence of memory

Packed away in a basket inside a box of forgotten things I found a small muslin bag the size of the palm of my hand. The size of the little muslin bags that tourist shops let you fill with as many polished stones as you can. This bag once held a hunk of pyrite, which my mom bought me in a little shop in Loudenville during the apple butter festival.
The pyrite is gone - I don't know what ever became of it. Inside the bag is now a box - polished wood with a mother-of-pearl in-lay, too small to ever hold anything practical. The box was a gift from a woman I am no longer friends with. She gave it to me wrapped in a scrap of purple fabric for my eighteenth birthday, and I remember right where I was sitting on the floor of my parents' living room when I opened it. 
Inside the box are six rocks - tiny, of various shapes and colors, each representing a moment I wanted to remember forever. I got the idea from an utterly forgettable movie with Brendan Fraser and Danny Devito - With Honors. Pale imitation of The Fisher King. I saw the movie twenty-five years ago but I remember one of the memories was of making love on the beach.
I don't remember what the rocks are for. One's a first kiss, I think. One might be prom. What did a teenage me consider worthy of always remembering? I only remember that every one of those moments seem unforgettable.