We have pea gravel in our playground area. It's mostly cream colored, but there's the occasional piece of clear quartz. When Rachel was little, say 3 or 4 years old, she would collect stones from the playground, particularly quartz ones, and ask me for a container. They were, I was informed, "meenie minie moe" rocks, and they were magic.
She never explained why they were magic, or what they did, or even how she selected them, but we had little containers of rocks stashed here and there for a long time. I even found one a few months ago, cleaning out the back hallway.
William has friends over today, and when they came in from playing in the back yard, the little brother had his pockets filled with rocks. I gave him a baggie to put them in, and you know, I guess they're still magic.