It was the summer between second and third grade IIRC and I was visiting my grandmother with my family. She lived in NW Alabama in a very small town called Collinsville and she was making some money by allowing a company to dig gravel out of a ridge on her land.
Now there is probably not anything more attractive to a small boy than heavy machinery so as soon as my parents weren't looking I was off to look at the bulldozers. And that is how my life changed forever.
After climbing around on the equipment for a bit I noticed that some of the gravel was funny looking. There were pieces that were cylinders with rings coming off them. It just didn't make sense. Why would all these rocks look like this?
I wasn't supposed to be anywhere near this quarry so I couldn't ask my parents or grandmother. But I thought I knew someone who would. During the school year my class had gone to the public library and the librarian had said we could always come ask questions and they would help us look stuff up. So I put one of the rocks in my pocket and kept it till I got home.
As soon as I could I got to the library and away from my mother and asked the librarian if she could tell me what this rock was. That was when I found out it was a fossil. She even helped me identify it. It was the stem of a crinoid which is a kind of marine invertebrate. Which confused me. How did a bunch, there had been a whole lot of these in the quarry, of sea critters wind up in NW Alabama hundreds of miles from the ocean? Up till then my exposure to "science" had mostly been through Sunday school which had taught me that the Bible was literally true and the world had always existed pretty much exactly as it was today. So I started reading about fossils and my world changed. I found that the pastor and Sunday school teachers were a liars. And if they were wrong about such a basic part of their beliefs what else were they wrong about? So I really started paying attention in church.
Stuff started standing out. The pastor gave these fire and brimstone sermons every week. But for who? Besides a handful of kids everyone in church was baptized and by the theory the church operated under "saved" and going to Heaven no matter what. Then there was the structure of the service itself. It all seemed setup to lead not to the sermon but to lead to the offering. The point of the church service seemed to be to make sure the pastor got paid. My faith left me. At one point I was sitting in the pew with my family and burst out laughing at the absurdity of it all. Which certainly wasn't the wisest way to announce my atheism.
But it all started with that "rock" and I have it to this day. Carefully cleaned and cased. It is a humble little fossil and would have wound up pulverized into gravel if not for a curious little boy. But it opened my mind to the wonders of the world.