I have a treasure box, a shoebox full of memorabilia I put together in elementary school. Inside are important letters from family and friends, an old coin, my grandfather’s pocket watch, a pen I won in a writing contest, a picture diary from first grade, a tiny sea shell and my autograph collection (with most of the signatures of neighbors and cousins forged by me).

There is something else–a green plastic Easter egg. Inside the egg is a layered ball made of aluminum foil, elastic string, yarn, plastic wrap, and who knows what all else. This is my homemade geode. One magical afternoon in fifth grade, I was wishing I had a dull brown rock that I could smash open to find a bunch of shiny crystals. I looked around in the backyard for awhile, but found only driveway gravel. Then I decided to make my own. I rooted through kitchen drawers and my bedroom closet, collecting stuff to wind up into a ball. I added layer after layer, then put the whole thing in a plastic Easter egg. I imagined that if I left it alone long enough, the layers of junk would transform into something else–magical crystals. It wouldn’t happen overnight. It would take ages, or eons.

I decided I would open it when I turned 40.

I turn 40 this month. All these years I’ve waited patiently, never losing the geode, never cracking it open early. It makes me a little sad to realize that if I do cut it open on my birthday, I’ll only find string and aluminum foil. Did I ever really believe that it could turn into something else? Why have I kept it all these years?

To the 11-year-old me, ever being 40 must have seemed just as unbelievable as junk turning to jewels. These days, 40 seems quite believable. Some of my hair is gray. The skin on my hands is less and less elastic–I can pull it up into little ridges. I can see the very beginnings of . . . jowls. Besides, everyone around me is already over 40. I was born in the very last year of the Baby Boom, so I always have a crowd of people hitting all the milestones in front of me.

The strange thing is, I never would have imagined that being 40 would feel like this–like the regular old me. Sometimes in bed at night, when I’m not quite asleep, I jolt into consciousness with the realization that I’m really not 11 anymore. When I was a kid I thought being grown-up would feel grown-up. Surely there would be some significant transformation, perhaps even magical, when I turned 21, or got married, or became a mother, or turned 40. Wouldn’t I have found a few answers to life’s big questions? Or be a little more confident? I am like the homemade geode, made up of layer upon layer of life experiences, but not essentially different at my core.

Maybe not different at my core, but yes I have changed, changes that have piled up so gradually it’s hard to say when they happened. I’m more comfortable being myself rather than trying to be what I imagine someone else wants me to be. I’m not as afraid to say what I think and feel, and I’m not as afraid to try new things. I have finally started to floss.

I don’t think I will crack open my geode. Instead I will keep it. It is a gift from the 11-year-old who thought I would be something unimaginably different at 40. It is a reminder to me that life is not a series of magical transformations, but layers of slow and incremental change. My body will change, my personality will grow, but I will never be a collection of sparkling crystals. I will always be me.

Besides, if ordinary household materials were to morph into crystals it would probably take more than 30 years. Maybe I’ll open it on my 70th birthday.