I have a strange brain

I'm wandering along a beach on Cape Cod, the wind in my hair, the sun on my face, and what am I wondering about? Science projects.

Well, science projects about sand, anyway.

I mean, most of the rocks you see in the beach are darker than the sand, so what makes the sand sand colored? I'm guessing that sand is made up of very old shells as well as very old rocks, and crushed shells are lighter in color, but how do you turn that into a science project? Do you sort the sand into sizes and look for shell bits with a microscope? Or can you melt the very old shells the way you can dissolve the calcium out of an eggshell with vinegar or whatever it is...

And if you can, how do you make a science project out of it that a sixth grader can do?

Yes, my brain is strange...