I thought the title would have been enough, but I've had some questions on this photo, so I included my brief explanation below.
To me, this is what I see: The marble is actually clear, but it's reflecting the sky and some cool shadows, some trees in there too, and some glares from the sun. It kind of literally makes it a blue marble. But it's a reference to the Apollo photo taken of the earth from space where they referred to it as "the blue marble." It's kind of like that photo at the macro scale of the whole earth, where it looks like such a small object compared to the vastness of space, except here, it actually is a small object, a marble, sitting between two weathered wood planks, reflecting the vastness of earth. Juxtaposition of scale per se. It might be one of my favorite photos I've taken in a long time. (reference: https://en.wikipedia.org/wiki/The_Blue_Marble)
I was just messing around when I took this shot, but as I flipped through them in post, it really struck me that I like this photo a lot. I might take one of these marbles with me to a few different places and see if I can make it better, considering the reflections and all. What do you think?