I picked it up and walked the broken mirror home. Why. Who knows. But it did end up sitting under my porch the entire winter, so I'm fairly certain it never had an original purpose. As my niece (pictured below) pointed out, I could break it up into pieces and put it into my garden. Very ingenious. I wish I had that kind of foresight when I was 10.
Alas, as we were packing to move last month, I realized there was no way I was moving a broken mirror....which had quite literally been someone else' trash.. I had enough of my own junk to move at that point.
When you don't move it, capture it.
I'm also now of the opinion that all pictures in mirrors should be broken.