These are small compared to some and this area has a bunch of clay banks of with concretions of various sizes. None are as big as the one that is 1.5 meters on Wikipedia. Take a look yourself at http://en.wikipedia.org/wiki/Concretion and you'll see what I mean.
I have read that concretions are the "buttons" found at Button Bay State Park in Ferrisburg on Lake Champlain. They aren't as easy to find now but probably as the waves move in and out, some become visible...kind of like finding sand dollars at the ocean 30 years ago. Anyway, these little geological wonders spark the imagination.
Walking the gardens in fall highlights pieces, leftovers, discards, some out of place, some just cast off. It's part of operating a business. The pieces of metal on the granite block in the first picture are pieces pushed up by winter freeze-thaw cycles. I like to straighten things up in the fall as I pick up the pieces. You can too!
Writing from the mountain above Peacham Pond where a barred owl has decided 256 Peacham Pond Road is a good place to hunt. He's in a white birch right now, looking at a merganser on the trout pond.
Fall gardening wishes and kind business thoughts for whatever you are contemplating.