After every major rain, I end up finding old shards of glass at the low point of our yard. You can tell it is old because the colors are clearly from a different era. There are usually interesting surface marks, too. I find fragments of pottery, bottles, the lot. Of course, I am collecting it. The best origin theory I've heard so far is the one my son put forward: that a gardener from a previous generation lined flower beds with this stuff to help with drainage. I keep hoping gold coins would turn up, but no such luck. Which tends to support the drainage theory.
