Tough, clear glass is a miracle. It was invented in Italy. It's one of the most useful things ever made.
Ordinary glass has been round for thousands of years. It was used by the Egyptians and Greeks and Romans and the Mesopotamians and Phoenicians and Chinese. Ten thousand years before that it was used by the Tasmanian aborigines.
When people look right through me I know what it feels like to be a pane of glass. Fragile. Nothing to notice. I'd rather be a mirror. Then people who looked into me would just see their own, ugly selves.