I always thought scratched up rocks at digs were trash, but a professor at UNM showed me a 3000 year old scraper with similar wear marks and explained use patterns. Now I check every flake before tossing it, anyone else second guess their field sorting after a good lithics lecture?
Forty years of hauling junk to the dump taught me most people can't tell treasure from trash, and that scraper story makes me wonder how many good tools I've tossed in a landfill.