An
archaeological term used to refer to things that have not been modified by humans, but are still of interest to
archaeologists because they can help tell us what people were doing. For the most part, these are things that have been carried places by humans.
Examples of ecofacts are caches of stone that were collected to make tools (but if they were stored in a structure, that's an artifact or a feature), bones or shells that were left after a meal, and any type of stone, wood, shell, etc, that was carried from it's naturally occurring locale.
Any item that has been intentionally modified for artistic, functional, or recreational purposes is an artifact, not an ecofact.