It looks like it was struck from a Core for use for something. You can see where other pieces were struck off before it. Could just be a waste flake and it could be a Flake Knife.
This is a core that has had blades like yours removed. It is smaller than the core your blade came off of. This one is modern, one I made for a reference.
You could think of your blade as a disposable razor knife. It keeps its razor edge for a short time then is tossed. It's still sharp, but not razor sharp, which is necessary for fine cutting. Gary
Despite only being 50 miles from an abundant source of obsidian, I never see any larger chunks of obsidian laying around.
They must have buried these cores near their seasonal camps and made use of every single piece that could be used.