Very cool find and I'll say knife. I've thought about this and what really would be the purpose and practicality of a stone 'spear point'? Possibly for lances in combat or buffalo hunting, or just to look impressive when you took the field against your opponents. Used as a spear, points this long would pretty much be a one time use thing, as due to their form they would probably shatter a lot on impact. I just don't think there was a lot of spear use goin on until the Spanish entradas. The Kiowa and Commanche had a big time fightin with the Spanish Lancers. The Lancers used metal tipped lances or spears, and the Southern Plains tribes took an immediate liking to them. They captured some and copied them for their own use. Just something to speculate about.