Those are not run of the mill mounds then, certainly not middens. I have one 9 inch blade, very thin found in Hays county. Closest ID is a Caddoan Blade.
Couple experts agree it must be ceremonial only as it's too well made and fragile to be utilitarian. Overall blade design looks Covington teardrop.
My thought is that there are surely " camps " on the property in the vicinity of each mound but level with the present surface...tough to locate but would
be very interesting to identify exactly what type & age points of the people that might be responsible for the mounds.
A pic or two would be interesting to our readers,,,if your in the mood