I have found many similar pieces of flint like those, on the Ohio River banks. The biggest piece I have found was just a little bigger than a golf ball. They seem to be high quality flint but small. They have that smooth finish on the outside which may be from rolling or being washed in the rivers for a long time. The lighter brown exterior colored one looks like pieces I have found in creeks around Carter Caves, Kentucky. Again, they have good quality flint but small and thin exterior finish on them( not a chalky cortex). I always find them on creeks or rivers, that look like those. Found some on the Greenbrier River in West Virginia and I actually found some quarter size pieces in black, in Colorado on the side of a rocky slope. Broke a couple open and they had that smooth hard glassy look.
I always thought it was cool to find them. Those small pieces could be used to start a flint and steel fire or make a small flint for a flintlock muzzleloader or just a quick cutting edge for something if needed.
I do not know how they are formed or what type of flint they are, but they are found in many places. They also have a distinct outside appearance that is noticeable once you know what to look for.
Just some of my observations...
