Did Indians use this type black rock?

[3ChordTruth]

Those look water worn. Most likely spent some time in a river or stream. Hence, the smooth rounding edges like river rocks have.

X2. Doesn’t look like it will “flake” off like flint/chert rocks will, but still could have been put to other uses by those early, early Texans.

[MontagueMech]

When I hit them against each other the larger one flaked off leaving sharp edges.

I’ll have to wait another day to scout that hill out some more.

[KGreene]

That’s the kind of rock they threw at the dog when he chewed up his favorite pair of moccasins.

[Jon Stewart]

Could be obsidian. Post a photo of the struck piece

[Texas Grown]

Could be obsidian. Post a photo of the struck piece

That thought crossed my mind.

[brokeno]

When they ran out of arrows they could have chunked those rocks at something. Fjb