yesterday i found a nice, bigger cobble of extremely hard flint/cortex material. and on my way back i found what i thought was a nice sized { golf ball} piece of very large grain sand stone. come to find out it aint sand stone at all. i broke it hitting the flint with it. almost in half. got one big piece and two smaller pieces. kind of crystalized on the inside. guess what?
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it sparks like crazy if you scratch it with that flint cobble.just tryed it outside in the dark. my son says "dad you could start a fire with that!" i was like, yep, i bet i could.
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ill post a pic after a bit.
come to find out, a rock i thought would make a good hammer stone also produces sparks hitting the flint.....Tony
on the left side is that broke piece of rock.bottom left 2 pieces of flint that spark with rocks in picture.on right top that hammer stone that produces sparks when it hits them flint pieces.