[tet68]

I seem to recall that Hannabal used vinegar and heat to
cut rocks when crossing the Alps.
Maybe it was the romans, I’m a little fuzzy on that.

We do not give our ancestors enough credit. They knew
their materials much better than we give them credit for.
It is my theory that copper tools could have been much
more effective if surfaced with copper oxides which can
reach up to 7 on the hardness scale.

[Openurmind]

I agree, there is much past knowledge that has been lost or destroyed.