hmmmm. I thought most IDE cables were copper, like the one in the pic there. I tried pulling the side wire off to strip it and thought how small it was(thought most IDE cables were thicker), so I got another one with thicker wires(the ones we mostly see).
Wellll, turns out they're aluminum, both the older one I was wondering about, and the thicker size IDE, and they both melted over a lighter flame. I stripped one of the tinier copper ones, and the tip burned, but it mostly just glowed red, and was still intact when I removed the flame