Alumina (aluminum oxide) is what you are extracting from aluminum ore and tough as fuck, which is why it’s easier to dissolve the rest of the stuff around it first.

Oxygen is mainly that other “junk” you have to separate with electricity. While the smelters only run at 4.5 volts (per cell), they have to push about 300kA to get the stuff up to ~950°C which breaks its chemical bond.

You probably have never even touched pure aluminum before. Aluminum and oxygen react so quick, all we typically ever see and touch is a alumina shell.