It is often asserted that Spin is a uniquely Quantum Mechanical phenomena, why?

Question

Conversely, it's often said there is no Classical analog to Spin. Spin was so named because classically a spinning charged particle would possess a magnetic moment. Isn't this the analog?

Why would Spin have no classical analog, but Orbital Angular Momentum would? Is it because Spin has only 2 states?

Answer 1

Because it isn't really spin. Orbital angular momentum doesn't need a classical analog, it is classical. Electron spin is not orbital angular momentum. Every electron has the same value of 'spin' which can't be changed. It probably would have been less confusing if they named this quantum parameter in the same manner they named quarks, like up, down, strange, and charm. You know they are meaningless names and you don't try to picture a particle matching the name.