Monolithic just means one-piece, so it doesn't matter how many strings or where the strings are located as long as they are within the magnetic field.
The ferrite clay contains iron oxide (the ferrite component). I'm not sure if that's the same thing as a regular ferrite ceramic magnet. They are regular to me, we've always used the same ones.
The clay comes from Kentucky. The red color of many clays comes from the iron oxide.
