I cover a nut I cover a plane I keep you afloat I keep you intact in outer space I’m actually quite common place

What starts with a P, ends with an E, and has thousands of letters? Anwer is two Words connected, E ReadingRoom, not Reading room.

I’m made of many materials; most notably gold or pearl. I’m used to gain entry. I can also be an ending to words to indicate a scanda, like water or Iran.

My essence is of life, yet can choke the living. My existence is omnipotent yet can be more valuable than sterling. I can catch ablaze yet can smother my flames. I can be dirty black or crystal clear, and my purity would remain the same.

I rise above the ground to watch the land, sometimes I hold a clock, sometimes a bell’s command. In stories, a princess may wait inside my wall, stone and shadow standing tall.