Answer:
There are millions of me. I am very small but when moving fast I am deadly.
It's in your hand though you can not feel it. Only you and time can reveal it.
Halo of water, tongue of wood. Skin of stone, long I've stood. My fingers short reach to the sky. Inside my heart men live and die.
I dig out tiny caves and store gold and silver in them. I also build bridges of silver and make crowns of gold. They are the smallest you could imagine. Sooner or later everybody needs my help. Yet many people are afraid to let me help them.
What is weightless but takes two people to hold it?
What covers its face with its hands, speaks no language, yet most known what it's saying?