Answer:
People need me, yet they give me away every day. What am I?
It's in your hand though you can not feel it. Only you and time can reveal it.
I dig out tiny caves and store gold and silver in them. I also build bridges of silver and make crowns of gold. Sooner or later everybody needs my help yet many people are afraid to let me help them.
Though not a plant I have leaves. though not a beast I have spine. Though many wouldn't need me I am more valuable than wine.
I am the kind of nut that is empty at the center and has no shell.
In your fire you hear me scream! Creaking and whining yet I am dead before you lay me in your hearth.