Answer:
Taken from a mine and then locked up in a wooden case. I am used by students everyday.
Dead on the field lie ten soldiers in white killed by one blade yet there was no fight. What are they?
I shrink smaller every time I take a bath.
I am a box which holds keys but not locks. With the right combination, I may unlock your soul. What am I?
Take away my first letter and I still sound the same. Take away my last letter I still sound the same. Even take away my letter in the middle I will still sound the same. I am a five-letter word. What am I?
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.