Answer:
What is the center of gravity?
It can be cracked, It can be made, It can be told, it can be played. What is it?
You use it between your head and your toes, the more it works the thinner it grows. What is it?
The buyer doesn’t want it, the producer doesn’t need it and the user doesn’t know their using it.
Precious stones in a pack of cards.
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.