Answer:
You can break it or drink water from it.
Once you know it exists, it no longer exists. What is it?
What instrument can you hear but never see?
How many months of the year have 28 days?
Kids play it and Michelangelo sculpted with it.
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.