Answer:
You see a boat filled with people. It has not sunk but when you look again you don't see a single person on the boat. Why?
I am the minerals vital for your good health.
I can only be played on a windy day
You can catch me but cannot throw me.
I have feathers that help me fly; with head and body but I'm not alive. Very skinny and a fixed length how far I go depends on your strength.
It flows out of the soil, It burns you if it boils, And holds us in its coils, More valuable than gold, As black as it is old.