Answer:
A mile from end to end, yet as close to as a friend. A precious commodity, freely given. Seen on the dead and on the living. Found on the rich, poor, short and tall, but shared among children most of all.
Upon me you can tread, though softly under cover. And I will take you places, that you have yet to discover. I'm high, and I'm low, though flat in the middle. And though a joy to the children, adults think of me little.
You throw away the outside, eat the inside, then throw away the inside. What is it?
Neither bought nor sold but more valuable than gold. It is built but not by hand. What is it?
How can you burn an apple, blueberry, rose and pumpkin without leaving any ashes but retaining the smell of it?
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.