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.
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.
I have rivers without water. Forests without trees. Mountains without rocks. Towns without houses.
Sleeping during the day, I hide away. Watchful through the night, I open at dawn's light. But only for the briefest time, do I shine. And then I hide away. And sleep through the day.
What has 13 hearts but none beat?
If it’s information you seek, come and see me. If it’s pairs of letters you need, I have consecutively three. What am I?