tree / acorn identification

[trout at ACM.ORG]

Hi! I have an acorn I'd like to have identified.  It is very large, about two inches across, with a very thick cup-part.  I do not know where it is from.  I wwas given two and I planted one which has grown into a "normal" looking little
tree with about 10 inch long leaves.  I'd like to know where to go to 
identify the tree or if anyone knows what it is, as I don't know if this is
a tropical species and it's getting cold where I live.  My email address is
trout at acm.org.  Thanks!