Ahhh, I see you are an ignorant american, and didn't realize that it is ACTUALLY called the philosopher's stone, and was published under that name in Britain, which is where JK Rowling is from.
The philosopher's stone is a long sought after alchemical substance capable of turning base materials into gold, along with other properties such as granting eternal life. It has been studied by many great minds, including Sir Isaac Newton. Nicholas Flamel actually did live and reputably succeed in creating the philosopher's stone. Ironically his tomb is empty to this day, and books were published under his name well after his death in 1410.
Ravenclaw for me.