What happens to the pope's ring after he dies?

On our last trip we had a guy ask us about what happens to the pope's ring after he dies. Another person in the group he was with said that it was ground into a powder and buried with the pope, at least according to Angels and Demons. Unfortunately being in a Dan Brown book almost guarantees that the fact is either widely exaggerated or flat out wrong.

However in this case it appears to be true. The pope's ring (otherwise called the Fisherman's Ring) was used in past centuries to seal papal documents. Upon the death of the pope it is destroyed to prevent forgeries. The conclave (or the cardinals who elect the new pope) are given the responsibility of destroying the ring

13. In one of the Congregations immediately following, the Cardinals, on the basis of a prearranged agenda, shall take the more urgent decisions regarding the beginning of the election. In other words:
g) they shall arrange for the destruction of the Fisherman's Ring and of the lead seal with which Apostolic Letters are despatched; (Universi Dominici Gregis)

This document doesn't specifically say how the ring is destroyed, but there are many sites that suggest that it's face is marred by scratching it and then it is crushed with a silver hammer. The pieces are then buried with the pope along with other symbols of his office.

I can't find an online resource to verify this, but this blog details the ceremony surrounding the pope's death based on the book "The Church Visible: The Ceremonial Life and Protocol of the Roman Catholic Church" by James-Charles Noonan, Jr.

Also, Catholic Answers has an Ask an Apologist thread on the topic, unfortunately the link they give is now out of date.