The Wikipedia article on the papal tiara is also excellent.
As I have posted previously, I do have to wonder how the people of Milan felt about Paul VI, their former archbishop, just giving away the tiara they, following a traidition, had paid for as a gift to him and to the Church. Once someone renounces a coronation (it could have been modified rather than abolished) and its accoutrements, it is virtually impossible for the successor to take it up again. The current pope is known to “dress to the nines” as it were and more power to him. I have to guess that if he had his druthers, the tiara would still be in use. Still, he is the pope who has replaced the tiara with the mitre in the papal coat of arms, a sure symbol that this neat thing is gone forever except in the Vatican museums.