I had a piece of an alum block that was about a diagonal half of a Bloc Osma. It seemed to have a more glassy texture than the Bloc Osma, but seemed to have worn at about the same rate as my more recently acquired Bloc Osma. It took me 6 or 7 years to use that piece up, so this owl says 12 to 14 years. Good thing I bought 3 of them!