Osma Tradition Alum Block 100g. Osma alum stones are made from a 100% natural crystal. Alum is a well-known astringent mineral that has been used as a cosmetic for more than 2000 years. Because even the most agile hands are never shielded from the forgery movement, Osma Tradition Alum stone will allow you to stop any small cut produced during shaving or close any open pore. Features: Made from a 100% natural crystal Made in France