Alum stone is the active ingredient in antiperspirants. This stone, which is similar to a mineral salt, is extracted from natural quarries. Presented in the form of a stone that can be held in the hand, it has astringent properties that have been recognised for thousands of years. Once the crystals have been extracted, the natural salts of alum are dissolved in water to remove impurities, then concentrated and dried. Their form can be rough or cut and polished, depending on the use. The process is therefore not synthetic, and nothing is added to the original ingredients of alum.