Synthetic Alum Stone
Potassium alum, the raw ingredient of alum stone (also known as crystal deodorant), is very commercially appealing and has subsequently led to the evolution of synthetic potassium alum. Potassium alum is a naturally occurring mineral salt, but it can be chemically synthesized by mixing aluminum hydroxide with potassium sulfate. Aluminum hydroxide is a cosmetic colorant and opacifying agent. It appears as a white, opaque powder. When the aluminum hydroxide powder or the alunite ore after treatment is mixed with potassium sulfate the result is a white, opaque crystalline potassium alum powder, which is then used for alum stone production.
Due to the cost of extraction and the rarity of the mineral, natural alum stone is becoming increasingly harder to find. However, the difference in appearance between the natural and synthetic alum stone tells all. The synthetic alum stones are opaque and white. The natural alum stones are colorless and translucent.