Which filtering agent is NOT typically used for vodka?

The choice of filtering agent that is not typically used for vodka is the one associated with amber stones. Vodka is known for its clean flavor profile, and its production often involves various filtering processes to remove impurities and enhance purity. Common filtering agents used in the vodka-making process include silver and platinum, which are effective at adsorbing impurities, thereby refining the spirit.

Crushed diamonds may also be used in certain high-end vodka brands as an extravagant filtering method, owing to their purity and ability to enhance flavor and texture.

Amber stones, however, do not have a traditional role in the filtration of vodka. While amber may have historical or decorative significance, it lacks the effective filtration properties that other options possess. Thus, it does not align with industry practices for vodka production, making it the correct choice in this context.