The best materials for a whiskey decanter are glass or crystal. These materials are durable, transparent, and non-porous, which makes them well-suited for storing and serving whiskey. Glass is a common choice for decanters because it is inexpensive and widely available, and it allows the user to easily see the contents of the decanter. Crystal, on the other hand, is a more expensive and luxurious option that is prized for its clarity, shine, and weight. Some people prefer crystal decanters because they believe that the extra weight and thickness of the material can help to enhance the flavor and aroma of the whiskey. Ultimately, the choice of material for a whiskey decanter is a matter of personal preference and budget.