A quadruple-distillation process made Crystal Head as pure as vodka can be, but the quest for an almost mystical purity continued. As a final stage, the liquid was filtered through 500-million year-old crystals known as Herkimer diamonds. These quartz crystals are found in very few places in the world, including Herkimer, New York and regions in Tibet and Afghanistan. Perhaps because they share the raw material from which the original crystal heads were carved, they are thought to have similar spiritual qualities.