A Fulgurite, also known as a Living Act Of God, is a rare item needed in spells dealing with powerful supernatural beings. Its first known use was to bind Death.
Fulgurites are very rare due to only being created when lightning hits the sand on the right spot, forming a crystal. After Crowley slips them the ritual to bind Death, Bobby goes looking for the materials. He finds one, which was recently bought by a rich couple. At the mansion, Sam grabs the crystal from its case, and puts it into a bowl where he smashes it into dust.
Hayley, the woman involved with the titan Prometheus, noted that fulgurites were not as rare as once thought and could actually be bought in charms and talisman shops. Fulgurite, along with the bone of a worshipper, was also used to summon Zeus, the greek god of the sky and thunder.