Bobby indicates that fulgurites are very rare, and created by lightning hitting sand and crystallizes into a perfect shape of its self. While the method of a fulgurite's creation is accurate, they are not necessarily rare, as one can make 'homemade' versions, using a lightning rod or rebar on a stormy night. Bobby also indicates that they need a large one. The length of the fulgurite used in the summoning spell was about 12 inches or so, but in reality, some of the largest that have been on display measured 13 to 16 feet long.