#FG-9 Egyptian Fulgurite specimen, approximately 1 inch long. Each one unique.
Fulgurites (from the Latin Fulgur, lightning) are produced by lightning striking exposed surfaces. These Fulgurites have been found at the feet of sand dunes of the Great Sand Sea, in the southwest of Egypt. Their tubular shapes are typical of lightning striking sands. On rocks, they may have different shapes. It has been estimated that each flash of lightning releases an average energy of 1 billion Joules. Air temperatures may reach momentarily 10,000 degrees K, even sometimes 30,000 degrees K. The peak currents measured range from 10 kA to 100 kA but they last only a few microseconds. This high energy will melt or vaporize the sands or rocks with formation of amorphous glass, named by A. Lacroix who studied this phenomenon since 1915: Lechatelierite (after the French mining engineer, Le Chatelier.) Tubular Fulgurites are known that exceed 8 meters but their recovery as a whole is impossible; they are very fragile and are usually found in pieces of 10 to 15 cm, with diameters ranging from 5 to 20 mm.