Fulgurite = Latin word ‘fulgur’ which means thunderbolt. Fulgurite is created when lightning strikes sand. The high temperature of lightning, air-temperatures over 30,000 °C have been measured, is far higher than the sand melting point of 1800 °C. The silica that sand is made up of fuses together, creating the so-called lightning glass or lightning sand.
Fulgurite Sphere. Also known as Lightning Glass, these delicate, root-like formations are created when lightning strikes rock, instantly melting and fusing the stone into a preserved model of the lightning.
A Fulgurite or Petrified Lightning is made when lightning strikes loose sand. It vaporizes a thin wormhole and melts the zone around it, creating an instant froth of natural glass. In 1996 the International Center for Lightning Research and Testing excavated this fulgurite to a depth of nearly 6 meters, then removed it for museum display.
When Lightning Strikes Sand. Fulgurites (Latin, meaning "thunderbolt") Sometimes referred to as petrified lightning, they are natural hollow glass tubes formed by lightning strikes in quartzose sand, silica, or soil. (Wikipedpia)