fulgurite
noun
ful·gu·rite ˈfu̇l-g(y)ə-ˌrīt 
ˈfu̇l-jə-,
ˈfəl-
: an often tubular vitrified crust produced by the fusion of sand or rock by lightning
Example Sentences
Recent Examples on the Web That means the lightning strikes initiate a geological stopwatch the moment a fulgurite is created. 
Nikk Ogasa, Science | AAAS, 16 Dec. 2020 If the soil composition is right, something called a fulgurite can also be created — fused soil that looks like coral. Joaquin Palomino, San Francisco Chronicle, 26 Jan. 2018
Nikk Ogasa, Science | AAAS, 16 Dec. 2020 If the soil composition is right, something called a fulgurite can also be created — fused soil that looks like coral. Joaquin Palomino, San Francisco Chronicle, 26 Jan. 2018 Word History
Etymology
International Scientific Vocabulary, from Latin fulgur
First Known Use
1823, in the meaning defined above