[fuhl-gyuh-rahyt] 
| a tubelike formation in sand or rock, caused by lightning. |
| ful·gu·rite (fŏŏl'gyə-rīt', -gə-, fŭl'-) n. A slender, usually tubular body of glassy rock produced by lightning striking and then fusing dry sandy soil. [Latin fulgur, lightning; see fulgurate + -ite1.] |
fulgurite
a glassy silica mineral (lechatelierite or amorphous SiO2) fused in the heat from a lightning strike. Fulgurite is a common mineral with two varieties. Sand fulgurites, the more common, are branching, more or less cylindrical tubes that are about one centimetre (one-half inch) to several centimetres in diameter; they are commonly less than 3 metres (10 feet) long but sometimes reach 20 m (66 ft). The central cavity is usually lined with glass, and the exterior shows adhering sand grains. The shores of Lake Michigan and the Atlantic coast are typical sites
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gyəˌraɪt