Fulgurite
Image: James St. John (CC BY 2.0)
Mineral NameFulgurite
Chemical FormulaSiO2
Mohs Hardness6
Crystal Systemamorphous
Streak ColorWhite
CleavageNone
Fractureconchoidal
Specific Gravity2.2
Colorslight brown, tan, grey
Transparencytranslucent to opaque
Type LocalitySahara Dune Field, Morocco
Mineral GroupMineraloid (amorphous silica)
Usesscientific study, collector's item
Associated Mineralsquartz, feldspar, clay minerals
Rarityuncommon
Description
A tubular, rough, light brown to tan object with a hollow, irregular interior, exhibiting a vesicular texture. The exterior shows a textured, somewhat granular appearance.
Geological Context
Fulgurites are formed when lightning strikes the ground, instantly melting silica-rich sand or soil, creating a glassy, tubular structure of lechatelierite (amorphous silica).
