mineral
Sand Fulgurite
Lechatelierite (Silica glass tube)
Hardness of 6 to 7 on the Mohs scale, typically gray, brown, tan, or black with a rough, sandy exterior and a glassy, smooth interior. Vitreous to dull luster. Amorphous crystal structure (glass). Specific gravity around 2.2.
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Physical properties
Hardness of 6 to 7 on the Mohs scale, typically gray, brown, tan, or black with a rough, sandy exterior and a glassy, smooth interior. Vitreous to dull luster. Amorphous crystal structure (glass). Specific gravity around 2.2.
Formation & geological history
Formed when a high-voltage lightning strike (at least 1,800 degrees Celsius) instantaneously melts and fuses loose silica sand or soil. Geological age is recent to ancient depending on when the lightning event occurred.
Uses & applications
Valued by mineral collectors, researchers studying ancient climates and lightning strikes, and sometimes used in educational displays.
Geological facts
Fulgurites are colloquially known as 'petrified lightning'. The tube can sometimes extend several meters underground depending on the depth of the sandy soil.
Field identification & locations
Found in sandy deserts, beaches, and dunes worldwide. Field identification relies on finding irregularly shaped, glass-lined sandy tubes or crusts where lightning is likely to have struck.
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