Tegurite

Tegurite is a natural glass produced when a powerful electrical discharge, typically lightning, fuses silica-rich materials such as sand, soil, or rock. In common usage tegurite is considered a form of fulgurite, although some sources reserve the term for particular morphological types or settings.

Formation: A lightning strike concentrates heat along a narrow channel, melting surface materials to a molten glass. Upon rapid cooling, the glass solidifies, often forming hollow tubes, branched networks, or irregular nodules that trace the strike path. The glass is mainly silica, with possible inclusions of minerals present in the target material.

Appearance and composition: Tegurites are glassy and can be colorless, brown, green, or iridescent. They typically show a smooth outer crust with a fused inner matrix and may contain gas bubbles or mineral inclusions. Texture ranges from vitreous to crusty.

Occurrence and geology: Tegurites occur wherever silica-rich materials are exposed to intense electrical discharge—deserts, beaches, riverbanks, and other sedimentary settings. They are found worldwide, often in association with natural fulgurites rather than meteorite impact glass.

Dating and significance: The formation event is a lightning strike; dating the glass itself is challenging, but associated sediments can sometimes be dated to constrain age. Tegurites are studied to understand past atmospheric electricity and surface processes.

See also: Fulgurite, tektite. Noting distinction: Tegurite is a lightning-induced glass, whereas tektites form from meteorite impacts, and fulgurite is the broader category of lightning glass.