Bourg-St-Pierre Fulgurite - Natural Glass - Specimen 03/09 - Switzerland

This Bourg-St-Pierre fulgurite is a flattened, wing-shaped piece of glossy green glass with a thin, tapering edge. It is presented in a clear display box with a printed card showing the village of Bourg-St-Pierre in the Val d’Entremont.

Bourg-St-Pierre is a village in the Val d’Entremont, in the canton of Valais in the Swiss Alps, on the old route to the Great St Bernard Pass. The fulgurites from this area are pieces of natural glass formed where lightning struck the ground, and they are notable for their olive to yellow-green colour and glossy, often bubbly surfaces.

A fulgurite forms in a fraction of a second. The temperature inside a lightning channel can exceed 30,000 kelvin, and where the discharge enters the ground it melts the surrounding soil or rock, which then cools quickly to glass. Fulgurites are classed as mineraloids rather than minerals because they are largely non-crystalline. Researchers group them by the material they formed in, from tubes in sand to glassy crusts and droplets on soil and rock, so the shape and colour of each piece reflect the ground the lightning struck.

Fulgurites are not meteorites, but they sit naturally alongside tektites, impact glasses and other natural glasses as products of sudden, extreme heat. For collectors, Bourg-St-Pierre fulgurites offer a striking green glass with a precise Alpine locality, and no two pieces are alike.

OuterSpacer Meteorites acquired these specimens directly from Samuel Filliez at the Sainte-Marie-aux-Mines Mineral & Gem show in Alsace in 2025, where the Bourg-St-Pierre fulgurites were first presented to the public. Each piece carries a direct line of provenance back to the mineralogist who traced and documented the site.

Samuel Filliez tells the full story of the discovery in his article Lightning in Bourg-St-Pierre, which he has kindly allowed us to share. Read the English translation by Jet Mahoney (PDF).