Ceyssat

The name for a French village became a general term for the diatom earths of four neighboring departments.

Ceyssat is a commune in the Puy-de-Dome, in the volcanic Chaine des Puys. By 1914 the name had spread well past the village itself: a survey in the Bulletin de la Societe francaise de Mineralogie that year covered the ceyssatites of the Ardeche, the Puy-de-Dome, the Cantal and the Haute-Loire. The material is diatomite, amorphous silica accumulated from dead diatoms in crater lakes.