Ref.: G. Demarcq, 1973, "Guides Géologiques Régionaux : Lyonnais, Vallée du Rhône" , p. 88, Masson.
Quarries on East side of Saint-Priest hill.
Silicified conglomerates, with flint layers and flint breccias, above volcanic tuffas.
Geyserites (http://www2.ac-lyon.fr/enseigne/biologie/excurs/saint_et/saint_et4.html)