Opal-CT (variety lussatite) after fossil (Helix ramondi)

Les Rois Mine, Mur-sur-Allier, Pont-du-Château, Clermont-Ferrand District, Puy-de-Dôme Department, Auvergne-Rhône-Alpes  France

Specimen size: 6.9 × 5.1 × 3.2 cm = 2.72” × 2.01” × 1.26”
Main crystal size: 2.2 × 2 cm = 0.87” × 0.79”