La coquille flammée du casque rouge, Cypraecassis rufa

Abstract

The flame structure of the red helmet shell, Cypraecassis rufa (Linnaeus, 1758) Among molluscs with so-called “porcelaneous” shells, consisting of non-nacreous aragonite, we chose a gastropod, Cypraecassis rufa, to show an example of flame structure on cabochon-cut samples. The crossed structure of this shell, formed of lamellae of different orders, is present in its body. On fragments with a polished flat surface, a moiré effect can be seen. Moreover, on the curved surfaces of the cabochons, a kind of pseudo-chatoyancy appears. The flames are due to the reflection of light on second-order lamellae stacked in first-order lamellae of alternating orientation around their stacking axis.