A RAINBOW RELIC
© Alamy
On display at the Campania Mineralogical Museum in Vico Equense, Italy, is this 71-million-year-old ammolite. This rare organic gemstone originates in marine fossils, such as ammonites, which have been exposed to extreme pressure and heat. The rainbow iridescence of the ammolite comes from layers of aragonite that have deposited onto the ammonite shell. The structure of these layers splits the wavelengths of visible light into its constituent colours.