Iridescent ammonite fossil
Iridescent ammonite fossil. This fossilised ammonite displays pearl-like colours of iridescence, which only become visible when the outer shell has been peeled away. Iridescence is an optical phenomenon caused by interference within light rays reflected from a translucent multilayered surface. In this case, the surface is the finely layered aragonite in the ammonite shell. This ammonite (20 centimetres across) is Cleoniceras cleon, from Cretaceous sediments in Madagascar. Ammonites displaying iridescence like this are often sold as gemstones, and have been officially recognised as such under the name ammolite.
© DIRK WIERSMA/SCIENCE PHOTO LIBRARY
Prehistoric skeletons. These two embracing neolithic skeletons are called the Valdaro Lovers, They are believed to be a man and woman in their early twenties who died about 5000-6000 years ago. They were found at Valdaro-S.Giorgio, near Mantova (Mantua) in Lombardy, Italy. Photographed in the archaeobiology laboratory at the Musei Civici in Como, Italy.
© PASQUALE SORRENTINO/SCIENCE PHOTO LIBRARY
Fossilised remains of a conifer related to present-day pines (Araucaria spp
Fossilised remains of a conifer related to present-day pines (Araucaria spp.), preserved by opalisation and silification, dating back 65 to 250 million years, in Shamrock Street, the towns main street. In the background the Major Mitchell Clock remembers the explorer who passed this way in 1846. Blackall, central west Queensland, Australia