The beauty of shells
Belemnites are the backbone for the reconstruction of Jurassic-Cretaceous seawater properties like temperature. Here you see an image of a thin section of such an belemnite (Gonioteuthis, Upper Cretaceous, NW-Germany) under crossed polarizers. Clearly one can recognize the calcite fibre-bundles the belemnite is made of.
Rene Hoffmann (distributed via imaggeo.egu.eu)