2.9" Polished Jurassic Fossil Sponge (Solenopora) - England

This is a Jurassic aged, fossil sponge of the species Solenopora jurassica from Gloucestershire, England. Locally these sponge fossils are known as "Beetroot Rock" because of their coloration.

One very interesting aspect of this fossil is recent studies have shown that the reddish hue is likely to have been the same tone as the original coloration of the animal. The coloration comes from natural pigments suffused by the element boron. The same study concluded the banding on these fossils is due to seasonal growth. A link to the paper originally published in the Proceedings of the National Academy of Sciences can be found below.

Geochemical Evidence of the Seasonality, Affinity and Pigmenation of Solenopora jurassica