Turtle Stone Tabletop

March 27 2009, 1:56pm

A Tabletop Composed of a Section of a Septarian Nodule We have just received the first image of one of the extraordinary tabletops that will be in our exhibition ‘On Tops’ in May!  This tabletop is made from a section of a septarian nodule, a remarkable type of geological formation also known as “turtle stone” for its characteristic pattern of radiating cracks. Septarian nodules are created when the pores in a mass of sedimentary rock (often composed of fossils dating from the Cretaceous period, 50-70 million years ago) are filled in with jelly-like mineral deposits, which harden into a spherical or ovoid form.  The exact cause of the cracks, or septaria, that are found inside the nodules is something of a mystery; but their striking beauty is undeniable! Septarian nodules have been found to be as large as 9 feet in diameter: the Moeraki Boulders of New Zealand were known to reach this size. Smaller concretions were found in the Oxford and Kimmeridge Clays along the Wessex Coast of England. It is likely that the present tabletop was made using a septarian nodule from this area.