Frosterley Marble - the font.

Frosterley is a village in County Durham, in England. It is situated in Weardale, on the River Wear. A black limestone containing fossil corals of the Carboniferous Period, some 325 million years ago is mined there. When cut and polished the result is a beautiful ornate stone, much desired for church decoration, particularly during the Middle Ages
Frosterley Marble was used for the decorative columns found in Durham Cathedral date which date from about 1350.

This shot is from the font near the north-west door of St Peter's Church (674 AD), Sunderland.