Stalactite or flowstone
This is a very large section of rock that was once the surface of a crack, known as a gully, cutting through the Portland Limestone. Calcium-rich waters flowed over the surface for thousands of years, and flowstones or stalactites have formed.
This block is probably upside down; notice how the structure starts to form thin sheets called ‘curtains’. Curtains hang down from the cave roof or wall but here they are the wrong way around.
Find out more on the rocks and pseudofossils page.