The oolitic limestone of the North York Moors was laid down in a warm tropical sea about 160 million years ago in the Jurassic Period. In close-up, oolite resembles tiny round white fish eggs, hence the name.
The spiral shells are, as you might suspect, molluscs, but the thick mussel-shaped shells are brachiopods, also known as lamp shells because of their resemblance to Roman oil lamps.
View from Beech Farm Cottages
I spotted them in the walls of Beech Farm Cottages, Wrelton.
Calcite crystals have replaced the original material in this fossil mollusc shell.Shelly limestone: these brachiopod shells are mostly aligned concave side upwards, probably because of a current sorting the sediment and depositing them on this part of the seabed. Because this block has been built into a wall, we can’t tell which way up it was when the shells were deposited.
Entrance to Beech Farm Cottages. These corners stones or quoins are traditionally made from sandstone in the North York Moors because limestone isn’t as suitable for cutting to a sharp edge. In the absence of suitable slate or flagstones, pantiles became the preferred material for roofs. The stone bracket at the corner of the roof is a kneeler.
