What do Warwick Castle, Liverpool Cathedral and the doorway to 10 Downing Street have in common?
They are all made of sandstone from Grinshill in Shropshire.
This summer I am having a break from compiling geotrails but have ended up working on building stones. How a geophysicsist ends up working on building stones is a long story but I’m having to take a crash course in the local natural building materials. The biggest problem that I have is that most of the local building stones are red sandstones, but from a whole variety of different stratigraphic layers.
To try to get a handle on the characteristcs of some building sandstones I visited Grinshill Quarry in Shropshire which has supplied a variety of buildings including those listed above. This Lower Triassic sandstone is formally known as the Helsby Sandstone Formation, but to stonemasons it is the Grinshill Sandstone. In fact the nomenclature is quite bewildering. Its lateral equivalents to the east are, in West Staffordshire, the Bromsgrove Sandstone Formation and in East Staffordshire, the Hollington Formation. Hollington Stone is quarried for building stone at Hollington, near Uttoxeter and is commonly used in Staffordshire. All of these formations used to be called the Lower Keuper Sandstone. You see the kind of problems I have to deal with.
In just the Grinshill Quarry there are three predominant colours, a red, a white and a pale yellow.
The quarrying operation is quite interesting. In order to split the rock into large blocks without damage from blasting, a series of holes are drilled in a line and then liquid expanding mortar is poured into the holes. The stress induced by the expanding mortar causes fractures to connect the holes with very little other damage to the rock.
The split blocks are then cut to the required shape on this rock saw.
So that is just one of the formations I have to work with. Now I just have to get my head round all the Carboniferous gritstones…