Ham Hill Stone - Somerset (Lead author: SA)

Series	Stage	Ma	Traditional		South Dorset		South Somerset	Use
Middle Jurassic	Aalenian	174.1	Inferior Oolite Group
Lower Jurassic	Toarcian	182.7	Upper Lias	Lias Group			Ham Hill Limestone Member	Building Stone
						Bridport Sand Formation
					Downcliff Clay Member			Brick Clay
			Middle Lias		Beacon Limestone Formation
	Pliensbachian

Ham Hill Stone (aka Hamstone) is a Lower Jurassic limestone of limited extent (Toarcian, Upper Lias).   At Ham Hill (west of Yeovil) the relatively soft poorly-fossiliferous quartzose sandstone of the Bridport Sand Formation (previously Bridport & Yeovil sands) is represented by 15-20 m of bioclastic limestone.  This must have been deposited in a high energy, shallow sea with a reduced input of quartz sand and an abundant supply of shell debris. 

Ham Hill Stone is a well-cemented medium to coarse grained limestone characterised by its oxidised honey-gold colour due to iron content.  It shows marked cross-bedding and moulds of shell debris.  Some horizons have a blue grey centre where the iron has not oxidized. The stone contains thin beds of poorly cemented material and some small soft clay inclusions. These areas weather differentially to give exposed Ham Hill Stone its furrowed appearance.

Ham Hill stone is currently quarried in only two areas on the top of Ham Hill.  The older northern quarry, (Ham Hill and Doulting Stone company) near the stone circle and famous monument, extracts stone from just beneath the surface.  The stone extracted from the southern, Norton Quarry (Harvey Stone), is found some 20-30 metres below the surface

Ham Hill Stone has been used extensively in South Somerset and Dorset for substantial buildings and churches as it is easily worked for corners, quoins, mouldings of arches, doorways and windows.  A large number of Dorset Churches make use of Ham Hill Stone in the window tracery.  Ham Hill Stone is also used in pillars, war memorials, monuments and freestone sculptures which take advantage of the decorative nature of the stone.
                                                                                                                                                                        
​Text and Images: SA/WGT Mar 2017

Crewkerne Parish Church – St Bartholomew

1. The church dates from the 15th century. View from NW.

3. View to south with Church hall to the right.

5. The west wall

7. Ham Hill Stone: close-up of mouldic biocalcarenite.

2. Church Interior

4. The Church Hall, dated from 1636.

6.

WGT 14 Mar 2017