Geology Site Account
Moat Farm Sarsen Stone, Gestingthorpe, GESTINGTHORPE, Braintree District, TL816367, Potential Local Geological Site
Moat Farm Sarsen Stone, Gestingthorpe
A very fine mammillated sarsen stone 1.2 metres by 1 metre (4 feet by 3 feet) in size sits near the junction outside Moat Farm.
Sarsens are remarkably abundant in the area around Gestingthorpe village. Boswell (1929) mapped their distribution in the Sudbury district and stated that over sixty ‘blocks of sarsen-stone’ were present in Gestingthorpe parish. There are unfortunately far fewer visible today.
Sarsens are extremely hard boulders of sandstone formed around 55 million years ago when the climate of Britain was hot and a layer of sand beneath the surface of the ground became cemented with quartz. They are thus very resistant to erosion and have survived the rigours of the Ice Age. They probably originated on the chalk downland of south Cambridgeshire and after retreat of the ice they became concentrated in river valleys such as The Stour.
The remarkable 'mammilated' surfaces on some sarsen stones are called ‘growth structures’ which were formed as the quartz slowly crystallised between the sand grains.
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Reference: Boswell 1929, Lucy 2003a
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