See caption
Hamstone wall from Tithe Barn, Haselbury Mill, Haselbury, Somerset
Wikimedia Commons

Hamstone is a golden-brown building stone from Ham Hill, Somerset, widely used in the construction of Somerset church towers.[1] It is a sedimentary rock formed in a shallow-marine environment about 174–183 million years ago, during the Jurassic period. It is generally composed of coral and shell fragments deposited in the carbonate sea that once covered the area.[2]

Weathering causes the stone to darken to richer-coloured tones.[2] While generally well-cemented, hamstone is characterised by marked bedding planes of clay inclusions and less well-cemented material, which weather differentially to give exposed blocks a characteristic furrowed appearance.[3]

Modern quarrying

Today hamstone is quarried in only two areas of Ham Hill. The North quarry, the longest-running hamstone quarry in existence, is operated by Ham & Doulting Stone.[4] The Norton or South quarry, operated by Harvey Stone, was formed by the re-opening of workings that were abandoned in the 1930s, and extracts its stone from 20–30 metres below the surface. Hamstone House in Surrey was built in 1938 with the last significant supply of hamstone from the quarries on Ham Hill before their closure for forty years.[5]