Moon’s Hill is a basalt quarry situated approximately 1km south of Stoke St Michael in the eastern Mendip Hills and is a SSSI. The locality represents the most southerly known outcrop of Silurian strata in Great Britain and the rocks occupy the core of an anticline with an east-west trending axis and a southerly dipping axial plane.
These clastic (rocks composed of broken pieces of older rocks) and volcaniclastic sediments have yielded a fairly rich, mineralised fossils referrable to the Lower Wenlock Series, in the Silurian period, between the Devonian period: 418 mya and Ordovician period: 444mya. This extrusive igneous (Basalt) suite represents the sole example of Wenlock-aged volcanic rocks of Andesite lavas in England.
Due to the presence of shale and mudstone below the volcanic rocks and sometimes interbedded with them, volcanic activity took place in a marine environment and the whole sequence of lavas, ashes and agglomerates can be readily identified and measured because the beds are now standing vertically on end like books on a bookshelf.
Moons Hill Quarry was on the Knatchbull family estate, and John Wainwright in partnership with the Luffs purchased the site in 1897. In 1902 Wainwright’s became a limited company. Between 1907-25 a narrow gauge railway connected Downhead and Moon’s Hill Quarries with the rail system at Waterlip, improving the transportation of stone. In 1934 Wainwright’s invested in their first coating plant for the making of concrete and tarmac. However, in the quarry, ‘stone getting’ was still a manual job, involving hand loading into large buckets which were then winched up to the crusher. This continued to be so until face shovels and Muir Hill dumpers were introduced more than ten years later. The subsequent development of the site was made in 1962, 1973, 2005/6 and more recently 2013.
From the earliest days of the quarry, particularly resilient material for road surfacing has been the main product although at times, particularly in the 1930s, concrete products have also been important. As Moon’s Hill is the only source of such tough material over a considerable area (including the whole of south-eastern England), the quarry is of interregional significance. One particularly interesting job was the production of aggregate to make concrete for bank vaults in the 1960s.
Historical Notes: British Geological Survey, Wainwright.co.uk, English Nature citation sheet.