Grime’s Graves: A Neolithic Flint Mine

This strange lunar-like landscape in the middle of Thetford Forest in Norfolk, England, looks very similar to mortar craters in Normandy and in Somme from the First World War. But these ones in Norfolk have a different origin, and despite their name, they are not graves. Grime's Graves is actually a large flint mining complex from the Neolithic age that’s at least 4,500 years old.

In the Neolithic era, flint —a hard, mineralized form of quartz—was a valuable natural resource and highly prized because of its tendency to break into thin flakes with a razor sharp edge that was very useful to make tools and weapons. Indeed, flint remained in use for many centuries even after men learned to make tools out of metals.

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Photo credit: www.english-heritage.org.uk

At the Grime’s Graves site, there are over four hundred vertical shafts dug into the natural chalk that reached seams of flint that lay underground. The largest shafts are more than 14 meters deep and 12 meters across at the surface. The sizes are impressive considering that the Neolithic miners used antlers for picks and wooden shovels. From the bottom of the pits, lateral galleries radiated outward along the flint seam to extract as much flint as possible. The galleries would often connect with those from adjacent shafts to form a network of tunnels. New shafts were sunk every one or two years, and the spoils extracted were filled into previously dug shafts.

The wide pits were lit by natural daylight but in the horizontal passageways light came from small lamps with floating wicks that were made by scooping out hollows in the chalk walls and filling them with animal fat or oil. You can still see soot marks on the roofs of the galleries.

It is estimated that a medium-depth shaft could have yielded as much as 60 tons of flint nodules that could have produced as many as 10,000 polished stone axes. Extrapolation across the site suggests that Grime's Graves may have produced around 16-18,000 tons of flint across the 433 shafts recorded to date.

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A reconstruction of Neolithic flint miners at work, extracting flint from galleries at the base of the mine shaft using picks made from red deer antlers. The flint was then hauled to the surface. Photo credit: www.english-heritage.org.uk

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A reconstruction of the Middle Bronze Age settlement at Grime’s Graves, with small fields and herds providing a mixed farming economy. Photo credit: www.english-heritage.org.uk

Flint mining at Grime's Graves is believed to have started at around the same time the Druids were erecting monuments at Stonehenge and at Avebury. This was a time when trade networks were extensive, and the Neolithic miners must have traded the flint they extracted with other societies. Mining continued at Grime’s Graves until about 1400 BC. In this later period, the pits became shallower and lacked underground galleries. As bronze tools became more common and items of status, they started to eclipse traditional flint tools. Lack of demand eventually led to the closure of the mines.

After the mines were abandoned, subsequent civilizations started using the shafts as garbage dumps. Excavation of these waste dumps have revealed valuable items of prehistory such as metalwork, pottery, textile, leather and woodwork, as well as bones of various animals.

During the Iron Age, some of the shafts became burial chambers.

Today, Grime's Graves is one of the few surviving Neolithic flint mines in the world. Now under the care of the English Heritage Trust, the site is open to the public and one of the pit can be descend by a 9-meter ladder and the radiating galleries explored.

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