Geology museums of Britain: Grime’s Graves – ancient mining and the stone beneath the Chalk
Jon Trevelyan (UK)
A landscape full of holes
Grime’s Graves does not announce itself with the drama of a great cliff, cave or quarry. On a low Chalk ridge in the Breckland of Norfolk, the most immediately striking feature is instead the ground itself. Across the grassland are hundreds of shallow hollows separated by low, irregular mounds. They might at first be mistaken for natural undulations. In fact, they are the surviving traces of one of Britain’s most remarkable prehistoric mining landscapes.
Between about 2650 and 2150BC, during the Late Neolithic, people came here to mine flint from beneath the Chalk. A later and generally shallower phase of mining took place during the Early to Middle Bronze Age, around 1550–1500BC. Grime’s Graves is one of ten known prehistoric flint-mining sites in England and is unique in Britain because visitors can descend into original underground workings.
From the surface, the scale of what happened here is easy to underestimate. Each hollow marks a shaft or pit that was eventually abandoned and infilled or collapsed; much of the excavated Chalk was left around it as spoil. Repeated over many centuries, this activity created the peculiar pock-marked landscape that survives today (Fig. 1).
The scale becomes still clearer from the air. What appears at ground level to be gently hummocky grassland resolves into a dense concentration of overlapping hollows, the cumulative result of generations returning to the same source of flint (Fig. 2).
Yet this was not a prehistoric industrial complex operating continuously. Estimates suggest that between about 500 and 1,000 shafts and pits may have been worked over roughly 1,100 years, when the later Bronze Age activity is included. In an average year, perhaps only one or two mines were active. The landscape therefore accumulated gradually, one episode of mining after another.
The most important part of a visit lies beneath it. Pit 1 allows visitors to descend roughly 9m below the modern surface into the Chalk and enter part of the original Neolithic workings. We shall return to it later, because experiencing those workings is central to understanding the achievement of the miners.
For the moment, however, the important question is why the mines exist at all. Flint was hardly scarce in Chalk country. It could be collected from surface deposits and places where Chalk and flint were naturally exposed. Why then, would people equipped only with prehistoric tools undertake the enormous additional labour of sinking shafts several metres into the ground?
The answer lies beneath the grass. Within the Chalk at Grime’s Graves are several flint horizons, of which three became particularly important to the prehistoric miners: the topstone, wallstone and floorstone. The deepest, the floorstone, was their principal target. Its depth varies across the site, reaching about 12m below the surface at Greenwell’s Pit, but only about 6m at Pit 15 (Fig. 3).
The miners were therefore exploiting something much more specific than “flint”. Their repeated success in reaching the deeper floorstone implies a practical understanding of the local geology: they knew that a particularly valued source of stone lay beneath the shallower horizons and were prepared to dig down to reach it.
That gives us the central question around which the rest of Grime’s Graves can be understood:
Why did Neolithic people go to such extraordinary trouble to mine flint underground when they could obtain flint at the surface?
Answering it takes us from a Cretaceous sea, through the geology of Chalk and flint, into prehistoric mining, knapping and the wider Neolithic world.
But first there is another puzzle to solve. If these hollows are mines rather than burials, why are they called Grime’s Graves?
Why “Grime’s Graves”?
The name Grime’s Graves sounds as though this ought to be a burial ground. In fact, neither part of the name tells us what originally happened here.
By the time Anglo-Saxon communities encountered the site, the main period of mining had ended thousands of years earlier. What remained was the extraordinary landscape of hollows and mounds we see today. With no knowledge of Neolithic flint mining, people had to find another explanation for it. The strange earthworks came to be associated with Grim, a name connected with the Anglo-Saxon god Woden, from which Grime’s Graves acquired its present name.
The “graves”, meanwhile, are not graves in the usual sense. They are principally the surface remains of abandoned mine shafts and pits. There is an irony here, because later communities correctly recognised that something unusual had been done to the landscape, while completely losing sight of who had done it and why.
Grime’s Graves continued to acquire new meanings long after mining ended. One surviving earthwork, Grimshoe Mound, became the meeting place of the local hundred court. In 1739, the Norfolk antiquary and clergyman Francis Blomefield recorded that the site was locally known simply as “the Holes”. He correctly associated Grimshoe with the hundred court, but believed that the surrounding pits were the remains of a Danish encampment, perhaps dug to conceal tents, with the mound serving as a watchtower or signal station. It was a reasonable interpretation of a landscape whose underground workings were still hidden.
A map of the manor of Weeting made in 1761 depicted the site as a group of circles, with Grimshoe Mound shown separately. The first Ordnance Survey map of 1824 likewise recorded the hollows on the low spur. But recognising that the pits were artificial was one thing; discovering what they were was another.
The first recorded archaeological excavations took place in 1852, when the Reverend S T Pettigrew and the Rev C R Manning investigated some of the pits; Manning returned in 1866. They did not excavate deeply enough to discover the mines beneath. Finding evidence including hearths in the upper fills, they instead interpreted the hollows as the remains of sunken Iron Age dwellings.
The breakthrough came with Canon William Greenwell, who excavated at Grime’s Graves between 1868 and 1870.
Greenwell kept going down. Beneath the material that had accumulated in one of the hollows, he found that the supposed pit continued as a deep shaft cut through the Chalk. At its bottom were underground galleries. Red-deer antler tools provided evidence of how the Chalk had been excavated, while a stone axe helped establish the prehistoric age of the workings. Greenwell had demonstrated that the mysterious hollows were the remains of flint mines.
Grime’s Graves consequently became the first prehistoric flint mine to be recognised as such in Britain. That discovery completely changed the interpretation of the landscape. The “graves” were not primarily graves, the hollows were not Danish defences and they were not the floors of prehistoric houses. They were the uppermost remains of shafts sunk by miners thousands of years before.
There is one final twist. Later people really did use parts of this mining landscape for burial. During the Iron Age, individuals were placed within the upper fills of abandoned shafts – something we shall return to when considering what happened to Grime’s Graves after mining ended. For now, it is enough to note how easily later activity could further obscure the original purpose of the site.
By the late nineteenth century, therefore, the central archaeological mystery had been solved. But Greenwell’s discovery created a geological one. The miners had not merely dug holes into the Chalk. They had sunk substantial shafts through it until they encountered particular layers of flint, and then excavated galleries along those levels.
To understand why, we need to look at the rocks beneath Grime’s Graves.
The geology beneath the mines
To understand why Grime’s Graves became a mining landscape, we have to travel back far beyond the Neolithic, to the Cretaceous Period, when this part of Britain lay beneath the sea.
The bedrock beneath the site is Chalk, a soft limestone formed largely from the microscopic calcareous remains of marine organisms that accumulated on the sea floor. Within it are repeated horizons of much harder flint. At Grime’s Graves, this alternating succession of Chalk and flint is known as the Brandon Flint Series.
The contrast between the two rocks could hardly be greater. Chalk is soft enough to be excavated with tools made from antler, whereas flint is a hard form of silica capable of producing extremely sharp edges when fractured. The presence of one enclosed within the other ultimately made deep mining at Grime’s Graves possible: the Chalk could be excavated to reach a much harder and more valuable geological resource.
Exactly how the flint came to be there deserves a little more explanation (see box: How does flint form in chalk?).
| How does flint form in chalk? |
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| Flint and Chalk seem unlikely companions. Chalk is a soft, white limestone composed overwhelmingly of calcium carbonate, whereas flint is an extremely hard form of silica. Yet, throughout the Chalk of southern and eastern England, dark flint occurs as nodules, bands and, in places, more continuous sheets. Both owe their existence to the Cretaceous sea that covered much of Britain. The Chalk accumulated from enormous quantities of microscopic calcareous remains settling on the sea floor. Silica was also present, much of it ultimately derived from organisms with siliceous skeletons. Flint did not simply form by these organisms being compressed directly into nodules. During early burial, silica dissolved and migrated through the sediment before becoming concentrated and reprecipitated within it. Burrows and other structures in the seabed could influence where this happened, helping to produce the extraordinary irregular shapes of many flint nodules. Repeated episodes of this process produced the flint horizons within the Chalk. At Grime’s Graves, three of the upper horizons became particularly important to prehistoric miners: the topstone, wallstone and floorstone. The deepest of these – the floorstone – became their principal target. |
We introduced these horizons in Fig. 3, but their significance becomes clearer when we consider the mines themselves. Their significance becomes particularly clear in Pit 1. Here, the topstone occurs at about 3m below the surface and the wallstone at around 7m. Yet the miners continued downwards until they reached the floorstone at approximately 9m. Only at this deeper level was the principal gallery system developed.
This was not simply a matter of digging until flint appeared. The miners were targeting a particular part of the geological succession.
Nor did the floorstone occur at a constant depth across Grime’s Graves. The surface and underlying strata vary sufficiently for the target horizon to lie about 12m below ground at Greenwell’s Pit, but only around 6m down at Pit 15. The depth of an individual mine therefore depended partly upon where it was situated.
The repeated success with which prehistoric miners reached the floorstone implies a considerable practical knowledge of the local geology. We should not turn Neolithic miners into modern stratigraphers: they possessed no geological maps, boreholes or formal understanding of sedimentary rocks. But experience accumulated from earlier workings must have allowed people to recognise a sequence within the Chalk and anticipate what lay beneath them.
The higher flint horizons could themselves have provided useful markers. Encountering one seam while sinking a shaft could indicate that another should occur further below. Generation after generation of mining would have added to that practical understanding.
The resulting mine geometry was therefore controlled by geology. A shaft first provided vertical access through the Chalk. Once the desired floorstone had been reached, the emphasis changed to lateral extraction, with galleries extending outward around the base of the shaft. Instead of removing an enormous volume of Chalk from the surface downwards, miners could concentrate their effort around the horizon containing the material they wanted.
The galleries beneath Grime’s Graves were therefore not random tunnels. Their position was determined by the distribution of the flint.
There was also younger geology above the mines. Sands and gravels overlie the Chalk, along with features produced by the much later cold conditions of the Pleistocene. These include the unusual periglacial stripes visible in parts of the site. We shall encounter these again when looking at the modern landscape in the concluding section.
A Cretaceous sea produced a succession in which hard silica-rich flint became concentrated within soft Chalk. Millions of years later, prehistoric communities discovered that some of those flint horizons were more desirable than others. They learnt where the best material occurred and developed a mining system capable of reaching it.
But this still leaves the most important question unanswered.
Why was the floorstone so desirable that people were prepared to dig as much as 12m through the Chalk to obtain it?
That is the question we turn to next.
Why dig so deep for flint?
The geology explains where the miners dug. It does not explain why they were prepared to dig so far. Flint was not scarce in prehistoric Britain. In Chalk country it could be collected from surface deposits, river gravels and natural exposures. Indeed, people had been using readily accessible flint for thousands of years before the mines at Grime’s Graves were opened.
Yet the Late Neolithic miners did something very different. They sank shafts through metres of Chalk, passing shallower flint horizons in order to reach the deeper floorstone. The most likely explanation is quality.
This is one of the fundamental questions surrounding prehistoric flint mining. It suggests that deeply buried flint was particularly suitable for producing large artefacts. Surface and outcropping flint had been used during the preceding Mesolithic, but mined flint became important where substantial pieces of dependable material were required.
The size of the material available could be impressive. Flint at Grime’s Graves occurs both as individual nodules and as more extensive masses, with some nodules exceeding 2m across. A large piece of sound flint offered the raw material from which substantial objects, including axe rough-outs, could be produced.
The miners were therefore not simply searching for the first flint they encountered. By passing the upper horizons and repeatedly targeting the floorstone, they demonstrated that this deeper material was worth the considerable additional labour needed to obtain it.
There may also have been more to the value of flint than its physical quality. Some flint objects from Grime’s Graves appear to have acquired social or ceremonial significance. The guide notes that some axes were apparently never used, while others may have been exchanged as gifts or deposited in hoards. We shall return to this in later, because it raises intriguing questions about what mined flint may have meant to the communities using it.
For now, the important distinction is between availability and desirability. Flint was available at the surface. But the miners wanted particular flint badly enough to go underground for it (see box: Why was floorstone worth all that effort?).
| Why was floorstone worth all that effort? |
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| Why sink deep shafts when flint could simply be collected from the surface? The most likely answer is that the miners valued the quality and size of the buried material. Mined flint was particularly suitable for knapping large artefacts, while surface and outcropping flint had already provided material for tools during the Mesolithic. At Grime’s Graves, the preferred floorstone lay beneath the topstone and wallstone. Its depth varied across the site, but prehistoric miners repeatedly organised their workings around this deeper horizon. That repeated targeting is important. It implies that the miners possessed enough practical knowledge of the local succession to anticipate where the desired flint should occur, even though they could not see it from the surface. Flint may also have possessed value beyond its usefulness as a raw material. Some axes were apparently retained for ceremonial purposes, exchanged as gifts or deposited in hoards. The floorstone was therefore not simply another band of flint within the Chalk. To the communities mining Grime’s Graves, it was a geological resource worth a remarkable investment of labour. |
Down into Pit 1
There is a point during a visit to Grime’s Graves when everything seen on the surface suddenly makes sense. It comes when you descend into Pit 1.
Above ground, the hollows show where shafts once existed and Fig. 2 can explain the basic arrangement of a mine. But neither quite conveys what was involved in reaching the floorstone. Pit 1 does. It is the only prehistoric flint mine in Britain where visitors can descend into original underground workings.
The descent is roughly 9m (Fig. 4). That is modest compared with the depths of later coal or metal mines, but such comparisons are misleading. This shaft was excavated about five thousand years ago through solid Chalk, without iron or steel tools. Everything removed from it had to be broken from the rock and carried back to the surface.
Pit 1 was archaeologically excavated in 1914 by A E Peake on behalf of the Prehistoric Society of East Anglia. Its shaft was almost 10m across at the surface, narrowing to about 3.6m at the bottom. There, instead of continuing downwards, the miners changed direction and excavated galleries laterally into the Chalk.
This was the essential geometry of the deep mines at Grime’s Graves: a shaft to reach the floorstone, followed by galleries to exploit it (Fig. 5). The diagram makes the arrangement easy to understand. Underground, however, what is most striking is the confined scale of the workings. These were not tunnels intended for comfortable movement. They were working spaces excavated for the specific purpose of following the flint (Figs. 6 and 7).
Some galleries elsewhere at Grime’s Graves were relatively spacious by prehistoric mining standards: those in Greenwell’s Pit include examples with around 1.5m of headroom. Many workings were considerably more restricted. Miners therefore had to work crouched or crawling beneath several metres of Chalk. And they did so with tools fashioned from natural materials (See box: Antler picks: the neolithic miner’s tool).
| Antler picks: the neolithic miner’s tool |
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| One of the characteristic tools of prehistoric flint mining was the red-deer antler pick. Antler combined toughness and resilience with a naturally useful shape: part of the antler could be gripped while a projecting tine was driven into the comparatively soft Chalk. Numerous antler picks have been recovered at Grime’s Graves, providing unusually direct evidence of how the mines were excavated. Canon William Greenwell recognised their importance during his nineteenth-century investigations, and further examples were found when Pit 1 was excavated in 1914. The picks also remind us of the enormous difference in hardness between the two principal rocks involved. The relatively soft Chalk could be excavated with antler tools; the hard flint enclosed within it was the prize. Mining nevertheless required much more than cutting Chalk. Spoil had to be removed from the working face, flint carried to the shaft and material raised to the surface. Evidence from Grime’s Graves shows that timber platforms were constructed across some shafts, while comparisons with other prehistoric mines suggest that notched tree trunks may have served as ladders. The technology was simple in its materials, but the mining operation itself was anything but simple. |
The miners could not simply remove everything surrounding the floorstone. The surviving pattern of galleries necessarily left Chalk between adjacent workings, allowing the flint horizon to be followed without excavating the entire mass of overlying rock (Fig. 8).
We cannot reconstruct every detail of how a mine operated, which is why Fig. 5 should not be read as an exact picture of Pit 1 at a particular moment. But the surviving workings reveal something far more organised than somebody simply digging a hole. And that is what makes Pit 1 the most memorable part of Grime’s Graves.
The visitor centre can display the artefacts, and the hollows outside reveal the extent of mining. Underground, the physical achievement becomes immediate. Daylight is metres above. Around you is Chalk. Opening from the bottom of the shaft are galleries excavated by people using antler, stone, timber and accumulated knowledge (Fig. 9).
Reaching the floorstone, however, was only half the achievement. The miners still had to turn the irregular pieces of flint they extracted into useful objects. And that depended upon a remarkable property of the stone itself.
From nodule to tool
Getting the floorstone out of the Chalk was not the end of the process. What the miners brought to the surface was still raw material, often covered by a pale outer cortex. Its value depended upon what a skilled knapper could make from it.
Flint is exceptionally well suited to tool-making, because it is hard but fractures predictably. A carefully directed blow produces the curved conchoidal fracture illustrated in Fig. 10, allowing a skilled knapper to detach flakes with extremely sharp edges.
Knapping was nevertheless far more sophisticated than simply striking one stone with another. The knapper had to judge the shape of the raw material, decide where to strike it and control the direction in which each fracture travelled. Every flake removed altered the geometry of the remaining piece and therefore the possibilities for the next blow.
Different stages could employ different techniques. A hard hammerstone was useful for removing the cortex and detaching relatively large flakes. As the intended form emerged, progressively more controlled blows – including the use of softer hammers – allowed the piece to be refined. Smaller tools could be produced directly from flakes and blades, with their edges subsequently modified by retouching.
The Late Neolithic toolkit represented at Grime’s Graves included scrapers, knives, piercing tools, arrowheads and axes, as well as the waste flakes and partly worked pieces left by the manufacturing process. These were not all made in precisely the same way, nor need every stage of manufacture have taken place at the mine.
Axes provide the clearest example. A suitable piece of floorstone could first be reduced by removing the cortex and large unwanted flakes. Continued knapping gradually produced an axe rough-out – recognisably axe-shaped, but still carrying the scars and irregularities produced by flaking. Grinding and polishing could then transform that rough-out into a much smoother finished tool with a carefully formed cutting edge (Fig. 11).
That final point is important. More than 300 axes or axe rough-outs have been recovered from Grime’s Graves, but nearly all are unfinished. This suggests that at least some of the material left the mining area as rough-outs and was finished elsewhere.
There were good practical reasons for doing so. Initial reduction at or near the source removed cortex and unwanted flint, allowing people to carry away a lighter and more useful piece rather than transporting an entire nodule. Final grinding and polishing could then take place wherever the axe was actually required.
Nor should the prominence of axes in discussions of Neolithic flint mining lead us to imagine that Grime’s Graves was simply an axe factory. Although more than 300 examples have been found, axes are not disproportionately common within the enormous quantity of worked flint recovered from the site. A much wider range of objects was being produced.
This is where the geological story of Grime’s Graves becomes something more. The Cretaceous sea supplied the silica. Geological processes concentrated it into flint within the Chalk. Neolithic miners located particular flint horizons and developed the means to extract them. Skilled knappers then exploited the physical properties of that stone to produce tools. In other words, geology had become technology (see box: How sharp is flint?).
| How sharp is flint? |
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| A freshly struck flint flake can possess an extraordinarily sharp edge. Its effectiveness comes from conchoidal fracture: when a blow is applied correctly, the fracture travels through the flint in a curved path rather than following a pre-existing plane of weakness. The resulting flake may preserve a striking platform where the blow was delivered, a bulb of percussion immediately below it and ripple marks produced as the fracture propagated through the stone. These features allow archaeologists to distinguish deliberately worked flint from many naturally broken pieces. However, for the prehistoric knapper, the important point was control. By choosing where and how to strike a core, successive flakes could be removed to create a predetermined form. Flakes themselves could provide sharp cutting edges, while further retouching could turn them into scrapers, knives, piercing tools and other implements. Flint therefore combined two apparently contradictory properties: it was hard enough to hold an extremely effective edge but brittle enough to be deliberately shaped by fracture. That is what transformed a geological material within the Chalk into a remarkably versatile technology. |
But practical usefulness alone may not explain the extraordinary effort invested in the mines – or what happened to some of the objects produced from their flint. To understand that, we have to consider what this material may have meant within the wider Neolithic world.
More than a raw material
It would be easy to describe Grime’s Graves entirely in practical terms. Good flint occurred beneath the Chalk. Neolithic miners dug down to obtain it. Knappers converted it into tools, which were then used for cutting, scraping, piercing and many other tasks. All of that is true. But the archaeology suggests that flint sometimes meant more than this.
We need to be cautious. Archaeology cannot recover the beliefs of people who left no written records, and an unusual object found underground does not automatically demonstrate a religious ceremony. Nevertheless, some discoveries at Grime’s Graves are difficult to explain solely in terms of the practical business of mining.
Pit 1 provides some of the most intriguing evidence. Six galleries radiated from the bottom of the shaft, following the floorstone; some extended for as much as 15m and connected with neighbouring workings. As we would expect, excavation recovered antler picks and other evidence of mining. But objects with no obvious role in extracting flint were also deposited underground, including pottery, flint implements and carved Chalk objects. Some of these deposits may represent ritualised practices associated with the continuation or renewal of mining.
Particularly striking are finds of Grooved Ware pottery from the workings. Two rare Late Neolithic Grooved Ware bowls were discovered on a Chalk platform at the bottom of a shaft. Whatever their precise significance, their presence demonstrates that objects were being taken underground that were not simply miners’ tools.
Perhaps the distinction between the practical and the symbolic is itself misleading. For the people working here five thousand years ago, descending into the earth, extracting a valued substance and bringing it back to the surface may not have been regarded simply as an engineering operation. Technical knowledge, social custom and beliefs about the landscape could have been intertwined in ways that we can no longer disentangle.
The treatment of the flint provides another clue. As we have seen, more than 300 axes or axe rough-outs have been recovered at Grime’s Graves, although axes were no more common than some other categories of tool. Nearly all appear to have been unfinished and were probably taken elsewhere for completion. Some axes were apparently retained for ceremonial purposes, used as gifts to reinforce social relationships or occasionally deposited in hoards.
A polished flint axe could therefore be much more than a woodworking tool. A completed axe embodied an extraordinary chain of knowledge and labour, from locating and mining the floorstone to knapping, grinding and polishing the stone. The finished object therefore connected its eventual owner with the geology beneath Grime’s Graves.
This becomes still more interesting when we place the mines within the wider world of Late Neolithic Britain. The principal phase of deep mining – approximately 2650–2150BC – coincided with considerable social change. It overlapped with major developments elsewhere in Britain, including activity at Durrington Walls and Silbury Hill, the appearance of Beaker pottery and changing burial customs. Long-distance journeys and extensive exchange networks continued, while metalworking technology was gradually beginning to appear.
Grime’s Graves was therefore not an isolated community digging flint in a remote corner of Norfolk. It formed part of a much wider and changing prehistoric world. Nor should we imagine hundreds of miners living permanently beside the shafts. Mining was intermittent rather than ‘industrial’ in the modern sense, and a reconstruction in the guide envisages temporary camps moving as activity shifted across the site.
Who the miners were, how far they travelled and exactly how Grime’s Graves flint circulated afterwards remain much harder questions. Nor should every piece of mined flint be turned into a prestige object. Scrapers, piercers, knives and other implements had thoroughly practical purposes. But some flint clearly entered a world of exchange, gift-giving, deposition and ceremony. That changes the way we should think about the mines.
Grime’s Graves was a place to which people returned over many generations. Knowledge of what lay beneath the surface had to be remembered and transmitted. The techniques required to reach and work the floorstone had to be learnt. And the material extracted from the Chalk could acquire meanings and values extending beyond its usefulness as a sharp-edged stone.
The mines therefore bring together several different kinds of knowledge: knowledge of the ground, knowledge of mining, knowledge of flint and knowledge shared within a community.
Eventually, however, the deep shafts ceased to be worked. The galleries were abandoned and the shafts began to fill. But people did not abandon Grime’s Graves. Instead, later communities found new uses for the landscape the miners had created.
After the miners
The end of deep Neolithic mining did not mean the end of human activity at Grime’s Graves. Instead, the landscape created by the miners acquired new uses. Some later communities still sought flint, but they did so differently; others lived among the abandoned workings, deposited rubbish in them, buried their dead there or simply incorporated the strange hollows into an increasingly ancient landscape.
A second phase of flint extraction took place during the Early to Middle Bronze Age, around 1550–1500BC. These later workings were generally shallower and simpler than the great Neolithic shafts. Instead of developing extensive underground galleries, Bronze Age miners exploited flint from pits and undercut niches around their sides.
Pit 3 illustrates the change particularly well. Steps were cut down one side of the pit, apparently supplemented by some form of ladder for the final descent. Niches were excavated at two levels: an upper level exploited scattered nodular flint, while lower workings reached discontinuous floorstone. The geology in this part of the site was less regular and lay close to the limits of the workable flint-bearing strata.
The contrast with the earlier deep mines is striking. The Late Neolithic miners had sunk substantial shafts to a persistent target horizon and then followed it laterally. Their Bronze Age successors worked a more irregular resource with shallower pits and niches.
Even the tools had changed. Bone picks from the Bronze Age workings have been found, including the extraordinary example of one made from a human thigh bone.
By about 1400–1200BC, mining had ended, but Grime’s Graves became the focus of a very different kind of activity. Archaeological evidence points to a Middle Bronze Age settlement at or close to the old minefield. No houses have yet been identified, but the evidence left in the abandoned workings is substantial.
Large quantities of domestic waste accumulated in former shafts. Some of these deposits are among the largest Bronze Age middens known in Britain, and together they extend across an area of about 6ha. More than 8,000 sherds of Deverel–Rimbury pottery have been recovered, together with animal bones, evidence of cereal cultivation and other traces of everyday life. The old mines had effectively become convenient hollows into which rubbish could be thrown.
But the inhabitants did not simply inherit the miners’ pits. They also inherited their waste flint. Around six tonnes of worked flint have been recovered from the Middle Bronze Age deposits, much of it recycled from the earlier mining dumps rather than newly quarried. The guide records flint being used for activities including butchery, food preparation, grain processing, carving, pottery manufacture and the working of hides.
There is an appealing reversal here. To the Late Neolithic miners, the important flint had been worth sinking deep shafts to obtain. Centuries later, people living among the abandoned workings could simply pick useful pieces from the enormous spoil heaps their predecessors had left behind.
Grime’s Graves changed again during the Iron Age. Between about 390 and 150BC, people returned to the site to bury some of their dead in the upper fills of abandoned shafts. Excavations in 1971 revealed the burial of a young adult woman accompanied by a decorated Chalk plaque, probably itself an older Neolithic object. A later burial of an adult man disturbed hers; two iron beads found with him may have formed part of a necklace or earrings. Evidence associated with both burials suggests ceremonies involving fires and the placing of offerings.
The choice of such a place may have been significant. The guide notes a wider Iron Age tradition in southern and eastern England of placing burials in abandoned pits, quarries and mine shafts, suggesting that the antiquity of such places may itself have carried meaning.
But by then, the original purpose of the mines may already have been fading from memory. That process eventually produced the name we encountered above. Anglo-Saxon communities associated the strange landscape with Grim or Woden, while in the medieval and later periods the site formed part of an agricultural landscape of pasture, warrens and temporary cultivation. Eighteenth- and nineteenth-century maps show the hollows surrounded by heath, sheep pasture and warrens, with some areas later affected by cultivation and woodland.
What survives today is therefore not a landscape frozen at the moment the Neolithic miners departed. It is a palimpsest.
The deep shafts belong principally to the Late Neolithic. Shallower pits record renewed Bronze Age mining. Middens preserve the rubbish of a later settlement. Iron Age burials turned abandoned shafts into places associated with the dead. Anglo-Saxon mythology supplied the name. Medieval and later farming altered parts of the surface again. And beneath all of those later stories remained the original geological reason why people had come here in the first place: flint within the Chalk.
That long sequence is important when we finally ask what Grime’s Graves is today. It is an archaeological site, a geological site, a prehistoric industrial landscape and a place where several thousand years of later history have accumulated above mines already ancient when Stonehenge itself was still developing.
It is also, rather unusually, a museum in which the most important exhibit is still exactly where prehistoric people left it.
The real museum is underground
Grime’s Graves is an unusual entry in a series about geology museums because, in the conventional sense, the museum itself is modest. The exhibition room is useful. It introduces the geology, shows examples of the materials used by prehistoric communities and displays some of the artefacts recovered from the site. It provides the context needed to understand what happened here (Figs, 12 and 13).
But the exhibition is not really the reason to come. The true strength of Grime’s Graves is that the geology, archaeology and landscape remain physically connected. Outside the visitor centre are the hollows and spoil mounds created by generations of mining. Beneath them are shafts and galleries cut through the Chalk. And in Pit 1, it is possible to descend into one of those original workings and stand where Neolithic miners once worked.
That changes the way the site is understood. A flint axe in a display case is an artefact. Underground at Grime’s Graves, it becomes the end product of a much longer story. The visitor can see the Chalk through which the shaft was sunk, the level at which the floorstone occurred and the galleries driven outward to exploit it. The relationship between rock, resource and technology is no longer abstract.
It is this connection that makes Grime’s Graves particularly interesting from a geological point of view.
The story began tens of millions of years before the miners arrived. Chalk accumulated beneath a Cretaceous sea. Silica was redistributed during early burial to form flint within it. Much later, prehistoric communities learnt that particular horizons contained especially desirable material. They developed the practical geological knowledge needed to find those horizons, the mining techniques required to reach them and the knapping skills needed to exploit the peculiar fracture properties of the stone.
The result was a remarkable transformation:
Cretaceous sediment became Neolithic technology.
That is perhaps the simplest way of understanding Grime’s Graves.
The site also reminds us that prehistoric people were not merely passive users of whatever stone happened to lie at their feet. They made choices about raw materials. They recognised differences in quality. They remembered what had been found beneath earlier shafts and used that knowledge when opening new ones. At Grime’s Graves, they were prepared to ignore accessible flint and undertake the formidable task of going underground for the material they preferred.
Nor was this knowledge temporary. Deep mining continued for centuries. The visible landscape accumulated gradually as successive generations returned to the same place, sank new shafts and added their spoil to that of earlier miners. What looks today like a field full of irregular depressions is therefore the surviving record of knowledge repeatedly passed on.
Later generations repeatedly reused and reinterpreted the landscape, but its most remarkable remains survived underground. The mines survived all of this largely because the essential structures were underground.
Today, the site has another value. Grime’s Graves is a Site of Special Scientific Interest (SSSI), protecting not only its archaeology but a distinctive Breckland landscape that includes Chalk grassland, sandy heath and acid grassland. The site also preserves periglacial features and provides habitat for wildlife, including bats.
Its modern protection therefore reflects several overlapping stories: geological, archaeological, historical and ecological. That makes Grime’s Graves rather different from a museum in which geological specimens have been removed from their original setting and arranged in cases. Here, much of the evidence remains in situ. The visitor moves across the mining landscape, looks into the hollows and then descends through the Chalk itself.
And that is why Pit 1 matters so much. Standing at its bottom, it is difficult not to reconsider the apparently simple question with which we began: why did people go to such trouble when flint could be found at the surface?
Part of the answer was practical. The deeply buried floorstone provided desirable raw material. Part was technological: flint could be shaped into exceptionally effective tools. And part may have been social or cultural, because some of the objects produced from it clearly acquired meanings beyond their everyday usefulness.
But underlying all of those explanations was knowledge.
The miners understood this landscape well enough to know that the visible surface did not contain everything of value. They knew that the Chalk concealed something better.
They knew where the good stone was. And they knew how to reach it.
Further reading
English Heritage Guidebook: Grime’s Graves, by Peter Topping
Website: https://www.english-heritage.org.uk/visit/places/grimes-graves-prehistoric-flint-mine/