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The ENCI quarry
(St. Pietersberg, Southern Dutch Limburg)

(In part adapted from Felder & Bosch 2000 and Rademakers 1998a

Geographical setting: View of the ENCI-quarry
View of the Southern part of the ENCI-quarry. Foto: Rengert Elburg, 2002.
  The ENCI-quarry is located on the not very aptly named St. Pietersberg (Saint Peter's Mountain), a less than impressive lump rising to 111 metres a.s.l., just South of Maastricht in Dutch Limburg (click here for an overview of the region).
It is a well known fact, that even if God created the world, the Dutch constructed The Netherlands, and they found the presence of such a protuberance like the St. Pietersberg in clear contradiction with the name of their country. Add to this the fact, that the underground near Maastricht consists mostly of chalk, it could serve very well to beautify the rest of the country in the form of cement and concrete. In the last fifty years, the destruction of the hill was very successful, and now the bottom of the chalk pit is there where it should be in the Low Countries: around sea-level.

The resulting 100 metre deep hole is a geologists' and flintsourcerers dream. Not only is this the type-locality for the Upper Cretaceous Maastrichtian stage, it is one of the best and most complete exposures of the uppermost part of this epoch, and full of flint as well.

As this is the best place to sample the most important "chalks-with-flint" in the western part of Dutch Limburg, we will give a short summary of the flint-related geology of the Upper Cretacous of the region. Good overviews can be found in the two hard-to-come-by volumes Krijt van Zuid-Limburg by W.M. Felder & P.W. Bosch (TNO-NITG, 2000) and De prehistorische vuursteenmijnen van Ryckholt-St. Geertruid (Nederlandse Geologische Vereniging Afd. Limburg, 1998), both in Dutch. A more consise description in English is published in Excavations of prehistoric flint mines at Rijckholt-St. Geertruid (Limburg, The Netherlands) by Felder, Rademakers & de Grooth (DGUF 1998). Another, although somewhat older overview is Felder, Felder & Bromley 1980.

During the earlier stages of the Cretaceous, Southern Dutch Limburg was part of Brabant- and Ardenno-Rhenish Massives which formed a large peninsula in the Cretaceous ocean consisting of the combined Paris- and North Sea-Basins. As the relative sea level rose during the later part of the Santonian and Campanian, thick beds of coastal sediments, mostly consisting of sands, were deposited. These are the Aken and Vaals Formations, which lie directly on top of the Palaeozoic basement. Only at the end of the Campanian, waterdepth was sufficient for chalks to be deposited. The first fully marine sediments are the Zeven Wegen chalk, the lowest member of the Gulpen Formation, still of Campanian age.
On top of this unit, an extensive sequence of chalks was deposited, whose lithostratigraphy is shown in the scheme below.

  Lithostratigrafical scheme
Lithostratigraphy of the Upper Cretaceous in Dutch Limburg after
Felder & Bosch 2000
  Even if most members contain flint of some sort, there are only four levels of chalk-with-flints that are archaeologically relevant: the Lanaye and Emael Chalk, and to a lesser extend the Lixhe and Valkenburg units. To the right of the chronological and lithological columns in the scheme above, we have correlated the most important flint types in the region with their stratigraphical position within the Gulpen and Maastricht formations. This seems quite straightforward, but Murphy's Law applies as usual: nothing is as easy as it looks. There are two major grounds for confusion in the area, one caused by the local geology, the other by the naming of the flint-types.

Due to the its location not too far from the former coast, there is a marked shift in facies of the Maastricht Formation between the Eastern and Western part of Limburg, a situation that probably starts already somewhere in the upper part of the Gulpen Formation. In the Western part, in which the ENCI-Quarry is located, the chalks of the Maastricht Formation are developped as the (pleonastic) "Maastricht Chalks", East of the river Geul as the "Kunrade chalk". The former consists mostly of fine- to coarsegrained chalks with varying amounts of flint, the latter are alternating banks of hard and soft chalk with less well developped banks of siliceous material.
Because of these differences in facies, we have been forced to put a questionmark behind the Simpelveld type and have omitted the important Lousberg Flint from the scheme. According to the literature the "Simpelveld Vuursteen" comes from "a part of the Eastern facies of the Lanaye chalk" (W.M. Felder 1998: 190), but up to now, the prehistoric extraction sites of this type of flint have not been exactly located, and therefore a secure correlation is not possible yet. On the other hand, we found flint of the Simpelveld type in the Western part of Limburg in the ENCI quarry. Even if the stratigraphic position of our sample isn't 100% secured either, it certainly comes from the lower part of the Maastricht Formation, probably the Valkenburg Chalk.

The same problem with differences in the Western and Eastern facies applies to the Lousberg flint, which is very similar to the Simpelveld-type with its bluish core and brown band under the cortex. Again according to the most comprehensive treatment of the subject in W.M. Felder 1998 (page 172), "At the moment we assume that the chalk (at the Lousberg) is part of the Eastern facies of the Lanaye Chalk, like the tabular flints from Laurensberg and Simpelveld".
So far for the geological uncertainties.

Similarities and differences: Another reason for confusion are the discrepancies between the names of the chalks, the flints, and the prehistoric mining districts. Although the matter is getting quite complicated, especially due to the differences in lithology outlined above, we will give it a try to sort things out:
  • Valkenburg Flint doesn't come from the Valkenburg chalk, but from the Emael chalk and probably the Schiepersberg Chalk, and is not limited to the area around the town of Valkenburg, but can be found in large parts of Dutch Limburg
  • .
  • The chalk-with-flints at Eben-Emael in Belgium, doesn't belong to the Emael member, but is the top of the Western facies of the Lanaye chalk
  • The name Rijckholt flint suggest this type of flint occurs exclusively at the prehistoric mining site of Rijckholt, which is certainly not the case. Even our correlation of Rijckholt flint with the Lanaye chalk is only partly correct, as similar flints can be found in the Lixhe chalk as well. The correct name should therefore be Lanaye-Lixhe Flint like suggested by P.Felder (1998: 159)
  • The names Simpelveld Flint (link to be added), Lousberg Flint, and like toponymic names for blue/grey flints with a brownish band under the cortex suggest an exclusive link with the "type localities" which is not justified. We found Simpelveld Flint near Kunrade (link coming up, and again a possible source of confusion, due to the name of the Eastern Facies of the Maastricht Formation, see above), as well as in the lower part of the Maastricht Formation in the ENCI quarry.
Fortunately, the differences between the materials are a lot clearer, although certainly not as perfect as many publications wish them to be.

Rijckholt (also spelled Ryckholt) flint is grey, but can vary from very light colours to nearly black, often with a slightly bluish hue. The darker material can be slightly translucent, but most varieties are opaque. Most material is spotted or patchy with a wide range of inclusions, as can be seen on the pages on the mining site of Rijckholt itself, as well as on the pages on the Lanaye and Lixhe chalk. The surface of artifical fractures is reasonably smooth, but always matte.

Simpelveld and similar types have a characteristic bluish dark grey core with a brownish band under the cortex. It is often slightly translucent, but less so than the more glassy and slightly banded Lousberg Flint, and artifical surfaces are slightly glossy. The flint often contains small quartz crystals that can be seen as small glistering points on fresh fractures and very numerous small fragments of fossils. If the typical brown band under the cortex is missing, the material can be very difficult to distinguish from finer, darker Lanaye-Lixhe-type flint.

Valkenburg flint is always coarse-grained, due to the arenitic nature of its parent rock, and the structure can therefore be quite similar to quartzitic materials. The colours range from nearly white to (brownish) grey and greyish brown, but are never very high in chroma. Thinner edges are mostly translucent, and again the flint can contain quite high amounts of quartz particles, giving it a glistering appearance on the always matte fresh fractures. Confusion with other types of flint is practically impossible.

Extractability and prehistoric use: In Southern Limburg and surrounding areas quite a few prehistoric flint mines and extraction points are known where the materials discussed above were exploited. Apart from the not very well known, and still not precisely located site near Simpelveld, most mining sites are found towards the Western part of the area, although only two lie West of the river Meuse.
The most famous and best documented site is of course the extensive mining field at Rijckholt-St. Geertruid, where shafts were dug to a depth of 14 metres into the Lanaye Chalk. All other known prehistoric flint workings are associated with the Emael Chalk or exploited the eluvial flint. As far as known now, no exploitation of Lixhe Flint sensu stricto has taken place, apart from a possible site just to the South of the Ryckholt mines (W.M. Felder 1998: 172)

Last modified on:
January 12, 2004
Contents primarily by:
Rengert Elburg
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