Millstones from Mow Cop - Tony Browne, Geology Department, Manchester Museum
The millstones made in the north of England were usually formed from coarse sandstone taken from the Namurian strata of the Carboniferous, formerly known as “Millstone Grit” . The majority were quarried in the Peak District, hence the trade name “Peak Stones” . They were monoliths i.e. single piece stones. Segmented millstones made from sections, which were cemented together and bound with iron bands were generally the French burrstones, made from fine-grained re-crystallised quartz deposits of the Tertiary Period, quarried in the Paris Basin. Pieces of rock were generally too small for monoliths(1). Peak stones were normally used for grinding animal fodder, and the French burrs for white flour due to their superior quality for separation of wheat grain components.
However there are segmented millstones found at some old mills in the NE Cheshire/ Staffordshire area, which are made from Millstone Grit. These have long been known in the trade as Mow Cop Stones(2).
Mow Cop, the folly topped hill on the Cheshire Staffs border, is noted for quarries in Namurian strata.
Attention is often drawn to a few unfinished millstones still attached to the quarry face, but the poor quality of the rock at these points strongly suggests that these, like the folly above, are ornamental.
However there is documentary evidence of millstone manufacture here. Tony Bonson(3) lists seven old mills having Mow Cop stones: of these, Nether Alderley, Leek, and Stretton are open at times to the public.
Dr Fred Broadhurst and I have examined those at Nether Alderley and Brindley Mill, Leek and confirmed a Millstone Grit composition. We have also added another near Alderley. The number of segments is usually less than in burrstones. This leads to the question, why were segmented millstones made at Mow Cop? Grinding quality would not be improved. Suggestions made involve ease of transport of smaller pieces, or sections made for other purposes then used for millstones.
But this demands the question “why not also in the Peak?”
Millstones from Mow Cop - sketch by Julie Ballard
Examining the quarries at Mow Cop one will notice the heavy faulting, with prominent slickensides and barite mineralisation. Incipient fractures within the rocks will cause splitting of rock when worked, and it follows that frustrated masons might well joint the pieces together, rather than start from scratch with the probability of a similar result. This faulting is not evident in the Peak quarries I have visited.
Since coming to this conclusion I have found verification from Robert Plot. Writing in “The Natural History of Staffordshire” in 1686 about the Mow Cop quarries Plot recounts how the rock frequently breaks: “Which it does so not withstanding their utmost care, that there is but very few of them that are not made up of two or three pieces, thus bound together with a hoop; nay so very subject is it to crack and flaw, that whenever it happens that they finish one intire (sic), yet it must be bound about thus with an Iron hoop to remain upon it in the Mill, to preserve it from falling asunder in the motion.”
Regarding the use of these stones, Plot writes, “Nor doe they ever use two of these stones together, but always pair them with a white sort of Millstone brought out of the Peak; the Molecop-stone (sic) being always the runner, and the Darby-shire stone, the Legier (bed stone)” This, however was not always the case as Bonson describes the Nether Alderley mill using Mow Cop stones for both, a point confirmed by Mike Redfern, the mill warden. Anyway problem solved.
But Plot gives us another. He writes of millstones being made from “great round pebbles” found near Blymhill in Staffs, one being large enough for three millstones to be made from it, and that their grinding qualities were not short of Colen (Cullin) stones. The latter being made of basalt from quarries at Andernach in the Rhine Valley, Germany, with Cullin being a corruption of Cologne through which the stones were shipped.
Now Cullins were said to be better than Millstone Grit but inferior to burrs, so I assume that these “pebbles” were glacial erratics and not local or Pennine sandstones. The erratics in this area derive from the north. Considering the Cheshire plain we have some large andesites from the Borrowdale Volcanics, and some smaller granites, mostly from Southwest Scotland. Some andesites would be large enough for monolithic millstones, but not the granites of the size found now. Could it be that there were large granitic erratics here at one time, from the Lakes or Scotland, and that they have been used up? Certainly granite has been used for millstones but I have not heard of andesite being used. One granite stone can be seen outside the Cheddleton flint mill, although this would not have been used there.
I would be pleased to hear of any Mow Cop stones from mills not referred to above, and andesite or granite millstones in the Midlands or North- West.
1. Owen Ward, French Millstones, Notes on the Millstone Industry at La-Ferte-sous-Jouarre, 1993.
2. Martin Watts, mill restorer, personal communication.
3. Tony Bonson, Mow Cop Millstones, Proceedings 19th Mill Research Conference 2003.