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A Building Stones Guide to Central Manchester
Third Edition (2014)
Four self-guided walks through the city centre
Now available to purchase

Newsletter - December 2018

The full, illustrated newsletter is available as a pdf for download. Text extracts are given below.

Morven Simpson

It is with regret that we have to advise of the death at 96 of Morven Simpson. Morven co-authored with Fred Broadhurst the original guide to building stones of Manchester. 'A Building Stones Guide to Central Manchester' was published in 1975. We believe this was the first guide to document a city's building stones for the general public. He co-led a field trip with Fred based on the second edition of the book in October 2007. The funeral was on Friday 14 December 2018 at 12.30pm Hutcliffe Wood Crematorium in Sheffield.

Niall Clarke

Morven Simpson died on 19 November 2018 at the age of 96. He will be remembered as a much loved member of the Geology Department, starting there in October 1951. Not many of you will have met him but, more recently, his name will seem very familiar. He was one of the original authors, with Fred Broadhurst, of the first two editions of 'A Building Stones Guide to Central Manchester'. The first edition was published by the Extra Mural Department in 1975 and the second in 2008 by the Manchester Geological Association. This edition was revised by Peter del Strother and Jennifer Rhodes in 2014.

Rosemary Broadhurst

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Magpie Mine and Deep Dale

Saturday 29 September 2018 was the occasion for this year's Fred Broadhurst Memorial Field Trip, which was led by Jane Michael. The location was near the village of Sheldon, Derbyshire; to the Magpie Mine and then on to Deep Dale. All the rocks traversed are mapped as Monsal Dale Limestone, assigned to the Brigantian sub-stage of the Carboniferous Period.

These rocks have dark and a light lithofacies. The lighter lithofacies are considered to represent a shallow shelf depositional environment that exhibits cyclicity and contains a variety of fossils. The darker lithofacies (due to clay and organic matter) are considered to have formed in deeper waters. The dark limestone is quite hard; and because and it can be given a good polish it is known locally as the Ashford Black Marble.

Subsequent stresses opened numerous fractures that acted as conduits for hydrothermal mineralising fluids. These deposited galena, fluorite, baryte and calcite in the limestones. Mineralisation appears to have occurred mainly in the late Carboniferous at temperatures between 70ºC - 120ºC.

Our guide for the Magpie Mine was one of the Peak District Mines Historical Society volunteers.The surface remains are said to be the best example in Britain of a 18th and 19th century lead mine.The miners were working numerous veins of galena (Fig. 1) that converge below the surface buildings. Several shafts are preserved and protected by surface grills. The guide explained the different techniques used by the miners to extract, crush and sort the ore.

As with all mines, profitability is dependent on the price the ore can command in the market, and the fortunes of Magpie Mine waxed and waned in response. At its peak, during the 18th and 19th Centuries, the nearby village of Sheldon the population grew by an influx of Cornish miners; most of the stone-built cottages date from this period. As the workings became deeper, the mine faced significant problems of flooding with many different strategies to remove the water being explored. This culminated in the building of a sough (1873-1881), taking mine waters a couple of miles north to the River Wye.

For a short time in the 1950s (linked to the Korean War), the mine was reopened and the 1869 Cornish engine house was brought again into action. However, since then the site has become a Scheduled Ancient Monument.

Deep Dale lies north west of the mine, although a detour was necessary to avoid a face-to-face encounter with a bull. We passed a small limestone pavement (sufficient to note the development of clints and grykes) and we knew we had reached Deep Dale when we saw the line of bell-pits, old lead workings that followed a rake, ahead of us. It was a reminder that the whole area is affected by mineralisation, not just those localities with mine buildings.

The formation of Deep Dale was the topic of much discussion. Cavern collapse was considered but rejected: as the Dale is long with only gentle curvature, and there is no base of chaotic fallen blocks. River erosion under today's conditions could not take place as the water table is too low and even when it rises to produce a surface flow, there is only a stream. One member of the party subsequently drew our attention to the following passage from "Geology Explained in the Peak District" by F. Wolverson Cope (1998, p.54): "It is quite impossible for this dry valley to have been eroded while the water-table was at its present level. The valley can only have been eroded when the water-table was at a relatively higher level than the present. The fall in level of the water-table to its present position could have been brought about by a regional uplift after this and other dry valleys were eroded."

On the Mine Tour, we learned about the building of a major sough to drain the mine. The Magpie sough tail is just about visible near the River Wye, but our journey back to the starting point was memorable mainly because of a steep climb up a scarp face and the need to avoid two bulls next to our trail. Damage to Jane Michael's reputation as a trip leader was avoided by the wonderful sunshine, the blue skies, and the stimulating conversations that helped make the trip so enjoyable.

David J. Tyler

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