Exploring the mines and minerals of Derbyshire
- Credit: Archant
Centuries of mining and quarrying have left a rich legacy of beautiful mineral specimens says Roy Starkey, author of a new book which tells the story of the Minerals of the English Midlands.
As a top tourist destination, Derbyshire conjures up pictures of rolling hills, green fields, drystone walls, and gritstone edges; features that are characteristic of the Peak District National Park in the northern part of the county.
The geology here is dominated by the Carboniferous limestones, sandstones and shales of the Derbyshire Dome, which host historically important lead-zinc-baryte-fluorite-calcite mineralisation.
Derbyshire's mines and quarries have produced an astounding variety of mineral specimens, some unique to the region, and many of which are to be found in mineralogical museums across the world.
Mineralogically, Derbyshire is probably best known to the non-specialist for the variety of fluorite known as Blue John, from which jewellery, ornaments, bowls and vases are made. Ashford Black Marble is also well known and was popular in the 19th century for ornamental inlay work. Nowadays artefacts made from this material are highly collectable.
In addition to the principal ore minerals - galena (lead sulphide), and sphalerite (zinc sulphide), and the gangue minerals fluorite, baryte and calcite, a range of secondary minerals is also found, some of which such as malachite and azurite are brightly coloured. Others occur only as microscopic crystals and a few are of world-renowned importance as mineralogical rarities.
The 'jewels in the crown' of Derbyshire mineralogy are undoubtedly matlockite and phosgenite, which were first described in the 18th century from lead mines near Cromford. Two minerals new to science, sweetite and ashoverite, were described from a quarry near Ashover as recently as the 1980s.
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Lead mining has been of significant importance to the economy of the Peak District for at least 2,000 years, with production peaking during the 17th and 18th centuries. The last lead mine, Millclose Mine in Darley Dale, closed in 1939.
During the 20th century, baryte and fluorite, minerals formerly considered as waste products, became economically important, in the production of drilling mud and as a flux for steelmaking, respectively. Many small-scale opencast operations enjoyed a brief resurgence during the latter years of the 20th century, but today only Milldam Mine under Hucklow Edge remains in production.
The lead mining landscape of Derbyshire is of national importance and there is much to interest the archaeologist and historian. The Peak District Mines Historical Society has been of critical importance for the past 60 years or so. It has recorded, preserved and conserved, surface and underground features which help to illuminate a way of life that was prevalent in Derbyshire for much of the past 2,000 years.
The area around Matlock, Matlock Bath, Wirksworth and Cromford is particularly rich in mines which have produced worthwhile mineral specimens, and of which many excellent examples survive.
To the east of the River Derwent, Dimple Mine and Riber Mine produced excellent crystals of calcite. West of the River Derwent, the hillside above Matlock Bath is riddled with mine workings and caverns, some of which are now operated as show caves.
Dimple Mine, which is commemorated in the name of the road running northwest from the River Derwent opposite Matlock railway station, worked the Seven Rakes Vein under Matlock Bank and was the only mine to operate a steam engine in the county in 1809. Water was often a problem in Derbyshire mines and so a number of soughs (drainage tunnels) were driven to lower the water table.
One of these, the Allen Hill Sough, which is perhaps better known as Allen Hill Spa, issues from a fine, restored portal in a small garden adjacent to the premises of Twigg Engineers' Merchants at the bottom of Dimple Road.
Wapping Mine and Cumberland Cavern lie beneath the hillside above the New Bath Hotel, on the west side of the A6 road which enters Matlock Bath from the south. Cumberland Cavern opened in 1780 as a show cave and is about 12 metres higher up the hill than Wapping Mine. The underground passages extend for 460 metres and are an impressive example of 20th century fluorspar rake and pipe working.
Running just beneath the A6 towards the northern end of Matlock Bath is Long Tor Mine, a small working and former show cave which has produced some fine specimens of yellow fluorite.
Bage Mine at Bolehill on the south-western flank of Cromford Moor, just north of Wirksworth, is perhaps the most revered of all Derbyshire's mines amongst mineralogists and collectors. The mine is the type locality for both phosgenite and matlockite, and the story of the discovery of these two minerals in the late 18th century is one of confusion and intrigue, involving several of the great names of mineralogy and chemistry of the time.
Much effort has been expended, by a number of authors, researchers and mine explorers over the intervening 200 years or so, to establish the precise location from where the original specimens of phosgenite were collected, and there seems now to be general agreement that they came from a specific area of the Wallclose Vein, worked from Bage Mine and discovered c.1784.
Matlockite was first noted by the legendary mineral dealer Bryce Wright, who had discovered some specimens of phosgenite on a spoil heap at Cromford in the 1850s, but it was not correctly analysed until 1933. It remains one of the most sought-after of Derbyshire minerals.
Gregory Mine is the most famous in the Ashover district, with exploitation commencing in 1734. In its heyday, the mine appears to have been fabulously profitable but nowadays all that remains are heaps of tailings, and the chimney. A superb suite of about 30 excellent specimens of galena, fluorite and sphalerite from the mine survives in the Devonshire mineral collection at Chatsworth House.
Brown 'Oakstone' baryte from Arbor Low is instantly recognisable to the trained eye. It was in common use as an inlay material in Ashford Black Marble ornaments and tables. The first published record of its use appears to be by William Adam in 1840, and the locality was 'rediscovered' in the 1960s by the late Trevor Ford and William (Bill) Sarjeant.
Curious features of Derbyshire geology are the so-called 'Pocket Deposits', formed in hollows in the ancient limestone land surface. These infilled 'hollows' have been an economically important source of silica sand for refractory brick manufacture. Whilst the pocket deposits are not hugely productive from a mineral specimen point of view the pit at Kenslow Knoll produced some attractive red crystals of quartz.
In addition to limestone the Peak District has also produced large tonnages of igneous rocks. Calton Hill Quarry near Taddington is well known among collectors for the quartz crystals that were relatively abundant when the quarry was operating. These range from druses of sparkling colourless pyramids to attractive specimens of dark red or smoky quartz, and occasionally, purple amethyst.
Walking along the line of Dirtlow Rake to the south of Castleton it is difficult to gain an appreciation of the scale of past excavations. Vast tonnages of fluorite have been extracted, and hundreds of thousands of tonnes of rock moved, and moved again, to restore the workings. The area is well-known for banded pink and white baryte which makes attractive specimens when sawn and polished.
The fluorite deposits of Treak Cliff are world famous for the banded white and purple fluorite known as Blue John, which has received more attention than any other Derbyshire mineral.
The history of naming of the various Blue John veins is a subject which inevitably attracts much debate amongst enthusiasts as to what exactly constitutes a different 'vein'. Names such as Twelve Vein, Five Vein, Millers Vein, Cliff Blue Vein and Winnats One Vein are now etched into the history of the area.
The presence of quartz crystals in the soils around Buxton has been known for centuries, and according to published sources, so-called 'Buxton Diamonds' were relatively abundant, and well known both to visitors and commentators. Like 'Bristol Diamonds' and the famous 'Herkimer Diamonds' of New York State, they are an example of a mineral that has become part of local folklore and language. These crystals were collected as curiosities some 280 or more years ago and gave rise to a popular tourist activity of crystal hunting, particularly in the Victorian era.
In the far south west corner of Derbyshire, close to the border with Staffordshire, is a small and overgrown copper and lead mine. Its recorded name is Snelston Mine and mining was carried on intermittently for at least 120 years. The mine produced some of the county's finest specimens of the copper carbonate minerals azurite and malachite.
Mention should also be made of the historically important gypsum and alabaster industries. Although gypsum is no longer worked in Derbyshire, mining of gypsum remains of major economic importance in neighbouring Leicestershire, Nottinghamshire and Staffordshire.
The Chellaston area has a long history of gypsum working dating from the Middle Ages. Initially, the principal demand was for monumental alabaster, an easily worked stone which could be carved and polished to a good finish. The material was used extensively in ecclesiastical sculpture from the 14th century onwards. Latterly gypsum was worked as a raw material for the production of plaster.
So, as you wander around the glorious Peak District, spare a thought for the quarrymen and miners who toiled above and below ground in pursuit of mineral riches, and wonder at the legacy of beautiful specimens that they have left behind.
The Wonders of the Peak Gallery at Buxton Museum is a great place to see a display of Derbyshire minerals, and while you are there don't miss the specially created Blue John window.