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| EDITORIAL |
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BECHERERITE |
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ARSENTSUMEBITE FROM DOLYHIR QUARRY Neil Hubbard • David Green Tom Cotterell |
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WAVELLITE David Green • Tom Cotterell • Ian Jones David Cox • Ron Cleevely |
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PARALSTONITE FROM DOLYHIR QUARRY Tom Cotterell |
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MINERALS OF THE SWISS JURA Paul Andermatt |
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HARMOTOME FROM RUTHWAITE LODGE Peter Todhunter |
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PETITJEANITE FROM CARROCK MINE |
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PREISINGERITE & ROOSEVELTITE FROM CARROCK MINE Mike Rumsey |
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NEW CLIFFE HILL QUARRY |
BOOK REVIEWS |
64 pages, full colour
A double page spread from the Wavellite article in this issue.
James Sowerby’s British Mineralogy is arguably the most important early illustrated description of the minerals of Britain and Ireland. More than a thousand specimens are painstakingly reproduced in 550 hand-coloured plates. Sowerby borrowed many of the specimens he figured from the collectors and scientists of the day. Relatively few of these have survived to the present. One of the last specimens illustrated by Sowerby was re-discovered in the early 1990s in the collection of Peter Golley. It is a scorodite from the parish of Perranarworthal in Cornwall, which was sent to Sowerby by the Cornish clergyman and chemist William Gregor. As the discoverer of the element titanium, Gregor has an honoured place in the history of chemistry. He analysed many other minerals, but did not have a personal collection. Very few of the specimens that passed through Gregor’s hands are known to have survived, and this makes the scorodite doubly important
James Sowerby’s illustration of the scorodite specimen,as plate 547 in the final part of British Mineralogy. As with all Sowerby illustrations, it is a mirror image of the real specimen.
The rare zinc sulphate-silicate mineral bechererite occurs as minute inverted trigonal pyramids in leadhillite-lined cavities on a dump at Raik’s Vein, Leadhills, South Lanarkshire. It also occurs as a component of a white earthy crust at the Charlotte United Mines, Perranuthnoe, Cormwall. These are the first Scottish and Cornish reports of the mineral. In both cases bechererite appears to have formed by post-mining oxidation processes in spoil containing zinc-bearing minerals.
Elongated trigonal bechererite crystals up to about 0.1 mm in length terminated by flat triangular pedion faces from Raik’s Vein, Leadhills, South Lanarkshire. Steve Rust collection..
Arsentsumebite, a rare member of the brackebuschite group of minerals, has been identified as drusy crusts of curved blocky mint green crystals up to 0.1 mm on edge at Dolyhir Quarry, Old Radnor, Powys. It is found with anglesite and other lead-bearing secondary minerals in tiny cavities in oxidised lead- and copper-rich veinstone. The crystals are of near end-member composition. This is the first Welsh and second British report of the mineral.
A scanning electron microscope image of curved blocky arsentsumebite crystals up to about 0.05 mm on edge from Dolyhir Quarry. A small fragment removed from National Museum Wales specimen NMW 2007.1G.M.1.
Wavellite has been identified at about thirty localities in Britain and Ireland. It is typically found in folded sedimentary rocks of Carboniferous age and in the hydrothermal veins associated with granitic intrusions. Although it was recognised as a distinct mineral in the last quarter of the eighteenth century it is generally acknowledged that Sir Humphry Davy provided the formal description of the species in 1805. Davy proposed the name hydrargillite rather than wavellite, based on chemical analyses of the mineral, but these were later shown to be inaccurate and the name gradually fell out of use. The name wavellite honours William Wavell, a Devon-based physician and collector. There is controversy about the circumstances of the original discovery at High Down Quarry near Barnstaple. Some contemporary mineralogists claimed that Wavell was the first to recognise the mineral while others attributed its discovery to John Hill. Nineteenth century mineralogists confused wavellite with fibrous zeolite group minerals, with tavistockite and with diaspore, largely because of the difficulties encountered in making accurate chemical analyses. Modern techniques make wavellite an easy mineral to identify. The thirty or so undoubted occurrences in the British Isles are described and early errors, some of which have propagated into more modern texts, are highlighted.
Translucent yellow-brown wavellite 3 mm across associated with a hemispheres of green variscite from High Down Quarry
Pale mint green wavellite specimen 45 mm tall in fractured Carboniferous shale collected recently from Laharran Quarry, Minane Bridge, Co. Cork.
A double page spread from this article.
The rare bismuth phosphate mineral petitjeanite occurs as small, dark brown, drusy crystalline aggregates in cavities in massive vein quartz at Carrock Mine in the Caldbeck Fells, Cumbria. Quantitative chemical analyses by wavelength dispersive spectrometry produce a chemical formula which can be written Bi2.99Ca0.05Al0.02Na0.01O(OH)[(PO4)1.65(AsO4)0.27(SiO4)0.07]. At Carrock Mine, petitjeanite is associated with a poorly defined russellite-like phase. Both are likely to have formed by the supergene alteration of primary bismuth minerals such as bismuthinite. This is the first report of petitjeanite in the British Isles.
Preisingerite and rooseveltite occur as grey glassy grains in fractures in massive vein quartz on an old museum specimen from Carrock Mine, Caldbeck Fells, Cumbria. The two species are visually indistinguishable and they are intergrown on a sub-millimetre scale. Quantitative wavelength dispersive spectrometry indicates that both are lead-rich. This has produced small distortions in the crystal lattices. The empirical formula for preisingerite is Bi2.69Pb0.17Fe0.06Ca0.03Al0.01[(AsO4)1.92(SO4)0.11(SiO4)0.02], and that for rooseveltite is Bi0.94Pb0.08Fe0.01Ca0.01Al0.01[(AsO4)0.93(SO4)0.05)]. Both minerals are likely to have formed by the supergene alteration of primary bismuth minerals such as joséite, bismuth and bismuthinite. This is the first report of preisingerite in the British Isles, and the first confirmed occurrence of rooseveltite.
An alternative mechanism for the formation of the remarkable copper deposit at New Cliffe Hill Quarry, based on a pond in a depression in the wadi where the deposit occurred is suggested and discussed in comparison with the oxidation of a hypogene vein proposed by Hubbard et al. (2005). It must be made clear that real evidence to support either mechanism does not exist, but it is hoped the discussion will be useful to future researchers in the area.
Robbing the Sparry Garniture: A 200 Year History of British Mineral Dealers 1750–1950
by Michael P. Cooper (2006)
David I. Green
Bonanzas and Jacobites: the Story of the Silver Glen
by Stephen Moreton (2007)
David I. Green
Goldscope and the Mines of the Derwent Fells
by Ian Tyler (2005)
David I. Green
The rare barium-calcium carbonate paralstonite has been identified in mineralised tension fractures in dolerite and Precambrian sedimentary rocks of the Yat Wood Formation at Dolyhir Quarry, Old Radnor, Powys. It forms inconspicuous crusts of minute dipyramidal crystals in association with harmotome, alstonite, ewaldite, calcite and quartz. This is the first report of paralstonite in the British Isles.
The Jura Mountains extend for about 270 km through northeastern Switzerland. They are made up of sedimentary rocks, primarily limestones, which were deformed and uplifted during the Alpine Orogeny. About 50 mineral species have been reported from the area. Calcite is abundant. Well crystallised specimens of celestite, dolomite, fluorite, goethite, gypsum, pyrite and sphalerite can also be found. A suite of uncommon soluble sulphate minerals has been identified in recent efflorescences and the rare sulphur polymorph rosickýite occurs in good specimens at the asphalt mines near Travers.
A double page spread from this article
The barium zeolite harmotome occurs as dense encrustations of prismatic ‘core-bit’ twin crystals up to 2 mm in length on quartz and galena at Ruthwaite Lodge Mine, Grisedale, Cumbria. This is the first report from the English Lake District. Analyses by wavelength dispersive spectrometry produce the chemical formula: (Ba2.01,Ca0.01,K0.23,Na0.26)[Al4.66Si11.37O32]·nH2O. At Ruthwaite Lodge Mine, harmotome is overgrown by wulfenite and phosphatian mimetite, an unusual combination which does not appear to have been recorded elsewhere in Britain.
Tabular wulfenite crystals to 2 mm showing two generations of growth with minor mimetite and harmotome on drusy quartz.