Mineral classics from Wales

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Tom Cotterell (UK)

Ask any mineral collector to name a classic mineral locality or region in Britain and they will probably think of Cornwall or Devon, perhaps Weardale in Co Durham, or even the Caldbeck Fells or the West Cumbrian iron mining district in Cumbria – but probably not Wales. This is not to say that Wales has no classic minerals, but is perhaps a reflection of collecting habits and the preference for large, brightly coloured crystals.

Wales has a long history of mining dating back to, at least, the Bronze Age, but, unlike some other regions, there does not appear to have been a desire by miners to extract mineral specimens for sale. Indeed, a network of mineral dealers, as was clearly present in Cornwall during the nineteenth and twentieth centuries, was totally absent in Wales.

One factor is that the establishment of a National Museum in Wales occurred relatively late (in 1907) and did not open to the general public until the 1920s. Before this, there was no central repository for specimens collected in Wales and, consequently, mineral collections with historical significance are rare in the Principality.

The university colleges founded during the 1870s and 1880s built up their own academic collections. Earlier still, the Royal Institute of South Wales (founded in Swansea in 1835), established geological collections, but its focus appears (from what records remain) to have been wide ranging and not specific to Wales. Therefore, during the heyday of mining in Wales, the lack of one overall institution focussing on the mineralogy of Wales appears to have resulted in a dearth of specimens being preserved.

Some historic Welsh material exists in older collections based in England, for example, the Natural History Museum in London, but, compared with other British mining regions, the number and quality of specimens is limited. Since its foundation, the National Museum of Wales has, acquired a number of private and academic collections containing old-time Welsh mineral specimens. This has clearly helped our understanding of Welsh mineralogy. Unfortunately, as with many old collections, provenance details are often vague or entirely absent.

What is a classic mineral?

In general, some experience is required to appreciate the minerals that occur in the Principality. In addition, to assess which Welsh minerals are ‘classics’, we must first decide what actually constitutes a ‘classic mineral’. Is it merely a case of something that is very old or maybe something of exceptional beauty? Perhaps, it could be a particular association or assemblage of minerals characteristic to a locality. A classic mineral is difficult to define and different collectors may have different opinions.

The most important factor is surely aesthetics. Attractive minerals are popular and remembered more than rare minerals that may be ugly. However, size is also important. Larger crystals get noticed more than smaller equivalents and, if a particular mineral represents the largest example ever discovered, it will certainly feature as a classic.

Type locality specimens, or those from the original locality of discovery for a species, are considered important and may also be termed ‘classics’. So to are minerals of particular cultural significance. In these cases, being attractive is not a prerequisite to being a ‘classic’.

The age of a specimen, or when it was discovered, quite often affects a collector’s opinion. Those minerals of historical significance often get described as ‘classics’, even though (physically) they may be no different to another discovered more recently.

Clearly, a large number of minerals will fall into one of these categories, but the real classics are those that satisfy several of these criteria. For the purposes of this article, a selection of classic minerals from Wales is described chronologically and not necessarily in order of importance.

Old time classics

Anglesite was first discovered at Parys Mountain, near Amlwch on Anglesey, during the late 18th Century (Monnet, 1779). However, for many years, it was described by its chemistry as “vitriol de plombe” or “sulphate of lead”. According to one early account, it was “found in great quantity” (Withering, 1783). However, it was not until 1832 that François Sulpice Beudant proposed the name ‘anglesite’, after the island of Anglesey, a name that has been used ever since. The majority of specimens were collected before Beudant’s description and, consequently, many specimens in older museum collections still bear labels containing the earlier, chemical-based names.

Sowerby (1806) produced one of the earliest pictures of anglesite in Volume 2 of his British Mineralogy publication (Fig. 1). The accuracy of Sowerby’s hand coloured plates is staggering when compared with modern photography.

Fig. 1. Sulphate of lead (anglesite), figured by Sowerby (1806).

Anglesite from Parys Mountain is not a particularly attractive mineral and crystals rarely exceed 1cm in length. However, specimens from this, the type locality, are much sought after and remain ‘classics’ to this day.

The mineral brookite is an iconic Welsh mineral. Fine crystals are figured in many mineralogical publications. “Oxide of titanium”, as it was known during early nineteenth century, was figured by James Sowerby in 1809 in Volume 3 of his British Mineralogy publication. At the time, the location was given as “near Snowdon”, but his son, George Brettingham Sowerby, later (in 1838) more specifically described it as “on the road side between Beddgelert and Tremaddoc, Carnarvonshire, about 8 miles from Snowdon”.

The specimen figured by Sowerby (1809) was not especially attractive, but collecting at the site in later years produced what are considered to be some of the finest examples of this species (Fig. 2). Unfortunately, the delicate nature of these crystals and the high value of good examples led to a number of mineral dealers fabricating specimens by gluing detached crystals onto similar looking matrix.

Fig. 2. Brookite. Tabular crystal 20mm across from Fron Oleu, Prenteg. NMW 75.38G.M.1. (Photo MP Cooper © Amgueddfa Cymru.)

The name ‘brookite’ was proposed by M Lévy in 1825 in honour of the British crystallographer and mineralogist, Henry James Brooke (1771 to 1857).

Recent discoveries in Pakistan and Madagascar have surpassed Welsh brookite specimens in terms of crystal size and abundance, but the classic status of the Welsh material is likely to remain as classics.

Another old-time classic is the nickel sulphide mineral, millerite, from the South Wales Coalfield. Sowerby (1809) figured a specimen in Volume 3 of British Mineralogy (Fig. 3) in argillaceous ironstone from “Wales”. At that time, it was believed to be a peculiar variety of pyrite, named “hair pyrites” on account of its appearance. Research by Professor William Hallowes Miller of Cambridge University showed this to be sulphuret of nickel (nickel sulphide) (Miller, 1842). In 1845, Wilhelm Haidinger named the species ‘millerite’ in honour of the professor.

Fig. 3. Hair pyrites (millerite) from Wales figured by Sowerby (1809).

Millerite, from the South Wales Coalfield, occasionally produces stunning display specimens (Fig. 4.). The best crystal sprays are attractive and, at up to 54mm across, are very large for the species and are as good as from anywhere in the world. Surprisingly, beyond our shores, very few people are aware of its presence in Wales.

Fig. 4. Millerite. Acicular crystal spray 42mm across with baryte in clay ironstone from Treharris, Glamorgan. NMW 52.385.GR.4. Photo TF Cotterell © Amgueddfa Cymru.

There is patchy evidence to suggest that, during Victorian times, a trade in quartz crystals developed in Snowdonia. Unfortunately, little is recorded and the validity of some specimens labelled as from “Snowdon” or “Snowdonia” is questionable. Quartz is a very common mineral, but some of the finest crystals from Britain have been obtained in the neighbourhood of Snowdon (Rudler, 1905). Occasionally, fine crystals are encountered in the slate quarries in Snowdonia or during the construction of forestry tracks. The crystal shown in Fig. 5 is one of the largest known from this area and was collected during the late nineteenth century.

Fig. 5. Quartz. 11cm tall crystal from Votty & Bowydd, Blaenau Ffestiniog. NMW 27.111.GR.140, ex GJ Williams collection. Photo DI Green © Amgueddfa Cymru.

The most culturally significant mineral from Wales is gold. Welsh gold holds a special place in people’s minds because of its links to the Royal family, who traditionally use Welsh gold in their wedding rings. Gold from Wales tends to be valued much higher (up to three times more) than standard gold, although, technically, the gold is no richer than that from any other country. Specimens of Welsh gold in matrix are especially sought after and command high prices.

During the later part of the 19th century, a gold rush occurred around Dolgellau in north Wales. The rush was caused by the announcement by Arthur Dean, in 1845, that he had discovered gold at Cwmheisian lead mine. This was followed by claims from others that they had also discovered gold in the area in 1836. Whatever the truth, it is really irrelevant. What is important is that it led to the discovery of the largest gold producing area in the British Isles. However, despite the deposits being exceptionally rich, the ore bodies were small and sporadic in nature. Therefore, they were quickly exhausted leading to a ‘boom and bust’ situation.

Gold is found in two distinct mineral assemblages in the Dolgellau area. The two major gold mines, Clogau St David’s and Gwynfynydd, are each typified by a distinctive assemblage. At Clogau, gold frequently occurs in association with silvery bismuth tellurides in quartz, while, at Gwynfynydd, gold is usually disseminated throughout sphalerite in quartz (Fig. 6).

Fig. 6. Leaf gold with sphalerite and quartz from Gwynfynydd mine, Dolgellau. Specimen measures 40mm x 20mm. NMW 72.33G.M.7. Photo MP Cooper © Amgueddfa Cymru.

During the late nineteenth and early twentieth centuries, one person stands apart from anyone else in terms of collecting Welsh minerals. Griffith John, or ‘GJ’ as he preferred to be known, was a keen amateur geologist and widely regarded as an expert on north Wales geology. A teacher by training, GJ spent most of his life teaching in Ffestiniog, but was appointed to the post of Assistant Inspector for Metalliferous Mines and Quarries for the North Wales and Ireland Division under Dr Clement le Neve Foster in 1895.

This position spurred on his interest in mineralogy, allowing him to collect specimens from all of the mines he visited. He collected with Arthur Ian Edward Montague Russell (later Sir) and made a number of new discoveries. His collection was acquired by the National Museum of Wales in 1927. Many of his specimens are classics owing to the fact that no one else collected from some of the sites he visited. One of GJ Williams’ most important discoveries was the barium feldspars, celsian (Fig. 7) and paracelsian (Fig. 8) at the Benallt manganese mine on Pen Llŷn. His specimens, collected in 1911, remain the finest crystallized examples of both species.

Fig. 7. Celsian. Manebach-Baveno fourling, 10mm on edge, from Benallt mine, Pen Llŷn. NMW 27.111.GR.381. ex GJ Williams collection. Photo MP Cooper © Amgueddfa Cymru.

Following the discovery of these two minerals, interest in the mineralogy of Benallt manganese mine grew. Researchers at the British Museum (Natural History) led by Walter Campbell Smith, studied the complicated mineralogy of the deposit. The chief geologist to the Iron and Steel Control of the Ministry of Supply, Dr Arthur William Groves, was primed to keep an eye open for any interesting looking minerals from the mine when it reopened after the onset of the Second World War. This resulted in the discovery of several mineral species new to science.

Fig. 8. Paracelsian. Prismatic crystals up to 25mm in length from Benallt mine, Pen Llŷn. NMW 27.111.GR.387, ex GJ Williams collection. Photo MP Cooper © Amgueddfa Cymru.

The rarest of these new minerals, hydrated barium feldspar, was named cymrite after the Welsh name for Wales, ‘Cymru’ (Fig. 9). It forms two different habits of crystal, both of which have recently been rediscovered on specimens from the mine dumps remaining at the site. The naming of this mineral after the country of its discovery, Wales, makes this a classic to people from Wales, but, more importantly, this is a very rare mineral worldwide and to find crystals is even more unusual.

Fig. 9. Cymrite. Scanning electron micrograph of a sheaf-like crystal aggregate from Benallt mine, Pen Llŷn. NMW 2006.15G.M.2h. Image MP Lambert/TF Cotterell, © Amgueddfa Cymru.

Modern classics

The modern age of mineral collecting began during the 1960s with active exploration by collectors and with the advent of micromineralogy. One of the major finds in Wales was the discovery of coarsely crystallized pyromorphite (Fig. 10) underground in Bwlch-glas mine, near Tal-y-bont, in north Ceredigion. The richest specimens are without question the finest examples of this mineral from Wales and the very best are comparable to classic specimens from the Caldbeck Fells and Cornwall. Some of the earlier samples were sold by mineral dealers as from Plynlimon, the highest hill in the area. Unfortunately, specimens were then relabelled as from Plynlimon Mine resulting in confusion over the exact source. Plynlimon mine has never produced specimen-quality pyromorphite.

Fig. 10. Pyromorphite. Grass-green prismatic crystals on quartz from Bwlch-glas mine. Specimen 10cm tall. Collected c. 1972. BR Moore collection. Photo MP Cooper © Amgueddfa Cymru.

In South Wales, the southern outcrop of Carboniferous Limestone has long been known to produce large calcite crystals (Fig. 11) of varying forms. However, it was not until the 1970s that the increasingly large quarries start to produce exceptional specimens. The enormous Taff’s Well Quarry, which has hollowed out Little Garth Hill, is the locality that most people have heard of. From the 1920s to the 1970s, it was known as Walnut Tree Quarry, then Steetley Quarry after the name of the operating company.

Fig. 11. Calcite. 22cm tall scalenohedral crystal from Taff’s Well Quarry, near Cardiff. R Sutcliffe collection. Photo MP Cooper © Amgueddfa Cymru.

The largest calcite crystals are known to exceed 30cm in length. In general, the larger the crystal, the more overgrowth there is and the uglier they become. However, for sheer size these calcites are British classics.

Across much of Wales, the legacy of mining has left its mark in the form of mine tips, derelict buildings and surface scars, such as opencast workings and mine shafts. Underground, secondary post-mining minerals continue to form on the sides of old mine tunnels where chemical reactions are taking place caused by the introduction of oxygen from the atmosphere through these man-made voids. Flowstones containing base metals are particularly prominent.

During the early 1980s, a new hydrated zinc copper sulphate hydroxide mineral was identified by researchers at the National Museum of Wales on post-mining flowstone that had been collected many years earlier by GJ Williams underground in Aberllyn mine, near Betws-y-coed. This mineral was named namuwite (Fig. 12) after the National Museum of Wales, where the specimen is housed. The naming of minerals after companies or institutions is now considered inappropriate making this species very unusual. Only one specimen from the type locality is known, although this mineral has since been discovered at a number of mines in mid-Wales.

Fig. 12. Namuwite. Pale blue microcrystalline crust. Specimen 6cm across. NMW 27.111.GR.414, ex GJ Williams collection. © Amgueddfa Cymru.

Post-mining secondary minerals also form inside mine tips, caused by the decay of base metal-bearing sulphides exposed to rainwater and the atmosphere. Many of these complex Pb-Zn-Cu bearing minerals are brightly coloured.

The Central Wales Orefield plays host to a huge range of secondary, predominantly post-mining, mineral species. In a number of cases, examples of minerals found in mine tips are far better than any discovered at other localities worldwide, albeit still only as millimetre-sized crystals! Classic examples include the world’s finest bechererite (Fig. 13), ramsbeckite (Fig. 14) and redgillite (Fig. 15).

Fig. 13. Bechererite. Crystal sprays to 1.3mm across from Esgairhir mine. SA Rust collection. Photo SA Rust © SA Rust. Fig. 14. Ramsbeckite. Emerald green crystals to 1.5mm across from Penrhiw mine, Ponterwyd. JS Mason collection. Photo DI Green © Amgueddfa Cymru. Fig. 15. Redgillite. Feathery redgillite crystal spray 1mm tall from Eaglebrook mine. JS Mason collection. Photo DI Green © Amgueddfa Cymru.
Fig. 14. Ramsbecktite. Emerald green crystals to 1.5mm across from Penhiw mine, Ponterwyd. Photo DI Green © Amgueddfa Cymru.
Fig. 15. Redgillite. Feathery redgillite crystal spray 1mm tall from Eaglebrook mine. Photo DI Green © Amgueddfa Cymru.

New discoveries continue to be made. Although active mining in Wales has ceased, in recent years, quarrying operations have revealed a few rare and bizarre looking minerals. At Dolyhir Quarry in the Welsh borders, superb microcrystals of the hydrated rare earth-bearing barium calcium carbonate, ewaldite (Fig. 16), have been found in some abundance.

Fig. 16. Ewaldite. Scanning electron micrograph of pyramidal ewaldite crystal surrounded by core-bit twinned prismatic harmotome crystals. Dolyhir Quarry. NMW 2007.22G.M.16. Image MP Lambert/TF Cotterell © Amgueddfa Cymru.

Inevitably, there will be some minerals that collectors feel have been omitted. However, part of any assessment involves personal preference. For a slightly different view on Welsh mineral classics, it may be worth consulting King, RJ (1991).

For further information on Welsh minerals, look at the Mineralogy of Wales website at: http://www.museumwales.ac.uk/en/mineralogy_of_wales/. This site provides up-to-date descriptions of all of the minerals that are known to occur in Wales and new findings or information can also be posted to the site. In part, the site is based on an earlier publication by Bevins, RE (1994).

Further reading

Bevins, R.E. (1994). A Mineralogy of Wales. 146pp. National Museum of Wales, Geological Series No. 16, Cardiff.

Dean, A. (1845). Notice on the discovery of gold ores in Merionethshire, North Wales. Report of the British Association for the Advancement of Science (for 1844), 56.

Haidinger, W. (1845). Handbuch der bestimmenden Mineralogie. Vienna.

King, R.J. (1991), Minerals explained 14: Some Welsh mineral classics. Geology Today, 145-148

Monnet, A.G. (1779). Nouveau Systême de Minéralogie. Paris.

Rudler, F.W. (1905). A handbook to a collection of the Minerals of the British Isles, mostly selected from the Ludlam collection, in the Museum of Practical Geology, Jermyn Street, London, S.W. 241 pp.

Sowerby, G.B. (1838). Locality for brookite. Annals and Magazine of Natural History, series 2, 2, 293.

Sowerby, J. (1806). British Mineralogy: or coloured figures intended to elucidate the mineralogy of Great Britain. Vol. 2. 199 pp.

Sowerby, J. (1809). British Mineralogy: or coloured figures intended to elucidate the mineralogy of Great Britain. Vol. 3. 209 pp.

Withering W. (1783). Outlines of Mineralogy.

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