A mineralogical tour of Ireland (Part 2): Munster
Stephen Moreton (UK)
In the second part of our tour of Ireland, we head for Munster, which occupies the southwest corner of the island. Geologically, the rocks are mostly inland Carboniferous shales and limestones, with Devonian sandstones forming the coastal peninsulas. All host mineral localities of note.
Starting in County Waterford, mineral collectors will tend to head for the copper coast – a group of nineteenth century copper mines centred on the coastal village of Bunmahon. The magnificent crystallised native copper and cuprite these mines yielded in the past are elusive nowadays. On the other hand, post-mining oxidation in the dumps and sea cliff levels and outcrops has produced an array of vividly coloured and sometimes rare secondary minerals. These include connellite, langite, atacamite, botallackite, brochantite, lavendulan and erythrite. The soft, wet, blue and green substances that coat the mine walls are amorphous gels that dehydrate and crumble to powder when removed to a dry environment. They are best left where they are.
Mention should be made of the Croaghaun Hill beryl occurrence inland from the copper mines. In a small outcrop of conglomerate, one of many among the scrub, patches and sprays of slender, sky blue beryl prisms occur in a quartz matrix. Unfortunately, the rock is so tough it defeats even the largest sledgehammer.
The beryl is curious in having the highest known moisture content for the mineral. As its discoverers remarked, in view of the influence of the Atlantic on Ireland’s weather, it is not inappropriate that the country should have the wettest beryl on record.
Inland, the county of Tipperary is home to one of the most historic mining districts in Ireland – Silvermines. As the name suggests, the ores here were exceptionally argentiferous, yielding up to 80 ounces of silver in every ton. About 50 different minerals are known from the district, although many are microscopic and accessible only to the expert ore mineralogist.
Historically, the mines date back to the Medieval period, when a group of Italian miners began work. They did not get on with the locals and the friction culminated in a brawl in which the local priest was beaten up. He retaliated by excommunicating the miners, who then refused to go underground for fear of perdition.
The next phase of mining, in the seventeenth century, also ended violently with a massacre of the miners’ families by a local thug during a period of political turmoil. When his elder brother, a prominent landowner, ordered the arrest of his sibling, the killer escaped justice by drowning himself in a river. Mining eventually resumed in the eighteenth century and peaked in the nineteenth. During this time, many fine specimens must have been found, but were sent to the smelter, as Ireland has never had a tradition of mineral collecting. Scattered reports of abundant cerussite, hemimorphite and malachite can only hint at what must once have been.
Activity resumed in the 1950s, but was beset by technical difficulties. Just when the company looked like it would go bust, it discovered one of the largest barite deposits in the world. A giant zinc/lead orebody soon followed. This latter – Mogul Mine – put Silvermines on the mineralogical map, as it produced some of the world’s finest galena and honey blende sphalerite specimens. Excellent bournonite and geocronite also turned up, along with rare silver sulphosalts. That this treasure was saved was down largely to the efforts of one commercial dealer, Richard Barstow, who bought specimens from the miners and thereby made it worth their while to save them. If only someone had done this in the preceding century.
The giant barite deposit was worked opencast by Magcobar. Its tips can be seen for miles, but are mineralogically poor. The same cannot be said of the opencast as it contained fine dodecahedra of pyrite up to about 2cm, cubes of the same up to 4cm, barite plates up to 3cm, needle quartz and honey blende. Unfortunately, little was saved as, by this time Barstow was dead and I was one of the very few active collectors in the country. As I had been told by geologists that the place was barren, I did not get around to visiting it until it was too late and it had flooded. The moral seems to be that, if someone says a place is barren, do not believe them. Always verify for yourself.
Further south, near to Tipperary town, is Gortdrum mine, the only mine in the British Isles that has produced mercury, albeit as a by-product of copper mining. The opencast is flooded, but acres of tips remain. Diligent boulder bashing, particularly near the old crusher and in the area fenced off by an electric fence beside the track nearby, yields micro cinnabar crystals, together with chalcopyrite and mercurian tennantite. Look for small cavities in veinlets of dolomite. Azurite and tyrolite can also be found, but gortdrumite, for which this is the type locality, has always been exceedingly rare.
In the east of the county, a giant stratabound zinc deposit is being extracted at Lisheen mine.
Moving on to County Cork, the shales of the Carrigaline valley, south of the city of Cork, have long been noted for wavellite. Laharran quarry, a tiny and long disused affair, still yields pretty specimens, including free-grown spherules, over a centimetre across. However, much laborious hammer and chisel work is required.
Further west, Glandore Mine is the type locality for corkite, a rare lead mineral. This is difficult to find now, but botryoidal black goethite and manganese ores (for which the mine was worked) are still present.
Out on the peninsulas are numerous old copper mines in the Devonian sandstone. Most were small and unprofitable affairs, but those at Allihies, on the tip of the Beara peninsula, were rich. The engine house of Mountain Mine (Fig. 7) is a magnificent local landmark and has recently undergone extensive conservation work. The stopes below have yielded fine postmining crusts of langite. Down on the shore, a sea cliff at Dooneen Mine is stained green by atacamite containing minor botallackite. Of the other mines, Ballycummisk can still offer modest specimens of “peacock ore” bornite, and micaceous hematite.
Two peninsulas are in County Kerry. The northern one – Dingle – is noted for “Kerry Diamonds”. These are rock crystals that occur in tension gashes in the sandstone. Magnificent crystal groups, often with green chlorite inclusions and occasionally with hexagonal plates of hematite, have been found at various points around the coast. The best tend to be in the most inaccessible points, and I have had the unnerving, but thrilling, experience of finding a huge crystal filled vug while dangling on a rope off a high sea cliff at Dunquin, near the tip of the peninsula.
Further up the coast, the black shale cliffs in the coves north of Ballybunnion have yielded a variety of rare minerals. The phosphates, wavellite, crandallite and turquoise, are present, as are the sulphates, sideronatrite, metasideronatrite, hydronium jarosite and basaluminite. The very rare selenite mineral, chalcomenite, was found on one occasion but not since. The occurrence has apparently been eroded away by the sea. Beware – the tides are treacherous here and have claimed lives.
Inland, Muckross Mine was worked for copper in the 1750s. The miners discarded as waste a dense grey ore, not knowing what it was. In 1795 Rudolf Erich Raspe, liar, thief, conman and author of the Baron Munchausen stories, identified it as an ore of cobalt, but not before an unknown person (not Raspe) had carried away and sold 20 tons of it for personal profit. When the ore’s identity became officially known, it was quickly gathered up and sold. What few fragments remained have since oxidised to vivid crimson and pink erythrite. Other unusual minerals formed by oxidation include the rare calcium arsenates, phaunouxite and rauenthalite, which alternate from one to the other depending on whether it is a wet or a dry day.
The copper mine at nearby Ross Island was home to serpierite and native copper, but these are not apparent nowadays. This mine is prehistoric and was worked in the brief “Copper Age” that preceded the Bronze Age. In view of its great archaeological importance, it is probably advisable to leave it alone.
Large (up to 20cm) nailhead crystals of calcite were found in the 1990s in Ballyegan quarry, near Castleisland. The vug that contained them was nearly two metres across. Other large vugs have turned up from time to time in this quarry, but, frustratingly, being high up on a working face, access is forbidden. Advance permission is recommended for visitors to this quarry.
Heading north, one passes through County Limerick, where again phosphates are in evidence in the shales. Ballycormick, just south of Shanagolden, has produced wavellite, cacoxenite, crandallite and turquoise accompanying smoky quartz crystals from a stream bed at the bottom of a field. Just along the road, Grouse Lodge quarry is an intermittent producer of wavellite, turquoise and the very rare iron phosphate, koninckite.
We finish this part of our tour in County Clare. Little remains of the handful of lead mines east of Ennis, which is sad, as they include Kilbreckan mine, the type location for geocronite (“kilbreckanite”). The bare limestone karst scenery of the Burren offers better prospects. This extraordinary landscape is actually artificial. Prehistoric farmers cut down the trees and the soil washed away exposing the bare rock. In the process, a scattering of small mineral veins was exposed. The most noteworthy is at Sheshodonnell East Mine, where a tiny calcite/fluorite vein yielded world class botryoidal green and yellow smithsonite. Sadly, the shaft has been filled in with rubbish and what little waste remained was bulldozed down it in spring 2005.
Finally, for the silver pick collector, Ireland’s largest rock shop at Liscannor (The Rock Shop) is well worth a visit and often has pretty specimens of Irish minerals for sale.
Further reading
Introducing Mineralogy, by John Mason, Dunedin Academic Press, Edinburgh (2015), 118 pages (Paperback), ISBN: 978-17-80460-28-4.
Minerals of Britain and Ireland, by A G Tindle, Terra Publishing (2008), 624 pages (Hardback), ISBN: 978-19-03544-22-8.
Rocks and minerals: The definitive visual guide, by Ronald Louis Bonewitz, Dorling Kindersley (2008), 356 pages (Hardback), ISBN: 978-14-05328-31-9.