Manganese ore was mined in two main areas of the former county of Merionethshire: in the uplands east of Harlech and Barmouth, and in the east of the county in the Arenig area between Trawsfynydd and Bala. In addition, there were a few mines in the north of the county on the southern slopes of Moelwyn Bach and some trials in the area to the south of the Mawddach.
Although there are suggestions of earlier working [Williams 1995: 5], the first mention of manganese in Merionethshire (and, for that matter, in Wales) occurs in the late 1790s when William Madocks sent samples of ore from Dolmelynllyn (the house that he owned at Ganllwyd) to his friend Miss Hayman [Beazley 1985: 46]. (Although there is no record of manganese being mined in Wales a that time there was a significant manganese mining industry in Devon during the last quarter of the eighteenth century. [Burt & Wilkie 1984])
Exploitation of manganese deposits in Merioneth appears to have begun shortly before 1823. Samuel Holland’s diary has an entry for January 7 of that year concerning manganese at Glanrafonddu (on the site of the later Moelwyn zinc mine) [NLW MS4987]. In April Holland recorded a conversation with John Paynter of Minffordd about manganese and there is an application by Paynter and a Mr Jones for a mining lease for manganese in Llanenddwyn in June [PRO CRES: 25/29 10307]. Also in that year, manganese was being mined and sold at Llan y Cil mine [PRO LRRO: 3/87] and there was a Crown Grant of a lease to William Sylvester Clarke for manganese in Llanycil parish dated 30 October [PRO LR: 1/266], all of which suggests there was an established, albeit small-scale, manganese mining industry in Merionethshire at this time.
Other references relating to manganese around this time are Clarke at Llanecil mines in 1823 and 1824 [PRO LRRO: 3/87], Jones and Paynter’s continuing operations at Llanenddwyn, 1824–1831 [PRO CRES: 25/29 10307, 10443, 10859, 12398] and [PRO LRRO: 3/87, 5/33], Ellis Jones at Llanbad [sic] (Llanbedr?) in 1824 [PRO LRRO: 3/87] and Richard Williams at Ralltgoch selling manganese in 1828 and 1829 [PRO LRRO: 5/32]. Crown Grants of lease for manganese at Mynydd Nodol in Llanycil were made in October 1838 to I Wood [PRO LRRO: 13/66] and November 1852 to William Hughes [PRO LRRO: 13/76]. (See Crown grants page for details.) There is mention of manganese production in Llanbedr and Llanenddwyn parishes [Lewis 1833] and an enclosure map [NLW MAP 10020] of 1836 for Llanaber-is-mynydd (the eastern part of the parish of Llanbaber) shows manganese ore outcrops.
From 1835 until 1840 outcrops of a thin (< .6 m) manganese bed were worked to the north of Barmouth and on Foel Wen and Moelfre in Cwm Nantcol. These were surface workings which exploited the altered (oxidised) ore at the outcrop and did not attempt to follow the bed beneath the overlying strata or glacial debris. The ore was sent to Glasgow for making bleaching powder; only the oxidised portions seemed of value and very soon the mines were abandoned. [Halse 1887: 104] No production figures exist, but probably only a few thousand tons of ore were extracted. Morrison  states that the manganese shales were not known before late 1884 or early 1885, so presumably these were opportunistic workings rather than a systematic exploitation of the ore bed.
Between 1840 and 1885, the only recorded manganese extraction in Merioneth was 83 tons of ore produced in the Arenigs 1867–1868 (33 tons from Mynydd Nodol in 1867 and 50 tons, which was sold for £250, in 1868 [Morrison 1974]). There is a suggestion in a letter in the Mining Journal that manganese was not considered to be of great value during this period (‘Manganese – The Little Down and Ebbor Rocks Mineral Mining Co’, a letter from A Broker of Newcastle on Tyne on the value of manganese [MJ 1857 p. 238]). However, there was interest in manganese during this period. In a diary entry for Tuesday 22 April 1845 Morris Jones, Graig Isaf, Cwm Nantcol writes “Mr Barker a J J yma yn edrych y mango” (Mr Barker and J J here looking [at] the manganese – ‘J J’ may have been a relative or neighbour as these initials occur elsewhere in the diary.) [Jones, G 2003] In 1868–9 the Mining Journal carried a series of advertisements and reports about the Great Northern manganese mine at Mynydd Nodol [MJ 1868 pp. 228, 529, 532, 579, 592, 893; 1869 pp. 24, 33, 150, 186, 222, 225, 613, 633, 913]. There is also mention of S J Hennis’ Cambrian Mine in Cwm Mawr where a 2000 ft wide seam of manganese had been found: “… this valuable property, as manganese is being daily brought into manufacturing purposes … and it is largely sought for in the manufacture of bleaching powder, purifying glass, paper making, hardening iron and steel, candle making, and many other purposes.” [MJ 1869 p. 336]
From 1883 interest in manganese revived because of the increasing use of manganese in steel production. An example of this can be seen in a series of enquiries in that year from various individuals about the possibilities of working manganese on the Rhiwlas estate near Bala [GAS DAO: Z/DDD/2/105, 128, 146]. It is worth noting that by this time the coastal strip of Merioneth was served by the Cambrian Railway (opened to Pwllheli in 1867) and the Arenig area was served by the Great Western Railway (opened to Blaenau Ffestiniog in 1882) which would have reduced the cost of transport of manganese from the area.
According to Down [1980: 5] the revival in west Merioneth was largely due to the proprietors of Mostyn Ironworks, Flintshire, who formed the Dyffryn Mining Company to develop the Merioneth deposits and supply ore to the ironworks. In 1885 the company developed its first mines, which produced ore in 1886. Twelve mines opened in Merioneth in 1886, most owned either by the Dyffryn Mining Company or its competitor the Merionethshire Mining Company. Clement Le Neve Foster  reports manganese ore being sent to Flintshire and Lancashire [possibly Barrow-in-Furness, see entry for Edward Wadham] in this year for the manufacture of ferro-manganese. About this time a number of Flintshire lead miners moved to the Llanbedr area to become manganese miners when the lead market collapsed [Jones, A 2003]. It is interesting to speculate that Dyffryn Mining Company might have been instrumental in recruiting them though its Flintshire connections. It is also worth considering the economic background of the period, the price of lead halved between 1883 and 1894 and the slate industry was starting to decline, but production costs were increasing. Consequently, it is possible that some of the interest in manganese around this time was the result of a search for more profitable minerals to exploit.
In 1887 recorded output peaked at 12,391 tons from 14 mines. Following lower outputs in 1888 and 1889 there was a further peak in 1890 of 12,018 tons from 17 mines. In 1891 there were still 17 mines but recorded output was only 8553 tons and both output and number of mines declined following that year. This was due in part to the poor quality of the ore and inaccessibility of the mines and also because sources of richer and cheaper ores were being developed which were thereafter able to sustain the British iron and steel industry. Halse [1892: 941] wrote of the Arenig area that it was “conclusively proved that ore does not occur in sufficient quantity to be worked profitably at present prices”. Only in the exceptional circumstance of the Russo-Japanese war (1905) and World War I (1914–1918) when imported manganese was unavailable was it possible for the Merioneth mines to be worked profitably again. In 1923 Dewey & Dines [1923: 63–70] reported 15 active mines (the majority of which presumably had been opened or re-opened during WWI) compared to the one working mine reported in 1915 [Dewey & Bromhead 1915: 49–54].
World War I affected the availability of labour for working the mines. There are reports in 1916 of mine owners and other employers appealing against conscription of their workers. In March, a mineral dresser and carter engaged in raising manganese ore at Llanbedr appealed against the refusal of the local tribunal to grant exemption to his son who, he said, was indispensable to him. The appeal was dismissed [Cambrian News 24/3/1916 p. 5]. In April, Messrs Davies Bros. (possibly Griffith and William Davies), Barmouth, appealed for temporary exemption for a traction engine driver, John Williams, who was engaged in hauling manganese for Government use. The application was supported by H. J. Wright on behalf of the Crown Agent. An exemption was granted until June [Cambrian News 14/4/1916 p. 2]. Wright's own son (also named Harry Johnson Wright) was in January 1918 approved placing on the deferred list for four months “that he may help his Father with the work of Manganese Mine at Llanbedr Merrion” [PRO ADM188/931/32398].
After the WW1 production peaked in 1923 and continued on a small scale with 1928 being the last year with recorded output (205 tons). One customer at this time was the glass industry at St Helens.
The above chart shows the recorded production of manganese in Merionethshire from 1867 to 1928 (the earliest and latest dates of recorded production). It is likely that actual production exceeded that recorded, possibly by a significant amount. No records are available for Merionethshire alone for the years 1914–1920, consequently the values shown are guesses based on the combined Caernarvonshire and Merionethshire production figures and the immediate pre- and post-war production ratios between the two counties.
During World War II the Merioneth mines were inspected and preliminary plans were made to reopen them. It was thought that two longwall faces, each 500' (150 m) long, advancing at 3' per day, could each produce 150 tons/day or 50,000 tons/annum (i.e. 100,000 tons/annum total), and so supply the greater part of British consumption of low-grade ore for basic iron blast furnaces. [Thomas 1961: 222] The working costs (exclusive of capital expenditure) would be about £1.50/ton. [Down 1980: 14]
The most recent known interest in manganese in Merionethshire was in the 1950s. In 1956 the Merioneth Mining Co. leased the rights to “manganese ore and other ferrous ores” on Hendre Coed Uchaf farm, Llanaber (which property included some of the Egryn mine) for 25 years at a surface rent of £2 per acre occupied. (Lease dated 16 February 1956) [Conveyance 1960] There is no indication of any work being done under this lease. In 1959 ICI geologists connected with the explosives manufactory at Penrhyndeudraeth surveyed Bronwen [Brown 2002]. Although a considerable resource of manganese-rich material remains in the area [Allen & Jackson 1985b: 79], it is thought that for both environmental and economic reasons it is most unlikely there will be any exploitation of it.
During the period winter 2008 to spring 2009 a number of the underground workings at various sites were fenced off and warning notices erected. (The sites involved are possibly those on Crown land or where the Crown holds the mineral rights.)
The employment provided by manganese mining was never very great, and the manganese miners never had the visibility of their counterparts in the slate industry. The peak year was 1886 when 280 men were recorded at work in Merioneth, 74% of whom were recorded as underground workers. The largest mine was Hafotty, employing more than 50 men in 1887. From 1891 to 1892 the number of manganese miners in Merionethshire halved from 175 to 87, and was down to only 8 men by 1896.
During the period discussed above, and for some time after, manganese was mined at Benallt and Rhiw mines on the Lleyn Peninsular in Caernarvonshire. From 1903 these mines produced the greatest part of the Welsh output of manganese and continued to operate until 1945 [Down 1980: 17–24]. Other Welsh manganese mines included the mines of St Tudwal’s peninsular on the Lleyn Peninsular [Bennett & Vernon 2002: chap. 5], Griffith Jones’s mine at Cwm Mach, Bangor (5 tons of ore in 1867), the Nant Uchaf haematite mine near Abergele, Denbighshire (569 tons 1880–1883) operated by the Abergele Hoematite Co. Ltd, other Caernarvonshire mines near Aberdaron, Clynog, Dolbenmaen, Llanaelhaearn, Llandudno, Llanllyfni and Llanor, C Herbert Stokes’s Royal Mines (also known as Drosgol) in Cardiganshire and Fishguard mine near Trecwn in Pembrokeshire.
Prior to 1886, England was the main source of UK-mined manganese. There were mines in Cornwall, Devon (Chillaton and Hogstor mines being significant) and Somerset, with production continuing on a very small scale until 1907 with a final isolated output in 1927 [Burt & Wilkie 1984]. Further small outputs (a few tons) were recorded for the Isle of Man and Derbyshire [Down 1980: 8]. Manganese was also mined at Hartshill Hayes [Brown 1997] and Purley Chase [Cook 2013] (both in Warwickshire) and in Scotland at Tomintoul, Banffshire [Aberdeen Journal 16/11/1943].
For information relating the economics of manganese mining in North Wales to the world trade in manganese see The manganese trade.