"Two defining industries of the British industrial revolution were cotton and railways. Both of these depended in part on the now almost forgotten manganese mining industry.

In the case of cotton, before the 19th century industrialisation of textile production, fabric was bleached by leaving it out in the sun in bleaching fields - a process that could take months. Factory manufacture of cloth required a quicker and more controllable process and this was provided by chlorine-based bleaching powders. These were made by reacting manganese ore with hydrocloric acid to produce chlorine.

The development of railways in the mid-19th century required improvements in the quality of steel used for rails. Adding manganese to the steel improved both its hardness and wearing qualities. Although not the sole source, manganese from north Wales was particularly important when foreign supplies were unavailable, such as in times of war.

The main manganese mining areas of north Wales were on the Llyn Peninsula near Rhiw, in the Rhinog Mountains east of Harlech and in the Arenig mountains between Trawsfynydd and Bala. By 1823 there was a small-scale manganese mining industry in Merioneth and from 1835 until 1840 manganese was worked to the north of Barmouth with the ore being sent to Glasgow to make bleaching powder for the textile industry.

From 1883, interest in manganese grew rapidly because of the use of manganese in steel production. Twelve mines opened in Merioneth in 1886, most owned either by the Dyffryn Mining Company or its competitor the Merioneth Mining Company, and manganese ore was sent to Flintshire and Lancashire for use in steel making.

Mining also commenced on the Llyn at this time. In 1887, recorded output in Merioneth peaked at 12,391 tons from 14 mines and there was a further peak in 1890 of 12,018 tons from 17 mines.

In 1891 the 17 mines in Merioneth produced only 8,553 tons and both output and number of mines declined from then on. This was due to the poor quality of the ore and inaccessibility of the mines and also because sources of better and cheaper ores were developed abroad which were able to sustain the British iron and steel industry. Only in the exceptional circumstance of World War I when imported manganese was unavailable was it possible for the Merioneth mines to be worked profitably again.

After the war production 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 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. The largest mine was Hafotty near Llanaber, employing more than 50 men in 1887. From 1891 to 1892 the number of manganese miners in Merioneth halved from 175 to 87, and was down to only eight men by 1896.

During World War II manganese was mined at Rhiw. Plans were made to reopen the Merioneth mines but no actual work was done.

Although a considerable resource of manganese remains in the area, for both environmental and economic reasons it is most unlikely there will be any exploitation of it. Little remains of the industry other than odd scattered pits and banks, some shallow underground workings and the ruins of small buildings such as smithies."