Although the ore here was of low quality, this was more than compensated for by the fact that it occurred in two large masses close to the surface. Initially ore was worked on the surface from shallow shafts, next by open-pit mining and finally underground from adits or from shafts. The ore was broken into small lumps by hand, the best ore being shipped to Lancashire or to the Lower Swansea valley in South Wales through the port of Swansea for smelting. Copper was concentrated and extracted from the remainder using kilns and furnaces on site. It was also discovered that purer metal could be obtained efficiently, although in small amounts, by its precipitation from drainage water with scrap iron in purpose-built ponds. Associated with the mines, important chemical industries were established on the Mountain based on by-products such as ochre pigments, sulphur, vitriol and alum. The processes were described by the German writer and translator, Augustin Gottfried Ludwig Lentin (1764-1823) who visited Parys Mountain in the 1790s and published his findings in Briefe über die Insel Anglesea: vorzüglich über das dasige Kupfer-Bergwerk und die dazu gehörigen Schmelzwerke und Fabriken (Leipzig: Crusius, 1800).