Tresminas is an ancient gold mining complex dated back to the roman period and, extensively explored in those times. It is, as many mines of those days, an open pit mine, with differentiated rock cuts still visible today. The complex is a classified as Immovable Heritage by the Portuguese institute DGPC.
The place and history of Tresminas
Integrated in the upper Tâmega river subregion, located in the municipality of Vila Pouca de Aguiar , the ancient mining complex can be found in the heart of the city parish Tresminas, one of the 14 city parishes of the municipality, embraced by the mountains of Alvão and Padrela, in the beautiful Trás-os-Montes region.
The mining complex was considered to be one of the largest mining exploitation sites of the Roman world.
Mining activity started ca. the reign of emperor Augustus (27 BCE – 14 CE), continued throughout the years, until the 2nd century BC, by the time of the emperor Settimo Severo.
Gold has been one of the most important metals since early ages of Human history, since it’s discovery , and the oldest gold mine goes back till the 12th Dinasty in ancient Egypt. The importance of gold during this period is beyond the scope of this article.
Roman period brought many advances in the metallurgy field and more efficient methods were introduced by the romans, like hydraulic mining methods and opencast.
The importance of gold in the Roman empire was paramount and with the expansion of the roman empire , always seeking for new locations for gold extraction.
Hispania region was an extremely important place for the roman gold exploration, with the most important places located in Las Medulas (Léon/ Hispania) and Tresminas (Lusitania) for what concerns the Iberia Region, thus making the region of particular importance for the empire, despite the huge distance from Rome.
Tresminas mine data
As mentioned, the mining complex is an open pit mine with three distinct irregular cuts still visible today:
Covas cut – with >430 mt in length and 60 mt deep
Ribeirinha cut – 370 mt and more than >100 mt deep
Lagoinhos cut – 100 mt by 9 mt deep (mining activity in Laguinhos were mostly performed underground)
For transport and drainage, the mines were prepared with galleries angle of draw accordingly the ore vein.
Pilar gallery – aprox. 250mt
Texugo gallery – aprox. 80mt
Alargamentos gallery – aprox. 150mt
Morcegos gallery – aprox. 150mt
Buraco Seco gallery – aprox. 90mt
Esteves Pinto gallery
Jürgen Wall gallery
The galleries are all visitable by foot.
Near the cuts, remains of the adjacent structures of the mine can be perceived and identified today as being residential areas, four ore processing areas and, other presumably ludic structures for the workers and, a necropolis.
Also, being part of the complex, there are hydric channels from Tinhela river and Fraga stream that supplied water essential for the mining activity.
The main minerals are, gold, arsenopyrite, pyrite, quartz, pyrrhotite in a mostly granitic matrix. Arsenic pollution is considered today to be way beyond the limit level and a major concern in the region. Along with gold production, silver and lead were also produced during roman times.
It is estimated that 10 million tons of material were processed here, by crushing and gravitational separation. The total gold production is estimated to be around 25 tons. An impressive amount.
The mine complex is supported by an Interpretative Center, were we can learn more about the mining activity in the region but also, to have a closer contact on some of the archeological findings left by the romans, now all belonging to the magnificent collection of the Center.
Also, guided field trips to the galleries can be made by appointment and it’s an experience that is a must to complement all the information provided at the Center.
For stay, I strongly recommend to find a local rural tourism place and enjoy the full beauty of the region and overwhelming silence and peacefulness.
Pedro Mendonça, born in Lisbon at December 3 of 1972, studied Organic Chemistry, with a passion for photography and architecture , mainly focusing his written work on industrial history and portuguese industrial heritage.