Panasqueira

It is also known worldwide in the tungsten (wolfram) industry, not only for its quality and volume of production, duration and adaptability of operation; but also due to the maturity of the technical solutions both underground and in ore processing.

The population of the neighbouring village of Cebola (current São Jorge da Beira) used the folds in the slopes to make terraces where they planted potatoes, corn or pasture.

At the end of the 19th century, the region was covered with thick heather scrub, broom, arbutus and pine trees, which were used in the production of charcoal for sale in Fundão and Covilhã.

One of these charcoal burners, known as "O Pescão de Casegas", found a shiny black stone and took it to Manuel dos Santos, in the parish of Barroca do Zêzere.

After visiting the site, dos Santos went to Lisbon and asked Professor of Mineralogy and engineer Silva Pinto to examine the place where the sample had been discovered.

The company's tenure was a time of great development with the opening of many galleries, expansion and modernization of the washing plants, and installation of a 5.1 km long aerial cable.

In 1928 with the entry of new shareholders, the name was changed and important work began, such as a new aerial cableway and a large washing plant in Rio (Cabeço do Pião).

Under the leadership of president and CEO Lewis Black[5], Almonty Industries, acquired the mine on 6 January 2016 and changed the name back to Beralt Tin and Wolfram.

Almonty industries and Lewis Black, President & CEO of the company have publicly committed to implementing the current Environmental, Social, and Governance (ESG) program at its Panasqueira mine in Portugal.

The main commercialized product, wolfram concentrates (wolframite in the case of Panasqueira) are a reference in the industry as they have had the highest grade and purity in the world for decades.

They are generally paid at a premium in relation to market prices and chosen by the manufacturers of intermediate or final products where a particular purity of the raw material is required.

Most of the samples are found in cavities in the veins, which in mining slang are called rotos, of variable size (on a centimeter to meter scale) and random occurrence.

The reason for the quality and perfection of the crystals is the high amount of volatile elements present in Panasqueira's veins, which allows the cavities to form under suitable temperature and pressure conditions.

There are mineral collections from the mine in other museums in Portugal such as the National Laboratory of Energy and Geology (LNEG) in São Mamede de Infesta.

Regarding the occurrence of wolfram and tin deposits in Portugal, the Iberian tin-wolfram metallogenic province extends east of the Porto-Coimbra-Tomar shear and northeast of the Juromenha thrust.

The Portuguese tin-wolfram metallogenic province develops throughout the central and northern region of Portugal where the vein deposits are of greatest economic importance.

The main occurrences of wolfram and tin are conditioned by structures inherited from early and late Variscan shears or fractures related to the installation of post-tectonic granites.

The Beiras group is formed by a dense series of thin lentils of marine origin, of clay and sandstone, which later underwent low-grade regional metamorphism (a facies of greenschist) during the initial compressive phases of the Variscan orogeny.

There are basic intrusive rocks identified as dolerites which occur as 0.5 to 3 m thick veins, mainly oriented north to south and vertically inclined.

In the eastern zone of the mining concession there are mottled schists with spots of biotite and chlorite, and less frequently chiastolite and cordierite which correspond to a contact metamorphism halo, which is considered to indicate the presence of an intrusion of an in-depth magmatic body.

The wolfram-tin-copper mineralized zone consists of sub-horizontal quartz dikes (usually with an inclination of less than 25º, increasing to 30–40º near the greisen dome) that overlap and fill in fractures mainly developed in schist rocks, with an average depth of 25 cm (ranging from 1 to 150 cm) and a width that can reach 200 m, with an average of 48 m. The most important mineral in economical terms is wolfram (wolframite); tin (cassiterite) and copper (chalcopyrite) are mining by-products.

However, Kelly & Rye (1979) defined four stages of deposition for the mineralogy of the veins: From a structural point of view, the mine region is characterized by the occurrence of a large number of faults and fractures, locally well marked, both in the type of filling they have and in their orientation.

Within the stope, manually filled wooden minecarts circulated that transported the disassembled ore to the pits where it dropped by gravity to the lower rolling level.

This method had several drawbacks such as a high labour demand and the loss of a large part of the finer fraction of the ore when it was violently projected against the stone walls.

The importance of investigating another support system that would at the same time allow greater mechanization of the remaining stoping operations resulted in the transition to the room and pillar method.

The pillars were successively reduced in size, and for the final phase of stoping two support methods were tested: reinforced concrete columns formed by overlapping tiles, and piles of wood stacked in various ways.

The room and pillar method allowed an increasing mechanization of the stoping operations that led to the use of drilling machines, first with compressed air and then with electro-hydraulic systems.

At the end of the 1980s, the Panasqueira mine was large enough that its drainage water was sufficient to supply the necessary flow to the entire industrial structure; thus between 1992 and 1996, in order to rationalize costs and due to environmental reasons all ore concentration operations were centralized at the Barroca Grande plant.

In the 1950s a wastewater treatment plant was installed, which, by alkalinization via the addition of lime, treats the water until heavy metals are precipitated into sludge which is then stored in the tailings dams.

The non-reusable effluent resulting from the process is dumped into the Bodelhão stream, complying with the monitoring program defined in the Environmental License, with monthly reporting to the relevant authorities.