Panasqueira

A charcoal burner picked up a shiny black stone in the scrub, and a mine has been running on that spot ever since.

Minas da Panasqueira is a set of integrated tungsten workings in central Portugal, spread between Cabeco do Piao in Fundao and the village of Panasqueira in Covilha, in Castelo Branco District between the Serra do Acor and the Serra da Gardunha. The valley's name comes from panasco, the local word for the grasses common in the region's rye fields.

The discovery is recorded precisely. At the end of the 19th century a charcoal burner known as O Pescao de Casegas found a shiny black stone and took it to Manuel dos Santos in the parish of Barroca do Zezere. Dos Santos went to Lisbon and asked the mineralogy professor and engineer Silva Pinto to examine the ground. Pinto came, saw how much wolframite was lying about, bought the collected ore and the land, and filed the first mining registration, published on 25 November 1898. A rudimentary manual washing plant soon employed almost 100 people.

It has operated nearly without interruption since 1901. Almonty, which owns it now, describes 126 years of more or less continuous operation staffed by fifth-generation tungsten miners. The First World War drove wolfram prices up and production to around 30 tonnes of concentrate a month with 800 direct employees, and the price collapse of 1918 cut the workforce to 100.

Wolframite is the ore that matters economically, with cassiterite and chalcopyrite as by-products, alongside muscovite, topaz, fluorite, arsenopyrite, sphalerite, siderite and more. Collectors know Panasqueira for something else. Its veins contain cavities called rotos in mining slang, from a centimetre to a metre across, opening at random as the workings advance. The high volatile content of these veins lets crystals grow inside them under near-ideal temperature and pressure, and collectible samples are taken daily as the mine progresses. Two minerals were first described here: panasqueiraite and thadeuite.

This is a working industrial operation, so see the results instead. The American Museum of Natural History shows 21 crystals from here and the Natural History Museum in London more than 100, making Panasqueira the largest single source in both. The parish council at Sao Francisco de Assis and the mining company have turned mine buildings into a museum, including an old diesel tank rebuilt as a three-storey exhibition space.