Panasqueira is one of the largest tungsten mines in the world. It is located in Covilhã, Castelo Branco, Portugal.
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The deposit is located in a region in which Precambrian shale, greywacke and sandstone units were intruded by the Panasquieira Granite. Contact metamorphism adjacent to the granite converted the shale into hornfels consisting of biotite, cordierite and andalusite. Quartz veins and masses were produced by regional metamorphism during the Hercynian orogeny. The upper part of the leucogranite batholith is associated with massive quartz greisen and veins within the hornfels and shale.
Mineralisation in the deposit includes an oxide-silicate stage consisting of wolframite, cassiterite, arsenopyrite, topaz, muscovite and tourmaline. This was followed by sulfide mineralisation consisting of further arsenopyrite, pyrite, pyrrhotite, chalcopyrite, sphalerite and stannite. A late stage of calcite and dolomite with minor sulfide minerals ended the mineralisation event.[1]
This classic locality has for over 100 years produced fine collector specimens. These include exceptional specimens of fluorapatite, ferberite, arsenopyrite, siderite, quartz and numerous other species such as: chalcopyrite, sphalerite, dolomite, calcite, mica, tourmaline, fluorite and topaz. It has also produced some very rare minerals and is the type locality for panasqueiraite and thadeuite.[1]
For many years the sale of mineral specimens from the mine was forbidden, as tungsten was a strategic mineral. Quite a few years ago, and at the same time as Portugal began to change after its entry into the European Union, things began to become easier. However, unfortunately, obtaining good specimens has once again become more difficult, but this time due to the way the mine is worked and the lower grade seams.