Trimouns Talc Mine, Luzenac, Foix, Ariège, Occitanie, Francei

Regional Level Types
Trimouns Talc Mine	Quarry (Active)
Luzenac	Commune
Foix	Arrondissement
Ariège	Department
Occitanie	Region
France	Country

Established in 1905, the vast talc quarry of Trimouns (Carrière de talc de Trimouns) is situated at 1800m altitude above the Ax valley in the commune of Luzenac in the Ariège department of Occitanie in southwestern France. It produces 400,000 tons of talc per year, employing 310 permanent workers and 110 seasonal workers. Because of its high elevation, the activity at the quarry is restricted to the period from April to November, but the factory functions year-round using the talc extracted during the warmer months.

Talc, a hydrated magnesium silicate, is the softest mineral on the Mohs scale. It is hydrophobic, inert and composed of layers; the seam at Trimouns has formed 300 million years ago in a fault between two masses of rock, one composed essentially of mica schist and the other of dolomite. In this fault, the rock was ground by the pressure of the two masses, allowing the infiltration of water containing large amounts of magnesium. The magnesium attached itself to the dolomite to form magnesium silicate - talc. In the same way, the mica schists were transformed into chlorite.

The exploitation of talc at Trimouns, even on a small scale, only began in the early 19th century. The soft, white stone was ground in flour mills and the resulting talcum powder brought to Toulouse to be sold to druggists and apothecaries. Until 1860 it was transported by mules (the difference in elevation is 1000m between the quarry and the village 15kms away). In 1888 mining began on a more organised scale and ox carts were used. It was the development of paper mills that launched the industrial era for Luzenac.
The arrival of the railroad in the Ax valley in 1888 and the installation of the first air transport in 1903 helped the business to develop. The corporation Talc de Luzenac was founded in 1905 and entered the Paris stock exchange in 1908.

The quarry itself is a grandiose spectacle - everything is gigantic; on huge terraces, enormous machines uncover, extract, sort and transport the talc with the peaks of the Pyrenean chain as a backdrop. A huge mass of overburden covers the vein of talc which must be removed in order to exploit the talc - 8 tons of rock for 1 ton of talc.

In recent decades, the Trimouns quarry has become well known as a source of outstanding crystals of several rare-earth element-bearing minerals, including familiar species such as allanite, parisite and bastnäsite, as well as very rare ones such as hingganite, iimoriite and dissakisite. Beautiful micromount-size specimens are the rule, but attractive crystals of several species exceeding 1cm have also been found. These minerals occur in dolomite vugs in a contact zone of the Trimouns talc/chlorite deposit, where large-scale mining for talc may now be approaching its end.

There is one guided tour per day from mid-May to mid-October - enquire at the tourist office in Ax-les-Thermes.

Note: Hoshino et al. (2008) have investigated the composition of dissakisite-(Ce) and allanite-(Ce) from this locality, and also publish 10 microprobe analyses from a single crystal. Their conclusion is that: Euhedral dissakisites from Trimouns dolomite mine, France, is compositionally zoned. Back-scattered electron (BSE) images reveal that each of the described dissakisite crystals has three distinct compositional zones: normal zoned core (Mg-rich), oscillatory zoned middle (Ca-Al-rich) and homogeneous rim (Fe-ΣREE-rich). The latter zone with Fe2+> Mg corresponds to allanite-(Ce). Dissakisite-(Ce) also displays pronounced zoning in Fe/Mg which may suggest that the temperature of crystallization continuously decreased from core to rim. Each individual crystal will probably, therefore, contain both species. Allanite-(Ce) is generally considered to be darker than dissakisite-(Ce), but this is not a definitive way to distinguish between the minerals.

Other Databases

Wikipedia:	https://fr.wikipedia.org/wiki/Carri%C3%A8re_de_talc_de_Trimouns
Wikidata ID:	Q2940301

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References