Phosphatières du Cloup d’Aural

Useful Information

Location: Bach.
Take D19 east to Varaire, after 1.4 km turn right.
(44.35215243943495, 1.690909352478695)
Open: Mid-APR to mid-JUN Mon-Sat 15, 16:30, Sun 15, 16, 17.
Mid-JUN to JUN daily 15, 16, 17.
1st week JUL daily 10-12, 14-16, tours hourly.
JUL to AUG daily 10-12, 14-16, two tours hourly.
Last week in AUG daily 10-12, 14-16, tours hourly.
AUG to mid-AUG daily 15, 16, 17.
Last week in SEP daily 15, 16:30.
All Saints School Holidays daily 15, 16:30.
Circuit des Phosphatières du Cloup d'Aural: no restrictions, good weather recommended.
Fee: Adults EUR 9, Children (5-14) EUR 6, Children (0-5) free, Students EUR 8.
Groups (15+): Adults EUR 7, Children (5-14) EUR 5.
Circuit des Phosphatières du Cloup d'Aural: free.
Classification: MineClay Mine TopicSentier Karstique
Light: LightIncandescent Electric Light System
Guided tours: D=1 h, VR=20 m.
Circuit des Phosphatières du Cloup d'Aural: self guided, L=9 km, D=2.5 h.
Photography: allowed
Accessibility: no
Bibliography: Adolphe Bobierre (1858): Du Phosphate de chaux et de son emploi en agriculture. Leçons professées à l'École préparatoire des sciences et des lettres de Nantes, Librairie agricole, Paris, 1858 online
Adolphe Bobierre (1861): Études chimiques sur le phosphate de chaux et son emploi en agriculture comprenant l'examen des coprolithes et nodules pseudo-coprolithiques des phosphorites d'Espagne, des guanos ferreux, etc., Librairie agricole, Paris, 1861 online
Adolphe Bobierre (1863): L'atmosphère, le sol, les engrais : leçons professées de 1850 à 1862 à la chaire municipale et à l'École préparatoire des sciences de Nantes, Librairie agricole, Paris, 1863 online
Thévenin Armand (1903): Étude géologique de la bordure sud-ouest du Massif central. Bulletin de la Société française de géologie, t. XIV, n° 95, 203 p.
Bernard Gèze (1994): La ruée vers le phosphate dans les cavernes du Midi de la France (1994): Comité français d'histoire de la géologie (COFRHIGEO), 1994, 3e série, tome 8 online
Thierry Pélissié, Jean-Guy Astruc (1996): Tectonique Synsédimentaire et dissolution d'évaporites dans les dépôts du Jurassique moyen et supérieur des Causses du Quercy, p. 23-32, dans Géologie de la France, 1996, no 4 pdf
Thierry Pélissié (1999): Les phosphatières du Quercy, p. 23-26, dans Spelunca, no 73 pdf
Thierry Pélissié (2006): 30 Millions d’Annees de Biodiversite Dynamique dans le Paleokarst du Quercy, Lalbenque – Limogne 1–3 Octobre 2005. pdf
Thierry Pélissié, Francis Duranthon (2009): L’exploitation des phosphates en Quercy : de la fièvre du phosphate au laboratoire naturel de l’évolution, p. 30-33, dans Géologues, septembre 2009, no 162. pdf
Jean-Michel Mazin, Thierry Pélissié, Pierre Hantzpergue, Carine Lézin (2013): Livret d'excursion : Le bassin du Quercy, Congrès de l'Association de paléontologie française, Toulouse, 10-12 avril 2013, dans Strata, 2013, no 15 (ISSN 0296-2055) pdf
Address: Phosphatières du Cloup d’Aural, 46230 Bach, Tel: +33-565-200-672, Tel: +33-565-200-672. E-mail:
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.


1865 Jean-André Poumarède, pharmacist, doctor and chemist in Caussade discovers the deposit.
04-JAN-1867 he wrote a letter to the prefect of Tarn-et-Garonne in which he announced his discovery.
1870s phosphate mining started.
1886 Service des Mines counted 161 mines in the area mining 30,000 tons of phosphor.
1887 112 phosphate mines closed.
1902 last two mines in Cajarc and Saint-Martin-Labouval closed.
1992 association Les Phosphatières du Quercy develop the Cloup d'Aural in Bach.
10-DEC-1998 listed as a historical monument.
2000 site opened to the public.


The phosphate deposits were formed in huge karst structures called karren, which are a result of the dissolution of limestone along cracks. The limestones and compact dolomites are from the Middle and Upper Jurassic, and very rarely of the Lias. While the cracks widened, they were filled by phosphate rich sediments, containing plants and dead animals.

It was at first unclear where the phosphor originated from. The first researchers explained that it had a hydrothermal origin. But the numerous bones led to an explanation by an animal origin. Various researchers, Louis Dieulafait (1884), Eugène Fournier (1900), Armand Thévenin (1903), and Bernard Gèze (1937), showed that the phosphates are due to karst phenomena. The phosphate was deposited in the Jurassic with the limestone, a result of decomposition organic matter in the sediment. The area became land at the very end of the Jurassic and was covered by a tropical forest during the Cretaceous. In this time the limestone was karstified with the formation of huge caves and underground rivers.

The carbonates which were dissolved on the surface released the insoluble phosphates in the form of whitish grey clay, which was accumulated. The clay filled the caves and the dolines of the time. The caves were filled completely with sediments, but finally the erosion reached the level of the caves and they were cut open. The upper part of the caves formed roofless caves which were filled with phosphates.


The Phosphatières du Cloup d’Aural (Phosphate Mines of Cloup d’Aural) are historic phosphate mines. The phosphate rich sediment was quite popular during the 19th century as fertilizer and was quarried in an open cast mine. In the phosphate numerous bones of animals were discovered. As a result the palaeontological remains are quite abundant.

The deposit was discovered by Jean-André Poumarède, pharmacist, doctor and chemist from Caussade 1865. He was visiting his brother-in-law in the hamlet of Cos, near Caylus. He noticed the greenness of the wheat in a field. In search for the reason of the fertility, he found bone debris and curious rocks in the fields. He was chemist and analyzed them, 70% to 80% tricalcium phosphate. On 04-JAN-1867 he wrote a letter to the prefect of Tarn-et-Garonne in which he announced his discovery. Since the 1870s they were mined.

In the area between Cahors, Figeac, Gaillac and Montauban hundreds trous à phosphates (phosphate holes) were discovered. In 1886 the Service des Mines counted 161 mines in the area mining 30,000 tons of phosphor worth one million francs. But the phosphorite of Quercy was found only in the karst forms of the limestone. The deposits began to run out 1887, after only a decade, and 112 phosphate mines closed. The mining continued for some time on a low level, but newly discovered deposits in Algeria and Morocco finally ended the mining. In 1902 the last two mines in Cajarc and Saint-Martin-Labouval were closed.

The deposits were full of vertebrate fossils of the Tertiary era, between the end of the Eocene and the beginning of the Miocene. More than 600 species of animals have been identified in the phosphates.

Many phosphate mines in the area were used as landfills. The site was protected by the association Les Phosphatières du Quercy since 1992. They developed it with trails and opened it in the early summer of 2000 to the public. The Réserve naturelle nationale d'intérêt géologique du département du Lot (Department Lot National Nature Reserve of Geological Interest) was founded in 2015 to protect the abandoned mine site from the looting of fossils.

The Circuit des Phosphatières du Cloup d'Aural is a 9 km long loop trail which connects the most interesting remains of the phosphate mining and the diverse karst features in the area. So it is actually a mine, karst and geological trail. It also follows one of the numerous Santiago Pilgrim Ways in one section. The trail is flat and without any difficulties. Start and end is at the parking lot of the Phosphatières du Cloup d’Aural at D19 east of Bach.