Phosphatière du Cloup d'Aural

Phosphatière du Cloup d'Aural is a former phosphate mine in the village of Bach, in the Lot department of southwestern France. The site combines a slice of 19th-century mining history with an exceptionally rich fossil record, and today it's open to visitors as a nature-and-history attraction on the limestone plateaus of Quercy.

What exactly is a "phosphatière"?

A phosphatière is a natural fissure or sinkhole in the limestone bedrock of the causse (the region's characteristic dry limestone plateau) that turned out, in the second half of the 19th century, to be packed with phosphorus-rich material. Cloup d'Aural is one such formation — mined out and later preserved both as a record of that mining era and as a site of major scientific value.

How was the deposit discovered?

The story begins in 1865, when Jean-André Poumarède, a pharmacist, doctor and chemist, spotted unusual stones and bone fragments in a field near Bach. Analysis of the samples revealed a tricalcium phosphate content of 70-80%, triggering a genuine phosphate rush. From the 1870s onward, hundreds of similar "phosphate holes" were found and worked across the region between Cahors, Figeac, Gaillac and Montauban, wherever Jurassic limestone outcrops in Quercy.

What will you see on site?

Visiting Cloup d'Aural means descending into a former open-cast working that today looks like a multi-level pit open to the sky, carved into the rock. Guides point out traces of the old phosphate extraction and explain how, over millions of years, animal remains accumulated inside these fissures. More than 600 animal species from the Tertiary period — roughly 50 to 20 million years ago — have been identified here, making it one of the key reference sites for that era's fauna in Europe. What makes Cloup d'Aural genuinely unique is that its fossil record spans the period before, during and after a major climatic cooling event, making it the only site in the world where the impact of that shift on fauna and flora can be studied directly.

How do you get there?

Bach sits on the high ground of Quercy, between Cahors and Figeac, in the heart of the Lot department. The site is reached via local roads winding through the region's typical dry limestone plateaus, fields and dry-stone walls. Cahors and Figeac are the nearest larger towns, both with signposted routes leading to Bach.

When to visit, and how does a tour work?

The site opened to the public in 2000, after the association "Les Phosphatières du Quercy" began developing it in 1992. For safety reasons, and to properly convey the site's geology and history, visits are guided only — there's no unaccompanied access to the former workings. The main visiting season runs through spring, summer and early autumn, with regular guided tour times during that window; it's worth checking current opening times before setting off, since the seasonal schedule can vary.

Who is it for?

Cloup d'Aural appeals both to visitors with an interest in geology and palaeontology and to families looking for an unusual educational outing in the Lot. It pairs well with a wider tour of Quercy's villages and caves, and offers a rare chance to see, first-hand, the physical traces of a phosphate-mining boom that lasted little more than a few decades.

Frequently asked questions

Can you visit without a guide? No. For safety reasons and to properly understand the site's geology and history, entry to the former mine is only possible as part of a guided group tour.

What exactly has been found at Cloup d'Aural? More than 600 animal species from the Tertiary period (roughly 50 to 20 million years ago) have been identified, making the site one of the key references for reconstructing European fauna of that era.

Why is this site considered unique worldwide? Its fossil record spans the period before, during and after a significant climatic cooling event, making Cloup d'Aural the only known site where the effect of that change on fauna and flora can be traced directly.

Who discovered the deposit, and when? Pharmacist and chemist Jean-André Poumarède noticed unusual stones and bone fragments in a field in 1865; chemical analysis then confirmed a high tricalcium phosphate content, kicking off the exploitation of the wider region.