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Origin and history

La phosphatière du Cloup d'Aural is an old phosphate mine discovered in 1865 by Jean-André Poumarède, pharmacist and chemist. Intrigued by bone debris and unusual stones in a field near Bach (Lot), it analyses samples and reveals a high level of tricalcium phosphate (70-80%). In 1867 he alerted the Prefect of Tarn-et-Garonne about the agricultural and paleontological importance of this discovery, marking the beginning of the exploitation of the Quercy phosphate fields.

Phosphate exploitation intensified in the 1870s, with hundreds of open sites between Cahors, Figeac, Gaillac and Montauban. In 1886, 161 centres produced 30,000 tons of ore, but the depletion of deposits and the discovery of phosphates in North Africa (Tunisia in 1899, Morocco) caused their decline. By 1887, 112 phosphates fermented, and in 1902, only two remained active. The large-scale Cloup d'Aural site (170 m long, 20 m deep) preserves operational traces and buildings in good condition.

The site is remarkable for its fossil richness: more than 600 species of animals from the tertiary era (between -50 and -20 million years) have been identified, serving as a reference for European fauna. After they are abandoned, the phosphates become landfills. In 1992, the association Les Phosphatières du Quercy valued the Cloup d'Aural, opened to the public in 2000. To protect fossils, the state created in 2015 the national nature reserve of geological interest of the Lot. The phosphatary is listed as a historic monument on December 10, 1998.

Quercy phosphates result from karst phenomena. 170 million years ago, a tropical sea deposited limestone sediments and phosphate from organic matter. After the sea retreat (-70 million years), erosion forms caves where clays and phosphates accumulate between -50 and -20 million years. Fossils, such as parasitoid wasps Xenomorphia (2018), preserve it. Scientists, including Louis Dieulafait and Bernard Gèze, explained this unique geological process.

The exploitation of phosphates in France begins late, after scientific debates. Jean-Baptiste Boussingault in 1840 opposed Justus von Liebig on their agricultural utility, favouring organic fertilizers. In 1855, Adolphe Bobierre proved the fertilizing effect of phosphate rocks, launching a rush to phosphate in Europe. In Quercy, this fever lasts until the depletion of the deposits and North African competition, leaving an exceptional geological and paleontological heritage.

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