The Saint-Astier® Quarry

Homogeneous limestone with unique properties

Our underground quarry contains limestone, our raw material for creating Natural Hydraulic Lime. This bank covers an area of 350 hectares and is more than 200 metres deep. It is located in the Vallée de l’Isle in the Dordogne, in the commune of Saint-Astier, whose name we have been proud to bear since 2017. Early in the 19th century, the qualities of Saint-Astier® limestone were discovered by Louis Vicat, who demonstrated the hydraulic properties of Saint-Astier® lime.

This deposit, unique in Europe, is said to be ‘almost inexhaustible’. It has a consistent, uniform mineralogy, which is what makes it so special. Thanks to its chalky, siliceous limestone, Saint-Astier® has been producing high-quality Pure Natural Hydraulic Lime for over 110 years.

In 2021, Saint-Astier® renewed its mining rights. This ensures the continuity of the company’s production for many years to come.

Process and Expertise

Authentic Expertise

Our job as master kiln operator requires absolute control of our manufacturing process. This process requires rigour and technical expertise throughout the production stage: extracting the limestone, operating the kilns to achieve optimum cooking and controlling the slaking of the quicklime.

Manufacturing Process

Blasting – Extraction – Crushing/Screening

The process of making pure natural hydraulic lime begins more than 20 metres underground. In this cathedral of rock, quarry miners examine and prepare the shots to extract the best from the limestone that is still slumbering…

For lime production, this extraction stage is essential. Perfect knowledge of limestone determines the characteristics and qualities of lime. Blasting in underground quarries is very rare. Saint-Astier® opted for this underground mining method because it would have no impact on nature (the biotope) on the surface, although it would be more complicated and expensive. This is a meticulous operation. The expertise of our miners means that we can guarantee consistent raw material quality and grain size.

These stones are then crushed, screened and mixed with the fuel. The mixture is then conveyed to the entrance of the surface furnaces.

Cooking

The kilns are those built from 1928 onwards. These traditional vertical kilns, with their specific internal brickwork, are still our current production tools. It takes years of experience to operate them.

Hydration/Slaking/Curing

Rock quicklime comes out of the kilns. It is then ground to a specific particle size to achieve optimum slaking. Quicklime is only slaked with rainwater, which is collected and stored in the quarry for this operation.

The quicklime then goes into maturing silos for an average of 30 hours. A unique slaking method, developed specifically by Saint-Astier® to guarantee the special qualities of our limes.

Selection, Grinding and Packaging

Following maturation, the hydrated lime obtained is selected by ventilation in cyclones (dynamic separators). The finest, lightest part of the hydrated lime is then retained. The coarsest part is ground and then re-selected until a powder of optimum particle size is obtained.

This selection, combined with the properties obtained in the previous stages, enables us to isolate different qualities of lime in dedicated silos. Depending on the specific characteristics and properties of the finished products required, we combine the limes previously selected according to their quality.

Finally, lime is stored in silos and packaged in bags, bulk and big bags. They are also distributed on our site dedicated to the production and colouring of mortars.