The Calonne quarry, formerly known as the "Broquet" quarry, is a historic limestone quarry near the French-Belgian border. The quarry yielded Tournai limestone ("Pierre de Tournai" or "Black Stone of Tournai"), a compact, tough, and light grayish-blue rock. This rock, formed in the Early Carboniferous (Lower Carboniferous) period, is rich in calcite (75–80%) and also contains silica, dolomite, and pyrite.

From the 19th century onward, the quarry played a prominent role in the region's stone and lime industry: the extracted limestone was processed in lime kilns along the Scheldt River for the production of lime and cement. Several lime kilns existed on the banks of the Scheldt, including the famous "Fours Thorn" (Thorn Kilns), which were in use for centuries. The extracted limestone was transported via the Scheldt. The quarry's location close to the waterway allowed for efficient transport, which increased its economic value. Moreover, Tournai stone contributed to the construction of many religious and civil buildings in the region and beyond.

Today, the quarry is abandoned and partially submerged because the extraction pit is connected to the underground aquifer ("nappe aquifère"). Traces of its industrial past are still visible: old rails, trains, and wrecked materials bear witness to its quarrying past. The approximately 13.8-hectare site is managed as a reserve, and nature has reclaimed its place. The steep walls and water basins form dangerous zones, so the public usually has no free access. Ecologically, the quarry is important: a typical calcareous flora thrives there, and the water features are home to, among other things, the red crab ( Astacus astacus ), a species that indicates good water quality.