The Spiennes neolithic flint mines, in the municipality of Mons, province of Hainaut, are on the list of UNESCO World Heritage Sites. They are described as "the largest and earliest concentration of ancient mines in Europe" and UNESCO cites the level of human technological development they demonstrate as justification for their inclusion.
The mines cover some 100 hectares of downland near Mons and are interesting for showing the transition between opencast and underground mining for the flint nodules. The nodules were extracted using deer antler picks. The stones were then knapped into rough-out shapes of axes, and finally polished to achieve the final state.
The rough-outs were traded over a wide area, and were often polished at their destination. Polishing strengthens the final product, making the axe-head last longer. The axes were used initially for forest clearance during the early Neolithic period, and for shaping wood for structural applications, such as timber for huts and canoes.