Round profiled stone, blue

The mining of the Belgian lumps was mentioned in writing for the first time in 1625. But already Pliny (23-79 A.D. Roman scholar) mentioned the special grinding stones from the Ardennes in his writings.
Until today this deposit is unique in the world because of its natural composition.

In the approx. 480 million years old slate sedimentary rock of volcanic ashes and clays, finest garnets (5-20 microns) are embedded in veins of 5-20 cm. After diamond, corundum and beryl follows the hardness garnet. Similar to a soccer, its surface is divided into facets. (rhombic dodecahedron).
Exactly these characteristics, hardness and roundness of the garnet particles, lead to these excellent sharpness properties.