Saddle quern and rubbing stone ö Basalt and limestone ö 7000 BCE ö Harvested grains were ground with a crudely shaped rubbing stone. It was pushed back and forth over grain that had been placed on the surface of a wider, heavier stone, called a quern, which was set in the ground. Alveolate basalt was an ideal stone for making querns because it has a very rough surface and is very hard.