Click Photo for Larger Version
View of three of the grinders in the interior of one of the over 30 bakeries that have been discovered at Pompeii.
The grinders are composed of a black volcanic stone that has a rough surface. They are "hour–glass" in shape and are placed upon stationary stone cones. The hour–glass upper portion is turned by animals or humans, grain is placed into the top of it, and then the ground flour comes out the bottom.