Millstones have been in use since well before Biblical times. The wheels were made of various types of stone, both hard and soft, and in many different sizes. The thicker ones were used on their edge to do the crushing and can be up to a foot thick. They were often made in pairs. Used horizontally, the bottom stone (or bedstone) was stationary and slightly convex. Above this the 'runner' stone, slightly concave, turned and crushed the grain. The shape of the two stones forced the ground flour out to the edge where is was collected.
Millstones were often turned by wind or water. However, the thicker ones of 300mm thick, were turned by horse or bullock, on an axel perpendicular to the ground, around a stone circular trench. Some stones were used for crushing corn or wheat, while others were used for crushing fruit or making paper.
The very small millstones (300mm to 600mm), were used in domestic situations and turned by hand. You will see a 30mm hole on the surface of these smaller wheels where the miller moved the stone in a circular motion with one stone turning on top of another.
It is difficult to date mill wheels, they can be of any age simply as they erode very little. We have one here at Wells Reclamation which we feel is at least Anglo Saxon or even Roman as it was found about two metres under soil where its weight had taken it over the centuries.
We have about a hundred millstones at Wells Reclamation of various sizes up to nearly three metres across. They have lots of uses from making garden tables, to placing them into patios. Some smaller ones look good in the centre of a rustic internal kitchen floor. They would make a wonderful name plate for your home and old Millhouses definitely deserve one!