Grinding Stone

Millstones or mill stones are stones used in gristmills, for grinding wheat or other grains. They are sometimes referred to as grindstones or grinding stones.

Millstones come in pairs: a convex stationary base known as the ''bedstone'' and a concave ''runner stone'' that rotates. The movement of the runner on top of the bedstone creates a "scissoring" action that grinds grain trapped between the stones. Millstones are constructed so that their shape and configuration help to channel ground flour to the outer edges of the mechanism for collection.

The runner stone is supported by a cross-shaped metal piece ( millrind or rynd) fixed to a "mace head" topping the main shaft or spindle leading to the driving mechanism of the mill (wind, water (including tide) or other means).

History

The earliest evidence for stones used to grind food is found in northern Australia, at the Madjedbebe rock shelter in Arnhem Land, dating back around 60,000 years. Grinding stones or grindstones, as they were called, were used by the Aboriginal peoples across the continent and islands, and they were traded in areas where suitable sandstone was not available in abundance. Different stones were adapted for grinding different things and varied according to location. One important use was for foods, in particular to grind seeds to make bread, but stones were also adapted for grinding specific types of starchy nuts, ochres for artwork, plant fibres for string, or plants for use in bush medicine, and are still used today. The Australian grindstones usually comprise a large flat sandstone rock (for its abrasive qualities), used with a top stone, known as a "muller", "pounder", or pestle. The Aboriginal peoples of the present state of Victoria used grinding stones to crush roots, bulbs, tubers and berries, as well as insects, small mammals and reptiles before cooking them.

Neolithic and Upper Paleolithic people in Europe used millstones to grind grains, nuts, rhizomes and other vegetable food products for consumption. These implements are often called grinding stones, and used either saddle stones or rotary querns turned by hand. Such devices were also used to grind pigments and metal ores prior to smelting.

In India, grinding stones (''Chakki'') were used to grind grains and spices. These consist of a stationary stone cylinder upon which a smaller stone cylinder rotates. Smaller ones, for household use, were operated by two people. Larger ones, for community or commercial use, used livestock to rotate the upper cylinder. Today a majority of the stone flour mills (Atta Chakki) are equipped with lower stone rotating and upper stone stationary millstones also called Shikhar Emery Stones which are made from abrasive emery grains and grits, with a binding agent similar to Sorel Cement. These stones are made from two types of emery abrasives - Natural Jaspar Red Emery or Synthetic Calcined Bauxite Black Emery.

Millstones were introduced to Britain by the Romans during the 1st century AD and were widely used there from the 3rd century AD onwards.

Material

The type of stone most suitable for making millstones is a siliceous rock called burrstone