millstone

Millstone refers to one of a pair of stones used to grind grain in a mill. In a traditional setup, the bedstone is stationary while the runner stone rotates above it. Grain is fed from a hopper onto the center of the runner and ground between the furrows on the stone surfaces, with flour exiting at the periphery.

Millstones are made from hard, abrasive rocks such as sandstone or quartzite. Special varieties, notably French burr quartzite from the Paris Basin, were highly valued for producing fine flour, while more common stones offered a cheaper alternative. The surface is patterned with furrows and webs to optimize grinding and heat removal.

Historically, milling began with hand querns and evolved to water- and wind-powered mills. In many regions, water wheels or sail-driven mechanisms drove the runner stone, with later steam and belt drives in industrial settings.

Maintenance, known as dressing, involves re-cutting worn furrows and edges to restore cutting efficiency. Proper dressing and alignment are essential to avoid damaging the grain or the stones.

Today, traditional millstones remain in use in artisanal mills and in museum collections, while modern flour production relies on roller mills. Millstones also feature in culture as symbols of traditional industry and rural technology.