What does millstone look like?

A millstone is typically a large, circular stone used to grind grains into flour. It has a rough, textured surface with a central hole for a wooden shaft that connects it to a milling mechanism. Millstones are often made of durable materials like granite or limestone and can vary in size from a few feet in diameter to much larger. The top stone, known as the runner stone, rotates over the stationary bottom stone, or bedstone, creating a grinding action.