Quern-stones were hand-operated stone tools used world-wide for grinding cereals to make flour. Cereal grains cannot be digested unless their tough cellulose shells are crushed. Quern-stones were used to achieve this crushing. They became widespread during the Neolithic Period (5,500 – 2,500 BC ). The earliest known quern is from 9,000 BC (Syria).
The lower fixed concave stone was the bedstone or quern. The upper, hand-held, moveable stone was called the rubber or handstone. This was moved back and forward over the quern to crush and grind the grain into flour. Hemispherical handstones were operated with one hand. Cylindrical handstones were moved with both hands.
The saddle-quern was usually placed on the ground. The operator, often a woman, knelt behind it. The continuous grinding work was exhausting, and caused damaging strain to knee and hip joints, as described below. Skeletons from Abu Hureyra in Syria show deformities which are thought to be due to prolonged quern usage.
The hand-operated quern-stone was replaced by the rotary-quern around 500 BC. Rotary-querns were more efficient, and easier to operate, using a handle to rotate the upper stone.