"he went down to stop the grindstone turning"
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Creative Commons Attribution Share Alikeconfiguration 1 - Credit: Doron

Grindstones, commonly called millstones, are ingenious devices once used in almost all parts of Europe and Asia for grinding grain into flour.  Typically circular, they were often made from burrstone, limestone, or sandstone.                

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Creative Commons Attributionconfiguration 2 - Credit: David Shankbone