'Millstone' in the Bible

“No one shall take a handmill or an upper millstone in pledge, for he would be taking a life in pledge.

But a certain woman threw an upper millstone on Abimelech’s head, crushing his skull.

Who struck down Abimelech the son of Jerubbesheth? Did not a woman throw an upper millstone on him from the wall so that he died at Thebez? Why did you go so near the wall?’—then you shall say, ‘Your servant Uriah the Hittite is dead also.’”

“His heart is as hard as a stone,Even as hard as a lower millstone.