millstone

1. (geology) A coarse-grained sandstone used for making such stones; millstone grit.Examples: "In North America the millstone grit, and a grey sandy and slaty rock beneath it, occur three times; and it is exceedingly difficult to distinguish these rocks in hand specimens, without the aid of organized remains. And remains are almost exclusively confined to the grey rocks. Common quarrymen, farmers, and foreign geologists, apply the names, greywracke and millstone, to all these rocks promiscuously; neither having observed their different relative positions."; "From the above account it will be seen how closely the Millstone Grit and the Lower Coal Measures are like one another in their lithological character. Each is a group of thick sandstones parted by shales, and in each beds of coal are very generally found on the top of the sandstones. The differences are these. Among the Millstones the sandstones are thicker, fewer, further apart, more constant both in size and character, and as a rule coarse grits or conglomerates."

2. (figurative) Ellipsis of millstone round one's neck, a heavy responsibility that is difficult to bear (referring to Matthew 18:6 in the Bible).Examples: "Paying the mortgage every month is a millstone round their necks."; "[H]owever great and powerful England may be, the strain of such entanglements cannot but tell on her, and one day she may find herself in a predicament in which India may simply hang as a mill-stone round her neck."; "Furthermore, Colonel [Josiah Clement] Wedgwood was dead against special representation being given to landlords or even to universities. "Let India beware," he declared, "of the expansion of communal representation which she will find as a mill-stone hanging about her neck which will grow heavier as time goes on.""abbreviationalt-ofellipsisfiguratively