Explained as: a coarse sandstone with a calcareous cement. Perhaps cf. German Quader ashlar, Quadersandstein type of light sandstone occurring in square blocks.
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1828 N. WebsterAmer. Dict. Eng. Lang.Quadrune, a gritstone with a calcarious cement.
This entry has been updated (OED Third Edition, December 2007; most recently modified version published online September 2021).