Also 7–9 kellus, 8 killos. [Cornish.] The Cornish Miners’ term for clay-slate; geologically, the clay-slate of Cornwall, of Devonian age, which rests on the granite.
1674–91. Ray, Coll. Words, Prepar. Metals (E. D. S.), 11. Above the spar lies another kind of substance like a white soft stone, which they call kellus.
1758. Borlase, Nat. Hist. Cornw., 92. Round the town of Marazion … there rises a very tender killas, of the cinereous, and also of the yellow colour.
1833. Lyell, Princ. Geol., III. 370. At the junction of the granite and killas in St. Michael’s Mount.
1875. Geikie, Life Murchison, I. 301. The Devonshire killas answered in point of geological time to the old Red Sandstone.
attrib. 1807. Vancouver, Agric. Devon (1813), 11, note. The shillot or killas rock … will always be found accompanied with a similar soil or covering.
