Since prehistoric times, it would appear that Slate has been worked and used in Cumbria. There is certainly evidence of its use during the Roman age, at their fort at Hardknott for example.
Outcrops of slate on the surface would be the source initially, developing into open quarries, although later the “metal” would be mined underground.
Workable slate is obtained from two main geological deposits in Cumbria. Together these deposits have given us the silver-grey slates of Coniston Old Man; the green slates of Broughton Moor, Hodge Close and Kirkstone; the blue-black slates of Brathay and Longsleddale; and the blue-grey slates quarried in Kirkby-in-Furness.
pictured: Westmoreland Green, Corfe Castle Church, Honister.