Slate

A compact fine-grained metamorphic rock formed by the effects of heat and pressure on shale. It can be split into thin layers along natural cleavage planes and is used as a roofing and paving material

Slate ranges in color from gray to black or from red to green, depending on the minerals contained in the shale from which it formed.

Slate is made from metamorphic rocks derived from clay or volcanic ash. The foliation, or splitting, of slate allows for theproduction of thin sheets for tiles. Slate roofing can be cut in uniform or varied sizes and comes in many colors …

Slate roofs require little maintenance and can last for more than a hundred years.

The color of slate often depends on where you source it from. Virginia and Quebec produce hard, unfading black slates.Vermont offers semi-weathering and unfading greens, grays, reds, purples and blacks. Pennsylvania once produced softer slates known as the Pennsylvania Black and Chapman Slates, but the quarries in Pennsylvania are no longer as active

- Chauncey Crail, "What is a Slate Roof and How Long Does It Last? Forbes Home (online October 2023)