Slate, originally used for tombstones, is one of the oldest natural roofing materials.
It's easy to cut and can be used to create all kinds of roofing accidents (e.g., verges, ridges, etc.). When it comes from a renowned basin (Anjou, Ardennes), its life would be almost limitless if we could prevent the oxidation of its fasteners (nails or hooks) and the effects of hail and frost. Along with metal, it is the roofing material that is most impervious to rain, snow, wind and dust.
Slate is suitable for all roofing shapes (turrets, domes, etc.) and slopes from 15˚ to vertical (brisis, rain-exposed wall cladding). It's a material of choice, often given preference for covering monuments.
On the other hand, its fragility makes it costly to maintain, requiring the use of scaffolding and specialized personnel.
The photographs are taken from the encyclopedia of trades "L'art du couvreur" and from the Angers slate quarries.