Technically not slate as defined by Welsh, Spanish. Italian , Canadian and Cumbrian grey slates, but a compressed sedimentary mudstone where the cleavage plane is the sedimenting plane. Other examples of this type of stone are Collyweston and Swithland Slates also Elland Flags.
Hard wearing and cost effective, but with more colour variability than other slates.
The dark grey riven slab is usually a dapple of lighter and darker sediments, medium grey to black, and can vary across a single slab to generate lighter or darker islands. The surface is very smooth with no discernable grain, similar to a leather topped writing desk. Occasionally there are fine steps, up and down in the surface as the cleavage plane jumps during splitting.
Colours can vary slab to slab from a darkish grey to almost black.
Honed slabs are completely different and are selected for their ‘map of the world’ appearance of land masses and oceans defined by contour lines of varying colour from light grey to black.
No other slate has this striking appearance, comparable with the intricacies of marbles.
Light grey is only available in the riven form, sometimes called green slate due to its “Battleship grey” colour.
However it should not be confused with the true Brazilian green slate which is of uncertain availability.
|Colour:||Light and Dark grey
Multi colours, medium to dark grey – honed only.
|Slab Thickness:||Dark grey and honed multi colour - 20 and 30 mm
Light grey – approx 25mm
|Raw slab size:||2.4 by 1.3 metres|
|Surface finishes:||Riven – light and dark grey
Honed – multi colour
|Cost:||Dark and Light grey – low
Multi colour honed – medium
|External use:||Not recommended as the product of some quarries does not meet European freeze/thaw test standards for paving.|