Schistosity is a thin layering of the rock produced by metamorphism that permits the rock to be easily split into thin layers or flakes.
(rocks with a high degree of schistosity are commonly known as schists. Typically, they have a “grainy” appearance)
Some schists look quite prosaic.
Others are very beautiful.
I think that today’s featured rock is a pelitic schist, derived from shale.
(I am not remotely a geologist, and am happy to be corrected)
In any event, today’s rock stands within a very few human footsteps of yesterday’s.
(photo is copyright Doug Spencer, taken at 2.16 pm on 20 September 2021)
The italicised quotation is from Wikipedia’s Schist entry, which is worth reading.