A large earth-fast boulder on open moorland below Glaisdale Head
The stone marks an ancient boundary, it has been carved with the dates of estate perambulations.
The carvings read EGTON, RG 1713, 1719, 1735RC, E1745, F1752, 1779, 1799, 1821, 1844.
The Grey Mare Stone
The Smell of Water 
Now, those stones could tell a story or two. Stay safe, John
Any relation to the Grey Horse stone over on Howdale Moor?
Maybe the Mari Lwyd (grey mare) down in Wales – if you squint your eyes it could look a bit like a horses skull?
Then again my eyes have seen(!) better days…..
The Grey Horse stone is probably a boundary stone and is also grey in colour, so there is a connection. My friend Tony reckons he can see a horses head in the Grey Horse stone, I can’t see it myself. Perhaps Mare is a corruption of Maen meaning stone. It’s a good excuse to drop two lovely words Pareidolia & mimetolith
Only yesterday i was googling a half remembered quote – “After the age of 80, everything reminds you of something else”
Got a few years to go but it sums me up perfectly.
I would not be suprised if the grey horse stone is prehistoric, with it being located alongside of a cluster of cairns and carved rocks (plus the giant’s finger marks!). It is also located in a ‘liminal’ (?) spot at the head of two watercourses, that were probably more visible in days of yore.
Just trying a wold top Headland Red now 😉