Stand Aside Mortals.
Geologist coming through!
Doesnt look like limestone from here, but then a photo isn’t ideal.
put some (a drop) of vinegar on it.
if it fizzes, it is Limestone of some sort (or at least calcitic)
if not, it looks like sandstone/gritstone to me.
where are you?
stone like that is ALWAYS local. (unless your the chump at one of our sites who insisted on importing welsh slate to clad a house in portishead. Looks crap as its totally out of place, and was heinously expensive…anyhoo, i digress.
look up your location on the “BGS Geoindex: Onshore”
and it will tell you what your local bedrock is.
its almost certainly that.
http://www.bgs.ac.uk/geoindex/