"It is customary to associated particular types of gravestones or environments with particular weathering processes. Marble gravestones, for example, are expected or rather assumed, to decay mainly by dissolution by acidic rainfall (remembering that natural rainfall is slightly acidic anyway being a weak carbonic acid with a pH of 5.6) Dissolution is assumed to remove matrix and grains from the surface of the gravestone producing a 'sugary' surface". [For the full story on the decay of monuments from the University of Portsmouth (UK) see this link.]
Ecclesiastical Curiosities - (1898)
Editor: William Andrews
"Yet there are prevalent ideas or notions, about the churchyard and its sleepers, as deep-rooted as any wild superstition, and perhaps as difficult to solve, or to trace to any rational source. I would here mention one of the most strange, and probably one of the most prejudiced notions to be met with relating to burial in the churchyard. I refer to the East Anglian prejudice of being buried on the north side of the church. That this prejudice is a strong one, among the country people in certain parts of England, is proved by the scarcity of graves, nay, in many instances the total absence of graves, on the north side of our churches".