Inchagoill Monastery. Lough Corrib.

PC - Dublin

If you have a look at the attachments, I find it hard to believe that the headstone dates back to the 6th. century. It has hardly weathered. If the dating is correct it must have been buried for a long long time?

Wibbs

I suppose it depends what kind of rock it was originally carved from. If it's a local rock - mostly carboniferous limestone - then yes it must have been buried for a very long part of it's history as that rock type in most cases weathers fast. Rain water will eat through it as the sinkholes and caves in the Burren attest. If it was an imported harder stone like sandstone or granite(esp the latter) then it could go a fair few thousand years exposed with little enough in the way of losses. From your pic it looks like limestone to me anyway.

Which begs another question. If it is a limestone and it had been protected by burial, surely it would be better for preservation to take it indoors and put an exact copy in it's place?