Lime window is a fascinating blog all about using a lime mortar for buildings rather than cement. Their about page has a lot of useful information about why lime is better than cement; not just better for the environment, but better for the building too.
Stone needs to move and settle within a structure. Cement once dried is too brittle to allow movement; hence cracks appear to accommodate expansion. Once cracked, moisture gets trapped within the wall and even within the stone.
However Lime is flexible so reduces serious cracking in stone from expansion.
It’s great when traditional building materials are superior to modern methods!