I recently travelled through Lincolnshire on my way home, and photographed these memorials, two in Local Lincolnshire limestone and the third in slate probably from Leicestershire. They are all from the mid-late 18th Century and they show how well the slate weathers. The lettering on the limestone has almost disappeared and is barely legible whereas the slate is like new. Lincolnshire limestone is soft and needs to be carved deeply to last. I suspect the lettering was never very deep as the detailing on the cherubic angels is still quite visible. Other limestones such as Hornton limestone or Portland limestone that have always been used a lot for carving and memorial work seem to weather a bit better on the whole and sandstone such as York stone will last much longer as it contains a lot of silica. There’s a lot of variation around the country though in terms of how things last, for example Kilkenny limestone from Ireland is very hard and is much more durable.
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