We recently purchased a Victorian Gothic home (our 3rd old house rennovation - you think we'd learn to stop this!). The house has limestone windowsills which have numerous stress cracks. One of the curved bottom sills (on the turret/tower portion) has a 1/4" crack running through it, which has resulted in a leak into the interior plaster. Nothing major - the plaster is intact, just surface bubbled. I've repointed 1870's brick before using a soft mortar mix - can I use this same mix for limestone? Thanks!