Much care is taken in replacing the old mortar. In this case, the mortar removed was from the original construction from over 150 years ago! The lime based mortar has been replicated with the addition of grey cement.
The following, true to traditional building style, is the back wall to the same building. The more dressed stones were selected and used for the front walls, as pictured above, with the offcuts and more random pieces used to construct the rear half of the house. Replacing and repairing the mortar on this bluestone cottage was long over due with the bottom image showing the difference of new, left, to old, right.
Mortar pointing/ jointing, for brick and stone buildings should be re-pointed every 30-50 years depending on exposure. Of course, a more hastened maintenance schedule, for aesthetic benefit, can be used and may be beneficial.