Timber Framers Guild Forums General This Old Building Field stone mason

Field stone foundations and dry laid stone work are two different styles. Most barn foundations I see around here use mortar between the stones.
Dry stone is not that hard either, provided you have good material(reasonably flat stone), unless you are talking about making fancy arches, etc. In that case I bow down to the experienced mason.
I would encourage anyone to try working with stones, especially field stone or rubble stone barn foundations. The stones you need to do the repair are usually laying right beside the wall, and there are probably plenty more laying around the farm, waiting for you to pick them up for free.
To mix mortar, get some clean sand, a couple bags of portland cement and a bag of lime that is meant to mix mortar with. Play around with your mixture, there should be some suggestions on the lime bag, it's been a while but I seem to remember 10 shovels sand, 3 portland and 1 lime... or was it 21 sand, 3 portland, 1 lime...