Sorry to push Tiez Breiz again. but I hosted a course of theirs on sand a couple of years ago (and got some rendering done for free as a consequence). It is really worth testing your local sand with different proportions of lime before you start. Put little tests on a wall or on some chip board, and leave to dry. Say dinner plate size, 1.5 cm thick. Too much lime and it is too hard, too little and it's too crumbly, too much clay content and it cracks as it dries. The tutor made me get samples from local quarries and his chosen and successful mix was 3 parts washed sand, 3 parts unwashed sand (which had to be sieved to get the sand out) and 1 part lime. Obviously more sand to lime is cheaper. The clay in the unwashed sand is contributing to the mix. The tutor brought samples of other sands and challenged the professional masons on the course to assess the sands and produce successful mortars. A granite sand mix was 2 sand to 1 lime, since there was no clay content, and a very low proportion of fine sand. The application is also significant. I used what had been a nice workable mix on walls for pointing a slate floor, but it was too soft and wore away.
Their publication: http://www.tiez-breiz.org/Sables.php