I have a concrete block building that about 30 yrs ago had a mortar and small white stone (like garden stone) surface put on it. It still looks pretty good, but it is starting to come off in a few spots and I wanted to know how to repair it.
If what you are talking about is a pre-cast stone veneer, then it is easily replaced. If you are having a hard time finding replacement stones there are places that make molds for stone veneer. Making your own pre-cast is easy. StoneCasterStudio.com has rubber-based molds that might help you with your needs. If there is nothing in stock they can create a custom mold. Hope this helps.