I have tons of sandstone rubble on my lot from walls that were built wrong by the previous owners. 

I am planning on redoing the walls in CMU (Concrete block), using Footings and Surface Bonding Mortar. I am then going to split and cut the rubble into something resembling ledgestone or coursed ashlar veneer and adhere it to the face of the block.

My question is:

I have only a few pieces that would be large enough to cut into veneer corners. Could I simply miter a flat piece, wrap the corner and fill the joint with colored grout to match?