In the photos below are three different projects showing two types of stone wall building.
1. - building a stone wall with a cmu ( concrete masonry unit ) sub straight
2. - building a solid stone wall - .. note the reinforcement bar extends up into the stone wall , thus lending tensile strength.
solid stone wall - no cmu
Upper wall is mortared stacked stone - no cmu substrate to bond to ( c . m. u . = concrete masonry unit )