Can Wall of Stone merge with gravel, riprap, ballast rock, aggregate, or other non-solid/non-compacted forms of stone?

Question

This stems from Mike Mearls' interpretation in the answers to this question:

Mike Mearls :@Daganev @wax_eagle Correct, you'd need rocks of some sort (ruins, boulders) to support it.

The RAW for wall of stone states that:

It must, however, merge with and be solidly supported by existing stone.

Does this mean that the supporting stone that the wall of stone is merging with must be contiguous stone (such as a large boulder, or rocky outcrop)? Or can a wall of stone bear on/merge with riprap, aggregate/gravel, or ballast rock, provided that the substrate can handle the forces without displacing excessively?

Answer 1

If the fragmentary stone can solidly support it, yes. If not, no.

Add some tolerances so that the wall doesn't fold like a cheap deck chair when any force beyond its own weight is applied to it, and that should holistically cover all uses that are reasonably fit within the spell description's use of "solidly supported."