Yes it is, plants grow in The Free State, Lesotho and KwaZulu-Natal between 200 and 2200 m in the frost, like Aloe polyphylla, the Draaialoe local Spiralaloe in English Cok.
So natural...is there any media on the rock? It`s growing just like that or you intentionally plant it when they still young? seems the root grasp tightly.
The stones are a bit holy, and I planted it small say 8 years ago. Cok