Crassula ausensis loves shooting out of rock crevices and as a result, will do well in your rock garden. As a native of the quartz and granite landscape of Namibia, it likes to stay low growing and small so it doesn't stick out too far from the rocky terrain.
They differentiate from their surroundings with their fuzzy leaves. They also bloom in late fall with white flowers. They can handle a wide range of light levels, from part sun to mostly shade. Of course like most succulents they tend to look their best with higher light levels.
Current batch looks like LAST 3 photos.