They are found in the mountains where there is layers and layers of leaf compost and no clay at all. They are not near water or lakes. We do have 'turtle rocks' which are bubbles that formed when lava was cooling in a lot of places but that is many miles from these rocks. It is not like any lava formations I have ever seen. They do not resemble the lava rock, they seem more like granite. The rocks are all squareish or rectangular. None of them look like the lava floes or cooled bubbles that we have near some of our hot springs. I had a hard time wrapping my head around a hard rock surrounding a soft rock. When I tried to chip the soft rock out I realized it was very hard but with no 'structure' and I could chip it. After planting in a shallow one I discovered that being kept wet allowed me to dig out the center. It is not important but every time I move them around I can't help but wonder what kind of rock it is.
