These concretions are frequently referred to and marketed as stromatolites (trace fossils of algal colonies), but are not actually fossils. When cut and polished they do not show distinctive layering patterns you would expect to see in a stromatolite. From reports on the location, the flower-like patterns are only seen on specimens exposed to the surface, indicating they are caused by erosion.
A concretion is a hard, compact mass of rock that forms around a nucleus and is found in sedimentary rock. The initial nucleus that starts the formation of the concretion is typically organic material. Concretions are commonly spherical or oval in shape, but can take on some very irregular shapes too.
