These round rocks are a unique feature to the Richmond landscape. They can vary in size from a golf ball to weighing many tonnes. Nodules are concretions formed by the accumulation of limestone cement (calcium carbonate) in the sediment. They form by natural chemical processes in the sediment and are not weather worn. Under ideal conditions a spherical shape will form but other factors such as sediment permeability and other chemical processes may lead to some quite bizarre shapes.
Richmond hosts the World Champion Moon Rock Throwing Competition every two years at its Fossil Festival.
Although the nodules are not fossils, they can and often do, contain fossils especially shells. Much less often, bones and wood are found in the concretions.