Unique Zebra Rock has been dated at about 600 million years old in the Pre Cambrian period.
The only known deposits in the world have been discovered in the East Kimberley region of Western Australia. It consists of fine-grained siliceous argillite (indurated siltstone or claystone) with rhythmic patterns of red bands or spots, contrasting sharply with a lighter background.
There are different theories of how the patterns were formed but it is thought that it was deposited as sediment under calm or deep water. The red bands or spots are coloured iron oxide. Weight 0.481kg 70mm diameter.