ORD RANGES, AUSTRALIA

As one of the earliest fossilized forms of life, a mystery still surrounds the creation of Tiger Iron almost 2 billion years ago -- during a hostile era when the newly formed continents were barren and life was confined to the seas. Scientists have suggested that it is a banded iron formation (layered sediments caused by photosynthetic cyanobacteria) or a Stromatolite (layers of algae), or even both. Simple photosynthesising life forms such as these dominated the first two billion years of life on Earth, and were probably the source of the Oxygen in the atmosphere.