Stromatolites are the oldest of fossils, but scientists disagree on how to define them. According to The Virtual Fossil Museum, a commonly accepted definition of Stromatolite is “laminated rock formed by the growth of blue-green algae,” but then goes on to state that this definition is “such a gross oversimplification as be scientifically useless.”
So, what exactly is Stromatolite?
In the simplest of terms, Stromatolites are evidence of layer-forming cyanobacteria – single-celled microbes that use sunlight to create food. As these microbes grow, they form multi-layered structures shaped in mats, mounds, columns, and/or sheets that can eventually become sedimentary limestone rocks, and they usually extend well above the sea floor.
Fossil Stromatolites are a record of Earth’s ancient life, and Stromatolite-building communities include the oldest known fossils, dating to about 3.5 billion years ago. Stromatolites span more than four billion years of geologic history and have lived across nearly every environment that has ever existed on our planet.
Modern Stromatolites are found in extremely salty freshwater lakes like those in Yellowstone National Park or in sheltered and very salty marine lagoons. The Hamelin Pool Marine Nature Reserve at Shark Bay, Western Australia has excellent living Stromatolite specimens, which were first discovered there in 1956. Other modern locations include Pampa del Tamarugal National Reserve in Chile and Lagoa Salgada, in Rio Grande do Norte, Brazil. Stromatolites are nearly extinct in marine environments, with very few known worldwide localities, except for Exuma Cays in the Bahamas and in the Indian Ocean.
On the market
Stromatolite is somewhat rare but occasionally available as slabs, cabochons or tumbled stones and nuggets. Bolivian material from the Miraflores Formation (Greysonia) is approximately 65 million years old, and has very clear banding and/or orbicular formations in black, ochre and various browns. Material from South Ural, Russia dates to between 1.35 and 1.65 million years old, and is typically dove gray to cream color, with distinct scalloped banding.