Era: Mesozoic
Period: Cretaceous (≈70 Ma)
Origin: Potosí (Bolivia)
Formation: El Molino
Piece Measurements: 96 x 96 x 7 mm / 3,77 x 3,77 x 0,27"
Weight: 146 g / 0,323 lb
Description: Striking section of a cut and polished stromatolite colony. The growth layers of these bacterial colonies can be clearly seen.

Stromatolites were the first oxygenators of the atmosphere and thanks to their function, the Earth experienced one of the most profound changes in its history.

These are colonies of microorganisms called cyanobacteria that obtain energy through photosynthesis. About two billion years ago, stromatolites covered all the shallow waters of the ocean, and thanks to the enormous amount of oxygen they produced through photosynthesis, the composition of our atmosphere changed radically.

At that time, iron dissolved in the oceans. When bacteria began releasing oxygen, some of it combined with the iron to form rust, which accumulated on the seafloor, creating huge layers of rock. When all the iron oxidized, there was nothing left for oxygen to react with, but the stromatolites continued to release it, and as a result, oxygen eventually escaped from the oceans and filled the atmosphere. This process created our planet's vital protective shield: the ozone layer, without which life on Earth could not exist.

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