Very large specimen weighing well over 1.5KG. It has nice ring patterns on the front side, that are partially obstructed by white calcite. Stromatolites are layered sedimentary formations created by the growth of microbial mats, primarily composed of cyanobacteria. They are among the oldest known fossils on Earth, with some formations dating back to about 3.7 billion years. However, this specimen hails from Bolivia’s Mesoproterozoic era, which places it roughly between 1.1 and 1.6 billion years old. Stromatolites form as a result of photosynthetic processes undertaken by cyanobacteria in shallow marine environments: the microbes absorb carbon dioxide (CO₂) and release oxygen (O₂), which raises the water’s alkalinity (pH) and triggers the precipitation of calcium carbonate (CaCO₃). This in turn buries the mats, and subsequent generations of cyanobacteria grow on top of the newly formed layers, repeating the cycle. Over millennia, this ongoing process creates the distinct, banded formations we recognise today. While stromatolites still form in a few modern settings, ancient ones have been compressed into solid stone. Bolivian stromatolites display characteristic brown and black bands, this because they are composed of silica and iron oxide. The presence of iron oxide in Bolivian stromatolites is primarily due to post-depositional mineralization, meaning it occurs after the biological formation of the stromatolite. Stromatolites are frequently sold in a polished state, which can strip away the intricate details that reflect their natural formation. The polishing process does, however, bring out the true colours of a stone or fossil. The same colours can be exposed by wetting the fossil, revealing the vivid natural colours that otherwise remain hidden, this does however only last for a few minutes. To create a permanent “wet look,” this fossil has been professionally coated in a very thin layer of a synthetic resin called "Paraloid B72," which, while being applied, was dissolved in ethyl acetate. Paraloid B72 is widely employed in the preservation and stabilisation of fossils and does not yellow over time. It is reversible and can be removed with ethyl acetate or acetone making it perfect for fossil preservation. After the ethyl acetate evaporates, the “wet” look remains, thanks to the way the deposited resin interacts with light and the surface of the fossil. This approach highlights the fossil’s authentic beauty and I’m thrilled to share these naturally preserved wonders with fellow fossil enthusiasts. Your item will be shipped with ample protective packaging and DHL, DPD, or PostNL track-and-trace service.