Algae

Shark tooth on pendant, Cretaceous, MAR

A slab that has been very well polished on both sides,the characteristic texture is clearly visible!You will receive a copy with a precise label; the photographs show various versions.Period: Precambrian, BIF Formation;Location: Pilbara, Western Australia, AustraliaSize: approx. 9 cm x 4 cm x 0.5 cmBanded iron formations (BIFs; also known as banded ironstone formations) are distinctive sedimentary rock units consisting of alternating layers of iron oxides and low-iron chert. They can reach a thickness of up to several hundred meters and extend laterally over several hundred kilometers. Almost all of these formations date from the Precambrian era and, according to one theory, are believed to document the oxygenation of Earth’s oceans. Some of Earth’s oldest rock formations, which formed about 3,700 million years (Ma) ago, are associated with banded iron formations.It is believed that banded iron formations formed in seawater as a result of oxygen production by photosynthetic cyanobacteria. The oxygen combined with dissolved iron in the Earth’s oceans to form insoluble iron oxides, which precipitated and formed a thin layer on the seafloor. Each band resembles a varve and is the result of cyclical fluctuations in oxygen production.Colors on product photos may differ from those of the original specimen due to technical reasons. Our pictures are for reference only. You will receive a specimen of equivalent quality with your purchase.