Gneiss from the Joshimath Formation at Jyotirmath (Uttarakhand, India).
This gneiss is from the Proterozoic Era (2.5 billion to 543 million years ago). It is 11.4cm wide at its widest.
Many important events occurred during the Proterozoic Era. Stable continents appeared, and began to grow larger by accretion, a process that took about a billion years.
The fossils of living creatures are abundant from this era – at first mostly bacteria and archaea, but eukaryotic cells begin to appear as fossils from about 1.8 billion years ago.
The first evidence of oxygen build-up in the atmosphere is from the beginning of the Mesoproterozoic Era (about 1.6 billion years ago). Many bacterial groups died off as a result, but eukaryotic forms benefitted greatly and their population exploded. These eukaryotic forms included multicellular algae, and the first animals appeared near the end of the Proterozoic Era.
