Graphite in 2.5 billion-year-old ruby linked to early life

Researchers from the University of Waterloo discovered carbon residue encased in a 2.5 billion-year-old ruby while analyzing some of the world’s oldest coloured gemstones.

The research team, led by Chris Yakymchuk, a professor of Earth and Environmental Sciences, embarked on a journey to investigate the geological conditions that aided the formation of rubies. 

During their investigation in Greenland, which has the world’s oldest known ruby deposits, the researchers unearthed a ruby sample that contained the carbon-based mineral graphite. This carbon is known to be a relic of early life.

“The graphite inside this ruby is really unique. It’s the first time we’ve seen evidence of ancient life in ruby-bearing rocks,” said Professor Yakymchuk. “The presence of graphite also gives us more clues to determine how rubies formed at this location, something that is impossible to do directly based on a ruby’s colour and chemical composition.”

The researchers were able to examine the isotopic composition of carbon atoms, a property that measures the comparative amounts of different carbon atoms, due to the presence of graphite. 

The isotopic composition revealed that more than 98 percent of carbon atoms have a mass of 12 atomic mass units, although a few atoms with a mass heavier atomic mass of 13 or 14 was detected.

“Living matter preferentially consists of the lighter carbon atoms because they take less energy to incorporate into cells,” said Professor Yakymchuk. “Based on the increased amount of carbon-12 in this graphite, we concluded that the carbon atoms were once ancient life, most likely dead microorganisms such as cyanobacteria.”

The graphite found in the rocks dated back more than 2.5 billion years when oxygen was scarce in the atmosphere and life was limited to bacteria and algal films.

Professor Yakymchuk’s team determined that this graphite not only connects the gemstone to early life but was also likely essential for the existence of this ruby. The graphite altered the chemistry of the surrounding rocks, allowing ruby formations. 

The research models showed that the formation of rubies in this area would not have been achievable without it.

The study is published in the journal Ore Geology Reviews. 

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By Ashikha Raoof, Earth.com Staff Writer