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(CNN) -
Scientists say they have found a trace of ancient life within a 2.5 billion-year-old ruby.
The ruby sample from Greenland, where the oldest known ruby deposits are found, contained graphite, a mineral made from pure carbon.
The chemical signatures on the carbon suggest that it was a residue from early life.
"The graphite within this ruby is really unique. It is the first time that we have seen evidence of ancient life in ruby rocks," said Chris Yakymchuk, professor of environmental and earth sciences at the University of Waterloo in Canada, in a statement. press.
Graphite is found in rocks more than 2.5 billion years ago, a time on Earth when oxygen was lacking in the atmosphere and single-celled life only existed in microorganisms and algae.
To determine whether the carbon was of biological origin, the researchers analyzed its chemistry, specifically the isotope composition of carbon atoms.
"Living matter is preferably made up of lighter carbon atoms because they require less energy to get into cells," Yakymchuk said.
"Based on the increased amount of carbon-12 in this graphite, we concluded that carbon atoms were once ancient life, most likely dead microorganisms like cyanobacteria."
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Scientists found the rock in Greenland while studying the geology of the rubies to better understand the conditions necessary for their formation.
Rubies are a red variety of the mineral corundum.
Sapphires are formed from the same substance.
In rubies, chromium produces the distinctive color, while traces of iron, titanium, and nickel produce sapphires of different colors, including the blue hue generally associated with the gemstone.
The team also found that the graphite likely changed the chemistry of the surrounding rocks to create favorable conditions for the ruby's growth.
"The presence of graphite also gives us further clues to determine how rubies were formed at this location, something that is impossible to do directly based on the color and chemical composition of a ruby," Yakymchuk said in the statement.
The research was published in Ore Geology Reviews last week.
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