(CNN) – Scientists say they have found a trace of ancient life inside a 2.5 billion-year-old sapphire.
The sapphire sample from Greenland, where the oldest known sapphire deposits were found, contains graphite, a mineral made of pure carbon. Chemical signatures on the carbon indicate that it was a leftover from early life.
“The graphite inside this sapphire is really unique. It’s the first time we’ve seen evidence of ancient life in sapphire rocks,” said Chris Yakimchuk, professor of Earth and Environmental Sciences at the University of Waterloo in Canada. In a press release.
Graphite was found in rocks more than 2.5 billion years ago, a time on Earth when a lack of oxygen in the atmosphere and single-celled life existed only in microorganisms and algae.
To determine if carbon is of biological origin, the researchers analyzed its chemistry, specifically the isotopic composition of carbon atoms.
“Living matter is preferably made of lighter carbon atoms because it requires less energy to reach the cells,” Yakimchuk said. “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.”
Scientists found rocks in Greenland while studying the geology of sapphires to better understand the conditions necessary for their formation.
Ruby is a red variety of the mineral corundum.
Blue sapphire is made of the same substance. In sapphires, chromium produces a distinctive color, while traces of iron, titanium, and nickel produce sapphires of various colors, including the blue that is generally associated with the gemstone.
The team also found that graphite is likely to alter the chemistry of the surrounding rock to create favorable conditions for sapphire to grow.
“The presence of graphite gives us more clues to determine how sapphires formed at this site, something that is impossible to do directly on the basis of sapphire color and chemical composition,” Yakimchuk said in the statement.
The search was published in rough geology reviews last week.